U.S. patent application number 11/811750 was filed with the patent office on 2008-01-03 for heat exchanger and use thereof in showers.
Invention is credited to John R. Nobile.
Application Number | 20080000616 11/811750 |
Document ID | / |
Family ID | 38925601 |
Filed Date | 2008-01-03 |
United States Patent
Application |
20080000616 |
Kind Code |
A1 |
Nobile; John R. |
January 3, 2008 |
Heat exchanger and use thereof in showers
Abstract
An improved heat exchanger design is disclosed. The design of
the heat exchanger provides for a safe separation of the flow
streams even in the event of leakage. An improved heat recovery
device for use in the drain conduit of standard shower
installations, comprising the heat exchanger of the invention, is
also disclosed.
Inventors: |
Nobile; John R.; (Fairfield,
CT) |
Correspondence
Address: |
John R. Nobile
65 Forest Avenue
Fairfield
CT
06824
US
|
Family ID: |
38925601 |
Appl. No.: |
11/811750 |
Filed: |
June 12, 2007 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60815773 |
Jun 22, 2006 |
|
|
|
Current U.S.
Class: |
165/47 ;
165/140 |
Current CPC
Class: |
F28F 1/06 20130101; Y02B
30/566 20130101; F28F 1/08 20130101; F28D 7/14 20130101; E03C
2001/005 20130101; F28D 21/0012 20130101; F28F 2210/06 20130101;
F28F 1/003 20130101; E03C 1/00 20130101; Y02B 30/18 20130101; Y02B
30/56 20130101; F24D 17/0005 20130101 |
Class at
Publication: |
165/047 ;
165/140 |
International
Class: |
F24D 17/00 20060101
F24D017/00; F28D 7/14 20060101 F28D007/14 |
Claims
1. A heat recovery device adapted for use in the drain conduit of a
shower installation having a hot water supply line, a cold water
supply line, a means for mixing water from both said lines to
deliver water at a suitable temperature to a shower head, and a
drain conduit for disposing of waste water passing out of the
shower installation, the heat recovery device transferring heat
from the waste water to the cold water supply before it enters said
mixing means, said heat recovery device comprising: A. a section of
generally tubular first conduit formed of a material having a
relatively high degree of heat conductivity, said first conduit
having an inlet end connected to an upstream portion of said drain
conduit and an outlet end connected to a downstream portion of said
drain conduit so that waste water passing through said drain
conduit also passes through said first conduit, said inlet and
outlet ends of said first conduit being connected to said upstream
and downstream portions respectively of said drain conduit in such
a manner that said first conduit between said inlet and outlet ends
is disposed at a lower level than said inlet and outlet ends so
that said first conduit remains filled with water at all times and
functions as a water trap, and contains at least one helical
convolution formed in the wall of said first conduit. B. conduit
means connected into said cold water line of said shower equipment
and being thermally operatively associated with said first conduit
such that cold water passes through said conduit means while
passing through said cold water line to be exposed to heat from
said first conduit from waste water passing therethrough, said
conduit means comprising a second conduit formed of a material
having a relatively high degree of heat conductivity, said second
conduit being disposed in intimate heat exchange relationship with
said first conduit, said second conduit having an inlet end
connected to an upstream portion of said cold water line and an
outlet end connected to a downstream portion of said cold water
line so that cold water passing through said cold water line also
passed through said second conduit and receives heat transferred to
said first conduit from said waste water, said second conduit
having an inner wall that comprises a layer of thermally conductive
material that conforms generally to the said helically convoluted
outer surface of said first conduit, said second conduit having an
outer wall consisting of a substantially tubular member that fits
closely to the largest diameter parts of said convoluted inner wall
and is suitably joined to it, so that the second conduit is
comprised of the helical lumen formed between said outer and said
inner walls, said outer wall containing at least one opening at
each end of the helical lumen for inlet and exit flow respectively
of said cold water supply suitable for adapting to common plumbing
fittings, whereby heat from said waste water is conducted through
said first conduit means to pre-heat cold water passing through
said second conduit means before reaching said mixing means.
2. The heat recovery device of claim 1 wherein said first conduit
is substantially straight and generally horizontal, said inlet and
said outlet ends are disposed at substantially 90 degrees to said
first conduit means, and disposed substantially vertically.
3. The heat recovery device of claim 2 wherein two assemblies of
said first conduits and said conduit means are connected in series
using a 180 degree conduit section to join them, and are arranged
substantially parallel to each other in the generally horizontal
plane, and said inlet end of the upstream section and the exit ends
of the downstream section of the first conduit sections are
disposed in a substantially vertical plane, so that they are
parallel to each other and in close proximity to each other.
4. The heat recovery device of claim 1 wherein said first conduit
forms a loop in the generally horizontal plane, or at a small angle
to the horizontal plane, said inlet and outlet ends disposed in
relative close proximity to each other, said inlet and said outlet
ends disposed at substantially 90 degrees to said first conduit
means, said inlet and outlet ends disposed substantially
vertically.
5. The heat recovery device of claim 1, wherein a spacer material
is located between the outer surface of the first conduit and the
outer surface of the inner wall of the second conduit.
6. The heat recovery device of claim 5, wherein the spacer material
is selected from the group consisting of high temperature fibrous
material, metal mesh, metal wire, glass fibers, carbon fibers,
aramid fibers, and ceramic fibers.
