U.S. patent application number 12/315239 was filed with the patent office on 2010-06-03 for drainpipe heat exchanger with heat storage.
Invention is credited to Winston MacKelvie.
Application Number | 20100132403 12/315239 |
Document ID | / |
Family ID | 42221561 |
Filed Date | 2010-06-03 |
United States Patent
Application |
20100132403 |
Kind Code |
A1 |
MacKelvie; Winston |
June 3, 2010 |
Drainpipe heat exchanger with heat storage
Abstract
The present invention is a drainpipe heat exchanger to heat cold
water using drainwater heat. A slit in a stiff exterior plastic
sleeve with band clamps combine with internal hydraulic pressure to
create a very high thermal contact force. Vertical and horizontal
embodiments with and without protected heat storage are disclosed
including a half jacket design for installation around operating
drainpipes. A horizontal embodiment discloses a two-piece
plastic-copper design. Double-wall construction and venting for
visible leak detection satisfies plumbing code requirements. Use on
vehicular or other combustion engine exhaust pipes is also
contemplated.
Inventors: |
MacKelvie; Winston;
(Knowlton, CA) |
Correspondence
Address: |
Winston MacKelvie
20 Kimball Road
Knowlton, Quebec
J0E 1V0
CA
|
Family ID: |
42221561 |
Appl. No.: |
12/315239 |
Filed: |
December 1, 2008 |
Current U.S.
Class: |
62/515 ;
62/285 |
Current CPC
Class: |
Y02B 30/56 20130101;
Y02E 60/14 20130101; F24D 17/0005 20130101; F28D 21/0012 20130101;
Y02E 60/142 20130101; E03C 1/00 20130101; Y02B 30/18 20130101; F28D
20/0034 20130101; F28D 7/0008 20130101; Y02B 30/566 20130101; E03C
2001/005 20130101; F24D 2200/16 20130101 |
Class at
Publication: |
62/515 ;
62/285 |
International
Class: |
F25B 39/02 20060101
F25B039/02; F25D 21/14 20060101 F25D021/14 |
Claims
1. A heat exchanger for heat transfer with a fluid within a
conduit, said heat exchanger comprising: a chamber having a portion
thereof for contacting at least a portion of said conduit, said
chamber having spaced inner and outer walls defining a cavity
therebetween; at least one fluid inlet to said cavity for a second
fluid; at least one fluid outlet from said cavity for said second
fluid; attachment means exterior of said outer wall for securing
said chamber to said conduit; the arrangement being that said inner
wall is conformingly tightened against said conduit by said
attachment means.
2. The heat exchanger of claim 1 including flow directing means to
direct said second fluid to flow over substantially the entire
inner surface of said inner wall.
3. The heat exchanger of claim 1 where, when said second fluid is
supplied under pressure said inner wall is further tightened
against said conduit.
4. The heat exchanger of claim 2 wherein said portion is formed
into a recess to receive at least a portion of said conduit.
5. The heat exchanger of claim 4 wherein said chamber has a
substantially cylindrical configuration.
6. The heat exchanger of claim 5 wherein said portion comprises a
passageway through said chamber.
7. The heat exchanger of claim 2 wherein said chamber has a
C-shaped configuration.
8. The heat exchanger of claim 2 wherein said chamber has a
U-shaped arcuate configuration.
9. The heat exchanger of claim 2 wherein said chamber has a
bar-shaped configuration.
10. The heat exchanger of claim 7 wherein said cylindrical chamber
has a gap to permit tightening of said inner wall onto said
conduit.
11. In a building having a plumbing system including a hot water
supply, a cold water supply and a drainage pipe, the improvement
comprising at least one heat exchanger mounted about said drainage
pipe, said heat exchanger comprising: a chamber having a portion
thereof for receiving said drainage pipe, said chamber having
spaced inner and outer walls defining a cavity, a fluid inlet
connected to said cavity, said fluid inlet being connected to said
cold water supply; a fluid outlet from said chamber being connected
to a water fitting; and attachment means for securing said inner
wall adjacent to said drainage pipe.
12. The improvement of claim 10 wherein said chamber has fluid
directing means within said chamber being arranged to direct fluid
flowing from said fluid inlet to cause maximum heat transfer
between fluid in said chamber and fluid flowing through said
drainage pipe.
13. The improvement of claim 11 wherein said drainage pipe has a
horizontal portion, said chamber being secured to said horizontal
portion.
14. The improvement of claim 11 wherein said drainage pipe has a
vertical portion, said chamber being secured to said vertical
portion.
15. The improvement of claim 12 wherein said chamber has a
substantially cylindrical configuration, said chamber having a gap
therein to permit tightening said inner wall onto said drainage
pipe.
16. The improvement of claim 14 wherein there are two separate said
chambers each encircling substantially half of said vertical
portion.
