Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
WO 2023/073358
PCT/GB2022/052713
Title
Burner vessel and fluid heater
Field
This invention relates to heaters for fluid heating systems. In particular,
but not exclusively, the invention
relates to boilers for wet heating systems or furnaces for air heating
systems, both of which can supply
heated fluid for heating spaces (such as via radiators) or heated tap water or
both.
Background
Gas boilers can provide wet heating solutions for hot water and heating needs.
For example, a domestic
gas boiler will often supply hot water for heating radiators within a heating
system and also provide on-
demand hot water to taps (e.g. for drinking, cleaning, washing). The two
supplies (heating and tap) are
kept separate since the heating water can become dirty as it passes through a
radiator circuit, whereas
tap water must be clean. Combination ("combi") boilers are popular as they
provide all of this functionality
within a sealed, high pressure environment within a single boiler housing with
a relatively small physical
footprint. Other types of boilers having separate tanks or cylinders are also
used.
Gas boilers burn fossil fuel. As a result, electric boilers are now emerging
as an environmentally friendly
alternative. An electric boiler will pass the water via an electric heating
element.
An electric combi boiler uses similar technology to an electric kettle. The
electric boiler is connected to the
mains electricity supply and is supplied with cold water from the mains. When
hot water is requested (e.g.
when a hot water tap is opened or the heating is switched on), the heating
element inside the electric
boiler heats up and passes this heat to the cold water. The heated water is
then pumped to the tap or
radiator where it is needed.
Storagc electric boilers include a hot water tank (either an internal tank
within the unit or an external
tank). This enables heating and storage of water at times when energy costs
are lower (e.g. overnight) for
subsequent use at times when energy costs are higher (e.g. the next day). Such
systems take up more
space.
Along the same theme, but offering some of the advantages of a combi boiler, a
combined primary
storage unit (CPSU) has the central heating boiler and hot water cylinder
combined in one big housing -
this provides large amounts of hot water whenever required. However, a lot of
space is required to house
this system.
All of these electric boiler systems use heating elements powered by the AC
(alternating current) mains
supply.
The inventors have realised that a better fluid heater and heater vessel can
be produced and have
created the claimed solution.
Summary
According to a first aspect of the present invention, there is provided a
burner vessel as claimed in claim
1. According to another aspect of the invention, there is provided a fluid
heater as claimed in claim 21.
Advantageously, a hybrid electric-combustible fuel burner vessel / fluid
heater arranged to heat fluid in
one or more fluid circuits that can efficiently heat a fluid based on either
or both of multiple energy
sources is provided. This type of heater is eco-friendly relative to pure gas
burning (or other combustible
fossil fuel burning) boilers. Fluid heating resource (from the electric source
or the combustible fuel source)
can be supplied intelligently based on a number of desired supply and demand
factors.
Optional features of the invention are as claimed in the dependent claims ¨
various advantages are
thereby provided as discussed in the detailed description. These optional
features add efficiency and
intelligence to the inventive heater setup. Any of these optional features may
be combined with any other
of the optional features as will be appreciated by those skilled in this art.
Brief Description of Drawings
Embodiments will now be described by way of example only with reference to the
accompanying
drawings, in which:
Figures 1 to 9 are schematic views, some with sections partially cutaway, of a
burner vessel of a first
embodiment of the invention; Figure 5 is a cross-section view through the line
A-A in figure 4; Figure 6 is
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a magnified view of section D in figure 5; Figure 7 is an exploded view
showing components of the vessel
of the first embodiment; Figures 10 to 12 are schematic views of a burner
vessel of a second embodiment
of the invention; Figure 11 is a cross-section view through the line B-B in
figure 10;
Figure 12 is a magnified view of section E in figure 11;
Figures 13 to 15 are schematic views of a burner vessel of a third embodiment
of the invention; Figure 14
is a cross-section view through the line C-C in figure 13; Figure 15 is a
magnified view of section F in
figure 14;
Figure 16 is an exploded view showing components of a burner vessel of a
fourth embodiment of the
invention;
Figure 17 is a schematic view, with a section partially cutaway, of the burner
vessel of figure 16;
Figures 18 to 20 are magnified versions of figures 6, 12 arid 15 respectively;
Figure 21 is a closeup view of part of a cross-section view through the burner
vessel of figure 16;
Figure 22 is a closeup view of part of a cross-section view through a burner
vessel according to a fifth
embodiment of the invention;
Figures 24 to 28 are schematic views, some with sections partially cutaway, of
a burner vessel of a sixth
embodiment of the invention; Figure 27 is a magnified view of section A in
figure 28; Figure 24 is a
closeup view of figure 27;
Figures 23, 29 and 20 are schematic views of a heating element or parts
thereof that forms part of the
vessel of figures 24 to 28;
Figures 32 to 34 are schematic views, some with sections partially cutaway, of
a burner vessel of a
seventh embodiment of the invention; Figure 32 is a closeup view of part of a
cross-section view through
the burner vessel of figures 33 and 34;
Figure 31 is a schematic view of a heating element that forms part of the
vessel of figures 32 to 34;
Figures 36 to 38 are schematic views, some with sections partially cutaway, of
a burner vessel of an
eighth embodiment of the invention; Figure 36 is a closeup view of part of a
cross-section view through
the burner vessel of figures 37 and 38;
Figure 35 is a schematic view of a heating element that forms part of the
vessel of figures 36 to 38;
Figures 39 to 42 are schematic views, some with sections partially cutaway or
components removed, of a
burner vessel of a ninth cmbodimcnt of the invention; Figure 39 is a cross-
scction view through the
burner vessel;
Figure 43 shows a schematic view of a fluid heater according to another aspect
of the invention including
the burner vessel of figures 1 to 9;
Figures 44 to 49 show schematic views, some with sections partially cutaway or
components removed, of
a burner vessel of a further embodiment of the invention; Figure 47 is a cross-
section view through the
line A-A in figure 46; Figure 48 is a magnified view of section Al in figure
47; Figure 49 is a close-up view
of figure 48;
Figures 49 to 53 are close-up cross-sectional views (equivalent to Figure 49)
of other embodiments of the
invention;
Figure 54 is a schematic view, with sections partially cutaway or components
removed, of another
embodiment of the invention; and
Figure 55 is a schematic view, with sections partially cutaway or components
removed, of another
embodiment of the invention.
For clarity, some components may be omitted in some of the drawings for ease
of viewing other
components or features.
Description of Embodiments
The exemplary embodiments described in the detailed description and claims are
not meant to be
limiting. Other embodiments may be used, and other changes may be made,
without departing from the
scope of the invention. Various embodiments are described. The specific
embodiments are not intended
as an exhaustive description or as a limitation to the broader discussed and
claimed aspects. Features
described in conjunction with a particular embodiment are not necessarily
limited to that embodiment and
can be incorporated into any other embodiment(s). Protection afforded by any
applicable doctrine of
equivalents is retained to its fullest extent.
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Terms such as up, down, top, bottom, left, right, inner, outer, vertical,
upstanding etc. have been used to
describe the invention simply and clearly. These terms are not to be
interpreted in a manner that would
be limiting. The person skilled in the art will envisage other suitable
embodiments within the scope of the
invention.
Referring to figure 1, there is shown an inventive burner vessel 100,
according to a first embodiment of
the invention, that is part of a fluid heater used to heat water for use in a
standard fluid circuit, such as a
radiator heating water circuit. Various aspects of the burner vessel and fluid
heater will be described in
detail with reference to non-limiting examples. Other details will be apparent
to the skilled person. In
particular, known boilers have burner vessels that are arranged to burn fuel
and efficiently transfer heat
(via a heat exchanger) to a fluid, such as water - aspects (including
undescribed aspects) of known
burner vessels and fluid heater systems can be incorporated and used with this
invention by a person of
ordinary skill in this field.
Generally, the fluid heater may be a tank-type boiler (known also as a system
boiler), or a combi boiler, or
any other known boiler type, or a furnace heater, such as a furnace air
heater. The skilled person will be
able to adapt the described embodiments to boiler types other than those
described. As is known, these
boiler types can be used to supply heating water (e.g. to a radiator circuit)
or potable water (e.g. to a
circuit of taps) or both. In other examples, instead of heating radiator
water, there may be another type of
heating fluid flowing through the heating system, e.g. another liquid, another
gas (e.g. air) or oil or any
combination thereof.
Such fluid circuits are well known in the field. The, any or each fluid
circuit may be a substantially sealed
fluid circuit in use and optionally may be pressurised. In a potable water
circuit, pressure from the mains
or gravity fed source drives water such that when a faucet / tap is opened,
water flows out of tap in
normal use. Typically, a radiator circuit is substantially sealed in normal
use. Bleed points or pressure
release points may be provided at convenient locations to allow inspection or
pressure release or fluid
release for maintenance and repair. It is known to use expansion tanks or
expansion vessels (which are
small tanks used to protect closed (not open to atmospheric pressure) fluid
heating systems and domestic
hot water systems from excessive pressure). Typically, expansion tanks are
partially filled with air, whose
compressibility dampens shock caused by water hammer and absorbs excess water
pressure caused by
thermal expansion. In an air heater, the fluid circuit usually comprises at
least one vent through which
heated air exits to the space to be heated. In such circuits, the air within
the circuit is not sealed from the
environment - it is typically at atmospheric or ambient pressure. In some such
systems, air is drawn into
the furnace during normal operation, heated and then blown around the heated
network.