7. A heat exchanger for transferring heat between a first liquid
and a second liquid, comprising: A. a section of generally tubular
first conduit for conducting a first liquid, having at least one
helical convolution formed in its wall; and B. a second conduit
being thermally operatively associated with said first conduit,
said second conduit being disposed in intimate heat exchange
relationship with said first conduit, said second conduit having a
convoluted inner wall that comprises a layer of thermally
conductive material that conforms generally to the outer surface of
said helically convoluted first conduit, said second conduit having
an outer wall consisting of a substantially tubular member that
fits closely to the largest diameter parts of said convoluted inner
wall and is suitably joined to it, so that the second conduit is
comprised of the helical lumen formed between said outer and said
inner walls, said outer wall containing at least one opening at
each end of the helical lumen for inlet and exit flow of the second
liquid, respectively.
8. The heat exchanger of claim 7, wherein a spacer material is
located between the outer surface of the first conduit and the
outer surface of the inner wall of the second conduit.
9. The heat exchanger of claim 8, wherein the spacer material is
selected from the group consisting of metal mesh, metal wire, glass
fibers, carbon fibers, aramid fibers, and ceramic fibers.
10. The heat exchanger of claim 7, wherein at least one of the
outer surface of the first conduit and the outer surface of the
inner wall of the second conduit, is grooved or textured.
11. The heat exchanger of claim 7, wherein a space is located
between the outer surface of the wall of the first conduit and the
outer surface of the inner wall of the second conduit, said space
being in gaseous or liquid communication with the surrounding
environment, said space providing a means for accidental leakage of
the first or second liquid to escape.
12. The heat exchanger of claim 7, wherein first and second
conduits are formed of a material having a relatively high degree
of heat conductivity.
13. The heat exchanger of claim 7, wherein the inner diameter of
the first conduit is between about 0.5 and about 8 inches, between
about 1 and about 6 inches, between about 1.5 and about 2 inches,
between about 2 and about 3 inches, between about 3 and about 4
inches, or larger than about 8 inches.
14. The heat exchanger of claim 7, wherein the inner diameter of
the second conduit is about 25 to about 50%, about 15 to about 25%,
or about 5 to about 15% of the diameter of the inner diameter of
the first conduit.
15. The heat exchanger of claim 7, wherein the pitch of the helical
convolutions is about 0.2 to about 12 inches, about 1 to about 8
inches, about 3 to about 6 inches, about 2 to about 3 inches, about
1.2 to about 3.5 inches, or about 1 to about 2 inches.
16. The heat exchanger of claim 7, wherein the first conduit has
two, three, four or more helical convolutions.
17. A heat recovery device for use in a personal shower
installation, said heat recovery device comprising the heat
exchanger of claim 7, wherein said first liquid corresponds to
waste water passing out of the shower installation, and said second
liquid corresponds to a cold water supply.
18. A heat recovery device adapted for use in the drain conduit of
a shower installation having a hot water supply line, a cold water
supply line, a means for mixing water from both said lines to
deliver water at a suitable temperature to a shower head, and a
drain conduit for disposing of waste water passing out of the
shower installation, the heat recovery device transferring heat
from the waste water to the cold water supply before the cold water
supply enters said mixing means, said heat recovery device
comprising the heat exchanger of claim 7, wherein the first liquid
corresponds to waste water passing out of the shower installation,
and the second liquid corresponds to the cold water supply.
19. The heat exchanger of claim 7 herein the helical convolutions
in the wall of the first conduit impart turbulence to the first
liquid.
20. The heat exchanger of claim 7 whereby a hydroforming process is
used to simultaneously form the first conduit and said inner wall
of the second conduit.
Description
RELATED APPLICATIONS
[0001] This application claims priority from U.S. Provisional
Patent Application Ser. No. 60/815,773, filed Jun. 22, 2006, which
is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
[0002] This invention relates generally to the field of heat
exchangers, and more particularly to a heat exchanger for use in a
personal shower environment which recaptures heat from waste water
passing through the shower drain and distributes that heat into the
cold water entering the shower to raise the temperature of the cold
water and thus reduce the amount of hot water required to maintain
a given shower temperature.
BACKGROUND OF THE INVENTION
[0003] This invention relates generally to the field of heat
exchangers, and more particularly to a heat exchanger for use in a
shower environment which recaptures heat from waste water passing
through the shower drain and distributes that heat into the cold
water entering the shower to raise the temperature of the cold
water and thus reduce the amount of hot water required to maintain
a given shower temperature.
[0004] It is well known that showering for the purpose of
maintaining cleanliness is almost universally practiced in
civilized society. There is hardly any form of habitation, whether
personal residences, commercial habitations, or miscellaneous
bathing facilities, that does not provide the necessary equipment
for showering. Showering has become, in modern society, so
commonplace that many individuals shower at least once per day.
Many prefer showering to bathing because it is ready for use more
quickly, cleans more effectively, and may require less hot water if
not excessive in duration.
[0005] Despite the fact that showers of reasonable length and
temperature may consume less hot water than bathing in a tub, the
fact remains that a substantial amount of hot water is lost down
the drain, since the shower water remains in the shower
installation for only a very brief period of time, in which only a
small portion of it's heat energy is utilized. This, of course, is
wasted energy, and represents an expense in fuel or electricity to
heat the water which could be substantially reduced if some of the
unused heat in the waste water could be recaptured and put to
use.