17. In a vehicle having an interior compartment requiring heat and
an exhaust pipe through which flows hot exhaust gases, the
improvement comprising a heat exchanger mounted about said exhaust
pipe, said heat exchanger comprising: at least one chamber having a
portion thereof for receiving said exhaust pipe, said chamber
having spaced inner and outer walls defining a cavity, a fluid
inlet to said cavity, said fluid inlet being connected to a fluid
supply to be heated; a fluid outlet from said cavity being
connected to said interior compartment, and attachment means for
securing said inner wall adjacent to said exhaust pipe.
18. The improvement of claim 14 wherein said chamber has fluid
directing means within said chamber arranged to maximize heat
transfer between said fluid and said exhaust pipe;
19. The improvement of claim 14 wherein said chamber has a
substantially cylindrical configuration, said chamber having a gap
therein to permit tightening said inner wall onto said exhaust
pipe.
Description
[0001] This application claims benefit from Provisional Application
No. 60/998,670 dated Oct. 12, 2007.
FIELD OF THE INVENTION
[0002] The present invention is a drainpipe heat exchanger for
drainwater heat recovery (DHR) from a building's regular drainpipe
plumbing system. It includes a cold-drainwater-protected heat
storage reservoir. Also disclosed is a one- and two-piece heat
exchanger design that can be installed over existing drainpipes
while they remain in full operation. The heat storage reservoir
uses the thermosiphon principle and makes DHR available from both
continuous plumbing fixture/appliance drain flows, such as a shower
or running sink, and batch drain flows, such as from a dishwasher
or filled sink. Thermosiphon is a well-known method of passive heat
exchange based on natural convection. (See, for example,
thermosiphon at Wikipedia.com.)
BACKGROUND OF THE INVENTION
[0003] The traditional drainwater heat recovery (DHR) heat
exchanger comprises a large diameter central copper tube (as used
for drainpipes) wrapped with a small diameter cold water tube also
of copper. It is based on the long-known Falling Film principle of
heat transfer. In Falling Film heat exchangers, a liquid is ideally
made to overflow into the top of a straight, large bore, vertical
tube. The flow is meant to be circumferential, flowing down in an
even, falling film clinging to the entire inner vertical tube wall,
from top to bottom. (More information on falling film heat
exchangers can be found at: The Chemical Educator, Vol. 6, No. 1,
published on Web Dec. 15, 2000, 10.1007/s00897000445a, .COPYRGT.
2001 Springer-Verlag New York, Inc., and, U.S. Pat. No. 4,619,311
to Vasile which discloses a equal flow Falling Film DHR heat
exchanger.) The falling film DHR is, in many ways, ideal because it
is not blocked by large solids and other matter contained in a
building's drainwater. In operation, cold, ground water feeding a
water heater first passes through the outer coil of tubing on its
way to the heater while drainwater is `falling` down the inside
tube and transferring its heat to the cold water in the outer coil.
Thus showering and sink rinsing are the principal
appliances/fixtures where such heat exchangers can work because
only then is cold water flowing into the hot water heater exactly
while the drain is flowing with the now-dirty used hot water.
[0004] However the traditional DHR design is not very cost
effective because their payback time or return on investment (ROI)
is too long in comparison to other energy saving strategies.
[0005] This can be attributed to:
[0006] 1. Too little use of the expensive heat transfer material,
which is usually copper, is actually used for heat transfer. For
example thermal contact is limited to a narrow spiral contact strip
between the outer coil's (conduit) contact surface with the inner
tube's wall. Because heat transfer is a direct function of surface
area, this limitation reduces performance which negatively affects
ROI. This limitation is so greatly increased when it is laid
horizontally which is often necessary (i.e., buildings without
basements), that horizontal use is not recommended. Also, in
regards the outer coil, the greatest part of the of its total
surface area is not used for heat transfer. Only that small inner
portion of the circumference actually contacts the drainpipe wall,
the remaining, larger, outer portion of the circumference does not
do heat transfer at all.
[0007] In the instant invention, instead of a coiled tube conduit,
sheet copper is used and is formed into a hollow jacket that serves
as the cold water `tube` or conduit. This dramatically lowers cost,
while increasing thermal contact area to nearly 100%. For example,
a 5 foot long, 4 inch diameter drainpipe, requires only 2/3 the
weight of copper for the cold water exchanger; plus sheet-form
copper is less expensive by weight than tube-form copper, and, a
much higher percentage of that copper is used for heat transfer.
Further, the instant invention allows for very compact, small
diameter DHR (i.e., for a 11/4 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 has offers
a shorter ROI allowing for wider use in all size buildings.