In this example (see figures 1 to 9 and 18), the burner vessel 100 is part of
a water heater that is a
system boiler. The burner vessel 100 comprises a vessel housing 102 to house
its components. A feature
of this burner vessel 100 is that it is compact and able to fit in a small
space. In many examples, this
invention includes features that make the burner vessel 100 compact to allow
the burner vessel to fit
within the same housing or space footprint as a typical known burner vessel,
even though the inventive
burner vessel comprises new components (as will be described in more detail
below).
The burner vessel 100 is arranged to heat water in a first circuit, wherein
the first circuit is a heating water
circuit. The heating water circuit comprises multiple components, including
standard domestic radiators
(not shown) in addition to the burner vessel 100. Water is used as the heating
fluid within the first circuit in
this example; other known heating fluids can be used in other examples.
The burner vessel 100 comprises a hybrid electric-combustible fuel vessel,
i.e. as well as providing
heating using a traditional combustion technique, the vessel also provides
heating via an electric source.
Within the same sealed, boiler vessel chamber are provided multiple heating
mechanisms. One is an
electric heating mechanism; the other is a gas burner mechanism in this
example. The gas burner
mechanism is substantially of a known type. Other examples may use other fuels
¨ e.g., suitable
combustible fuel may be a combustible fluid such as natural gas, hydrogen gas,
or propane gas or
methane gas, or ethane gas, or butane gas, or a suitable combustible oil or a
combustible solid or mulch,
such as woodchip or wood pellet, or any combination thereof. In this way, some
of the heating power is
provided by the electric component and some of it is provided by more
traditional burnt fuel.
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The electric heating mechanism can be in any suitable form. In this example,
it is in the form of electric
heating elements powered by a DC power supply, which is sufficiently large to
provide power to the
electrical heating element sufficient to provide all or most of the required
heated fluid / water (in other
examples, it may not be so large). This can help to add redundancy within the
system, or can be used to
operate efficiently in an environment where one or other power source is
scarce.
Relatively cold water from the first circuit enters the burner vessel 100 via
a cold water input pipe 104, is
heated and then relatively hot water exits the burner vessel 100 to the first
circuit via a hot water output
pipe 106. A first water duct 105 extends between the cold water input pipe 104
and the hot water output
pipe 106. The burner vessel 100 is a closed, sealed vessel and has a
combustion zone 112 therein, in
which fuel is burnt to supply heat to water flowing in the first water duct
105. The housing also contains a
burnt fuel heat exchanger 120 arranged to assist with transferring heat from
fuel being burnt in the
combustion zone to the water in the water circuit.
Within its housing 102, the vessel 100 contains a combustible fuel burner 110
of a known type. The
vessel 100 further comprises a fuel inlet pipe 108 in communication with the
fuel burner 110 and arranged
to convey an air-fuel mixture safely and efficiently to the burner in a known
manner. The vessel 100 also
comprises a flue 114 arranged to convey waste combustion gas away from the
combustion zone and the
vessel. In this example, the vessel 100 comprises a base frame 116, with which
the flue and hot water
output pipe 106 are integrally formed.
In this example, the burner 110 comprises a perforated burner bar 11 01 with
jet holes that allow for even
burning around the combustion zone. A sealing ring 1102 is arranged to seal
the bottom of the burner bar
1101 to minimise uncontrolled fuel burning, e.g. by preventing hot air and
uncombusted gas leakage from
the combustion assembly other than through the flue. A pair of igniters 1103
is configured to ignite the air-
fuel mixture on demand. The igniters 1103 are arranged to protrude from an
upper end of the housing in
use, for convenient access. In some examples, multiple burners may be
provided.
The burner 110 is arranged to provide efficient heating in the combustion zone
and to thereby transfer
heat via the burnt fuel heat exchanger 120 to the fluid in the first water
duct 105. The burnt fuel heat
exchanger increases efficiency of heat transfer from the burning fuel in a
known manner. In particular, in
this example, the heat exchanger is arranged to focus heat from the burning
gas (or other fuel in other
examples) on the fluid duct.
In other embodiments, instead of a water duct, a different fluid duct may be
provided ¨ e.g., in some
embodiments, the fluid being heated may not be a liquid, e.g., it may be air
in an air heating furnace and
a typical air heater duct is provided; in other examples, the water may be
potable water for use in a
potable water circuit; in other examples, the fluid may be oil in an oil
heater circuit.
In this example (see figure 7), the burnt fuel heat exchanger comprises a
generally cylindrical metal cast
heat exchanger body 121 of a known type. The heat exchanger body substantially
surrounds the
combustion zone to efficiently capture heat therefrom. The cylindrical wall of
the heat exchanger body is
about 6rnm thick in this example. In other similar examples, dependent on
materials used for
construction, it may be about 3mm to about 15mm thick. The upper limit is
chosen to avoid thermal mass
issues and potentially also casting issues; although it is possible to
construct a heat exchanger beyond
these limits, it may not be ideal. In this example, the heat exchanger body is
about the same thickness as
the duct, i.e., the thickness of the wall of the heat exchanger body is about
the same as the depth of the
duct ¨ different configurations will be apparent to the skilled reader; in
general, efficient heat transfer at
speed from the body to the fluid in the duct is provided. The base frame 116
is configured to seat the
cylindrical heat exchanger body such that exhaust gases from within the body
exit through the flue 114
and heated water from the first water duct 105 exits through the hot water
outlet pipe 106.
In this example (see figure 7), the housing comprises a multi-layer cover 130,
arranged to substantially
surround the burnt fuel heat exchanger. The multi-layer cover comprises a heat
insulant layer 131 (made
of a suitable material, such as ceramic wool or brick)) sandwiched between an
inner skin layer 132 and
an outer skin layer 133. The multi-layer cover is generally cylindrical to
efficiently cover the generally
cylindrical burnt fuel heat exchanger body 121. In another example, the
housing comprises a single layer
cover including a combined skin and insulating layer.
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As seen in figure 7, components of the vessel are designed for easy assembly
by placing (by sliding in
this example) them in a desired order over one another around the heat
exchanger body 121.
In this example, the first water duct 105 comprises a channel 1050 defined
between an outside wall of the
heat exchanger body 121 and an inner surface of the inner skin layer 132. The
inner skin layer 132 has a
section of the cold water input pipe 104 formed therewith and arranged to feed
relatively cold water to the
first water duct 105.
In other examples, other configurations for the duct and the cold water feed
are described below and yet
further examples will be apparent to a person skilled in this field. For
example, in some other
embodiments, the duct may comprise a sealed pipe arranged to pass through a
space or channel
between a wall of the heat exchanger and the cover; or a channel defined
entirely within the heat
exchanger, such as within the body of the heat exchanger; or a sealed pipe
arranged to pass through a
space or channel entirely within the heat exchanger; or a sealed pipe passing
through the housing,
optionally through the combustion zone, and optionally spaced from the heat
exchanger.
In this example, the outer wall of the heat exchanger body 121 comprises a
continuous open, C-shaped
recess in its outer surface, and the channel 1050 is defined between the
surface of the recess and the
cover (see figures 3, 6, 8 and 9). The channel extends in a spiral
configuration around the outer wall of
the heat exchanger from the first cold fluid inlet to the first hot fluid
outlet, downwardly in an in-use
configuration. The flow of water through the channel may be facilitated by a
pump (not shown), or an
otherwise pressurized fluid supply (e.g. mains water) or a gravity fed supply.
Water flows from top to
bottom and heats up as it flows along the spiral, in use.
The surface of the inner skin abuts and seals the open part of the channel
(see figures 6, 8 and 9) such
that water flows only along a desired circuitous path ¨ this encourages
efficient heat transfer as the time
and distance for the flowing water to absorb heat is increased / maximised.
In this example, the heat exchanger further comprises multiple heat exchanger
protuberances, in the form
of heat exchanger fins 122, arranged to efficiently transfer heat from the
burning fuel by increasing the
area and time available for interaction between the burning fuel and the heat
exchanger material. The fins
122 extend from the heat exchanger body towards the combustion zone and are in
thermal
communication with the heat exchanger body 121 ¨ the fins may be formed
integrally or separately from
the body 121. In this example, vertical fins 1221 are arranged concentrically
at regular intervals around
the combustion zone (extending from the heat exchanger body 121 near the
perimeter of the housing
102), and lateral fins 1222 are arranged at the base of the combustion zone
(towards the bottom of the
heat exchanger body 121). In this example, the fins are about 16mm deep (Le_
from tip to base). In other
examples, the fins may be any suitable depth, e.g. lcm to 4cm. in other
examples, the fin depth may be
different depending on factors such as vessel size, materials, power etc. In
combination with the wall of
the heat exchanger body, efficient heat transfer to a fluid in the duct is
thereby provided.
A compact, efficient burner assembly for transferring heat from burnt fuel to
the fluid (in this case, heating
water) is thereby provided. The skilled reader will understand that other
burner assemblies may be
configured differently and that the invention can be adapted to work with such
other assemblies.
This invention further provides one or more electric heating elements 140
arranged to heat water in the
first water duct 105. In this example, the one or more electric heating
elements 140 are contained in the
housing 102.
In this example, the electric heating element 140 comprises a continuous
spiral shaped element 1401
configured to fit in the spiral water channel 1050. The electric heating
element 1401 is located in the
channel 1050, near a base of its open recess, and is also (in this example)
spaced from the heat
exchanger body 121 such that it does not touch the walls of the heat exchanger
¨ advantages include: all
of the heat passes directly to the fluid to be heated without passing via the
heat exchanger; ease of
assembly! repair / servicing etc.; allows space for movement in case of
expansion / contraction caused
by heating. In this example, the heating element 140 is a metal sheathed,
ceramic powder insulated cable
with a high-power nichrome element. In other examples, ceramic preform beads
may be used instead of
powder. Such preform beads are often ground into powder during rolling / die-
drawing operations on the
cable. Electrical connectors 1402 extend from the element 1401 and protrude
from an upper end of the
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housing in use, for convenient access. The electrical connectors 1402 are
suitable for connecting the
element 1401 to a suitable power source.
