Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02611709 2007-11-30
SPECIFICATIONS
FIELD OF THE INVENTION
A heat exchanger for use on drain- or exhaust pipes for heat recovery and in
particular for
drainwater heat recovery in buildings and from individual plumbing fixtures
such as sinks and for
use over existing drainpipes that cannot have their flow interrupted by their
temporary removal/
replacement. Heating cold water to make hot water for cleaning and then
discarding the heat
along with the dirty hot water is expensive, wasteful and environmentally
damaging. It is
estimated that in North America some $15 billion dollars is spent annually on
fuel to heat water.
The fuel's exhaust and the discarded heat in the used hot water contribute
doubly to global
warming and a lower standard of living. Speeding up heating of vehicle
occupants using waste
exhaust heat is also contemplated.
BACKGROUND OF THE INVENTION
A shortcoming of traditional drainwater heat recovery (DHR) methods is cost
effectiveness.
This can be partly attributed to the poor use of the heat transfer surface
area of the expensive
copper tubing used. Even more so if laid horizontally which is often
necessary.
Traditionally, copper tubing is wrapped around a vertical copper drainpipe to
make the DHR
heat exchanger. It operates on a l long-known heat exchanger design called
Falling Film.
(In Falling Film heat exchangers, a liquid is made to flow, ideally, in an
even, tubular film or
sheet clinging to the entire inner vertical tube wall. More information on
falling film heat
exchangers can be found at: The Chemical Educator, Vol. 6, No. 1, published on
Web
12/15/2000, 10.1007/s00897000445a, 2001 Springer-Verlag New York, Inc., and,
US patent #
4,619,311 to Vasile discloses a equal volume Falling Film DHR heat exchanger.)
The traditional DHR is in many ways ideal for DHR because it allows the
passage of large
solids and other matter contained in a building's drainwater without blockage.
Cold water to be
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CA 02611709 2007-11-30
heated first passes through the outer coiled tubing at the same time as when
drainwater is
'falling' down the inside straight tube. Thus showering and sink rinsing are
the principal modes
for such DHR devices because only then is cold water flowing into the hot
water exactly while
the drain taking away the now-dirty hot water.
However the traditional coil-on-tube design results in a narrow spiral contact
patch totaling
less than a third of the available surface area of the expensive coiled copper
tubing. Thus the use
of copper tubing makes DHR cost-ineffective in many applications especially
where hot water
use is low. Further, the long length of the coil (up to 100 feet) and the fact
that it flattens
somewhat as it is wound, creates internal resistance to flow and an unwanted
drop in water
pressure which necessitates larger, more expensive tubing, and/or multiple.
parallel coils, both of
which add to cost.
In the instant invention, instead of tubing, sheet copper is used. This
dramatically lowers cost,
increases contact area, and eliminates pressure drop. For example, in a 5 foot
long, 4 inch
diameter drainpipe, only 2/3 the weight of copper is needed for the cold water
exchanger and, a
much higher percentage of that copper surface is used for heat transfer.
Further, the instant
invention allows for very compact, small diameter DHR (i.e., a 11/a inch
diameter sink drainpipe)
for individual fixtures and appliances which is not practical with wrapped
tube designs due to the
bend radius limitation of suitably sized outer tubing. Thus with the instant
invention DHR is
made significantly more cost effective and more widely usable.
SUMMARY OF THE INVENTION
In one embodiment, the instant heat exchanger invention sheet copper is formed
into a tubular,
hollow, pressurized jacket (with spaced inner and outer walls), and with a
longitudinal gap or
opening between the walls to allow for constriction by clamping onto a drain
tube by exterior
band clamps and by the effect of the internal pressure. Normal mains cold
water supply maintains
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an internal pressurize inside the jacket heat exchanger. This pressure would
balloon the inner
wall of the jacket but instead the force is applied to the surface of the
drainpipe about which it is
installed thereby creating an enormous contact force between the jacket and
the drainpipe for
best thermal conduction. An outer sleeve (or shaped shoes for the horizontal
embodiment)) and
clamps restrains the outer jacket wall.