[0008] 2. Lack of heat storage. The traditional DHR only works when
both the drainwater and the cold water are flowing simultaneously,
such as in showering or running sinks. This referred to as
`continuous` hot water use. It cannot recover heat from `batch` hot
water use such as from appliances/fixtures including wash machines
and filled sinks and tubs, since there is nowhere for any
meaningful amount of recovered heat to be stored. As a result, only
about 40% of the total used hot drainwater (continuous use) is
available for DHR with traditional non-storage DHR. And what little
heat is stored in the outer coil is lost immediately to any cold
drainwater which may flow at any time.
[0009] The instant design uses a separate reservoir to receive and
store heat from 100% of a building's drainwater no matter if it is
from a continuous- or batch use source. This remote heat storage
reservoir is mounted above the DHR so as to thermosiphon with the
cold water jacket or conduit when hotter drainwater is flowing
creating a thermal differential with the reservoir water. No moving
parts or controls are required. Further, thermosiphoning provides
automatic protection from heat loss to colder drainwater because
thermosiphoning stops when the temperature differential is
reversed. This further reduces the ROI.
[0010] 3. The long length of the coil tube (up to 100 feet long)
and the fact that it flattens somewhat as it is wound creates
internal resistance to flow and an unwanted drop in water pressure
for the heater. This then requires either larger, more expensive
tubing and/or a manifold arrangement of two or more coils to have
multiple, parallel flow, tube coils which again adds cost and
negatively affects the ROI.
[0011] In the instant invention, the jacket offers a direct flow
path from inlet to outlet and the passage can be as small or as
large as needed. This eliminates pressure drop and reduces
manufacturing cost.
SUMMARY OF THE INVENTION
[0012] In a building, a first heat transfer fluid, referred to
herein as drainwater, flows through a drainpipe. In the instant
drainpipe heat exchanger invention, sheet copper is formed into a
chamber or conduit. In one embodiment his chamber or conduit is in
the form of a jacket with a longitudinal gap, to encircle a round,
vertical drainpipe in the shape of a letter "C" in outline. In a
second embodiment it is in the shape of a `bar` or beam or trough
that fits below the flattened, `D` shaped, bottom portion of a
horizontal drainpipe. In both, the spaced inner and outer walls are
sealed at the ends and there are inlet and outlet fittings for
connection to a second heat transfer fluid which may be under
pressure such as the cold water supply for a water heater. The
inner wall contacts the drainpipe and matches its shape so as to
maximize the area of thermal contact. In the jacket, a longitudinal
gap or slit is provided where the inner and outer walls U-bend back
on themselves to create the chamber. This gap allows contraction of
the heat exchanger's inner wall to clamp tightly onto a circular
drain tube. The exterior wall has a stiff outer sleeve around which
are several band clamps. The outer still sleeve provides clamping
force distribution and heat insulation. The gap allows for intimate
contact and easy sliding assembly onto the drainpipe. When
connected to the pressurized water supply, the pressure adds to the
thermal contact force much like a blood pressure measuring cuff, to
further increase the all important rate-of-heat-transfer.
[0013] In one application the jacket is slid over and clamped onto
the exterior of an existing drainpipe. In another, it is
pre-assembled with a drainpipe forming a complete DHR heat
exchanger which then replaces a section of existing drainpipe.
[0014] In a third embodiment, the instant invention is fabricated
in two long half-cylindrical jackets (clam-shell like) which are
assembled onto a operating drainpipe without disrupting drainwater
flow.
[0015] A the second flat embodiment, the instant invention is
clamped between the flattened drainpipe and a shaped shoe or filler
piece to spread the clamping force along the entire length. Again,
the clamping plus the internal water pressure provide high
performance thermal contact with the drainpipe.
[0016] In a fourth embodiment, for flattened, D-shaped drainpipes,
the cold water heat exchanger may be in two parts: an upper
hemi-cylindrical plastic sealing portion bonded to a lower flat
sheet metal heat transfer portion. This would further lower costs
to improve the ROI.
[0017] In use, a sink or shower may have the heat exchanger lying
horizontally beneath it such that cold water is pre-heated before
reaching the cold water faucet. In this way, less too-hot water is
needed to mix with the now-warm-cold-water to achieve the desired
final comfortable temperature. Less hot water use saves energy and
money and pollution, and, if electrically heated, lowers peak power
demand.
[0018] During fabrication, the sheet copper should be slightly
creased diagonally on the inner wall to serve as a vent for visible
leak detection (a drip or air-drop onto the floor). The sheet is
then formed into a hollow structure either a tubular `C` shape or a
flat bar shape. The outer wall of the jacket is pierced to receive
soldered-on pipe fittings and the ends are sealed with
appropriately shaped copper (tubing, rod or twisted wire), soldered
into place. Alternatively, the jacket ends may be squeezed-closed
and soldered shut.