[0006] Devices for efficiently and economically exchanging heat
between two fluids have been well known for many years and are
widely used throughout industry. None of these devices, however,
would be practical or effective in the application of recovering
heat from the waste water passing through the drain conduit of a
shower installation because of the unique environment and
requirements of such a system, such as not interfering with the
free flow of drain water, not being conducive to clogging, being
easy to clear in the event of a clog using standard methods,
adapting to existing standard plumbing fittings, and fitting into
the typically available space. Additionally, this device must meet
the applicable plumbing standards & codes in order for it to be
legally and widely installed. Further, this device must have an
adequate heat recovery efficiency to justify its purchase &
installation cost to the consumer. U.S. Pat. No. 5,791,401
discloses a heat recovery device for personal showers, however the
designs disclosed therein are expensive to manufacture because of
the complex assembly process, and the inefficient use of materials,
and the device has a low operating efficiency.
[0007] Thus, there is a need for a more practical, less expensive,
more efficient, maintenance-free, and trouble-free device for
recapturing heat from shower waste water after it has entered the
shower drain and transferring it to the incoming cold water before
the cold water is mixed with the hot water and enters the shower
head.
BRIEF SUMMARY OF THE INVENTION
[0008] The present invention substantially if not entirely meets
all of the previously mentioned requirements for a heat recovery
device intended for use in the environment of personal shower
installations.
[0009] Thus, in its broader aspects, the present invention is a
heat recovery device adapted for use in the drain conduit of
standard shower installations having a hot water supply line, a
cold water supply line, a means for mixing water from both lines to
deliver water at a suitable temperature to the shower head, and a
drain conduit for disposing of waste water passing out of the
shower installation, the heat recovery device transferring heat
from the waste water to the cold water in the cold water supply
line. In this environment, the heat recovery device of the present
invention comprises a generally tubular first conduit formed of a
material having a high degree of thermal conductivity, this conduit
having an inlet that is connected to and in close proximity to the
shower drain so that waste water entering the drain will pass into
the conduit inlet end, and the exit end of the first conduit
connected to the waste water plumbing to receive the water exiting
the first conduit. A second conduit means is connected in series
with the cold water supply line and is thermally operatively
associated with the first conduit in such a way as to transfer the
thermal energy from the warm drain water passing through the first
conduit to the cold supply water passing through the second conduit
and thus raising the temperature of the cold supply water before it
reaches the mixing means.
[0010] In a more limited aspect, the area between the inlet and
outlet ends of the first conduit are disposed at a lower level than
the ends, so that conduit remains substantially filled with water
at all times and functions as a water trap. Preferably, the central
portion of the first conduit lies in a plane that is disposed at an
angle to the vertical plane that the inlet and outlet ends of the
first conduit lie in, and most preferably, the central area of the
first conduit lies in a substantially horizontal plane.
[0011] The heat recovery device comprises a second conduit formed
of a material having a relatively high degree of thermal
conductivity, and being disposed in an intimate heat exchange
relationship with the first conduit, and having an inlet end
connected to the upstream portion of the cold water supply line,
and a downstream portion connected to the mixing valve, so that
cold water passing through the second conduit receives thermal
energy from the warm waste water passing through the first
conduit.
[0012] In certain embodiments, the first conduit is formed with
helical convolutions in the outer surface, such that the external
surface of these convolutions, when combined with a surrounding
smooth tubular member, will form the second conduit means, thus
placing the two conduit means in intimate thermal contact with each
other. The convolutions in the wall of the first conduit also serve
to impart turbulence to the drain water passing therethrough, thus
increasing the convective heat transfer from the drain water to the
wall of the conduit. The convolutions in the wall of the first
conduit also serve to impart a spiraling flow to the drain water
passing through, thus increasing the velocity of the flow and
therefore increasing the rate of convective heat transfer from the
drain water to the wall of the conduit.
[0013] In one variation of this embodiment, the spiral convolutions
are comprised of a single helical groove.
[0014] In another variation of this embodiment, the spiral
convolutions are comprised of two or more helical grooves, which
are joined near the ends by a partial or complete circular groove
in said first conduit. These circular groove features allow the
multiple spiral flow paths of the second conduit to be in
communication with each other, and thus allow the cold water to
flow through all of them in parallel.
[0015] In another variation of this embodiment, the multiple spiral
convolutions are comprised of two or more helical grooves, but
rather than being joined by a circular feature near the ends of the
first conduit member, they are joined by circular features near the
ends of the outer tubular member. These features allow the multiple
spiral flow paths to be in communication with each other, and thus
allow the cold water to flow through them in parallel. Having this
feature on the outer tubular member, instead of the first (inner)
conduit member, has the benefit of removing the interruption to the
inner helical flow path that this feature creates in the first
conduit. Therefore, the inner helical flow will be more robust with
this configuration, and have improved convective efficiency.
[0016] In another variation of this embodiment, the spiral
convolutions are asymmetrical in cross section, such that the flow
in the first conduit will encounter steeper oblique obstructions
along the outer walls as it goes forward through the conduit, thus
imparting more rotational energy to the flow stream, and more
effectively increasing the velocity of the flow and convective
efficiency. The asymmetry of the helical feature provides a smooth
transition on the downstream side of the feature, thus encouraging
the flow to remain attached to the surface, and causing the next
steep oblique surface to be more effective in promoting the helical
flow pattern favoring convective efficiency.
[0017] I another variation of this embodiment, the outer wall of
the first conduit is made up of two layers of material. This
feature allows the second conduit to use the outer layer of the
first conduit as its functional inner surface, so that the first
and second conduit do not share a common wall. This is an important
and required safety feature (for example in U.S. plumbing
installations carrying drinking water), which is designed to
prevent a leak in any one conduit wall from flowing into the other
conduit. Preferably, a narrow gap is present between the two layers
of the first conduit wall, so that a leak from either conduit mean
will have a path to the outside and therefore be detectable. For
example, to ensure formation of said narrow gap during the
manufacturing process, a fibrous material that can withstand the
high temperatures and stresses of the manufacturing processes may
be placed between the two layers of the first conduit wall prior to
the forming process, so that a leak from either conduit mean will
have a path to the outside and therefore be detectable.