In one application the jacket is slid over and clamped onto the exterior of a
conduit, such as a
drainpipe, from which heat is to be transferred. In another it is pre-
assembled with a drainpipe
which then replaces a section of existing drainpipe. In yet another, it is in
two halves which are
assembled onto a drainpipe that remains in operation. A second embodiment for
horizontal
installation uses a flattened, half round, straight drain tube with the cold
water heat exchanger
taking the form of a flat, hollow, pressurized shallow trough located under
the flat drain tube and
bound to it with outer shaped restraining shoes and clamping bands. Internal
water pressure again
forces thermal contact therebetween. The trough may also be in the form of a
flat, hollow
rectangular tube. The flattened drain tube may be a composite of an upper
plastic portion bonded
to a lower copper portion to lower costs.
In use, a sink or bathtub-type shower may have the instant heat exchanger
beneath it such that
cold water is pre-heated before reaching the cold water faucet. In this way
less hot water is
needed to mix with the now-warm cold water to achieve the desired temperature.
Less hot water
use saves energy and money and pollution, and, if electrically heated, lowers
peak power
demand.
The sheet copper should be creased diagonally where thermal contact will occur
to serve as a
vent for visible leak detection (a drip path onto the floor). The sheet is
then formed into an
"outline C shape", or, double walled hollow tube structure with a longitudinal
gap. The outer wall
of the jacket is punched to receive soldered-on pipe fittings for the cold
water supply and the
ends are sealed with "C" shaped rings of copper tubing, rod or twisted wire,
dip-soldered into
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place between the tops of the walls. In another embodiment the fittings are
attached to the jacket
ends and the copper squeezed-close about the fittings and soldered. A thick,
stiff plastic sleeve
fits over the unit and band clamps around the sleeve completes the assembly.
The cold water pressure hydraulically clamps the jacket to the drainpipe which
clamping
movement is allowed by the longitudinal gap. This high-force hydraulic
clamping maximizes
heat transfer which increases with contact pressure. For example, if the
drainpipe is 3 inches in
diameter and the jacket 24 inches long and the cold water is at 50 pounds per
square inch
pressure, the contact force will be approximately:
3.14 (n) x 3 x 24 x 50 = 11,304 pounds, or 5'h tons of contact force!
Not only dose such an enormous force provide excellent heat transfer but it
does so evenly
over its entire length. This would be extremely difficult or impossible to
achieve by any
mechanical clamping method
Where the instant invention is to be installed on an existing drainpipe
already permanently in
place, the jacket may be made in two halves (or hinged) with duplicate
fittings to connect to the
cold water supply. The plastic jacket would also be in two halves (or hinged).
In some cases only
a lower half-jacket may be appropriate to reduce cost when using it on a
horizontal drainpipe for
example.
Use of the instant invention is also contemplated on vehicle exhaust pipes.
So, for example, a
stainless steel model, with a metallic outer retaining sleeve, may be fitted
to an exhaust pipe of a
car to provide double-walled-safe, hot air to the car interior in cold
weather. Although the internal
pressure-clamp feature may be duplicated using compressed air and flow
restrictors, the
complexity along with the huge temperature differential available (some 500
degrees F) may
obviate using only the simpler external clamping arrangement and internal fins
to transmit the
clamping force onto the inner wall of the jacket, especially since there is no
scum or solids that
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would lead to blockage. The recovered heat can be used to heat the vehicle's
interior and/or its
motor and/or a heat storage medium.