In this example, the power source is a DC power supply, in this example a DC
power supply in the form of
a battery pack (not shown), which is located outside the burner vessel 100.
In this example, the DC power supply has a capacity of 0.5kWh. In another
example, for a small gas-
electric hybrid boiler system setup, the battery capacity may be about lkWh ¨
this might be useful in a
small dwelling, such as a small apartment or it may be useful in a larger
dwelling as a boost to the usual
hot water supply. In another example, for a larger gas-electric hybrid boiler
system setup, the battery
capacity may be about 3 to 5 kWh ¨ this might be useful in a larger dwelling.
In another example, for a
large or industrial hybrid system setup, the battery capacity may be about
5kWh or above. In some
examples, the battery capacity may be about 90kWh, e.g. to supply heating
fluid and heated potable
water to larger buildings. The skilled person will understand that different
battery capacities may be
appropriate for different uses ¨ there is no upper limit to the battery
capacity that may be required / useful.
In this example, the peak power output of the DC power supply is between 10kW
and 20kW in some
examples, and upto 200kW in some examples. In low peak demand circuits, the
peak power output may
be 1kW or 2kW. Suitable peak power output provisions can be made according to
specific circuit
requirements and will be apparent to the skilled person. E.g. in one example
scenario, a 90kWh battery
might provide 350kW for 10 minutes.
In other examples, the power source is an AC power supply (e.g. mains AC). In
yet further examples, the
power source may be a combination of an AC and a DC power supply.
A computer implemented controller (not shown) is arranged to control the
amount of heating supplied to
the fluid by the combustible fuel burner and by the first heating element. The
control may be based on
one or more control factors, the control factors comprising: amount of heating
required; fluid input
temperature at an input point in the one or more fluid circuits; fluid output
temperature at an output point
in the one or more fluid circuits; fluid temperature at any predetermined
point in the one or more fluid
circuits; amount of heating capacity available from the first heating element;
amount of heating capacity
available from the combustible fuel burner; instantaneous demand for heating
fluid or potable water;
forecasted demand for heating fluid or potable water; and flow rate of fluid
to be heated.
One or more sensors (not shown) may be provided to sense information relating
to the one or more
control factors and to provide said control factor information to the
controller. In one example, for
efficiency, the controller may be configured to heat fluid primarily using the
electric heating element(s),
such as primarily via the DC power supply, when a demand for hot fluid is
first detected.
In general, the electric heating element of this invention can be wrapped
around pipes or components of
the first fluid circuit within the vessel ¨ benefits include ease of
manufacture, ease of reconfiguration /
replacement / upgrade / repair, if needed (because the heating element is
located externally of the pipe /
component (and the wet side need not be touched). The heating element is
easily visibly and so it is
convenient to inspect (e.g. during regular servicing) whether it is degraded.
Such heating elements are
also easier to clean. Such heating elements are not affected by sludge and/or
calcification within the
water circuit (this problem is common in radiator water circuits). In air
furnace circuits, similar problems
arise from build up of dirt, dust, other detritus.
In other embodiments, the electric heating element can be placed inside a
first circuit conduit / pipe ¨
benefits include compactness, less heat loss to the environment (heat is
retained almost entirely in the
desired water circuit during normal heating operation).
In other embodiments, the electric heating element can be built into the walls
of water circuit conduits of
the first circuit ¨ benefits are that these elements are robust, less
susceptible to damage by dirty water,
suffer less heat loss (than equivalent wrapped heating elements).
In other embodiments, the heating may occur in a chamber (rather than in a
pipe or channel). In such
embodiments, pipes of the first circuit may lead to and from the chamber and
one or more electric heating
elements may be provided within the chamber at any location or embedded within
walls of the chamber or
wound around the chamber walls or any combination thereof. An advantage of
using such a chamber
rather than just heating the water / heating fluid as it passes through a
fluid pipe of the circuit is that a
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longer or more circuitous path may be provided and may allow the heating fluid
to remain in proximity to
the heating element(s) for a longer time during which more heat can be
transferred (relative to a direct
path through a straight pipe section).
In yet further examples, dependent upon the specific application, there may be
a combination of types
and arrangements of electric heating elements used.
The, any or each electrical heating element can be located anywhere in or
around the burner vessel such
that water can be heated by either or both of the gas and the electric heating
mechanisms.
The heating elements can be electrical wires that can be heated by passing
electric current therethrough
and arranged suitably to deliver heat where needed. (E.g. wrapped around a
water pipe, or a baffle (or
any other component within the burner vessel).
In this specific example (see figures 6 and 18), the continuous spiral shaped
element 1401 is configured
to fit in the spiral water channel 1050 without touching the wall of the heat
exchanger. The element 1401
is formed continuously as a double spiral profile which doubles back on itself
from top to bottom, in use
corresponding to the profile of the spiral water channel 1 050 such that each
pocket of the channel 1050
contains two strands of the element, in use, when the element is placed in the
channel. As can be seen
from the figures, the element is located near an inner side of the channel
1050 in this example. Not
touching the wall of the heat exchanger results in an easy-to-assemble
arrangement and ensures that the
cable element 1401 can easily transfer heat to the water on all its surfaces.
In other examples, the cable
element may be located elsewhere in, e.g. in the middle of, the channel. The
cable element may be
configured with a spacer (such as a metallic spacer) to keep it in a desired
position. In the present
example, rigidity of the element 1401 maintains its desired position.
Furthermore, in some examples,
there may be a mechanism to increase surface area for heat transfer. For
example, the heating element
may have a non-circular cross-section, e.g. may be a fin cross-section.
In this example (and in many other described examples), the electric and
combustible fuel heat sources
are arranged to heat the fluid in the duct at the same location (or
overlapping locations in some
examples) in the fluid duct. In other words, fluid at a single location can be
heated by either the electric
heating element or the combustible fuel heat source or both simultaneously. In
this example, the electric
heating element and the gas burner are arranged to heat along substantially
all / most of the length of the
fluid duct that passes through the vessel. An effect of this feature is to
allow (in some examples) the
entire heating demand of a typical domestic water heater to be supplied by an
electric source if needed
(and to still have the option to use a gas source to heat the same fluid in
the same location too). Another
effect is to efficiently provide a more powerful instant response (e_g_, when
potable water is first requested
from cold, and a quick/instant response is desirable). Furthermore, as a
result of being configured to heat
fluid at the same location via combustible fuel or electric or both
simultaneously, another effect of some
embodiments is that the electric heating elements can be used on their own
initially, without any water
flow, to pre-heat water in the duct. Then, heating via combustible fuel can be
activated in the usual way
along with fluid flow. As a result, an initial period of cold water when first
turning on a tap can be reduced /
avoided altogether (in an efficient way that avoids wasting water and / or
burnt fuel).As previously
described, in this example, combustible fuel heating occurs via the heat
exchanger, and electric elements
heat water directly in the duct. In other similar embodiments, the electric
element may instead /
additionally provide heating via the duct walls (e.g. if the elements are not
completely located within the
fluid (e.g. if they are located outside the duct nearby, e.g., on its
surface)) or via the heat exchanger (e.g.
if the elements are arranged to heat the heat exchanger).
A burner vessel 200 according to another embodiment (see figures 10 to 12 and
19) of the invention
contains elements similar to those of the first described embodiment. For
conciseness, elements that are
identical / similar to their counterparts in the first embodiment will not be
described again in detail, and are
labelled with reference numerals in the format "2xx" / "2xxx" instead of "1xx"
/ "1xxx".
The burner vessel 200 includes a cold water input 204, a hot water output 206,
and a first water duct 205
therebetween. The vessel has a housing 202 containing a fuel burner 210, a
burnt fuel heat exchanger
220 and a multi-layer cover 230.
7
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The body 221 of the heat exchanger differs from the body 121 of the first
embodiment in that the outer
wall of the heat exchanger body 221 comprises a continuous open, C-shaped
recess in its outer surface,
and the channel 2050 is defined between the surface of the recess and the
cover, but the channel 2050
does not have a smooth base. Instead (see figures 11, 12 and 19), the base of
the channel 2050 has a
pair of grooves 2051 formed therein. The pair of grooves is formed in a spiral
configuration corresponding
to the shape and direction of the channel. The pair of grooves is configured
to receive and retain the two
strands of the heating element 2401. The grooves are sized and shaped to
receive the heating element
cable 2401 as a tight fit such that the element will not be dislodged by
flowing fluid during normal use.
However, in this example, the element can be forcefully removed for servicing,
repair or replacement.
In this example, the element is supported in the heat exchanger body 221 at
the base of the channel. In
other examples, the grooves may be formed elsewhere, e.g. at the sides of the
channel.
As a result of the heating element being partially embedded in the heat
exchanger, compared to the first
embodiment, better heat transfer to the heat exchanger body from the electric
heating element is
provided ¨ more gradual heat transfer to the fluid can be provided. The
heating element is still partially
exposed directly to the fluid.
A burner vessel 300 according to another embodiment (see figures 13 to 15 and
20) of the invention
contains elements similar to those of the first described embodiment. For
conciseness, elements that are
identical / similar to their counterparts in the first embodiment will not be
described again in detail, and are
labelled with reference numerals in the format "3xx" / "3xxx" instead of "1xx"
/ "lxxx".