[0018] In one embodiment of this invention, the single, helically
convoluted first conduit which extends substantially in the
horizontal plane and has ends that bend upward at approximately 90
degrees to the vertical plane, combined with the relatively smooth
outer tube over the convoluted area forming the second conduit
means, is substantially straight.
[0019] In another embodiment, the convoluted, horizontally
positioned part of the first conduit means is curved approximately
180 or more degrees while remaining in the substantially horizontal
plane, thus locating the ends relatively close to each other, more
closely representing the configuration of a conventional drain
trap. An exemplary drawing of this embodiment is shown in FIG.
9.
[0020] In another embodiment, two separate sections of the first
conduit are joined with an approximately 180-degree conduit
section, thus disposing the two sections in a substantially
parallel position to each other. The two respective second conduits
are connected by a connector conduit that provides for a flow path
from one second conduit means to the other.
[0021] In yet another embodiment, three, four or more sections of
the first conduit are joined with suitably angled conduit sections,
elbows or fittings, and the corresponding second conduit sections
are brought in fluid communication by two, three or more connector
conduits.
[0022] Having briefly described the general nature of the present
invention, it is a principle object thereof to provide a heat
recovery device adapted for use in the drain conduit of a shower
installation in which heat in waste water passing through a shower
drain conduit is recaptured by transferring it to the cold supply
water before it enters the mixing valve and is combined with the
hot water supply and enters the shower head.
[0023] Another object of this invention is to provide a heat
recovery device as disclosed which is designed and constructed to
replace the standard drain trap present in all shower equipment
installations and to function in the same manner as a water
trap.
[0024] It is another primary object of the present invention to
provide a heat recovery device as disclosed which can be easily and
economically manufactured and installed in new or existing shower
equipment installations and is entirely compatible with industry
standard plumbing equipment utilized in such installations.
[0025] It is still another object of the present invention to
provide a heat recovery device which is situated in a shower
equipment installation such that it is in close enough proximity to
both the shower drain and the mixing valve so as to minimize the
heat lost in the existing conduits.
[0026] It is still another object of the present invention to
provide a heat recovery device that provides an intimate thermal
contact between the drain water of a shower installation and the
cold supply water of a shower installation, such that a substantial
proportion of the thermal energy in the waste water is recovered by
transferring the energy to the cold supply water.
[0027] It is still another object of the present invention to
provide a heat recovery device that provides a safe separation
between the drain water of a shower installation and the cold
supply water of a shower installation, such that a failure of
either conduit means will not allow contamination from the water in
either conduit to enter the other conduit. It is still another
object of this invention to provide a heat recovery device that
requires a minimum amount of material & labor to manufacture in
order to be cost effective relative to the value of the heat energy
that it can recover.
[0028] It is another object of this invention to provide a design
that uses the most highly automated & accurately repeatable
manufacturing processes that can be economically employed to
produce the product.
[0029] It is another objective of this invention to provide a
design that has the highest possible efficiency for its size and
for the amount of material used in its construction.
[0030] The present invention includes a heat recovery device
adapted for use in the drain conduit of a shower installation
having a hot water supply line, a cold water supply line, a means
for mixing water from both said lines to deliver water at a
suitable temperature to a shower head, and a drain conduit for
disposing of waste water passing out of the shower installation,
the heat recovery device transferring heat from the waste water to
the cold water supply before it enters said mixing means, said heat
recovery device comprising a section of generally tubular first
conduit formed of a material having a relatively high degree of
heat conductivity, said first conduit having an inlet end connected
to an upstream portion of said drain conduit and an outlet end
connected to a downstream portion of said drain conduit so that
waste water passing through said drain conduit also passes through
said first conduit, said inlet and outlet ends of said first
conduit being connected to said upstream and downstream portions
respectively of said drain conduit in such a manner that said first
conduit between said inlet and outlet ends is disposed at a lower
level than said inlet and outlet ends so that said first conduit
remains filled with water at all times and functions as a water
trap, and contains at least one helical convolution formed in the
wall of said first conduit, said heat recovery device further
comprising conduit means connected into said cold water line of
said shower equipment and being thermally operatively associated
with said first conduit such that cold water passes through said
conduit means while passing through said cold water line to be
exposed to heat from said first conduit from waste water passing
therethrough, said conduit means comprising a second conduit formed
of a material having a relatively high degree of heat conductivity,
said second conduit being disposed in intimate heat exchange
relationship with said first conduit, said second conduit having an
inlet end connected to an upstream portion of said cold water line
and an outlet end connected to a downstream portion of said cold
water line so that cold water passing through said cold water line
also passed through said second conduit and receives heat
transferred to said first conduit from said waste water, said
second conduit having an inner wall that comprises a layer of
thermally conductive material that conforms generally to the said
helically convoluted outer surface of said first conduit, said
second conduit having an outer wall consisting of a substantially
tubular member that fits closely to the largest diameter parts of
said convoluted inner wall and is suitably joined to it, so that
the second conduit is comprised of the helical lumen formed between
said outer and said inner walls, said outer wall containing at
least one opening at each end of the helical lumen for inlet and
exit flow respectively of said cold water supply suitable for
adapting to common plumbing fittings, whereby heat from said waste
water is conducted through said first conduit means to pre-heat
cold water passing through said second conduit means before
reaching said mixing means.
