U.S. patent application number 13/490894 was filed with the patent office on 2012-12-20 for heat exchanger for drain heat recovery.
Invention is credited to David Cosby.
Application Number | 20120318483 13/490894 |
Document ID | / |
Family ID | 47352231 |
Filed Date | 2012-12-20 |
United States Patent
Application |
20120318483 |
Kind Code |
A1 |
Cosby; David |
December 20, 2012 |
Heat Exchanger for Drain Heat Recovery
Abstract
A heat exchanger includes an upright center tube for connection
to a drain line and an outer tube surrounding the upright center
tube so as to define an annular space for connection to a supply
line. Baffle portions are received within the annular space between
the upright center tube and the outer tube and so as to be arranged
to induce turbulence in the annular space while permitting the flow
to remain in a substantially axial direction of the tubes. Sleeves
may be used to connect the ends of the outer tube to the center
tube so as to define a single wall portion of the center tube
between the sleeves and double wall portions of the center tube
where the center tube is overlapped by the sleeves such that the
double wall portions are open axially outwardly and externally at
the end of the outer tube.
Inventors: |
Cosby; David; (Winnipeg,
CA) |
Family ID: |
47352231 |
Appl. No.: |
13/490894 |
Filed: |
June 7, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61577164 |
Dec 19, 2011 |
|
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|
61496633 |
Jun 14, 2011 |
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Current U.S.
Class: |
165/109.1 ;
165/154 |
Current CPC
Class: |
F28D 21/0012 20130101;
F28F 1/08 20130101; F28F 13/12 20130101; Y02B 30/56 20130101; E03C
2001/005 20130101; F28D 7/106 20130101; F28F 13/06 20130101; Y02B
30/566 20130101 |
Class at
Publication: |
165/109.1 ;
165/154 |
International
Class: |
F28D 7/10 20060101
F28D007/10; F28F 13/12 20060101 F28F013/12 |
Claims
1. A heat exchanger for use between a drain line having a first
fluid flow therethrough and a supply line having a second fluid
flow therethrough, the heat exchanger comprising: an upright center
tube extending longitudinally between opposing top and bottom ends;
the upright center tube being arranged for connection to the drain
line so as to receive the first fluid flow longitudinally through
the upright center tube; an outer tube surrounding the upright
center tube so as to define an annular space between upright center
tube and the outer tube which spans longitudinally along the
upright center tube between opposing top and bottom ends of the
outer tube; the outer tube being arranged for connection to the
supply line so as to be arranged to receive the second fluid flow
longitudinally through the annular space between the upright center
tube and the outer tube; and a plurality of baffle portions
received within the annular space between the upright center tube
and the outer tube and so as to be arranged to induce turbulence in
the second fluid flow while permitting the second fluid flow to
remain in a substantially axial direction of the tubes.
2. The heat exchanger according to claim 1 wherein the baffle
portions comprises wire members received in the annular space which
have a diameter which is equal to or less than half a radial
dimension of the annular space.
3. The heat exchanger according to claim 2 wherein the wire members
are wound helically about the center tube.
4. The heat exchanger according to claim 2 wherein the wire members
include a first wire member wound helically about the center tube
in a first direction and a second wire member wound helically about
the center tube in a second direction opposite to the first
direction such that the first and second wire members overlap and
intersect one another in a crosswise manner at a plurality of
locations axially spaced along the center tube.
5. The heat exchanger according to claim 1 wherein the baffle
portions comprise protrusions formed on at least one of the upright
center tube or the outer tube so as to project into the annular
space between the upright center tube and the outer tube and so as
to be arranged to induce turbulence in the second fluid flow.
6. The heat exchanger according to claim 5 wherein the protrusions
are arranged to span only partway across the annular space between
the upright center tube and the outer tube.
7. The heat exchanger according to claim 5 wherein the protrusions
are formed on an inner surface of the outer tube and extend
generally radially inwardly towards the center tube.
8. The heat exchanger according to claim 5 wherein the protrusions
are formed on an outer surface of the center tube and extend
generally radially outwardly towards the outer tube.
9. The heat exchanger according to claim 5 wherein the protrusions
comprise annular ribs which are longitudinally spaced apart.