In all embodiments, internal baffles, walls, dams (as in a weir) or fins can
be incorporated to
distribute fluid flow, optimize heat transfer and to distribute the external
clamping force.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows an partial section end view of the central heat transfer
portion of one embodiment
where the fluid to heated or cooled is shown entering the cold water heat
exchanger via a
bottom fitting;
Figures 2, 3, 4 shows the same embodiment in a sequence of forming steps to
seal of the two
ends of the lower conduit against the internal pressure of, for example, a
building's water
supply;
Figure 5 shows the same embodiment in side view showing the sealed ends of the
cold water heat
exchanger, its lower fittings, and, the adapted ends of the drainwater heat
exchanger that
connect to regular drainpipes and where the right end of the drainwater heat
exchanger is
shown to have an added adaptor while the left end is shown to have been formed
into a
short cylindrical shape in both cases the flow path is flush such that there
is no 'step-up'
to impede drainwater flow out of upper conduit;
Figure 6 shows an adaptor for the drainwater heat exchanger formed, for
example, from a
suitable plastic material;
Figure 7 shows an end view of another embodiment where the drainwater heat
exchanger's end's
are formed to rectangular sockets to receive rectangular solder-type plumbing
fittings and
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a plug, and where the excess material is closed off to be sealed by soldering
at the same
time that the fitting is inserted, and showing an internal distribution tube
enclosed therein;
Figure 8 shows a copper solder-type fitting having one end formed to a
rectangular shape for
insertion in the formed end socket of the drainwater heat exchanger;
Figure 9 shows a copper plug to be soldered in the unused socket openings;
Figure 10 shows a side view of the same embodiment as figure 7 showing the end
location of the
drainwater heat exchanger fittings. Figure 11 shows a top view in section of a
one-piece
heat exchanger into which a drainpipe/exhaust would be inserted through from
one end;
Figure 12 shows a top section view of a two-piece design for clamping about an
already installed
drainpipe/exhaust pipe;
Figure 13 shows a side view with the outer clamping sleeve and clamps in
section and showing
the fluid fittings and the location of the end sealing members;
Figure 14 shows a top view of the sealing ring member made from tube or rod
although a
stamped sheet design may be more economical in production;
Figure 15 show a side view of the sealing member;
Figure 16 shows a possible use of the joint flange where it has various
notches to direct the cold
water flow to be as even as possible over the inner wall so as to maximize
heat transfer by
maintaining the best temperature differential.
Figure 17 shows a thin, flat cold water tube clamped against the flat lower
surface of the
drainwater conduit;
Figure 18 is a cross section of the same embodiment;
Figure 19 is a cross section showing how the drainwater heat exchanger may be
a two piece
design with the upper portion in plastic and the lower in sheet copper bonded
together
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along the length, and, with tension walls of sheet copper to transmit the
internal pressure
in the cold water exchanger to the clamping structure;
Figure 20 is a side view of the same embodiment showing how the drainwater
flow may be made
to enter from the top at the inlet end and to collect in a cross tube
arrangement outlet
fitting at the exit end;
Figure 21 shows a perspective view of the outlet fitting;
Figure 22 is a top view looking into the vertical design for the top and
bottom where the cold
water is made to flow past a gap formed by an annular ring so as to sweep the
entire heat
circumference of the transfer surface area from bottom to top;
Figure 23 is a cross section side view of the same embodiment showing how the
cold water inlet
is located between the end cap and the annular flow dam- or weir ring;
Figure 24 is an end view of a horizontal drainwater heat exchanger's lower
surface with a gully
shape along the middle of the flow path to resist upward bulging;
Figure 25 shows the same embodiment shaped as an oval.
DETAILED DESCRIPTION OF THE INVENTION
Two basic embodiments are disclosed, vertical heat exchanger 100, and
horizontal heat
exchanger 200. One novel feature of the instant invention is the use of this
internal water
pressure to create very high thermal contact force with the drainwater heat
exchanger to provide
high performance heat recovery.
In Fig 1 vertical heat exchanger 100 has an upper drainwater heat exchanger 60
and a lower
cold water heat exchanger 50 held tightly together with bands 12 (Figs 5,10)
or a suitable sleeve
(not shown). Drainwater heat exchanger 60 comprises wall 1 with drainwater A
flowing along
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CA 02611709 2007-11-30
flattened bottom surface 1' of wall 1 to thereby form a hemicylinder that
transfers heat to fluid B
which enters and exists cold water heat exchanger 50 via fittings 10, 11 or
alternately via end
fittings 80.