[0031] In variation of this embodiment, said first conduit means of
said heat recovery device is substantially straight and generally
horizontal, said inlet and said outlet ends are disposed at
substantially 90 degrees to said first conduit means, and disposed
substantially vertically.
[0032] In a further variation of this embodiment, two assemblies of
said first conduits and said conduit means are connected in series
using a 180 degree conduit section to join them, and are arranged
substantially parallel to each other in the generally horizontal
plane, and said inlet end of the upstream section and the exit ends
of the downstream section of the first conduit sections are
disposed in a substantially vertical plane, so that they are
parallel to each other and in close proximity to each other.
[0033] In yet a further variation of this embodiment, said first
conduit forms a loop in the generally horizontal plane, or at a
small angle to the horizontal plane, said inlet and outlet ends
disposed in relative close proximity to each other, said inlet and
said outlet ends disposed at substantially 90 degrees to said first
conduit means, said inlet and outlet ends disposed substantially
vertically.
[0034] In certain embodiments, a spacer material is located between
the outer surface of the first conduit and the outer surface of the
inner wall of the second conduit. In other embodiments, the outer
surface of the first conduit and/or the outer surface of the inner
wall of the second conduit is grooved or textured. The spacer
material may be, for example, high temperature fibrous material,
metal mesh, metal wire, glass fibers, carbon fibers, aramid fibers,
or ceramic fibers.
[0035] The present invention also includes heat exchanger for
transferring heat between a first liquid and a second liquid,
comprising a section of generally tubular first conduit for
conducting a first liquid, having at least one helical convolution
formed in its wall; and a second conduit being thermally
operatively associated with said first conduit, said second conduit
being disposed in intimate heat exchange relationship with said
first conduit, said second conduit having a convoluted inner wall
that comprises a layer of thermally conductive material that
conforms generally to the outer surface of said helically
convoluted first conduit, said second conduit having an outer wall
consisting of a substantially tubular member that fits closely to
the largest diameter parts of said convoluted inner wall and is
suitably joined to it, so that the second conduit is comprised of
the helical lumen formed between said outer and said inner walls,
said outer wall containing at least one opening at each end of the
helical lumen for inlet and exit flow of the second liquid,
respectively.
[0036] In some embodiments, the heat exchanger of the invention
further comprises a spacer material, which is located between the
outer surface of the first conduit and the outer surface of the
inner wall of the second conduit. In certain embodiments, the
spacer material may be metal mesh, metal wire, glass fibers, carbon
fibers, aramid fibers, or ceramic fibers. In other embodiments, the
outer surface of the first conduit and/or the outer surface of the
inner wall of the second conduit is grooved or textured. In these
and other embodiments, a space is located between the outer surface
of the wall of the first conduit and the outer surface of the inner
wall of the second conduit, said space being in gaseous or liquid
communication with the surrounding environment, and said space
providing a means for accidental leakage of the first or second
liquid to escape.
[0037] In preferred embodiments, the first and second conduits of
the heat exchanger are formed of a material having a relatively
high degree of heat conductivity.
[0038] In some embodiments of the invention, the inner diameter of
the first conduit may be between about 0.5 and about 8 inches,
between about 1 and about 6 inches, between about 1.5 and about 2
inches, between about 2 and about 3 inches, between about 3 and
about 4 inches, or larger than about 8 inches.
[0039] In some embodiments of the invention, the inner diameter of
the second conduit is about 25 to about 50%, about 15 to about 25%,
or about 5 to about 15% of the diameter of the inner diameter of
the first conduit.
[0040] In some embodiments of the invention, the pitch of the
helical convolutions is about 0.2 to about 12 inches, about 1 to
about 8 inches, about 3 to about 6 inches, about 2 to about 3
inches, about 1.2 to about 3.5 inches, or about 1 to about 2
inches.
[0041] In some embodiments of the invention, the first conduit has
two, three, four or more helical convolutions.
[0042] In certain embodiments of the invention, the heat exchanger
of the invention is adapted for use in a heat recovery device for
use in a personal shower installation, wherein waste water from the
shower installation passes through the first conduit, and cold
water supply passes through the second conduit.
[0043] In other embodiments, the invention includes a heat recovery
device adapted for use in the drain conduit of a shower
installation having a hot water supply line, a cold water supply
line, a means for mixing water from both said lines to deliver
water at a suitable temperature to a shower head, and a drain
conduit for disposing of waste water passing out of the shower
installation, the heat recovery device transferring heat from the
waste water to the cold water supply before the cold water supply
enters said mixing means, said heat recovery device comprising the
heat exchanger of the invention, wherein waste water from the
shower installation passes through the first conduit, and cold
water supply passes through the second conduit.
[0044] In some embodiments, a hydroforming process is used to
simultaneously form the first conduit and the additional layer of
material over said first conduit which forms the inner wall of the
second conduit.
DESCRIPTION OF THE DRAWINGS
[0045] FIG. 1 is a general diagrammatic perspective view of a
typical individual shower equipment installation incorporating one
embodiment of the heat recovery device of the present
invention.
[0046] FIG. 2 is an enlarged perspective view of the heat recovery
device utilized in the shower equipment shown in FIG. 1.
[0047] FIG. 3 is a sectional view of the heat recovery device in
FIG. 2, showing the internal structure of the device.
[0048] FIG. 4 is an enlarged detail sectional view of the end of
one conduit section the heat recovery device, shown without the 90
degree end fitting in place.