The burner vessel 300 includes a cold water input 304, a hot water output 306,
and a first water duct 305
therebetween. The vessel has a housing 302 containing a fuel burner 310, a
burnt fuel heat exchanger
320 and a multi-layer cover 330.
In this embodiment, the positioning of the spiral cable element 3401 in the
channel 3050 is different to the
positioning of the spiral cable element 1401 in the channel 1050 of the first
embodiment. The cable
element 3401 is wound to fit against the insulated cover 330 (see figures 15
and 20). As a result, the
heating effect is spread across the breadth of the channel, more so than in
the first embodiment.
In this example, since the cover 330 is a multi-layer cover, the element abuts
against the inner skin layer
333. The cable element 3401 is located completely in the fluid channel, i.e.
not at all embedded in the
heat exchanger or cover in this example. In other examples, the cable element
may be partially or fully
embedded in the cover.
A burner vessel 400 according to another embodiment (see figures 16, 17 and
21) of the invention
contains elements similar to those of the first described embodiment. For
conciseness, elements that are
identical / similar to their counterparts in the first embodiment will not be
described again in detail, and are
labelled with reference numerals in the format "4xx" / "4xxx" instead of "1xx"
/ "1xxx".
The burner vessel 400 includes a cold water input 404, a hot water output 406,
and a first water duct 405
therebetween. The vessel has a housing 402 containing a fuel burner 410, a
burnt fuel heat exchanger
420 and a multi-layer cover 430.
In this embodiment, the electric heating element 440 is of a different form to
the electric heating element
140. Instead of a cable heating element 1401, the electric heating element 440
comprises a spiralled wire
element 4401 (as seen clearly in see figures 16, 17 and 21). The spiralled
element 4401 has an enamel
coating for electrical insulation. The spiralled element 4401 fits loosely in
the channel 4050. As a result,
this arrangement is easy to assemble, repair and replace. In some examples,
one or more spacers may
be provided to locate the element 4401 in a desired position in the channel.
A burner vessel 500 according to another embodiment (see figure 22) of the
invention contains elements
similar to those of the previously described embodiment. For conciseness,
elements that are identical!
similar to their counterparts in the first embodiment will not be described
again in detail, and are labelled
with reference numerals in the format "5xx" / "5xxx" instead of "4xx" /
''4xxx".
The burner vessel 500 includes a cold water input 504, a hot water output 506,
and a first water duct 505
therebetween. The vessel has a housing 502 containing a fuel burner 510, a
burnt fuel heat exchanger
520 and a multi-layer cover 530.
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In this embodiment, the electric heating element 540 comprises a spiralled
wire element 5401 that is
partially embedded in a pair of grooves 5051. The base of the channel 5050 has
a pair of grooves 5051
formed therein. The pair of grooves is formed in a spiral configuration
corresponding to the shape and
direction of the channel. The pair of grooves is configured to receive and
retain the two strands of the
spiralled wire heating element 5401. The grooves are sized and shaped to
retain the heating element
cable 5401 such that the element will not be dislodged by flowing fluid during
normal use. However, in
this example, the element can be forcefully removed for servicing, repair or
replacement.
In this example, the element is supported in the heat exchanger body 521 at
the base of the channel. In
other examples, the grooves may be formed elsewhere, e.g. at the sides of the
channel.
As a result of the heating element being partially embedded in the heat
exchanger, compared to the first
embodiment, better heat transfer to the heat exchanger body from the electric
heating element is
provided ¨ more gradual heat transfer to the fluid can be provided. The
heating element is still partially
exposed directly to the fluid.
A burner vessel 600 according to another embodiment (see figures 23 to 30) of
the invention contains
elements similar to those of the first described embodiment. For conciseness,
elements that are identical /
similar to their counterparts in the first embodiment will not be described
again in detail, and are labelled
with reference numerals in the format "6xx" / "6xxx" instead of "1xx" /
"lxxx".
The burner vessel 600 includes a cold water input 604, a hot water output 606,
and a first water duct 605
therebetween. The vessel has a housing 602 containing a fuel burner 610, a
burnt fuel heat exchanger
620 and a multi-layer cover 630. The burnt fuel heat exchanger 620 has
vertical fins 6221.
In this embodiment, the electric heating element 640 is preformed and
configured to wrap around the heat
exchanger fins 6221 (as seen clearly in see figures 24 to 26). The preformed
element 6401 has an
enamel coating for electrical insulation. The preformed element 6401 comprises
a continuous thin wire
element that is arranged in a preconfigured flat pattern (pre-wound / formed
into flat or pyramidal spirals)
and is configured to be easily pushed (telescopically) into place on a fin
during assembly and fixed in
position, to achieve the desired coverage of the fin by the heating element.
In other examples, different types of heating element may be wrapped around or
partially or completely
embedded in the heat exchanger fins 6221. Similar heating element arrangements
may be provided for
lateral fins 6222 (not shown).
A burner vessel 700 according to another embodiment (see figures 31 to 34) of
the invention contains
elements similar to those of the first described embodiment. For conciseness,
elements that are identical /
similar to their counterparts in the first embodiment will not be described
again in detail, and are labelled
with reference numerals in the format "7xx" / "7xxx" instead of "lxx" / xxx".
The burner vessel 700 includes a cold water input 704, a hot water output 706,
and a first water duct 705
thcrcbctwccn. Thc vessel has a housing 702 containing a fuel burncr 710, a
burnt fuel heat cxchangcr
720 and a multi-layer cover 730.
In this embodiment, the electric heating element 740 comprises a thick film
heating element 7401. As
seen in figure 32, the heating element 7401 comprises a flat conductor 7403
encapsulated by an
encapsulating film 7404. The encapsulating film 7404 is a high temperature
film (i.e. arranged to
withstand high temperatures). The thick film heating element 7401 is not at
all embedded in the heat
exchanger or the cover in this example (but might be in other examples).
Reduced direct contact with the
fluid to be heated and with the heat exchanger leads to a higher life
expectancy for the heating element.
Furthermore, heat provided by heating the conductor 7403 is efficiently and
consistently dispersed across
a relatively large area (the surface area of the encapsulating film 7404).
A burner vessel 800 according to another embodiment (see figures 35 to 38) of
the invention contains
elements similar to those of the first described embodiment. For conciseness,
elements that are identical /
similar to their counterparts in the first embodiment will not be described
again in detail, and are labelled
with reference numerals in the format "8xx" / "8xxx" instead of "1xx" /
"lxxx".
The burner vessel 800 includes a cold water input 804, a hot water output 806,
and a first water duct 805
therebetween. The vessel has a housing 802 containing a fuel burner 810, a
burnt fuel heat exchanger
820 and a multi-layer cover 830.
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In this embodiment, the electric heating element 840 comprises a cylindrical
sleeve thick film heating
element 8401. The sleeve heating element 8401 can be made by spiralling (e.g.
like a cardboard tube) or
rolling and joining together a flat sheet. The heating element 8401 comprises
a flat conductor 8403
encapsulated by an encapsulating film 8404 in the form of a sleeve. The
encapsulating film 7404 is a high
temperature film (i.e. arranged to withstand high temperatures). The
cylindrical sleeve thick film heating
element 8401 is placed around the generally cylindrical heat exchanger body
821. In this example, the
sleeve element 8401 is sandwiched between the cover 830 and the heat exchanger
body 821.
A burner vessel 900 according to another embodiment (see figures 39 to 42) of
the invention contains
elements similar to those of the first described embodiment. For conciseness,
elements that are identical /
similar to their counterparts in the first embodiment will not be described
again in detail, and are labelled
with reference numerals in the format "9xx" / ''9xxx" instead of "lxx"
xxx".
The burner vessel 900 includes a cold water input 904, a hot water output 906,
and a first water duct 905
therebetween. The vessel has a housing 902 containing a fuel burner 910, a
burnt fuel heat exchanger
920 and a multi-layer cover 930.
In this embodiment, the heat exchanger body 921 and the heating element 940
are formed together as a
single inseparable unit. The heating element 940 comprises a metal-sheathed,
ceramic powder insulated
cable with a high power nichrome element (e.g. Kanthal (ATM)). The cable is
cast into the metal of the
heat exchanger during manufacture. The material of the sheath is able to
withstand the molten metal of
the casting during manufacture. The cable is immune to calcification since it
is remote from the fluid being
heated. In another similar example, the electric heating assembly can be
overmoulded, e.g., with die cast
aluminium. In this example, the cylindrical wall of the heat exchanger body is
thicker than in similar
examples without a heating element cast therein (perhaps about 140% to 200%
thicker in some cases); in
this example, the cylindrical wall of the heat exchanger body is about 10mm
thick.
The features of any of the described embodiments can be used with the features
of any other of the
described embodiments - disclosure is made of any such combinations and
protection is sought for any
such combinations. In particular, different types of element (e.g. cable or
spiralled wire or flat
encapsulated or sleeved) may be used together. In particular, electric heating
elements can be
embedded in the heat exchanger or cover or both, whether partially, completely
or not at all or in any
combination within the same embodiment. In particular, heating element(s) can
interact as previously
described in any combination with the heat exchanger fin(s) or the heat
exchanger body or within the fluid
channel or any combination thereof.