10. The heat exchanger according to claim 5 wherein the protrusions
are formed on both an outer surface of the center tube and an inner
surface of the outer tube so as to project into said annular
space.
11. The heat exchanger according to claim 1 wherein at least one
outer end of the outer tube is joined to the center tube by an
auxiliary sleeve supported about the center tube so as to define a
double wall portion of the center tube at the auxiliary sleeve and
a single wall portion of the center tube at an intermediate
location between opposing ends of the outer tube which is not
overlapped by the auxiliary sleeve, the auxiliary sleeve being
joined to the outer tube at a location which is spaced axially
outward in relation to a connection between the between the
auxiliary sleeve and the center tube.
12. The heat exchanger according to claim 11 wherein both ends of
the outer tube are joined to the center tube by an auxiliary sleeve
such that the single wall portion is defined between the auxiliary
sleeves.
13. The heat exchanger according to claim 11 wherein an annular
space between the center tube and the auxiliary sleeve at the
double wall portion is open axially outwardly and externally of the
center tube at the outer end of the outer tube.
14. The heat exchanger according to claim 11 wherein the single
wall portion is longer in an axial direction than the double wall
portion.
15. The heat exchanger according to claim 11 wherein the auxiliary
sleeve portion is thinner in radial thickness than the single wall
portion of the center tube.
16. The heat exchanger according to claim 11 wherein the center
tube is thinner in radial thickness at the double wall portion than
at the single wall portion thereof.
17. The heat exchanger according to claim 11 wherein the auxiliary
sleeve protrudes axially outward beyond the respective outer end of
the outer tube.
18. The heat exchanger according to claim 11 wherein the center
tube protrudes axially outward beyond an outer end of the auxiliary
sleeve.
19. The heat exchanger according to claim 11 wherein the end of the
center tube is enlarged in inner diameter at an end portion
overlapped by an outer end of the auxiliary sleeve and the outer
end of the outer tube such that the end portion is arranged to
receive a portion of a drain line therein having an outer diameter
which is substantially equal to an outer diameter of the single
wall portion.
20. A heat exchanger for use between a drain line having a first
fluid flow therethrough and a supply line having a second fluid
flow therethrough, the heat exchanger comprising: an upright center
tube extending longitudinally between opposing top and bottom ends;
the upright center tube being arranged for connection to the drain
line so as to receive the first fluid flow longitudinally through
the upright center tube; an outer tube surrounding the upright
center tube so as to define an annular space between upright center
tube and the outer tube which spans longitudinally along the
upright center tube between opposing top and bottom ends of the
outer tube; the outer tube being arranged for connection to the
supply line so as to be arranged to receive the second fluid flow
longitudinally through the annular space between the upright center
tube and the outer tube; and at least one auxiliary sleeve
supported about the center tube and joining a respective outer end
of the outer tube to the center tube so as to define a double wall
portion of the center tube at the auxiliary sleeve and a single
wall portion of the center tube at an intermediate location between
opposing ends of the outer tube which is not overlapped by said at
least one auxiliary sleeve; said at least one auxiliary sleeve
being joined to the outer tube at a location which is spaced
axially outward in relation to a connection between the between the
auxiliary sleeve and the center tube; and the double wall portion
of said at least one auxiliary sleeve being open axially outwardly
and externally of the center tube at the respective outer end of
the outer tube.
Description
[0001] This application claims the benefit under 35 U.S.C. 119(e)
of U.S. provisional application Ser. No. 61/496,633, filed Jun. 14,
2011 and U.S. provisional application Ser. No. 61/577,164, filed
Dec. 19, 2011.
FIELD OF THE INVENTION
[0002] The present invention relates to a heat exchanger for
exchanging heat between a first fluid flow in a drain line and a
second fluid flow in a water supply line, and more particularly the
present invention relates to an upright center tube and a
surrounding outer tube arranged for connection with the drain line
and the water supply line to receive the first and second fluid
flows respectively.
BACKGROUND
[0003] Various devices for recovering heat in waste water are known
to reduce energy consumption in heating supplied water. Examples of
typical heat exchanger devices are disclosed in U.S. Pat. Nos.