Cold water heat exchanger 50 is shown being made of flat sheet copper formed
with
longitudinal hems 4 that are solder joined to create a generally "C shaped"
hemicylindrical
conduit with flat surface 5. Hem 4 also serves as a heat conductive fin and,
as a result of the bend
curvature 6, provides a longitudinal vent 6 to the ambient for leak detection.
In one embodiment, wall 2 of conduit 50 has wings 3 which contact the side of
the drainwater
heat exchanger 60 to create additional surface for heat transfer. In Figs 2,
3, 4 cold water heat
exchanger 50 is shown having a short end portion of hem 4 folded flat in
preparation for sealing
the ends. The wings 3 are pinched closed and excess metal is pulled into
additional seams 3'. In
Fig 4 is shown a dotted line 2 that represents the original cold water heat
exchanger 50 shape.
In Fig 7 is shown an alternate way of sealing the ends of cold water heat
exchanger 50 so as to
provide in-line connection sockets 33', 34'. The two sockets at each end (4 in
total) are formed
on each side of hem 4 using an appropriate mandrel about which the remaining
wall 3 and wing 2
are squeezed to bring them together as a seam to be soldered. Appropriate
surfaces can be
'tinned' with solder prior to the forming and soldering.
In Fig 8, fluid fitting 80 has rectangular end 33 inserted and soldered into
socket 33' or 34' (at
each end of cold water heat exchanger 50) or both, and has a round end 30 for
connecting to
standard plumbing. Fitting 80 may also be an end of a longer tube where
installation conditions
warrant. Alternatively one of the two rectangular shapes 33' and 34' may be
blocked with a
simple plug 34 as indicated in Fig 9. Interior to cold water heat exchanger 50
and inline with the
socket 33' and/or 34' is a plastic fluid distribution tube 35' which extends
full length and is
closed at the far end and has cross apertures at intervals. The purpose of
tube 35' is to direct fluid
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B to cause at least some second fluid to flow at least partially crosswise
creating turbulence and
evening out flow velocity across the width of cold water heat exchanger 50.
In Fig 5 horizontal heat exchanger 200 is shown having the upper drainwater
heat exchanger
60 made from a flattened tube, and lower cold water heat exchanger 50 (for,
say, cold water)
formed of sheet material bound together by bands 12. In some uses the upper
drainwater heat
exchanger 60 may also be formed from sheet to reduce cost. In either case the
ends of drainwater
heat exchanger 60 can be adapted to connect with existing round drain pipes
the right end of the
drainwater heat exchanger having a separate, bonded-on adaptor 70, while the
left end adaptor 70
is shown as having an integrally formed round end 20'. It is important that
the drainwater heat
exchanger provides a flush flow path especially at the exit end so that solids
in the drainwater
will not hook and collect at the region of transition from flat to round. This
can be achieved by
forming a recess in the "D' shaped end of the bonded on adaptor equal to the
thickness of the
drainwater heat exchanger material. The bonding region is shown at overlap
20'.
Fig 5 shows fluid B, such as cold water for a water heater, entering fitting
10 at the left to
counterflow horizontally under the drainwater water heat exchanger 60 and exit
via fitting 11 on
the right having absorbed (or given up) heat from warmer (or colder)
drainwater'. Drainwater A
flows horizontally with a first temperature A' at inlet on right side and a
different temperature A"
at outlet on left side. Fig 6 shows adaptor 70 having a "D" shaped first end
20' for bonding to
drainwater heat exchanger 60 and a round end 20 for connecting to existing
drainpipe. Adaptor
70 may also be made of molded rubber with a shaped shoe 22 under the flat
portion 20' to
provide even clamping pressure.