According to another embodiment of the invention, referring to figure 43,
there is shown a fluid heater
4300 arranged to heat fluid in a fluid circuit. The fluid circuit comprises a
radiator circuit comprising at
least one radiator 4310. In this example, the fluid heater comprises a system
boiler 4300 having a boiler
housing 4301. Within the boiler housing 4301, the boiler comprises the burner
vessel 100 of the first
embodiment and a controller 4302 in communication with the vessel 100 and
arranged to control the
amount of heating supplied to the water in the fluid circuit of by the
combustible fuel burner 110 and by
the heating element 140. The controller controls operation of the burner via
suitable control circuitry in a
known manner, and operation of the heating element 140 by controlling the
current flowing therethrough
with suitable control circuitry.
The fluid heater comprises a DC power supply (of the type previously
described) in the form of a battery
pack 4303 arranged to power the heating element 140.
The fluid heater also has an AC connection (not shown) in order to power small
electronic components
(these have a relatively low power demand compared to the power required to
heat water during normal
boiler operation) such as switching circuitry, boiler display screen, boiler
user interface, sensors, Wi-Fi,
Bluetooth, sub 1GHz comes etc, led lighting and other standard boiler
components. Other such
components include: igniter or spark generator; ignition electrode /
ionisation electrode; pressure sensor /
transmitter (water), also water pressure switch, flow sensor / switch (makes
sure that the gas / air mix is
flowing correctly before allowing ignition); combustion sensor (thermal switch
¨ sometimes stated
separately to temperature sensors by manufacturers); thermostat; thermocouple
/ PRT; control PCB;
multi-media interface; power electronics for powerpacks; pumps (simple
electrical or possibly more
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complex with drive electronics) for water & gas. In some examples, this power
may be provided by
renewable heat sources too, such as solar or wind or a heat pump or any other
suitable source. In some
examples, these small electronic components are powered directly from the DC
power supply - there is
no AC connection to the boiler in this case.
In other examples, the fluid heater (and its electric heating element) is
arranged to be powered, instead or
in addition, by an AC power supply, such as mains AC.
In this example, the boiler also comprises an electric control unit (not
shown) arranged to control any one
or more of: heating, battery charging, battery discharging, system
requirements, switching of the DC or
AC power supply.ln this example, the boiler also comprises a thermal beak or
heat shield (not shown)
located between the DC power supply and the vessel. The thermal break or heat
shield may comprise
any one or any combination of: an air gap; a gap filled (partly or fully) by a
thermal insulation material; a
gap filled (partly or fully) by an infrared-reflective material; a gap filled
(partly or fully) by an insulator or
low thermal conductivity material.
In some examples, the heat shield may include an associated heat shield
cooling mechanism arranged to
transfer heat from the heat shield area towards another area in which it is
safer to dissipate heat and
comprising any one or more of:
= a fluid material that takes heat away from the area (e.g., from the heat
shield area to a dissipation
area (i.e. another area in which it is safer to dissipate heat than in the
heat shield area));
= an active cooling mechanism, such as a Peltier device (that actively
moves heat from one side to
the other, e.g. towards another area in which it is safer to dissipate heat
than in the heat shield
area);
= a chilled cabinet located inside the boiler housing (similar to a typical
refrigerator) and arranged to
substantially enclose the DC power supply; and
= an air flow mechanism, such as a blower, arranged to draw air in from
outside the housing, or
from inside the housing, to provide the required cooling effect.
The boiler of this embodiment also comprises a cooling system (not shown). The
electronics can get
hotter than on a normal boiler because of the extra switching because of
operation of the controller and
its related circuitry aimed at using DC-v-AC intelligently.
In some examples, the heater comprises a high-power switching module arranged
to efficiently switch
high currents such that power can be varied in the same resistant electric
heating element and smoothly
change fluid temperatures. This is especially important in the potable water
circuit. This features allows
pulse width modulation within the control circuitry. The high-power switching
module may be arranged to
switch 30amps or more.
In examples containing a battery charging mechanism, the inventor further
found that heat generation
within the battery charging system can be a problem ¨ specifically in an AC-DC
converter battery
charging system, which allows a voltage to charge the DC battery packs/cells.
This type of battery
charging system does not exist within any boiler systems or boiler housings
yet, and generates heat. A
further advantage of some examples of the present invention is therefore to
use the cooling system (or to
provide a further separate cooling system) as a heat sink to cool the battery
charging mechanism too.
The battery charging mechanism cooling system can be particularly useful since
charging can (and
should) also occur when the system is not heating a building or providing hot
potable water (e.g., in the
middle of the night). The present invention's cooling system allows for
running the heating system to
leach heat away during charging. The controller may be arranged to run fluid
through the fluid heater
system to cool the battery charging mechanism even when heated fluid is not
required, e.g., the controller
may act in response to predicting or being informed or sensing that the
battery charging system should be
cooled (e.g., via feedback from a temperature sensor located near the battery
charger or after the battery
has been continuously charging for a threshold minimum time period). This
battery charging mechanism
cooling feature can be implemented with any of the described embodiments
containing a battery charger
to create a new embodiment of the invention.
In some examples (e.g., in which flow of the heating fluid / potable water is
participating in the cooling),
when the heating system is running (e.g., potable water or heated radiator
fluid is being demanded), then
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cooling occurs via flow of the heating fluid / potable water past the
controller! battery / battery charger.
However, when the heating system is not running, this invention allows for
operation of the charger
cooling system (whether via flow of the heating fluid / potable water or via
its own dedicated coolant within
its own dedicated coolant circuit) specifically for the purpose of cooling the
battery charger.
In some examples, the cooling system uses some of the water output from the
radiators, which arrives at
the cold input pipe (typically at about 35-40 degC) for cooling the
electronics, which are much hotter
(ideally, the intention is to keep the electronic components well below 100
degC). In some examples, an
element of the cooling system comprises locating the first circuit pipework
from the input within the boiler
adjacent or near to the components that require cooling. As a result, overall
efficiency of the fluid heater is
enhanced, and its electronics can be made more compact / simpler due to a
reduced need for perfect
electronic efficiency with switching power.
The cooling system of this example also includes a coolant circuit having a
closed coolant pipe system
(not shown) through which coolant is pumped. The closed coolant pipe system is
configured to encourage
heat transfer between the coolant and the boiler's cold water input so as to
transfer heat away thereto as
well as to encourage heat transfer between the coolant and the DC battery
cells (if present in any
particular embodiment) or other components so as to transfer heat away
therefrom. This is achieved by
routing the pipe system close to any one or more of the boiler components,
battery cells and cold water
input at appropriate locations.
In some such examples, e.g. in examples where an air intake is used to aid the
combustion process (e.g.
when burning a gas or other combustible fuel), the cooling system can include
using the air intake to cool
the battery pack and / or electronic components since the air taken in will be
relatively cool; at the same
time, the air will become heated and will make the combustion process more
efficient. This can be
achieved by locating the air intake path near to the battery pack or
components that need cooling.
In this example, the boiler 4300 is configured to be compact. The boiler
housing 4301 has dimensions
400 cm width by 300 cm depth by 700 cm height and houses the vessel 100 and
any required control
circuitry. In other embodiments, the housing may have different dimensions,
e.g.: W39Ornm, D270mm,
H600mm; or W400mm, D300mm, H724mm; or W400mm, D31Ornm, H724mm; or W440mm,
D365mm,
H780mm; or W440mm, D364mm, H825mm; or W440mm, D365rnm, H780mm; or any other
suitable
dimensions that will be apparent to the skilled person.
Providing further compactness, the DC power supply is located at a front side,
in use, of the boiler
housing, substantially fills the space between front and back ends of the
housing, and also substantially
fills the space between left and right sides of the housing. The boiler has
walls on its left and right sides
that are relatively inaccessible in use. The front side is relatively
accessible and is usually used to access
internal components when servicing.
In some examples, the fluid heater housing comprises an access door arranged
to allow access to
internal components of the heater (such as for servicing or repair) and the DC
power supply is arranged
within or integrally with the access door. This also adds to the overall
compactness and also ensures that
the DC battery does not need to be further removed or manipulated to access
the internal boiler
components (e.g for repair / servicing).
One or more electric heating element(s) can be wrapped around pipes or
components of the first circuit
outside of the vessel 100, and inside the boiler housing 4301 ¨ benefits
include ease of manufacture,
ease of reconfiguration / replacement / upgrade / repair, if needed (because
the heating element is
located externally of the pipe / component (and the wet side need not be
touched). The heating element
is easily visibly and so it is convenient to inspect (e.g. during regular
servicing) whether it is degraded.
Such heating elements are also easier to clean. Such heating elements are not
affected by sludge within
the water circuit (this problem is common in radiator water circuits).
In some examples, the vessel contains at least one baffle arranged to divert
air heated by the fuel burner
and arranged to increase thermal communication between the heated air and the
heat exchanger. The,
any or each electric element may be partially or completely embedded within
the at least one baffle or
wrapped around the at least one baffle.
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In other embodiments, the electric heating element can be placed inside a
first circuit conduit / pipe
(outside the vessel 100 and inside the boiler housing 4301) ¨ benefits include
compactness, less heat
loss to the environment (heat is retained almost entirely in the desired water
circuit during normal heating
operation).
In other embodiments, the electric heating element can be built into the walls
of water circuit conduits of
the first circuit (outside the vessel 100 and inside the boiler housing 4301)
¨ benefits are that these are
robust, less susceptible to damage by dirty water, suffer less heat loss (than
equivalent wrapped heating
elements).
The controller 4302 is arranged to control the amount of heating supplied to
the fluid based on or in
response to any one or more control factors, the control factors comprising:
amount of heating required;
fluid input temperature at an input point in the one or more fluid circuits;
fluid output temperature at an
output point in the one or more fluid circuits; fluid temperature at any
predetermined point in the one or
more fluid circuits; amount of heating capacity available from the first
heating element; amount of heating
capacity available from the combustible fuel burner; instantaneous demand for
heating fluid or potable
water; forecasted demand for heating fluid or potable water; and flow rate of
fluid to be heated.