[0019] The unique, high-force hydraulic clamping action maximizes
heat transfer by increasing thermal contact force. For example, if
the drainpipe is 3 inches in diameter and the jacket 48 inches long
and the cold water is at 50 pounds per square inch pressure, the
contact force will be approximately: 3.14
(.pi.).times.3.times.48.times.50=22,000 pounds, or 11 tons of
contact force!
[0020] Not only does such an enormous force provide fast heat
transfer over the entire length, but it forces intimate, conforming
contact between the form-able sheet metal inner wall and drainpipe
wall surfaces that may be imperfectly fitted. This would be
extremely difficult or impossible to achieve by any mechanical
clamping method.
[0021] 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 inlet and outlet
fittings to connect to the cold water supply. The outer plastic
sleeve 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 large diameter, round, horizontal drainpipe, for
example.
[0022] In a sixth embodiment a remote reservoir is part of the
pressurized cold water system and is located above the instant
vertical or horizontal drainpipe heat exchanger. The reservoir is
connected with inlet and outlet tubes to the cold water heat
exchanger jacket or conduit. The reservoir preferably has a high,
horizontal orientation to provide maximum thermosiphon effect. One
tube between the reservoir and heat exchanger terminates low in the
reservoir and the other tube terminates above the first. Natural
temperature gradients (layering or stratification) in the reservoir
means that lower layers are always colder and heavier that upper
layers. Thus whenever warm drainwater (first heat transfer fluid)
heats the cold water (second heat transfer fluid) in the cold water
heat exchanger, it will also be made lighter and will therefore
automatically be displaced upward into the reservoir by the heavier
colder reservoir water sinking downward. This circulation of
reservoir water will continue for as long as a temperature
difference exists. In that way the reservoir become heated and the
cold water heat exchanger is cooled for best heat transfer.
[0023] When cold water is required by the water heater (hot water
is being used) the cold water under pressure flows first into the
center of the cold water heat exchanger, then through the
connecting tubes at each end and into the reservoir, and then out
of the reservoir into the water heater. The outlet tube therefore
can have two way flow depending on whether thermosiphon or pressure
flow is occurring. By having these two flow paths any heat received
from the flowing hot drainwater by the cold water conduit will
either be picked up directly under forced flow (hot water being
used) or by thermosiphonic action (no hot water being used). If
cold water is flowing as, for example, in the case of replacing the
hot water being used in a shower, it will directly be heated by the
hot shower drainwater. If no cold water is flowing but hot
drainwater is, the heat will automatically transfer by
thermosiphonic action into the reservoir. Here, the heat is stored
until some future hot water use causes the now-pre-heated cold
water from the reservoir to flow into the water heater to reduce
energy use.
[0024] In a seventh embodiment the same remote reservoir concept is
applied to a horizontal drainpipe heat exchanger. here the
reservoir may be vertical or horizontal. In the event that the
water heater is properly positioned with appropriate upper and
lower water connections, (one somewhat above the other) this
embodiment may be plumbed directly to the heater using, for
example, T-fittings at the heater's inlet and outlet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 shows a partial section end view a middle portion of
one embodiment of the drainpipe heat exchanger having an upper
conduit for drainwater and a lower conduit for cold water with
forced thermal contact all along their flat surfaces;
[0026] FIGS. 2, 3, 4 show the same embodiment in a sequence of
forming steps to squeeze-close and solder-seal the two end portions
of the lower exchanger;
[0027] FIG. 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 upper conduit that connect to regular
round drainpipes, and where the right end 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 in or out;
[0028] FIG. 6 shows an adaptor for the drainwater heat exchanger
formed, for example, from a suitable plastic material;
[0029] FIG. 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 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 fluid distribution tube enclosed therein;
[0030] FIG. 8 shows a copper solder-type fitting having one end
formed to a rectangular shape for insertion into the end
socket;
[0031] FIG. 9 shows a copper plug to be soldered in unused socket
openings;
[0032] FIG. 10 shows a side view of the same embodiment as FIG. 7
showing the end location of the drainwater heat exchanger
fittings;
[0033] FIG. 11 shows a top view in section of a cylindrical,
jacket-style heat exchanger having a longitudinal gap to allow
clamping motion, which would be slid over a drainpipe/exhaust
pipe;
[0034] FIG. 12 shows a top section view of a two-piece design for
clamping about an in-use drainpipe/exhaust pipe;
[0035] FIG. 13 shows a side view of the embodiment in FIG. 11
showing the outer sleeve and band clamps and showing the fluid
fittings and the location of the end sealing members;
[0036] FIG. 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;