In use, by connecting cold water heat exchanger 50 to a pressurized fluid
supply, an enormous
thermal transfer contact force is created between the flat surfaces of heat
exchangers 50 and 60
and is restrained by bands 12 (or a sleeve, not shown) to provide exceptional
heat transfer
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therebetween. For example, with a 4 inch wide flat that is 50 inches long and
with a pressure of
40 pounds per square inch, the contact force is some 8,000 pounds. This force
custom forms
typically imperfectly flat surfaces 1' and 5 into intimate contact.
With the instant invention, horizontally flowing drainwater, whose valuable
heat energy is
normally wasted, can be cooled by this low profile heat exchanger 200 by heat
transfer to the
cold water supply of the water heater to thereby shorten the time it takes to
fully heat hot water
and which, in turn, saves energy and money and provides more hot water due to
faster recovery
after its use. It may also be used to cool a flow of warmer water feeding, for
example, an ice cube
maker, using colder drainwater from a ice-filled sink. In all figures the
drainpipe or exhaust pipe
is indicated as A and the fluid whose temperature is to be changed is B. Heat
exchanger 20 may
be used to heat or cool fluid B. Although gaps between surfaces are shown in
the figures (for
clarity) it is understood that there is intimate contact between heat transfer
and clamping
surfaces.
In Figs 11-13 heat exchanger 100 is a jacket(s) comprising an inner heat
transfer wall 5 and
outer retaining wall 2 spaced apart for fluid flow therebetween with minimal
resistance. This
space may be, say,'/a inch. The walls are contiguous and formed from a single
piece of thin sheet
metal (copper) using reversing bends 112 and lap joint 5'. This leaves a
longitudinal opening or
gap 111 between bends 112 to accommodate movement from external mechanical
clamping
forces and internal hydraulic clamping forces. The jacket may also be formed
by extrusion in
which case finning 115 (representative fins only, shown in Fig 11) and fluid
control elements 114
may be easily included on the inner wall 5 and/or outer wall 2. Outer clamping
sleeve 116 with
gap 113 closes tightly around and distributes clamping forces from band or
hose clamps 12 to
prevent expansion or bulging of outer wall 2 from the internal pressure of
fluid B such as that
CA 02611709 2007-11-30
from a building's cold water supply. Inner wall 1 is however free to bulge
against drainpipe 1 by
that same internal pressure.
Joint 5' is a soldered lap joint and may include longitudinal joint flange 110
which can act as a
fluid flow equalizer and a stabilizer/spacer for aligning the sheet metal
during soldering. Inlets(s)
and outlet(s) 11 are connections for fluid B whose temperature is to be
changed.
Representative fluid control element 114 may be many in number and take
various shapes such
as mesh, rods, screen, angles, etc., such as to direct, for example, flow of
fluid B over element
114 as indicated by dashed flow arrow 114', to help effect best heat transfer
from inner wall 5 by
the fluid 'sweeping' the surface of inner wall as fully as possible.
Element(s) 114 may also be
used to create turbulent flow which is known to improve heat transfer. Element
114 may also be
shaped and located to deflect fluid B inflow at inlet 10 to avoid erosion
corrosion of the small
area of the inner wall by the fluid impinging on it perpendicularly at full
velocity.
Fig 12 shows the hollow, tubular nature of the heat exchanger 100 as fitted
onto a vertical
drainpipe A. Sealing rings 34 are shown in dotted line and are soldered into
the annular space
between the inner and outer wall ends at top and bottom. Although a tubular
shape is shown,
other shapes such as oval are contemplated where, for example, fitting
clearance is a concern.
Figs 14 and 15 show the sealing member 34 which can be made from rolled rod,
tube or
twisted wire bundle to fit snugly into the annular space and have a gap 111'
to coordinate with
gap 111. They may be made by winding a long piece onto a mandrel of the
correct diameter into
the form of a coil spring and then sawing through the coil to free individual
rings which are then
made planar as in Fig 15. Dip soldering is a fast method of construction.