Furthermore, the fluid heater comprises one or more sensors arranged to sense
information relating to
the one or more control factors and to provide said control factor information
to the controller 4302. Some
of the sensors 4305 are located inside the boiler housing 4301 (e.g. to
measure water temperature or flow
rates within the boiler). Some of the sensors 4306 are located outside the
boiler housing 4301 (e.g. to
measure water temperature or flow rates at a desired location in the first
circuit outside the boiler, such as
in a room of a building). The controller acts in response to information from
such sensors to instruct
heating of the fluid by the fuel burner and electric heating element.
The controller may have a memory (not shown) associated therewith (either
integrally or separately), the
memory being arranged to store information about any one or more aspects of
the system, such as
historic or sensed information relating to any of the control factors, control
factor information, sensed
information from any of the sensors, desired output information (e.g. desired
room temperature). The
controller is able to access information from the memory in a known manner.
The controller and memory
may be implemented in a standard computerised network and system.
Figures 44 to 49 show a burner vessel 4400 according to another embodiment. In
this example, the
burner vessel 4400 is part of a water heater that is a combi boiler supplying
heated fluid to two fluid
circuits, a first circuit containing radiator fluid and a second circuit
containing potable water. The burner
vessel 4400 comprises a vessel housing 4402 to house its components. A feature
of this burner vessel
4400 is that it is compact and able to fit in a small space. In many examples,
this invention includes
features that make the burner vessel 4400 compact to allow the burner vessel
to fit within the same
housing or space footprint as a typical known burner vessel, even though the
inventive burner vessel
comprises new components.
The first circuit is a heating fluid circuit, and comprises multiple
components, including standard domestic
radiators (not shown) in addition to the burner vessel 4400. Water is used as
the heating fluid within the
first circuit in this example; other known heating fluids can be used in other
examples. The second circuit,
a potable water circuit, comprises multiple components, including standard hot
water taps (not shown) in
addition to the burner vessel 4400.
The burner vessel comprises a hybrid electric-combustible fuel vessel, i.e. as
well as providing heating
using a traditional combustion technique, the vessel also provides heating via
an electric source. Within
the same sealed, boiler vessel chamber are provided multiple heating
mechanisms. One is an electric
heating mechanism; the other is a gas burner mechanism in this example. The
gas burner mechanism is
substantially of a known type_ Other examples may use other fuels ¨ e.g., as
specified earlier in relation
to other embodiments. In this way, some of the heating power is provided by
the electric component and
some of it is provided by more traditional burnt fuel.
The electric heating mechanism can be in any suitable form. In this example,
it is in the form of electric
heating elements powered by a DC power supply, which is sufficiently large to
provide power to the
electrical heating element sufficient to provide all or most of the required
heated fluid / water (in other
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examples, it may not be so large). This can help to add redundancy within the
system, or can be used to
operate efficiently in an environment where one or other power source
(gas/electric) is scarce.
Relatively cold water from the first circuit enters the burner vessel 4400 via
a first cold radiator water input
pipe 4404a, is heated and then relatively hot water exits the burner vessel
4400a to the first circuit via a
first hot radiator water output pipe 4406a. A first water duct 4405a extends
between the cold water input
pipe 4404a and the hot water output pipe 4406a.
Relatively cold water from the second circuit enters the burner vessel via a
second cold radiator water
input pipe 4404b (via a mains water feed in this example), is heated and then
relatively hot water exits the
burner vessel 4400 to the second circuit via a second hot potable water output
pipe 4406b. A second
water duct 4405b extends between the second cold water input pipe 4404b and
the second hot water
output pipe 4406b.
The burner vessel 4400 is a closed, sealed vessel and has a combustion zone
4412 therein, in which fuel
is burnt to supply heat to water flowing in the water ducts 4405a, 4405b.
Within its housing 4402, the vessel 4400 contains a combustible fuel burner of
a known type. The vessel
further comprises a fuel inlet pipe in communication with the fuel burner and
arranged to convey an air-
fuel mixture safely and efficiently to the burner in a known manner. The
vessel also comprises a flue 4414
arranged to convey waste combustion gas away from the combustion zone and the
vessel. In this
example, the fuel burner is arranged horizontally in use.
In this example, the burner comprises a perforated burner bar 4408 (similar to
that described in relation to
previous examples) with jet holes that allow for even burning around the
combustion zone. A sealing ring
is arranged to seal the bottom of the burner bar 4408 to minimise uncontrolled
fuel burning, e.g. by
preventing hot air and uncombusted gas leakage from the combustion assembly
other than through the
flue. A pair of igniters is configured to ignite the air-fuel mixture on
demand.
The burner is arranged to provide efficient heating in the combustion zone and
to thereby transfer heat to
the fluid in the first and second water duct 4405a, 4405b. In this example,
heat is transferred from the hot
gas in the combustion zone to the fluid in the ducts via the duct walls, which
are configured to efficiently
transfer heat in a known way.
In this example, but not in all examples, the vessel housing further contains
a baffle 4407 located in the
combustion zone and arranged to divert gas heated therein along desired routes
to increase thermal
communication between the heated air and the duct walls. In particular, the
baffle encourages movement
of hot gas towards radially outer regions of the generally cylindrical
combustion zone, which is where the
ducts are located.
In other embodiments, instead of a water duct, a different fluid duct may be
provided ¨ e.g., in some
embodiments, the fluid being heated may not be a liquid, e.g., it may be air
in an air heating furnace and
a typical air hcatcr duct is provided; in other examples, the water may be
potable watcr for usc in a
potable water circuit; in other examples, the fluid may be oil in an oil
heater circuit.
In this example, the combustion zone, housing and ducts comprise a generally
cylindrical configuration of
a known type. The ducts 4405a, 4405b substantially surround the combustion
zone in a spiral
arrangement to efficiently capture heat therefrom. The duct pipes spiral
around near the perimeter of the
housing to efficiently capture generated heat. There are gaps between adjacent
parts of the duct to allow
hot gas to flow therethrough, and thereby to transfer heat to the fluid in the
duct and to efficiently travel to
the flue thereafter.
Exhaust gases from within the combustion zone exit through the flue 4414 and
heated water from the
ducts 4405a, 4405b exits through the hot water outlet pipes 4406a, 4406b. The
baffle guides hot gas
movement along desired paths.
In this example, the first water duct pipe 4405a is spirally arranged near a
mouth of the combustion
chamber and adjacent to the burner bar. The second water duct pipe 4405b is
spirally arranged at a distal
end the combustion chamber away from the burner bar. Hot air still reaches and
effectively flows over
and around the second water duct pipe 4405b encouraged by the baffle 4407.
Other specific
configurations will be apparent to the skilled reader.
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In this example, each duct 4405a, 4405b has an elongated oval shaped cross
profile extending in a
direction radially away from the centre of the combustion zone ¨ this can be
seen schematically in figure
48 and figures 49 to 53. This feature allows for a longer contact time between
the hot gas and the duct.
The ducts extend in a spiral configuration around the outer wall of the
housing from their respective cold
fluid inlets to their hot fluid outlets, from right to left, in use, as viewed
in figure 47. The flow of water
through each duct may be facilitated by a pump (not shown), or an otherwise
pressurized fluid supply
(e.g. mains water) or a gravity fed supply.
A compact, efficient burner assembly for transferring heat from burnt fuel to
the fluid (in this case, radiator
fluid and potable water in different circuits) is thereby provided. The
skilled reader will understand that
other burner assemblies may be configured differently and that the invention
can be adapted to work with
such other assemblies. For example, the invention can be easily adapted to
work with only a single fluid
circuit, e.g. in a system boiler arrangement.
This invention further provides one or more electric heating elements 4440
arranged to heat water in the
first and second ducts 4405a, 4405b. In this example, the one or more electric
heating elements 4440 are
contained in the housing 4402.
In this example, the electric heating element 4440 comprises a continuous
spiral shaped element
configured to fit around, and follow closely the spiral path of, the ducts
4405a, 4405b. The element 4440
is held in place relative to the ducts, by spot welding in this example.
The electric heating element 4440 is located externally of the ducts and
radially spaced further from the
centre of the combustion zone than the ducts.
In this example, the hcating clement 4440 is a metal sheathed, ccramic powdcr
insulated cable with
multiple high power nichrome elements therein (2 elements are shown in the
figures; there may be up to
7 elements in the example shown). Electrical connectors 4502 extend from the
element and protrude from
an upper end of the housing in use, for convenient access. The electrical
connectors 4502 are suitable for
connecting the element to a suitable power source.
In this example, the power source is a DC power supply, in this example a DC
power supply in the form of
a battery pack (not shown), which is located outside the burner vessel.
In this example, the DC power supply has a capacity of 0.5kWh. In another
examples, capacity may be
similar to that previously described for other examples.
In this example, the peak power output of the DC power supply is between 10kW.
In another examples,
peak power output may be similar to that previously described for other
examples. E.g. in one example
scenario, a 90kWh battery might provide 350kW for 10 minutes.
In other examples, the power source is an AC power supply (e.g. mains AC). In
yet further examples, the
power source may be a combination of an AC and a DC power supply.
A computer implemented controller (not shown) is arranged to control the
amount of heating supplied to
the fluid by the combustible fuel burner and by the first heating element. The
control may be based on
one or more control factors, the control factors comprising: amount of heating
required; fluid input
temperature at an input point in the one or more fluid circuits; fluid output
temperature at an output point
in the one or more fluid circuits; fluid temperature at any predetermined
point in the one or more fluid
circuits; amount of heating capacity available from the first heating element;
amount of heating capacity
available from the combustible fuel burner; instantaneous demand for heating
fluid or potable water;
forecasted demand for heating fluid or potable water; and flow rate of fluid
to be heated.