[0049] FIG. 5 is a side view of a single heat exchanger subassembly
of the heat recovery device of the invention, for the purpose of
showing the location of sections B-B and D-D.
[0050] FIG. 6 is enlarged sectional view B-B depicting interior
features.
[0051] FIG. 7 is enlarged sectional view D-D depicting interior
features.
[0052] FIG. 8 is a perspective view of an embodiment of a
simplified heat recovery device made from a single continuous
conduit section.
[0053] FIG. 9 is a perspective view of heat exchanger made from a
single tubular assembly, the horizontal section of which is formed
at an angle of slightly more than 180 degrees.
[0054] FIG. 10 is an enlarged detail sectional view similar to FIG.
4, but showing an embodiment incorporating asymmetric helical
features to improve mixing and heat transfer efficiency.
DETAILED DESCRIPTION OF THE INVENTION
[0055] An improved heat recovery device is disclosed which is
adapted for use in the drain conduit of standard shower
installations having a hot water supply line, a cold water supply
line, a means for mixing water from both lines to deliver water at
a suitable temperature to a shower head, and a drain conduit for
disposing of waste water passing through the shower installation,
the heat recovery device transferring heat from the waste water to
the cold water flowing through the cold water supply line, thus
reducing the amount of hot water required for a shower of a given
temperature & duration. The heat recovery device consists of a
three-layer structure that has a first inner conduit connected into
the drain conduit of the shower installation, and an integrally
formed second outer conduit connected into the cold water supply
line leading to the mixing means and then to the shower head, and
in intimate thermal contact with the first conduit. The integrally
formed second conduit comprises of a second layer of material to
provide a safe separation between the two flow streams, which
generally follows the surface of the first conduit and is in close
thermal contact with the first conduit. The outer wall of the
second conduit is formed by a third layer, which may be a
substantially straight tubular structure that is brazed or
otherwise joined to the outermost surface of the second layer. The
first conduit functions as a drain-trap, and is substantially
unobstructed to prevent clogging, and the second conduit guides the
cold water helically around the outer perimeter of the first
conduit to provide the maximum possible thermal energy transfer
between the conduits. The first conduit also contains said helical
features in the wall that maximize the convective heat transfer
from the drain water by increasing the flow velocity and turbulence
of the drain water.
[0056] In one embodiment, the heat recovery device of the invention
is used to preheat the incoming cold supply water, which reduces
the amount of hot water required for a given shower temperature and
thus reduce energy usage. It has been estimated that approximately
$360 per year could be saved by the average homeowner with electric
hot water with a family of four who all shower daily if the heat
recovery device of this invention were utilized. The savings for
gas or oil hot water would be about $120 per year. By multiplying
these amounts by the number of shower installations in the United
States alone, one can appreciate the significance of the economic
and environmental impact of the present invention.
[0057] The novel design disclosed herein provides substantial
advantages in manufacturability, material usage, operating and
efficiency, which leads to critical improvements in the
cost-effectiveness and thus marketability of this device.
[0058] Referring to FIG. 1, one environment in which an improved
heat exchanger device of the invention may be used is shown in a
general diagrammatic perspective view, indicated generally by
reference numeral 10. The shower equipment 10 includes a hot water
line 12 which is connected to a suitable hot water source,
typically at a temperature of about 140 degrees Fahrenheit,
indicated by the letter H. The downstream end of 12 is connected to
the shower valve 20. The shower equipment 10 also includes an
upstream cold water line 14 which is connected to a suitable cold
water source, indicated by the letter C, which is not regulated in
temperature but is typically 50 to 60 degrees Fahrenheit. The
downstream end of the cold water line 14 is connected to the cold
water input end of heat recovery device of the present invention,
which is generally indicated by numeral 18 and is fully described
herein below. Said cold water input of 18 is the downstream end of
the heat recover device with respect to waste water flow, indicated
by letter S. The cold water line also has a downstream portion 16,
the downstream end of which connects to the shower valve 20, and
the upstream end of which connects to the warmed water exit end of
the heat recovery device of this invention, which is the upstream
end of the heat recovery device 18 with respect to shower waste
water flow, indicated by the letter W. The valve 20 has an exit
line 22 that transports the mixture of hot and warmed supply water
to the shower head indicated by the numeral 24, which is typically
desired at a temperature of about 105 Fahrenheit. The purpose of
the heat recovery device 18 of the present invention is to deliver
the warmed cold water flow to the mixing valve 20 at the highest
possible temperature, thus reducing the requirement of hot water to
the least possible flow rate and saving the maximum amount of
energy. As the mixed shower water W is used it flows into the drain
28 and then into the heat recover device, possibly via a short
section of conduit 26, where it transfers some of its heat to the
incoming cold supply water C before exiting via drain conduit 30
and traveling into a sewer or septic system. The exiting drain
water S will exit the heat recovery device at a lower temperature
than when it entered the device, since much of its heat has been
transferred to the cold water flow stream. It should be understood
that in a conventional shower equipment installation that does not
have the heat recovery device in place, the adjacent ends of the
upstream 26 and downstream 30 drain conduit are connected via a
standard water trap, which is always filled with water in order to
prevent offensive odors or dangerous gasses from traveling up
through the shower drain.