Fig 16 shows a method of using the longitudinal joint flange 110 as a flow
controller by
providing restriction to flow directly from fitting 10 such that fluid B is
forced through spaced
vias 120 to travel across inner wall 5 to reach outlet 11 thereby improving
heat removal from
drainpipe I. Flange 110 may also simply be more simply double-tapered (not
shown) from full
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. . ... . _. . .. .:.v -.n..~~v_...e._...b.,._.._ _.. ....... .. , . .. .
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width at the center tapering to nil at each end to even out flow along its
length, especially if the
fittings 10 and 11 are positioned centrally and opposite one another.
Fig 12 shows the cold water heat exchanger in two halves with inlets 10 and
outlets 11 on each
half. The outer sleeve 116 and clamps 12 are not shown. The outer sleeve 112
would of course be
in two pieces either separate or hinged for ease of assembly onto the
drainpipe in a building. The
sealing rings 34 (not shown in Fig 12) would of course be four in number each
being a half ring,
one at each of the four ends.
Fig 17 shows another embodiment of horizontal heat exchanger 200 where the
cold water heat
exchanger 2 comprises a sheet copper duct or tube in the form of a flat,
rectangular hollow strip
or bar. It is sealed at each end and may have flow-forming controllers to
ensure that the entering
cold water flows as a flat sheet of water to the outlet so as to recover heat
from the entire heat
transfer surface area. Fig 18 shows a cross section of the same embodiment
where the drainwater
heat exchanger is shown to be a flattened, hemi-cylindrical tube 1 forced into
intimate,
conforming thermal contact therewith with shoes 130, 131 and clamp bands 12.
Fig 18 shows a
cross-section of the heat exchanger 200.
In Fig 19 drainwater heat exchanger I is comprised of a trough-like lower
portion in sheet
copper through which heat transfer takes place and a U-shaped plastic upper
portion bonded lb
thereto, the two creating a hybrid drainpipe of rounded rectangular form. This
heat exchanger is
conceived as a low cost device for use where there are no large solids in the
drainwater, more
specifically for use under a shower or sink. Interior longitudinal supports lc
act to transmit
compressive load from cold water heat exchanger 2 to shoe 130 and bands 12
thereby
maintaining a flat profile for the trough. Supports lc may be wavy to create a
desirable turbulent
flow. Supports Ic also act as fins to extend heat transfer surface area.
Fig 20 shows the same embodiment with different drainpipe connection fittings.
Inlet 200" is a
vertical right angle inlet centered on plastic top la and outlet 200' is a
horizontal right angle
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CA 02611709 2007-11-30
fitting shown in more detail in Fig 21, having an end cap and a slot 201 which
matches the shape
of the end of heat exchanger 1, la, lb (Fig 19) and is bonded and sealed
thereto. A slight slope to
outlet 200' carries away the final drainwater drips to drain heat exchanger 1
dry.
In Fig 22 vertical heat exchanger 100 has an inner heat transfer surface 5 and
ring-shaped flow
controller 110' dam which leaves an annular gap 120' adjacent heat transfer
surface 5. End seals
34 (Fig 23) and flow controller 110 are spaced apart vertically creating a
circular chamber so that
fluid fitting 11 feeds fluid therebetween. Fluid B then must leave the chamber
as a full curvilinear
sheet flow B' against heat transfer surface 5 so as to sweep heated (or
cooled) fluid towards the
outlet which is similarly configured. This ensures that a maximum temperature
differential can be
maintained to optimize heat transfer. This annular flow control arrangement
may be used to
advantage in all the aforementioned heat exchangers. In the case of horizontal
heat exchangers
200 the controller would take the form of a rectangular bridge held raised a
small distance below
the heat transfer surface by stand-off formations at the controller ends.
Figs 24 and 25 show variations on the profile of the flow surface 1' of the
drainwater heat
exchanger 1 with the purpose of stiffening the flow surface 1' to resist
upward bulging from the
expansive potential of the pressurized cold water exchanger below. The cold
water exchanger 2 is
shown to be conforming in shape so as to maintain maximum thermal contact.
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