In some multiple fluid circuit (e.g. combi boiler) examples, the controller is
arranged to instruct exclusively
using combustible fuel for heating purposes (e.g. heating radiator fluid) and
exclusively using electric for
heating potable water.
One or more sensors (not shown) may be provided to sense information relating
to the one or more
control factors and to provide said control factor information to the
controller. In one example, for
efficiency, the controller may be configured to heat fluid primarily using the
electric heating element(s),
such as primarily via the DC power supply, when a demand for hot fluid is
first detected.
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In general, the electric heating element of this invention can be wrapped
around pipes or components of
the first and/or second fluid circuit within the vessel ¨ benefits include
ease of manufacture, ease of
reconfiguration / replacement / upgrade / repair, if needed (because the
heating element is located
externally of the pipe / component (and the wet side need not be touched). The
heating element is easily
visibly and so it is convenient to inspect (e.g. during regular servicing)
whether it is degraded. Such
heating elements are also easier to clean. Such heating elements are not
affected by sludge within the
water circuit (this problem is common in radiator water circuits).
Figures 49 to 53 show close-up views of pairs of heating element and duct
arrangements from different
embodiments. Features of these embodiments are similar to those of the
previously described
embodiment unless otherwise stated.
In the example of figure 50, the heating element is in the form of a metal
sheathed, ceramic powder
insulated cable with multiple high power nichrome elements therein. The cable
is welded to the duct in a
similar manner to that of the embodiment of figures 44 to 49, but is radially
closer to the centre of the
combustion zone than the duct, i.e. it is on an inner side, or flame side, of
the duct. In other examples,
instead of being welded, the cable may be (vacuum) brazed to the duct.
In the example of figure 51, the electric heating element is placed inside the
duct pipe ¨ benefits include
compactness, less heat loss to the environment (heat is retained almost
entirely in the desired water
circuit during normal heating operation).
In the example of figure 52, the electric heating element is in the form of a
conductive coating 5201
around the outside of each duct. The conductive coating is arranged to heat up
when an electric current is
passed therethrough, and thereby to efficiently transfer heat to fluid in the
duct. The conductive coating
can be applied by spraying. Insulating layers are provided inside and outside
of the conductive coating ¨
the conductive coating is sandwiched between these insulating layers. The
insulating layers are plasma
sprayed or applied by dipping, in this example. Other techniques for applying
these layers will be
apparent to the skilled reader. In some examples in which the heating element
is to be provided in distinct
zones (not continuously along the entire length of the duct), gaps between the
distinct zones can be
formed by masking gap sections of the duct (e.g. with a spray mask) during the
coating / spraying
process.
In the example of figure 53, the electric heating element is in the form of a
conductive coating 5301 on the
inside of each duct. The conductive coating is arranged to heat up when an
electric current is passed
therethrough, and thereby to efficiently transfer heat to fluid in the duct.
The conductive coating can be
applied by spraying. Insulating layers are provided inside and outside of the
conductive coating ¨ the
conductive coating is sandwiched between these insulating layers. The
insulating layers are plasma
sprayed or applied by dipping, in this example. Other techniques for applying
these layers will be
apparent to the skilled reader.
In other embodiments, the electric heating element can be built into the walls
of ducts of the first and
second circuits ¨ benefits are that these elements are robust, less
susceptible to damage by dirty water,
suffer less heat loss (than equivalent wrapped heating elements).
In yet further examples, dependent upon the specific application, there may be
a combination of types
and arrangements of electric heating elements used.
The, any or each electrical heating element can be located anywhere in or
around the burner vessel such
that water can be heated by either or both of the gas and the electric heating
mechanisms.
The heating elements can be electrical wires that can be heated by passing
electric current therethrough
and arranged suitably to deliver heat where needed. (E.g. wrapped around a
water pipe, or a baffle (or
any other component within the burner vessel).
In another embodiment (see figure 54), a burner vessel 5400 comprises a
generally rectangular box-like
housing 5401 and a rectangular block-like heat exchanger 5402 towards an upper
end (in use) of the
housing. Many features of this example are functionally similar to that of the
first-described example, and
so will not be described again for conciseness. In this example, a water duct
5403 is completely
embedded in the heat exchanger (shown cut away in figure 54). The water duct
is fed from a cold inlet
5404 and doubles back on itself twice within the exchanger (to enhance heat
transfer). Heated water exits
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from a hot water outlet (not visible in figure 54, as it is on the other side
of the housing). A burner 5405
heats gas in a combustion zone 5406 within the housing to heat the heat
exchanger and thereby the
embedded duct and fluid conveyed within the duct. A flue 5407 is provided at
the top of the housing for
exhaust gases.
In yet another embodiment (see figure 55), a burner vessel 5500 comprises a
generally rectangular box-
like housing 5501 and a rectangular block-like heat exchanger 5502 towards an
upper end (in use) of the
housing. Many features of this example are functionally similar to that of the
previously described
example, and so will not be described again for conciseness. In this example,
a water duct 5503 is
completely embedded in the heat exchanger (shown cut away in figure 55). The
water duct is fed from a
cold inlet (not shown) and doubles back on itself twice within the exchanger
(to enhance heat transfer).
Heated water exits the vessel housing 5501 from a hot water outlet 5504. A
burner 5505 burns gas in a
combustion zone 5506 within the housing to heat the heat exchanger and thereby
the embedded duct
5503, and the fluid conveyed within the duct. A flue 5507 is provided at the
top of the housing for exhaust
gases.
1 5 The burner vessel housing 5501 is contained within a larger boiler
housing (not shown), which houses the
vessel 5501 along with other boiler components (such as electrical boiler
components, a computer control
system comprising switches and valves for controlling operation of gas and
electric heating power in a
standard manner).
The outlet 5504 leads to a nearby further duct section 5508. The further duct
section 5508 is located
within the boiler housing. Electric heating elements 5410 are arranged to heat
fluid conveyed within the
further duct section 5508. In this example, the electric heating elements 5510
are located within the
further duct section 5408. In this example, the further duct section 5508
comprises a duct section that is
doubled back on itself twice in order to provide a compact arrangement to
enhance efficiency of heat
transfer to the fluid in a small space. In this example, heating elements 551
0 are located in each of the
three branches of the further duct section 5508 ¨ in other examples, heating
elements are located only in
some branches.
In the examples of figures 54 and 55, heat may be supplied to the fluid being
conveyed through the
burner vessel either by electric heating or by burning gas or both. Hardware
or software (or a combination
thereof) computer control may be used to intelligently decide when to use
either or both fuel sources.
In yet further examples (not shown), heating elements may be associated both
with the duct section in the
burner vessel and the further duct section outside the vessel.
These examples help illustrate that the skilled reader may find multiple
example configurations within the
scope of this invention.
Various modifications may be made to this invention without departing from its
scope.
The hcat exchanger may bc configurcd to focus hcat not only from thc burning
fuel, but also from thc,
any or each electric heating element onto the fluid duct containing the fluid
to be heated.
The heat exchanger can be made of any suitable material, e.g. metal or
ceramic. In some examples, the
heat exchanger may be in the form of one or more plates (e.g. metal plates)
arranged partially or
completely around the water pipe. Electric heating elements can be arranged
between the plates. In
another example, the heat exchanger may comprise a block of suitable material
(e.g. a ceramic block)
arranged around the water pipe.
For example, although examples of the invention have been described in
relation to water boilers, the
same inventive concepts can be applied to other (partially or wholly) electric
fluid heaters, for example, air
heaters (also known as furnaces) are common in North America. Such systems
usually include a fan to
blow the heated air ¨ this is not shown in any drawings for clarity. Systems
that heat other fluids will be
apparent to those skilled in this field.
In some embodiments, a or the heating element can be powered by both the DC
power supply and an AC
power supply. In such embodiments, the DC power supply is arranged to at least
partially power the
heating element In some such embodiments, the DC power supply may power the
heating element
completely at some times and partially at other times (depending on factors
such as time of day, or
availability of electricity from a renewable source etc.).
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In some examples, fluid in multiple, independent fluid circuits is heated,
e.g. a first circuit for radiator
water and a second circuit for potable water as in a combi boiler. In such
examples, the second circuit
has a different conduit arrangement, i.e. different ducts / pipework to the
first circuit so that the fluids
within the two circuits do not meet (e.g. so that the potable water is not
contaminated by the radiator
water). The person skilled in this field will have knowledge of how to
construct suitable vessels to
accommodate independent fluid circuits. For example, a suitable vessel may
include a second fluid inlet
and a second fluid outlet with a second fluid pipe therebetween, wherein the
burning of fuel in the
combustion zone or heating of the electrical element or both is / are arranged
to heat fluid in the second
fluid pipe.
One or more or all of the heating elements may be located outside of the
burner vessel (but still inside a
larger boiler (or other fluid heater, e.g. air furnace) housing). Such
examples may be particular suitable for
retro-fitting electrical heating capability to existing gas boilers. For
example, electric heating elements
may be coated on, coated within, sprayed, contained in, wrapped around,
partially or totally embedded in,
or otherwise associated with, a duct section at or near: its exit from the
burner vessel: its entrance to the
burner vessel; or both. The heating element(s) may be powered by DC, AC or a
combination thereof. In
some examples, a battery, such as a large battery of the type previously
described, may be attached to
the burner vessel along with a control mechanism (e.g. control electronics
and/or software) to control the
amount of heating provided by the electric heating element(s) compared to the
combustible fuel source.
