Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1 320~75
IMPROVED HOT WATER SYSTEM
WITH ATMOSPHERIC GAS 8URNER
~ACKGROUND OF T~E INVÆNTION
Eield Oe the Invention
The present invention relates to an improved hot
water system which uses an atmospheric gas burner Eor
heating the water which it stores and supplies. More
particularly, the invention relates to an improved gas
burning hot water system which stores hot water and which
heats the hot water by removing a portion of the water
from a ~torage vessel, heating it and placing it back into
the storage vessel.
Description of the Prior Art
Prior art hot water systems which use
atmospheric gas burners to heat water typically include a
metal pressure vessel and a gas burner disposed beneath
the vessel. In these systems, the burner heats the water
by heating the bottom of the vessel. However, these
systems suEfer a number of disadvantages. First, scale
which forms on the inside surface of a metal pressure
vessel as a result of heating or rusting accumulates at
. :
-
.
., . .
t 32n~75
the bottom of the vessel and forms a thick layer of
sediment. This material acts as an insulator and prevents
effective heating of the water.
Second, the inside surface of a metallic
pressure vessel ruqts or corrodeq. To prevent such
corrosion from occurring, the manufacturers of these metal
vessels provlde a protection system in the inside of the
vessel, including an anode rod. A by-product of this
protection system i9 hydrogen gas. This ga~ presents a
significant danger to the user of the hot water system,
since its ignition may cause a destructive explosion.
Eliminating this problem increases the complexity and c03t
of these~ prior metal vessels.
Third, the temperaturle of the water at the top
of these prior metal tanks may ~iffer Çrom that at the
bottom by as much as 40 to 50~. This diEferential occurs
due to the Eollowing: The metal tanks typically receive
water at the bottom where a the~mostat takes temperature
readings. The thermostat initi~ltes heating every time the
water temperature decreases below a predetermined level.
This usually occurs every time fresh, cold water enters
the vessel at the bottom of the vessel. However, the
water at the top of the vessel usually has a higher
temperature. Moreover, although metal tank systems heat
the water by heating the bottom of the tank, a portion of
this heat transfers to a ~lue pipe which extends
vertically through the center of the vessel and heats the
water at both the top and bottom. Therefore, the repeated
h~ating raises the water temperature at the top of the
vessel. These conditions combine to raise the
temperature of the water at the top of the vessel to as
- . . - ,
1 320375
high a level as 170F. Water at this temperature scalds
the user of the water. Moreover, heating water in this
manner wastes energy.
Recently, manufacturers of hot water systems
have begun to market an increasing number of systems with
thermoplastic, thin-walled pressure ve~sels. These
pressure vessels have composite outer shells of
continuously wound glass filaments impregnated with a
thermose~tting resin material and inner liners made out of
thermoplastic material. Their sidewalls are relatively
thin and light making them easy to handle and construct.
Although these vessels have relatively thin sidewalls, the
material~3 used to construct them are poor conductor~ of
heat. Thus, a burner disposed c)utslde of the vessel
cannot heat the water inside. In addition, placing a
flame on the outside surface of these thin-walled pressure
vessels damages them. Therefor~, it is not possible to
use the standard gas heating sy~,tem with these new thin-
walled thermoplastic tanks.
The improved hot wa~er sy~tem of the present
invention avoids the disadvanta~es of the prior hot water
systems which use metal pressure vessels and allows the
use of thermoplastic pressure vessels with a gas heater
system. The system of the present invention moves water
from the bottom of the system pressure vessel or draws
water directly from the fresh water source, heats the
water at a heat exchanger disposed outside of the pressure
vesQel and returns the heated water back into the bottom
of the pressure vessel for storage. Moreover, the system
.: :
':
-
1 320815
maintains the temperature of the stored water at arelatively constant temperature throughout the pressure
vessel.
The improved hot water system of the present
invention includes a thin-walled pressure vessel and a
heat exchanger which receives water from the pressure
vessel or a fresh water source and brings it into heat
exchange relation with an atmospheric gas burner so that
the water may receive the heat provided by the burner.