[0037] FIG. 15 show a side view of the sealing member;
[0038] FIG. 16 shows a possible use of the joint flange where it
has various notches to distribute the fluid flow evenly over the
jacket's inner wall so as to maximize heat transfer by maintaining
the best temperature differential;
[0039] FIG. 17 shows a thin, flat cold water (or other fluid)
conduit clamped against the flat lower surface of the drainwater
conduit;
[0040] FIG. 18 is a cross section of the same embodiment and
showing one internal stiffener in the cold water exchanger to
prevent bulging;
[0041] FIG. 19 is a cross section showing how the drainwater heat
exchanger may be a two piece design with the upper, non-heat
transfer portion in plastic and the lower heat transfer portion in
sheet copper, bonded together along the length, and, with tension
walls of sheet copper to transmit the internal pressure in the cold
water exchanger to the external clamping member;
[0042] FIG. 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 outlet arrangement at the exit
end;
[0043] FIG. 21 shows a perspective view of the outlet fitting of
the embodiment;
[0044] FIG. 22 is a top view looking into the vertical heat
exchanger where the cold water is made to flow past a distribution
gap formed adjacent an annular ring and the jacket's inner wall so
as to sweep the entire surface along its vertical length;
[0045] FIG. 23 is a cross section side view of the same embodiment
showing how the cold water inlet is located between the sealing end
cap and the annular ring with the single-sided arrows representing
the resulting sheet-like flow;
[0046] FIG. 24 is an end view of an embodiment of a upper conduit
having a lower surface with a gully-shape along flow path, to
resist upward bulging from the force of contact generated by the
internal pressure in the shaped cold water jacket below;
[0047] FIG. 25 shows the same embodiment but with an oval shaped
lower flow surface;
[0048] FIG. 26 shows another vertical embodiment with a remote heat
storage reservoir connected with tubes for thermosiphoning with the
cold water heat exchanger and central feed into the cold water heat
exchanger;
[0049] FIG. 27 shows a horizontal embodiment of a drainpipe heat
exchanger with a remote heat storage reservoir;
[0050] FIG. 28 shows the same embodiment in partial section;
[0051] FIG. 29 shows the embodiment of FIG. 12 but as would be used
on a horizontal drainpipe where only a lower half is used (no
exterior clamping shown);
[0052] FIG. 30 shows the same embodiment having a plastic outer
wall for fluid containment joined to a metal inner wall for fluid
containment and for heat transfer;
[0053] FIG. 31 shows another embodiment where the metallic cold
water and drainwater conduits are fabricated to fit snugly within
an outer plastic reinforcing tube;
[0054] FIG. 32 shows the same embodiment where plastic is used in
the conduits where no heat transfer takes place so as to lower
costs;
[0055] FIG. 33 shows an end seal for the embodiment shown in FIG.
31 with the cold water fitting attached to the outside;
[0056] FIG. 34 shows the same end seal but the inner surface with
flow distribution holes.
DETAILED DESCRIPTION OF THE INVENTION
[0057] Vertical drainpipe heat exchangers and horizontal drainpipe
heat exchangers are disclosed each with unique embodiments. Each
has two conduits in thermal contact. One conduit is a straight pipe
or tube that typically carries a waste fluid from which heat is to
be recovered, and the second conduit is for the second fluid to
which heat is to be transferred (although the heat transfer could
be reversed for cooling). Generally the conduits are metal and
preferably copper for fast heat transfer. The instant drainpipe
heat exchangers may comprise both conduits as a single assembly or
just the second conduit which can be fitted to and existing first
conduit.
[0058] The two conduits are co-operatively shaped and tightly
clamped together so as to provide maximum thermal contact area and
high thermal contact force again for rapid heat transfer. In the
horizontal embodiment the waste conduit is normally on top of the
second conduit (waste fluid has heat to be recovered), while in the
vertical embodiment the waste conduit is encircled by the second
conduit.
[0059] One novel feature of the instant invention is the use of the
internal water pressure in the cold water conduit to add to the
thermal contact force to provide even faster heat transfer. Faster
heat transfer makes DHR more cost effective.
[0060] In FIG. 1 horizontal heat exchanger 200 has an upper
drainwater conduit 60 and a lower cold water conduit 50 held
tightly together with clamping bands 12 (FIGS. 5 and 10) around a
suitable force distribution sleeve (not shown). Drainwater conduit
60 comprises wall 1 with drainwater A flowing along flattened
bottom surface 1' (of wall 1) to thereby form a hemicylinder that
transfers heat to fluid B which enters and exists cold water
conduit 50 via underside fittings 10, 11 or alternately, via end
fittings 80.
[0061] In FIG. 1-5, 7, 10, cold water conduit 50 is shown being in
the shape of a trough made from sheet copper and 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 to the ambient for leak
detection.
[0062] In one embodiment, wall 2 of conduit 50 has wings 3 which
contact the side of the drainwater conduit 60 to create additional
surface for heat transfer. In FIGS. 2, 3, 4 cold water conduit 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
conduit 50 shape.