[0059] Referring to FIG. 2, a perspective view of one embodiment of
the heat recovery device utilized in the shower equipment shown in
FIG. 1 is shown. This embodiment comprises two generally straight
and parallel sections indicated by numerals 39 and 40, which are
connected in series with respect to the waste water flow via two
elbow fittings 37 and 38, of approximately 90 degrees each. It is
appreciated that a single fitting of approximately 180 degrees can
be substituted for the two 90 degree fittings, or the 180 degree
turn can be integral to the straight sections. The open waste water
input end 33 is comprised of an approximately 90 degree fitting 36
that transfers the flow from vertical to horizontal, and directs
the flow into the first straight section of the heat exchanger. The
exit opening for the waste water 34 is comprised of an
approximately 90 degree fitting 35 that transfers the flow of waste
water from the downstream generally horizontal straight section 40
to a generally vertical upward flow. These 90 degree entrance and
exit features may also be created integrally to the straight
sections if desired. This geometry comprising a generally
horizontal section with generally vertical entrance and exit
sections for the waste water allows the heat recovery device to
always remain full of water, therefore acting as a water trap, and
also increasing the efficiency of the device.
[0060] The cold water enters the heat recovery device through a
fitting 32 at the end nearest the waste water exit 34, and travels
through the device in the opposite direction as the waste water. A
cross-over tube 41 is located at the opposite end of the straight
sections with respect to the input fitting 32 and the exit fitting
31. The cross-over tube allows the cold water flow to travel from
one straight section 40 to the other straight section 39. The
warmed cold water flow exits the heat recovery device through
fitting 31.
[0061] The path of the cold water through the heat recovery device
is readily understood from the sectional perspective FIG. 3. The
section is taken from a horizontal plane cut through the centerline
of the straight waste water conduits, and then the section
continues along the conduit centerlines until the vertical entrance
and exit areas 33 & 34. As can be seen from this figure, the
first conduit (i.e. the waste water conduit), indicated generally
by reference numeral 1, is comprised of a tubular section,
preferably made from a high thermal conductivity material, and
contains a helical feature 48 in the wall of the tube. As can be
seen in enlarged sectional FIG. 4, there is an additional layer of
material, preferably a highly thermally conductive material
indicated by numeral 47, which is integrally formed against the
outer surface of conduit 1 and forms a sleeve. Said helical feature
48, when combined with the additional layer 47, and enclosed by the
cylindrical outer jacket 42, forms a continuous helical second
conduit 44 through which the cold water can pass and be in intimate
thermal contact with the waste water. The cylindrical outer jacket
42 is formed from a highly thermally conductive material, and
bonded, preferably via a brazing process, to the outermost surface
49 of the helical features 48 of the additional layer 47. The
contact between the inner and outer tubular structures 47 and 42
further increases the energy transfer to the cold water flow by
allowing outer jacket 42 to be heated by the waste water flow.
Outer jacket 42 contains integrally formed features 43 on opposite
ends that allow the entrance and exit tubes for the cold water to
be attached. Said features 43 may be located on opposites sides of
outer jacket 42.
[0062] The first conduit, particularly represented by 40 in FIG. 4,
and the integrally formed sleeve layer 47 are not bonded to each
other but are in intimate thermal contact. A hydroforming process
is employed to form the structure comprising the first conduit and
the sleeve part simultaneously. The inner conduit 1 is formed from
a straight tube with the outer sleeve concentrically in place with
a close clearance fit. The assembly is placed in a female die
containing the desired outer geometry of the final assembly, and
when the first conduit is expanded from the interior using a
pressurized fluid against said die, the tube assembly will take the
outer shape corresponding to the die shape. This process allows
simultaneous forming of the first conduit 40 and sleeve 47, and
guarantees that the two parts will be in close thermal contact. In
one embodiment, a layer of fibrous material that can withstand the
high temperatures of the brazing process is used between the two
formed layers, which will create a very small air gap between the
fibers and allow leaking fluid from any of the conduits to escape
and thus be detected. In an alternative embodiment, sleeve part 47
is manufactured with a grooved or textured inner surface that would
ensure the presence of small gaps between first conduit 40 and
sleeve part 47, thus allowing water to escape from the assembly in
the event that one of the inner walls starts to leak. In addition
to, or in lieu of, this grooved or textured inner surface of sleeve
part 47, the first conduit 40 may be manufactured with a grooved or
textured outer surface to ensure the presence of said small gaps
between first conduit 40 and sleeve part 47. The flow direction of
cold water through fitting 34 into the second conduit is indicated
by arrow 45. The flow direction of waste water out of the first
conduit is indicated by arrow 46.
[0063] FIG. 5 is a side view of an individual heat exchanged tube
for the present device. This view depicts the location &
orientation of section B-B (FIG. 6) and D-D (FIG. 7).
[0064] FIG. 8 shows how the helical features 48 in the first
conduit create the inner wall of the second conduit 44 (the sleeve
layer 47 is not shown for clarity)
[0065] FIG. 9 shows an embodiment of the heat exchanger that
comprises a single conduit assembly which is formed with a
centrally located bend of slightly greater than 180 degrees, which
simplifies the device relative to the previous embodiments by
eliminating the 180 degree fittings 37 and 38 and crossover tube
41. This embodiment is more thermally efficient because the section
comprising said slightly greater than 180 degree bend is part of
the active heat exchange area.
[0066] FIG. 10 Is a sectional detail view of a first conduit
embodiment depicting helical features which are asymmetrical. The
upstream side of the helical feature 50 is much steeper than the
downstream side 51, which causes rotational energy to more
effectively be imparted to the waste water stream W, increasing
convective heat transfer from said waste water.