The system also includes conduit means defining
passageways through which the water flows from the
pressure vessel to the heat exchanger and back to the
vessel and a pump for lnducing this Elow.
SUMMARX QF ~HE INVENTION
It is a generaI object of this invention to
provide an improved hot water slystem which uses an
atmospheric gas burner for heatlng the water which the
~ystem stores and supplies.
It i5 a more specific object of the present
invention to provide an improved gas-fired hot water
system which includes a thin thermoplastic pressure vessel
for storing the water heated by the system; a heat
exchanger coil and an atmospheric gas burner for heating a
portion of the water outside of the vessel; and a conduit,
check valve and pump arrangement for circulating the water
for heating.
It is another object of this invention to
provide an improved hot water system which heats and
stores water by receiving water from a fresh, cold water
.
' ' ';
:
1 32087~
-5-
source or by removing a portion of water contained by the
pressure vessel, heating it at a heat exchanger outside of
the vessel and placing it in the vessel for storage.
Other objects, advantages and features of the
present invention will become apparent upon reading the
eollowing detailed description and appended claims, and
upon reference to the accompanying drawings.
In the preferred embodiment of the present
invention, an improved hot water system includes a
pressure vessel di~posed in an insulated housing. The
vessel, generally referred to as a plastic tank, is a
cylindrical enclosure capable of containing various fluids
at high pressures and temperatureq. In the preferred
embodiment, the tank comprises a hollow shell having an
elongate cylindrical body and substantially
hemispherically shaped top and bottom portionq. But the
vessel may have any other sultable shape or configuration.
The hollow shell includes an inner liner made of
a suitable thermoplastlc materlal such as polybutylene.
The outer shell covers the innee llning and provides
strength, rigidity and structural integrity to the vessel.
It is a composite material comprising glass Eilaments
impregnated with a thermosetting resinous material.
However, this outer shell may be a metal structure, a
combination of the composite and metallic materials, or
any suitable material which provides strength, rigidity
and structural integrity to the vessel without
substantially increasing its size and weight.
Additionally, the inner liner may be made from any other
suitable non-metallic material.
`
. .
,: ^
1 32C)~75
--6--
The vessel includes a dip tube which lies in the
vessel and extends from the top of the vessel down to the
bottom. The bottom of this dip tube is closed except for
a number of small openings. In the illustrated
embodiment, a fitting disposed at the top of the vessel
secures the dip tube in place and connects it with a Eresh
water source. This fitting also connects the fresh water
source and the dip tube to a conduit which provides a
passageway to a heat exchanger.
The heat exchanger is a conduit formed into an
elongated coil, providing an increased area for heat
exchange. This coil or heat exchanger lies vertically in
an insulated housing proximate the pressure vessel. It is
made from metal or any other material having a hlgh
thermal conductivity; and it has a frustoconlcal shape
with a large bottom opening for receiving a vertically
mounted atmospheric gas burner and a smaller top opening.
This conflguration allows the coil to trap the heat
provided by the burner and acilltate heat transfer.
The atmospheric gas b~rner used with the system
of the present invention has an elongate housing, and it
lies vertically along the pressure vessel housing. It
includes a tube having a dome-shaped inlet segment for
receiving both fuel gas and air, an opposite, flaring end
segment, and a constricted middle portion. This
configuration produces a "venturi effect" i.e., suction at
the inlet of the tube. In addition to the suction, the
tube inlet has an enlarged size which allows the burner to
receive an increased amount of air for efficient burning
of the fuel gas.
':
:
., ~.
.
- : ~
1 320875
The burner also includes a barrel disposed in
communication with the outlet opening of the inlet tube.