[0063] In FIG. 7 is shown an alternate way of sealing the ends of
cold water conduit 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 in preparation for final soldering.
[0064] In FIG. 8, fluid fitting 80 has rectangular end 33 inserted
and soldered into socket 33' or 34' (at each end of cold water
conduit 50), 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 conduit 50 and
inline with the socket 33' and/or 34' is a 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
distribute fluid B (i.e., cold water) to cause a crossflow creating
turbulence and evening out flow velocity across the width of cold
water conduit 50.
[0065] In FIG. 5 horizontal heat exchanger 200 is shown having the
upper drainwater conduit 60 made from a flattened tube, and lower
cold water conduit 50 (for, say, cold water) formed of sheet
material bound together by exterior clamping bands 12. In some uses
the upper drainwater conduit 60 may also be formed from sheet to
reduce cost. In either case the ends of drainwater conduit 60 can
be adapted to connect with existing round drain pipes the right end
of the drainwater conduit being shown having a separate, bonded-on
adaptor 70, while the left end 70' is shown as having an integrally
formed round end 20'. It is important that the drainwater conduit
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 conduit material. The bonding region is
shown at overlap 20'.
[0066] 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 conduit 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.
[0067] FIG. 6 shows adaptor 70 having a "D" shaped first end 20'
for bonding to drainwater conduit 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 (shown in dotted outline) under
the flat portion 20' to provide even clamping pressure for
sealing.
[0068] In use, by connecting cold water conduit 50 to a pressurized
fluid supply, an enormous thermal transfer contact force is created
between the flat surfaces of conduits 50 and 60, restrained by
bands 12 (over a stiff sleeve, not shown), to provide exceptional
heat transfer 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 imperfect flat surfaces 1' and 5 into intimate
contact.
[0069] With the instant invention, horizontally flowing drainwater,
whose valuable heat energy is normally wasted, can be cooled by
heat transfer to the cold water supply of the water heater to
thereby shorten the time it takes to fully heat hot water which, in
turn, saves energy and money and provides more hot water due to
faster recovery. 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.
[0070] In all figures the drainwater flow or exhaust gas inlet flow
is indicated as A' and A'' and the fluid whose temperature is to be
changed is B and B'. Heat exchanger 200 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.
[0071] 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, 1/4 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 from a building's cold water
supply. Inner wall 1 is however free to expand every so slightly to
provide a tight, intimate thermal contact with drainpipe 1 using
that same internal pressure.
[0072] In FIG. 11, 12 lap joint 5' is a soldered and may include
longitudinal joint flange 110 which can act as a fluid flow
distribution ring and a stabilizer/spacer for aligning the sheet
metal during soldering. Inlets(s) 10 and outlet(s) 11 are
connections for fluid B (such as cold water) whose temperature is
to be changed. Representative fluid control element 114 may be
several in number and take various shapes such as mesh, rods,
screen, angles, etc., that 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 the inner thermal contact 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 over long years of
daily use.
[0073] FIG. 12 shows the hollow, tubular nature of the heat
exchanger 100 as fitted onto a vertical drainpipe 1. 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.
[0074] 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 tube 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.
[0075] FIG. 16 shows a method of using the longitudinal joint
flange 110 as a flow distributor 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 1. Flange 110 may also simply
be more simply double-tapered (not shown) from full 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.
[0076] FIG. 12 shows the cold water conduit in two halves with
inlets 10 and outlets 11 on each half. The outer sleeve 116 and
clamps 12 of FIG. 11 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 while it remains in
operation. 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.
[0077] FIG. 17 shows another embodiment of horizontal heat
exchanger 200 where the cold water conduit 2 comprises a sheet
copper duct or tube in the form of a flat, rectangular hollow
strip. It is sealed at each end and preferably has flow-formers to
ensure that the cold water flows as a flat sheet of water across
the entire width of the heat transfer surface so as to keep the
surface as cool as possible, thereby maximizing delta T for faster
heat transfer.
[0078] FIG. 18 shows a cross section of the same embodiment where
the drainwater conduit is shown to be a flattened, hemi-cylindrical
tube 1 forced into intimate, conforming thermal contact with cold
conduit 2 using shaped pressure distribution shoes 130, 131 and
clamp bands 12.
[0079] In the embodiments shown in FIGS. 18 and 19, and all
embodiments of the horizontal drainwater heat exchanger, the cold
water conduit may have internal baffles 2'' comprising one or more
flattened tubes soldered between the top and bottom surfaces that
will prevent excessive bulging of the conduit in reaction to the
water pressure inside. This will help maintain flat drainwater heat
exchange surfaces.