4,352,391 by Jonsson and 4,619,311 by Vasile et al. In each
instance, a central drain tube receives waste water from a plumbing
fixture in a building. A jacket surrounds the center drain tube to
define a space therebetween which receives the flow of supply water
in a counter flow configuration such that heat from the waste water
in the drain is transferred to the supplied water in the jacket
while the flows remain separated from one another. The open annular
configuration of the jacket space receiving the supply water in
each instance typically causes the supply water to flow in a
laminar configuration in a direct path between inlet and outlet
ports of the jacket such that heat is only exchanged with a thin
film of the water in direct contact with the center tube which
reduces the efficiency of the heat transfer due to the boundary
layer formed about the center tube.
[0004] A common variation to a heat exchanger for recovering waste
water heat is disclosed in U.S. Pat. No. 7,322,404 by Van Decker et
al. and US Patent Application Publication 2009/0139688 by McLeod.
In each instance the supply water tube is arranged as a helical
tube about the outer circumference of the central drain tube. While
this overcomes the problem of short circuiting in the examples
noted above, the flow through the helical supply tube remains
substantially laminar such that the boundary layer in the fluid
flow forming a thin tube along the surfaces in contact with the
drain tube is the only volume of water effectively exchanging heat
such that the efficiency remains limited.
SUMMARY OF THE INVENTION
[0005] According to one aspect of the invention there is provided a
heat exchanger for use between a drain line having a first fluid
flow therethrough and a supply line having a second fluid flow
therethrough, the heat exchanger comprising:
[0006] an upright center tube extending longitudinally between
opposing top and bottom ends;
[0007] the upright center tube being arranged for connection to the
drain line so as to receive the first fluid flow longitudinally
through the upright center tube;
[0008] an outer tube surrounding the upright center tube so as to
define an annular space between upright center tube and the outer
tube which spans longitudinally along the upright center tube
between opposing top and bottom ends of the outer tube;
[0009] the outer tube being arranged for connection to the supply
line so as to be arranged to receive the second fluid flow
longitudinally through the annular space between the upright center
tube and the outer tube; and
[0010] a plurality of baffle portions received within the annular
space between the upright center tube and the outer tube and so as
to be arranged to induce turbulence in the second fluid flow while
permitting the second fluid flow to remain in a substantially axial
direction of the tubes.
[0011] By providing baffle portions which span only partway across
the annular space between the upright center tube and the outer
tube, the flow in the annular space remains generally in the
longitudinal or axial direction, but the baffle portions induce
turbulence in the flow so as to disrupt the boundary layer and
encourage mixing of the flow so that a greater volume of the flow
comes into direct contact with the center drain tube for optimal
heat transfer efficiency.
[0012] According to a preferred embodiment the baffle portions may
comprise wire members received in the annular space which have a
diameter which is equal to or less than half a radial dimension of
the annular space.
[0013] Preferably the wire members include a first wire member
wound helically about the center tube in a first direction and a
second wire member wound helically about the center tube in a
second direction opposite to the first direction such that the
first and second wire members overlap and intersect one another in
a crosswise manner at a plurality of locations axially spaced along
the center tube.
[0014] In preferred embodiments at least one outer end of the outer
tube is joined to the center tube by an auxiliary sleeve supported
about the center tube so as to define a double wall portion of the
center tube at the auxiliary sleeve and a single wall portion of
the center tube at an intermediate location between opposing ends
of the outer tube which is not overlapped by the auxiliary
sleeve.
[0015] Preferably the auxiliary sleeve is joined to the outer tube
at a location which is spaced axially outward in relation to a
connection between the between the auxiliary sleeve and the center
tube, and an annular space between the center tube and the
auxiliary sleeve at the double wall portion is open axially
outwardly and externally of the center tube at the outer end of the
outer tube.
[0016] Preferably both ends of the outer tube are joined to the
center tube by an auxiliary sleeve such that the single wall
portion is defined between the auxiliary sleeves.
[0017] Preferably the single wall portion is longer in an axial
direction than the double wall portion.
[0018] Preferably the auxiliary sleeve portions are thinner in
radial thickness than the single wall portion of the center tube
such that the center tube will fail from erosion at the double wall
portion prior to failing at the single wall portion.
[0019] The center tube may be thinner in radial thickness at the
double wall portion than at the single wall portion thereof.
[0020] The outer tube may also thinner in radial thickness than the
single wall portion of the center tube and the auxiliary sleeve
members such that the outer tube will fail from erosion before the
center tube.