This barrel has a large number of ports which vent the air
and fuel gas mixture which the burner receives. Upon
ignition of this mixture , a thin, bluish and nonluminoius
combustion layer forms around the burner. This combustion
layer burns hot and raises the temperature of the barrel
to a level at which it glows red hot and radiates infrared
heat. The barrel extends into the heat exchanger housing
and into the bottom portion of the central opening through
the middle of the coil. There, it provides heat for
heating the coil and the water which flows through it.
A conduit disposed between the heat exchanger
and the pressure vessel providesl a ~luid passageway
between the bottom o the heat e!xchanger and the vessel.
In breaks along this conduit, the system includes a pump
which induces flow of the water through the dip tube,
through the heat exchanger, and back into the vessel. It
also includes a check valve which prevents the water from
~lowing in this direction without sufEicient pressure
provided by either the pump or other means. This check
valve also prevents the water from 10wing in the opposite
direction, l.e., out of the pressure vessel through a port
at the bottom of the vessel, upwardly through the heat
exchanger and back into the pressure vessel through the
dip tube. A thermostat disposed at the ~ottom of the
pressure vessel takes temperature readings of the water at
this location and initiates the heating cycles.
In operation, water flows from a fresh water
source into the system through the fitting disposed at the
top of the vessel. Since the dip tube openings at the
,,
..
- ,,
,
- : ` ~
-- ' ~: .
1 320~75
bottom of the pressure vessel are small, the water flows
into the conduit connecting the heat exchanger with the
pressure vessel, rather than into the bottom of the vessel
through the dip tube. It then flows through the heat
exchanger and into the bottom of the vessel through the
port disposed at the bottom of the vessel. The line
pressure of the fresh water is sufficient to overcome the
resistance provided by the check valve. In response to
the flow of cold water, the thermostat activates the
1~ burner and the pump. As more cold water flows into the
system, the burner heats it as it passes through the heat
exchanger.
Even though the system heats the fresh water
before it flows into the pressure vessel, the temperature
level of the body of water in tlle pressure vessel
typically decreases below a desLred level. To raise the
temperature level, the thermostat activates the pump and
the burner so that the water at the bottom o~ the vessel
flows into the dip tube, through the heat exchanger, and
back into the vessel through the port at the bottom of the
vessel.
., .
8RIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of this
invention, one should now refer to the embodiment
illustrated in greater detail in the accompanying drawings
and described below by way of an example of the invention.
In the drawings:
I
1 320~75
Fig. 1 is a sectional view of the hot water
system of the present invention, showing the overall
structure and the conical heat exchanger coil.
Fig. 2 is a perspective view of the atmospheric
gas burner used in the hot water system of the present
invention.
Fig. 3 is a perspective view of the check valve
used in the hot water system of the pre~ent invention.
While the following text describes the invention
in connection with a preferred embodiment, one should
understand that the invention is not limited to this
embodiment. Furthermore, one should understand that the
drawings are not necessarily to scale.
DETAILED DESCRIPTION OF T~E DRAWINGS
AND ~E PR~ERREI) EM~ODI~ENT
.
Turning now to the drawings, Fig. 1 shows the
hot water system of the present invention generally at 11.
The system includes a plastic pressure vessel 13. This
vessel 13 is a cylindrical plastic tank capable of
containing various fluids at high pressures and
temperatures. It comprises a hollow shell having an
elongate cylindrical body and substantially
hemispherically shaped top and bottom portions. But the
vessel may have any other suitable shape or configuration.
The hollow shell includes an inner liner 15 made
of thermoplastic material such as polybutylene. The
vessel also includes an outer shell 17 which covers the
inner liner 15 and provides strength, rigidity and
' ' ' . ', ,'
, .': ' :
.. . . . .
' ~ ' ' : -: '' -
- .- , '. , ~
1 320~75
--10--
structural integrity to the vessel. This outer shell 17
is a composite material comprising glass filaments
impregnated with a thermosetting resinous material.
However, it may be a metal structure, a combination of the
S composite and metallic materials, or any suitable material
which provides strength, rigidity, and structural
integrity to the vessel without substantially increasing
its size and weight. For insulation and further
structural support, an insulated housing 19 fully enclQses
the pressure vessel.