[0080] In FIG. 19 drainwater conduit 1 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 1b
thereto, the two creating a hybrid drainpipe of rounded rectangular
or hemicylindrical form. This embodiment is for the lowest cost
device. Interior longitudinal supports 1c act to transmit bulging
force from cold water conduit 2 to shoe 130 and bands 12 thereby
maintaining a flat profile for the trough. Supports 1c may be wavy
to create a desirable turbulent flow. Supports 1c also act as fins
to extend heat transfer surface area. Supports 1c may be eliminated
and baffles 2'' in the cold water exchanger may be used to prevent
pressure bulging of the flat surfaces.
[0081] FIG. 20 shows the same embodiment with different drainpipe
connection fittings. Inlet 200'' is a vertical right angle inlet
centered on plastic top 1a and outlet 200' is a horizontal right
angle 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, 1a, 1b (FIG. 19) and is bonded and sealed thereto. A slight
slope to outlet 200' carries away the final drainwater drips to
leave drainwater conduit 1 dry.
[0082] In FIG. 22 vertical heat exchanger 100 has an inner wall 5
(heat transfer surface) and ring-shaped flow distribution ring 110'
which provides an even annular gap 120' adjacent wall 5. End seals
34 (FIG. 23) and flow distribution ring 110' are spaced apart
vertically creating a circular chamber into which flows fluid B,
which then must leave the chamber in a full curvilinear sheet flow
B' (half arrows) against inner wall 5 so as to sweep heated (or
cooled) fluid towards the outlet, which is similarly configured.
This ensures that a maximum temperature differential, or delta T,
can be maintained to optimize heat transfer. This annular flow
control arrangement may be used to advantage in all the
aforementioned heat exchangers including the two-piece embodiment
of FIG. 12. In the case of horizontal heat exchangers 200 the
distribution ring would take the form of a rectangular bridge held
a small distance below the heat transfer surface by stand-off
elements.
[0083] FIGS. 24 and 25 show variations on the profile of the flow
surface 1' of the drainwater conduit 1 with the purpose of
stiffening the flow surface 1' to resist upward bulging from the
expansive potential of the pressurized cold conduit below. The cold
water conduit 2 is shown to be conforming in shape so as to
maintain maximum thermal contact.
[0084] FIG. 26 shows a vertical drainpipe heat exchanger 500 having
a remote heat storage reservoir 400 which is always pressurized
with the cold water supply B and lies in series with the cold water
flow into, say, a water heater. Outlet 11 connects to external
plumbing to provide, pre-heated water C to a water heater or other
fixture/appliance. Cold water B enters via fitting 10 into jacket
or conduit 2. Two central flow distribution rings 110' ensure that
the up and down vertical flow through jacket 2 is adjacent inner
heat transfer wall where it then passes under two additional upper
and lower flow distribution rings 110' into the collection area
(between end seal 34 and ring 110') and out through fittings 213
and 214. Now cold water B (preheated by drainpipe 1, or not) passes
through connecting tubes 401 and 402 into reservoir 400 via
fittings 410 and 411 respectively. Tube 402 terminates higher in
reservoir 400 than tube 401. Thus tube 402 terminates in the
warmer, lighter layers of water filling reservoir 400.
[0085] In operation four scenarios are possible: [0086] 1. Hot
water, is being used and used hot drainwater A' is flowing, such as
in showering. Here the cold water B will be pre-heated in jacket 2
and flow upwards through tubes 401 and 402 (arrows 403, 404) into
reservoir 400 and out outlet 11. [0087] 2. Hot water is being used
but no drainwater is flowing such as when filling a wash machine.
Here the cold water B simply passes through jacket 2 and through
tubes 401 and 402 into reservoir 400 and outlet 11 (arrows 403,
404). With fitting 11 on top, any previously recovered heated water
will be the first to flow out because it is lighter and rises.
[0088] 3. Hot drainwater A' is flowing but no hot water is being
used, such as when an appliance drains. Then, if the in water B in
jacket 2 is being heated by drainwater A' and is thereby made
lighter, thermosiphoning will automatically take place, whereby any
water in reservoir 400 which is colder than that in jacket 2, will
cause the heavier cold water to sink down tube 401 (arrow 403) into
jacket 2 via fitting 214, then travel up through jacket 2 picking
up heat and out outlet 213 to return to the upper region of
reservoir 400 via tube 402. This continues as long as there is a
temperature differential (weight difference) between the water in
the reservoir and the water in the jacket, that is as long as
heated drainwater continues to flow. The net result is that the
water in the reservoir is heated ready to flow into a water heater
or other appliance/fixture [0089] 4. Cold drainwater is flowing.