The control mechanism may also control the amount of heating provided by DC,
AC or a combination
thereof.
In most of the examples described above, the heating element extends along
substantially the whole of
the fluid duct. In other examples, one or more heating element(s) is provided
only in some parts of the
fluid duct; in other parts, there is no significant heating caused by the
heating element(s). As a result, a
more resource-efficient system that is easier to assemble may be provided.
In the described examples, the heating element(s) are powered by passing a
current therethrough. In
other examples, the heating elements may have a different configuration, e.g.
such that they can be
powered by induction (without direct contact).
In some examples, multiple distinct sections of heating element are provided
within the fluid duct, and
each section may be controlled together or separately, e.g. to provide
different levels of heating at
different section locations. This is efficient in situations where combustion
heating levels are different in
different locations of the burner vessel ¨ the electric heating element(s) may
provide less heating in
sections where the burner is able to provide more heating and the electric
heating element(s) may
provide more heating in sections where the burner is able to provide less
heating. In another use case, it
may be desirable to provide different heating levels at different sections of
the fluid path, such as upon
initial heating start-up when a fluid is first heated from cold, such as when
a tap is first turned on, more
intense heating may be provided at the beginning of the fluid path than at the
end because the initial input
fluid is particularly cold.
In some of these examples, the elements may be completely embedded in the
fluid duct such that no part
of them emerges or protrudes from the duct (e.g. there is no external
electrical connection point).
In examples with multiple fluid circuits, e.g. combi boiler examples, the
first heating element (powered by
a DC power supply or an AC supply or a combination thereof) may be arranged to
heat fluid only in one of
the first and second circuits, and the combustion heater may be arranged to
heat fluid only in the other of
the first and second circuits, e.g. the tap water is heated only by the
electric source and the heating water
is heated by the combustible fuel source. In some examples, the controller is
arranged to control the
heater such that gas (or other combustible fuel) and electric hybrid heating
is used only for heating fluid
(e.g. radiator water) in the first fluid circuit and only electric heating is
used for heating potable water in
the second fluid circuit.
More than one heating element may be provided per vessel.
Any of the examples may include a DC power supply interface arranged to
receive the DC power supply,
wherein the DC power supply interface is configured to receive more than one
type of DC power supply,
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such as any combination of an Ni-MH battery cell pack, an Ni-Cd battery cell
pack and a lithium battery
cell pack or a mixed pack containing a mixture of any of these types of cells.
Any of the examples that include DC power supply cells may include a safety
shut-off mechanism
arranged to disconnect the cells from powering the electric heating element.
The safety shut-off
mechanism may comprise a master switch or automatic master switch; in some
examples the safety shut-
off mechanism comprises a contactor. Advantageously, a safe, simple DC
switching mechanism is
thereby provided.
Within the examples in which the circuit comprises a heating water circuit
such as a radiator circuit, the
boiler / heater also comprises a pump such as a water pump (not shown for
clarity in any of the drawings)
as is known in the field.
Within the examples in which the circuit comprises a potable water circuit,
the input is usually from a
mains water input, which is pressurised and so no pump is required. In some
examples, where the input
is from an unpressurised clean water source, then a pump may be provided.
In some examples, the DC power supply is located within a top portion of the
boiler housing. In such
examples, wet components (such as pipes or chambers containing fluid) are
located underneath the DC
power supply only. The DC power supply may occupy about the top 80% of the
space within the housing
in some examples.
In some embodiments, the heating element is arranged to provide heating
exclusively in the first fluid
circuit, and the second heating element is arranged to provide heating
exclusively in the second fluid
circuit, or vice versa. E.g. one heating element may be dedicated to providing
heating for a radiator circuit
whilst another heating element may be dedicated to providing heating for a
potable water circuit Suitable
bespoke, dedicated elements can thereby be used for different circuits with
different needs.
In any of the described examples, the, any or each heating element may be any
element that emits heat
when an electric current is passed therethrough, such as any resistive wire,
or arrangement of wires, that
emits heat when a current is passed therethrough, such as (but not limited
to):
Thin film (polyirnide over conductive metal);
Ceramic (ceramic sheath with embedded nickel chrome aluminium etc.) wire;
Bare wire (nickel, nichrome, Kanthal, stellites etc. Tungsten);
Encapsulated wire ¨ e.g. silicone jacketed nichrome;
Mineral insulated wire - copper sheath / nichrome, cupronickel / Inconel,
steel sheath / nickel,
Inconel sheath / nickel allow wire and all sorts of mixtures of these.
Elements may be drawn to
size or manufactured at finish size etc. Insulation generally A1203 or MgO;
Plain wires, spiralled (helical) wires, busbar wires with wound elements
between.
In any example where a single heating element is described, it may be replaced
by one or more different
heating elements as will be apparent to the skilled reader.
Embodiments of the invention have been described in relation to vessels having
a spiral fluid channel
defined between the heat exchanger body and the cover. Other configurations,
e.g. without such a
channel, are within the scope of the invention. For example, in other
embodiments, instead of (or in
addition to) such a fluid channel, a sealed fluid pipe (e.g. carrying potable
water in a potable water circuit)
may pass through the vessel and be heated by fuel burning in the combustion
zone.
In some embodiments, the fluid heater may have a DC connection or an AC
connection or both
(combined AC and DC) through which power is transferred to the electric
heating element(s). In any
embodiments with a battery pack, the battery pack may be inside the fluid
heater, or may be outside of
the fluid heater.
In some embodiments, the heat exchanger and the duct are not separate
components. The heat
exchanger and duct are formed by a common element. For examples, the duct may
comprise a pipe of a
suitable construction such that its wall(s) transfer heat from its surrounding
(e.g. from the combustion
zone) to the fluid, inside the pipe, that is to be heated. The pipe may have a
heating element(s) wrapped
around, or embedded (partially or completely) in its wall(s) or located
therein (e.g. in direct contact with
the flowing fluid.
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In other embodiments, the heat exchanger and the duct are separate components.
In many embodiments, the one or more electric heating elements are able to
provide sufficient heat in
isolation to supply all of the heating requirement (without burning fuel),
including potable water. In that
regard, for the purpose of this specification, the heating elements may be
high-power heating elements,
e.g., powered by a large battery (e.g. the DC power supply having a capacity
of at least 0.5 kWh, or at
least 1kWh, or at least 5kWh or at least 20kWh), or via similarly powerful AC
power supply, e.g. via a
national grid. In such examples, the peak power output of the DC power supply
is between 10kW and
20kW in some examples, and upto 200kW in some examples.
The combustible fuel is able to provide sufficient heat in isolation to supply
all of the heating requirement.
The combustible fuel and electric heating elements heat fluid at the same
location within the single
chamber at least in some areas (i.e. they completely or partially overlap with
regards to heat supply along
the extent of the fluid duct). The combustible fuel and electric heating
elements can also be used in
combination, if desired, to provide the heating requirement.
As previously described, in some examples, combustible fuel heating occurs via
the heat exchanger, and
one or more electric element heats water directly in the duct. In other
embodiments, the one or more
electric elements may instead / additionally provide heating via the duct
walls (e.g. if the elements are not
completely located within the fluid (e.g. if they are located outside the duct
nearby, e.g., on its surface)) or
via the heat exchanger (e.g. if the elements are arranged to heat the heat
exchanger) or any other
suitable configuration as will be apparent from the teachings in this
specification.
In some examples (including most of the above-described examples), the
electric and combustible fuel
heat sources are arranged to heat the fluid in the duct at the same location
(or overlapping locations in
some examples) in the fluid duct. In other words, fluid at a single location
can be heated by either the
electric heating element or the combustible fuel heat source or both
simultaneously. In some such
examples, the electric heating element and the gas burner are arranged to heat
along substantially all /
most of the length of the fluid duct that passes through the vessel. An effect
of this feature is to allow (in
some examples) the entire heating demand of a typical domestic water heater to
be supplied by an
electric source if needed (and to still have the option to use a gas source to
heat the same fluid in the
same location too). Another effect is to efficiently provide a more powerful
instant response (e.g., when
potable water is first requested from cold, and a quick/instant response is
desirable). Furthermore, as a
result of being configured to heat fluid at the same location via combustible
fuel or electric or both
simultaneously, another effect of some embodiments is that the electric
heating elements can be used on
their own initially, without any water flow, to pre-heat water in the duct.
Then, heating via combustible fuel
can be activated in the usual way along with fluid flow. As a result, an
initial period of cold water when first
turning on a tap can be reduced / avoided altogether (in an efficient way that
avoids wasting water and /
or burnt fuel).
In many of the described embodiments, the combustible fuel and electric
heating elements are arranged
to heat the fluid in the fluid duct with a single sealed fluid heater vessel
chamber. An advantageous effect
is the lack of need for a main burner chamber and a supplementary heating
chamber (such as a buffer
tank, which may be heated electrically). This is especially true for air
furnaces.
In some examples, the cooling system might be a passive cooling system
(instead of or in addition to the
previously-described cooling systems) arranged to transfer heat away from
components to be cooled
(such as the boiler electronics or DC power supply or battery charger or any
combination thereof). The
passive cooling system may not comprise a flowing fluid. The passive cooling
system may comprise a
thermal heatsink (e.g. an aluminium block, such as a 20mm x 40mm x 80mm
aluminium block, with
natural convection fins for heat dissipation into the environment. The passive
cooling system may
comprise a large thermal mass, such as the heater housing.
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