The pressure vessel includes a number o inlets
and outlets as described in the following text. It has a
port 21 at the bottom which serveq as a drain for the
vessel 13. I~ also includes a port 23 through its top. A
lS fitting 25 disposed in this por~: 23 secures a dip tube 27
in place lnside the pressure vecisel.
This dip tube 27 exterlds from the fitting down
to the bottom portion Oe the pressure vessel and has a
constricted outlet. The dip tu~e 27 shown in ~ig. 1 has a
closed bottom with a number of glmall side openings 29
which Eorm the constricted outlet. Alternatively, an open
and pinched end may also provide a constricted outlet for
the tube. The dip tube 27 is made from a corrosion
resistant plastic or any other suitable material.
The fitting 25 connects the dip tube 27 with a
fresh water source (not shown) from which the pressure
vessel receives fresh, cold water. ït also connects a
conduit 31 to the dip tube 27 and the fresh water source.
Although the illustrated embodiment shows a three-way
fitting 25, other connecting devices and arrangements may
provide the desired connection. For example, the vessel
I 320~375
may have two ports at the top, one to provide
com~unication between the vessel 13 and the conduit 31 and
the other to provide communication between the vessel and
a fresh water conduit.
This conduit 31 is a fluid passageway between
the pressure vessel 13 and a heat exchanger 33. Like the
dip tube 27, the conduit 31 may be made from a corrosion
resistant plastic material or any other suitable material.
The heat exchanger 33 is a conduit formed into
an elongate coil, providing an increased area for heat
exchange. It lies vertically in an insulated heat
exchanger housing 35. The heat exchanger coil 33 is made
from any ~uitable metal, since metals are good conductors
of heat. However, any other suitable mat~rial having a
hLgh thermal conductivity may se!rve as an ade~uate
~ubstitute. In addition, the cc~il has a tubular and
frustoconical oonfiguration with the 1argest diameter at
the botto~. This configuration allows the coil to trap
the heat provided by the system's burner and facilitate
heat transfer to the water flowing through the coil.
Alternatively, any other suitable configuration, e.g., a
cylindrical conEiguration with a constant diameter or one
which defines a serpentine path with legs disposed
longitudinally of the exchanger, provide the same
function. The housing 35 has an opening 37 at the top
through which the conduit 31 extends to communicate with
the heat exchanger 33 and an opening 39 at the bottom
through which an atmospheric gas burner 41 extends to heat
the coil and the water which flows through it.
.
.
1 320875
The burner 41 lies vertically next to the
insu1ated housing 19 which encloses the pressure vessel
13. The burner includes an inlet tube 43 and a barrel 45.
(See Fig. 2) The inlet tube 43 has a domed end segment, an
opposite, flaring end segment and a con~tricted middle
portion for producing a "venturi effect", ~, suction at
the inlet of the tube. In addltion to the suction, the
tube'q domed inlet has an enlarged size which allows the
burner to receive an increased'amount of air for efficient
burning of the fuel gas which Elows into the inlet tube 43
through a conduit 47. This conduit 47 extends into the
inlet op~ening of the tube to supply the burner with euel
gas. Sultable connectlng means ~not shown) mount the
burner 41 to the hou91ng 19.
The barrel 45 extends thcough the opening 39 Oe
the heat exchanger housing 35 and lnto the bottom of the
coil's central opening 49. The heat rises through the
central opening 49 of the coll and heats the remaining
portion oE the coil whlch extends a ~ub~tantial dlstance
'~0 above the burne~ barrel 45. The fuel ga~ and alr mixture
which flows lnto the barrel 45 of the burner 41 vents
through a plurality oE holes ~not shown) formed around the
barrel. Upon ignition, small flames form at each one of
these ports and they combine to form a combustion layer
around the barrel. This combustion layer emits heat which
heats the bottom end of the heat exchanger coil 33 and
also heats the barrel 45, raising its temperature to a
point at which the barrel glows red and emits infrared
heat which further increas~es t~he heat productlon of the
30 burner ~1. Co-pending Canadian Application Serial
~-555,989- of ~.N. Jackson , entitled "Improved
. .