[0067] The devices of the invention will advantageously be
manufactured from materials of high heat conductivity. Preferably,
such materials are metals. Where the heat exchanger of the present
invention is to be used in a shower drain or other plumbing
fixture, it will preferably made from copper, a copper alloy, or
copper-plated aluminum. Notwithstanding the general preference for
metals, some parts of the devices of the invention may be made from
other suitable materials, even if they have a low heat
conductivity. For example, one or more fittings (elbows &
u-turns) or other parts may be made of plastic (e.g. PVC or ABS)
although performance will be slightly better with metal fittings
since these will create additional heat convection surfaces and
conduction areas. In any event, the conduits should be manufactured
from materials able to withstand the chemical and temperature
properties of the liquids they are designed to carry. It is also
contemplated that the inner surfaces of the conduits are coated
(for example galvanized) with material suitably chosen to withstand
the chemical and temperature properties of the liquids.
[0068] Since standard residential shower drains are between 1.5 and
2 inches in diameter, the diameter of the first conduit of the heat
exchanger of the invention should preferably be between 1.5 and 2
inches. For other heat exchange applications, such as industrial
process heat recovery, the diameter of the first conduit can be any
suitable diameter (for example, between about 0.5 and about 8
inches, between about 1 and about 6 inches, between about 1.5 and
about 2 inches, between about 2 and about 3 inches, between about 3
and about 4 inches, or larger than about 8 inches.).
[0069] Since the wall of the first conduit is convoluted, it has a
variable diameter, with a minor inner diameter at its narrowest
parts and a major inner diameter at its widest parts. In various
embodiments, the major inner diameter is about 25 to about 50%
larger, or about 15 to about 25% larger than the minor inner
diameter.
[0070] The pitch of the helical convolutions of the first conduit
may range from about 0.2 to about 12 inches, about 1 to about 8
inches, about 3 to about 6 inches, about 2 to about 3 inches, about
1.2 to about 3.5 inches, or about 1 to about 2 inches.
[0071] Several considerations are to be contemplated when choosing
the helical pitch of the wall of the first conduit of the heat
exchanger of the present invention. A lower pitch distance will
result in more. "wraps" of the second conduit around the first
conduit, resulting in a longer second conduit and thus a larger
area for heat transfer. However, if the pitch is too small, the
flow inside the first conduit will not rotate optimally, reducing
the convection rate in the first conduit. Furthermore, a longer
second conduit may will result in reduced pressure, which may not
be desirable. On the other hand, a larger pitch will result in
fewer wraps, and a shorter second conduit. This may be remedied at
least in part by introducing double, triple, or more helical
convolutions (i.e. creating two or more parallel flow paths in the
second conduit).
EXAMPLE
[0072] A heat exchanger of the general design depicted in FIG. 8
(without the sleeve layer 47 shown in FIGS. 6 and 7) was
constructed from copper. The first (inner) conduit was 92
centimeters long, formed from a single first copper tube having an
inner diameter of 1.5 inches and a wall thickness of 0.080 inches.
Symmetrical helical convolutions were generated by a hydroforming
process wherein the first copper tube was placed in a die
containing the desired geometry of the desired convolutions, and
expanded from the interior using a pressurized fluid against said
die. Thus, the first copper tube took the outer shape corresponding
to the die shape. The inner diameter of the thus convoluted first
conduit ranged from 3.8 to 5.1 centimeters, with a helical pitch of
1.25 inches. The convoluted first conduit was then inserted into a
single second copper tube (corresponding to feature 42 in FIG. 8)
having a wall thickness of 0.058 inches, wherein the inner diameter
was equal to or slightly larger than the maximum outer diameter of
the convoluted first conduit. This assembly was then braised such
that the outer surface of the outermost helical portions of the
first conduit were bonded to the second copper tube. This heat
exchanger was then integrated into a heat recovery device in a
personal shower device, with the general structure depicted in FIG.
1 (with the exception that the heat exchanger consisted of a single
straight section).
[0073] The measured temperature of the hot water supply was 125 F,
and the measured temperature of the cold water supply entering the
heat exchanger was 42 F. The mixing valve of the personal shower
device was adjusted such that the measured temperature of the water
exiting the showerhead was 105 F. The measured temperature of the
drain water, as it entered the drain, was 100 F. The drain (i.e.
waste) water flowed at approximately 2 gallons per minute, while
the cold water flow rate was 0.75 gallons per minute. The cold
water and drain water flowed through the heat exchanger in opposite
directions. The measured temperature of the cold water exiting the
heat exchanger was 72 F (as compared to 42 F when entering the heat
exchanger, see above). Thus, the calculated heat exchanger
effectiveness for heating cold water was 52%.
[0074] Based on this measured temperature increase in the cold
supply water from 42 F to 72 F, it was calculated that the
percentage of hot water used to achieve a 105 F temperature at the
shower head was reduced from 76% (without the heat recovery device)
to 62% (with the heat recovery device), resulting in an 18%
reduction in the volume of hot water consumed.
[0075] For the purpose of comparison to the above described working
example, it was calculated that in order to achieve a heat
exchanger effectiveness of approximately 50% with a conventional
straight-walled (i.e. non-convoluted) design, the heat exchanger
would have to be approximately 4 meters long (compare to 0.92 meter
length of the device tested in the present Example. Thus, the heat
exchanger device and heat recovery device of the present invention
represents a very significant improvement over previously known
heat exchangers suitable for this purpose, while reducing the
installed size of the device in the drain area of a tub or shower,
reducing the cost of the device, and greatly shortening the pay
back period (amortization) of the device.
[0076] While the invention has been described in conjunction with
the above working example, it will be understood that it is not
intended to limit the invention to such embodiment. On the
contrary, it is intended to cover all alternatives, modifications
and equivalents as may be included within the spirit and scope of
the invention as defined by the appended claims.
* * * * *