The water in the jacket 2 is the first to become cold and therefore
also becomes heavier. Thermosiphoning cannot occur with the
reservoir 400 since cold water cannot rise into it and therefore
whatever heat is present in the reservoir will not be lost to the
cold drainwater. This automatic cessation of thermosiphoning
provides protected heat storage for the recovered heat in the
reservoir.
[0090] Cold water reservoir 400 may be the reservoir may be a
rectangular shape or a square tube shape or a cylindrical shape and
mounted or hung some distance from the drainpipe heat exchanger and
as high as practical, such as being hung from a ceiling. This will
increase thermosiphon action (speed the flow) to improve
performance provided tubes 401, 402 are of sufficient diameter. In
such cases tubes 401 and 402 should be well insulated to maintain
the best temperature differential and to prevent heat loss to the
ambient.
[0091] In the event that it is desired to discard heat, as in, for
example, a cold water drinking fountain, the arrangements may be
reversed so that the coldest water remains in the reservoir ready
to move to the drinking outlet. Then, the reservoir would be below
the heat exchanger and the tubes 401 and 402 arranged such that
hotter water in the reservoir rises to be cooled by colder
drainwater from the fountain and returns cooler, thus keeping the
reservoir cool and the drinking water cold as desired.
[0092] FIG. 29 shows how drainpipe heat exchanger 600 is a half
jacket with a continuous inner and outer wall 2, 5 that may be used
on the bottom portion of a horizontal drainpipe 1 such as one of
copper or steel (cast iron) carrying drainwater A. Cold water B
passes through exchanger 600 on its way to the water heater. This
minimizes material and so improves the ROI. In FIGS. 29 and 30 none
of the required external clamps or reinforcing sleeves are shown
for added clarity.
[0093] FIG. 30 shows horizontal drainpipe heat exchanger 700 of
composite construction where inner wall 2 is metal joined to a
thick outer wall 222 made of plastic to further reduce cost and
improve ROI.
[0094] FIG. 31 shows a preferred embodiment where the upper and
lower conduits are formed each with outward radiuses (for example
2'') that match that of a plastic reinforcing and insulating sleeve
70. Sleeve 70 has a longitudinal gap 70' that allows external band
clamps (not shown) to tighten the sleeve and compress the two
conduits together under high force to improve heat transfer. The
inward radiuses of both conduits are also matched but are much
larger (for example 10'') to create a flatter, broader heat
transfer flow path in the upper drainwater conduit for better heat
transfer therebetween. The ends of the lower cold water conduit are
closed with form-fitting end pieces 71 soldered in to make it a
pressure tight conduit. The end pieces 71 may be made from tubing
appropriately formed to match the radiuses and having a cold water
fitting 10 towards the exterior. Its interior may have a row of
holes 10' to direct the cold water flow evenly across the heat
transfer surface. The conduits 1 and 2 can be made from sheet
material and solder joined. Filler piece 75 indicates how a join
may be made to leave the exterior wall butted for a smooth
circumference for seal-clamping with rubber couplers (not shown) to
the building's round drainpipe stubs.
[0095] In operation, the internal cold water pressure will urge the
two conduit's thermal transfer walls 1', 5 together under
considerable hydraulic force as previously explained. In an
unreinforced flat contact surface between the conduits, the
conduits would bulge balloon-like under the hydraulic pressure into
the interior of the upper conduit diverting flow from the surface.
It would be difficult and expensive to contain such bulging. The
solution shown in FIG. 31 is to use a slightly curved contact
surface and restrain bulging by using the opposite force generated
by tightly clamping exterior sleeve 70. Sleeve 70 will try to make
surface 1' more concave (smaller radius, downward push) and
therefore apply force onto the top surface of wall 1'. Hydraulic
force from within conduit 2 will do the opposite pushing wall 1'
up. The result is both forces increase the net thermal contact
force and bulging is restrained.
[0096] FIGS. 33 and 34 show each side of a boat-shaped or arcuate
end piece 71, made from tubing, with the cold water B inlet 10 and
the distribution outlet holes 10'. The arcuate shape has two radii
to match R1 and R2 of conduit 2. Such a design may also be used on
the opposite outlet end of conduit 2. Fresh cold water B exits end
piece 71 via holes 10' (or other shapes of paths) across the
interior wall 5 of the cold water conduit thereby providing more
even heat removal from the whole heat transfer surface. This, in
turn, lowers its temperature which improves the .DELTA.T and thus
the rate of heat transfer, raising performance.
[0097] FIG. 32 shows the same embodiment with non-heat transfer
surfaces replaced with plastic upper 223 for upper conduit 1 and
plastic bottom 222 on lower conduit 2, both to reduce cost. The
plastic portions may be bonded and/or mechanically interlocked with
the metallic portions. For example the thicker plastic may have a
longitudinal slit formed along the edges to receive the thinner
metal portion. An adhesive can be first applied in the slit.
* * * * *