~: . .
,
.
1 320~75
l3
Atmospheric Gas Burner', and assigned to the assignee of the
present application, discloses the burner 41 in greater detail.
A conduit 51 forms a passageway between the bottom end
of the heater coil 33 and the bottom of the pressure vessel 13.
Along breaks in this conduit, the system includes a check valve 53
and a pump 55. As shown in Fig. 3, the check valve 53 includes a
houslng 57 which defines a chamber in communication with opposite
ends of the break in the condult 51. It lncludes a float (not
shown) whlch rlses and enters a seat at the inlet of the housing,
sealing the chamber and preventing water from flowing downward
when the system 11 does not receive iresh, cold water or when the
pump 55 does not operate. Thus, the check valve 53 prevents cold
water ln the coil from flowlng downward and lnduclng warm water ln
the tank from flo~lng out of the vesse] 13 into the coil 33 where
it could cool wlthout the burner 41 operatlng. In preventing such
flow from developing the check valve 53 greatly lmproves the
ef~iclency of the system.
The float also prevents water from flowlng upward at all
times.
:
. :
~, . .
1 320875
A thermostat 65 disposed at the bottom of the
pressure vessel takes temperature readings of the water at
the bottom of the vessel. It communicates with the water
through the port 63 and it act~tes the burner 41 and the
pump 55 when the temperature o the water decreased below
a predetermined level. `
In operation, water flows from a resh water
source into the system 13 through the fitting 25 disposed
through the top of the vesse:l 13. Since the dip tube
openings 29 at the bottom of the pressure vessel are
small, the water flows into the conduit 31 connecting the
heat exc:hanger 33 with the pressure vessel 13 rather than
into th~ bottom of the vessel. It then flo~s through the
coil 33 and into the bottom of the vessel through the port
63. The llne pressure of the ~resh water is sufficient to
move the float in the check valve away from its seat at
the inlet o~ the housing 57. In response to the flow of
cold water into the system, the thermostat activates the
burner 41 and the pump 55. As Inore cold water flows into
the system, the burner 41 heats it as it passes through
the heat exchanger 33. Thus, the system heats the water
before it even enters the pressure vessel.
Even though the system heats the fresh water
before it allows it to flow into the pressure vessel, the
temperature level of the body of water in the pressure
vessel typically decreases below a desired level. To
raise the temperature level, the thermostat 65 activates
the pump 55 and the burner 41 so that the water at the
bottom of the vessel 13 flows into the dip tube 27,
through the conduit 31, through the heat exchanger 33 and
back into the vessel through the conduit 51. The system
.
., , -
. : : :
. . - . ~ . ~ , ,
.
1 320875
-15-
continues to move the stored water in this manner until
the water rises to a predetermined temperature level.
Every time the temperature of the water decreases below
this level, the system initiates this process.
S Thus, the applicant has provided an improved hot
water system whlch uses an atmospheric gas burner to heat
water. The 3ystem includes a pressure vessel in
communication with a heat exchanqer disposed outside of
the vessel. Water flows from the vessel to the heat
exchanger where an atmospheric gas burner heats it. The
heated water then flow3 back into the pressure vessel
whlch store3 it until the user draws it out.
Whlle the applicant ha3 shown one embodiment oE
the lnventlon, one wlll understand, o~ course, that the
lnventlon is not llmlted to this embodiment ~;ince those
skilled in the art to whlch the invention pertains may
make modi~icatlons and other embodiments of the principles
of this invention, particularly upon considering the
Eoregoing teachings. The applicant thereEore by the
appended clalms, intends to cover any such modieications
and embodlment3 as incorporate those features which
constitute the essential features of this invention.
~.~