[0021] The auxiliary sleeve preferably protrudes axially outward
beyond the respective outer end of the outer tube and the center
tube preferably protrudes axially outward beyond an outer end of
the auxiliary sleeve. In this instance, the connection of the outer
tube to the sleeve and the connection of the sleeve to the center
tube does not interfere with an annular space between the center
tube and the auxiliary sleeve at the double wall portion being open
axially outwardly and externally of the center tube.
[0022] The end of the center tube may be enlarged in inner diameter
at an end portion overlapped by an outer end of the auxiliary
sleeve and the outer end of the outer tube such that the end
portion is arranged to receive a portion of a drain line therein
having an outer diameter which is substantially equal to an outer
diameter of the single wall portion.
[0023] According to a second aspect of the present invention there
is provided a heat exchanger for use between a drain line having a
first fluid flow therethrough and a supply line having a second
fluid flow therethrough, the heat exchanger comprising:
[0024] an upright center tube extending longitudinally between
opposing top and bottom ends;
[0025] the upright center tube being arranged for connection to the
drain line so as to receive the first fluid flow longitudinally
through the upright center tube;
[0026] an outer tube surrounding the upright center tube so as to
define an annular space between upright center tube and the outer
tube which spans longitudinally along the upright center tube
between opposing top and bottom ends of the outer tube;
[0027] the outer tube being arranged for connection to the supply
line so as to be arranged to receive the second fluid flow
longitudinally through the annular space between the upright center
tube and the outer tube; and
[0028] at least one auxiliary sleeve supported about the center
tube and joining a respective outer end of the outer tube to the
center tube so as to define a double wall portion of the center
tube at the auxiliary sleeve and a single wall portion of the
center tube at an intermediate location between opposing ends of
the outer tube which is not overlapped by said at least one
auxiliary sleeve;
[0029] said at least one auxiliary sleeve being joined to the outer
tube at a location which is spaced axially outward in relation to a
connection between the between the auxiliary sleeve and the center
tube; and
[0030] the double wall portion of said at least one auxiliary
sleeve being open axially outwardly and externally of the center
tube at the respective outer end of the outer tube.
[0031] In other embodiments of the present invention as described
herein the baffle portions may comprise protrusions formed on at
least one of the upright center tube or the outer tube so as to
project into the annular space between the upright center tube and
the outer tube and so as to be arranged to induce turbulence in the
second fluid flow.
[0032] The protrusions may be formed on an inner surface of the
outer tube to extend generally radially inwardly towards the center
tube as well as being formed on an outer surface of the center tube
to extend generally radially outwardly towards the outer tube.
Preferably each protrusion on the outer surface of the center tube
is longitudinally spaced from adjacent ones of the protrusions on
the inner surface of the outer tube such that the protrusions
alternate between the center tube and the outer tube in a
longitudinal direction.
[0033] The protrusions may be arranged to span only partway across
the annular space between the upright center tube and the outer
tube such that second fluid flow remains primarily in the
longitudinal direction between longitudinally opposed ends of the
outer tube.
[0034] The protrusions may comprise annular ribs which are
longitudinally spaced apart. The ribs may be of any shape including
rounded, squared or angled, and may be of any depth, or any height
relative to the based pipe diameter.
[0035] A plurality of protrusions may also be formed on an inner
surface of the center tube to project generally radially inwardly
so as to be arranged to induce turbulence in the first fluid
flow.
[0036] In some embodiments the protrusions formed on the inner
surface of the center tube are aligned with respective recessed
areas on an outer surface of the center tube in communication with
the annular space between the upright center tube and the outer
tube.
[0037] In alternative embodiments the protrusions formed on the
inner surface of the center tube are aligned with respective ones
of the protrusions projecting into the annular space between the
upright center tube and the outer tube.
[0038] The heat exchanger may further comprise recessed areas
formed on an outer surface of the center tube in communication with
the annular space between the upright center tube and the outer
tube.
[0039] In some embodiments the recessed areas may be adjacent to
respective ones of the protrusions projecting into said annular
space. Alternatively the recessed areas may be longitudinally
spaced from respective ones of the protrusions projecting into said
annular space.
[0040] In further embodiments the protrusions may be arranged in a
helical pattern about a longitudinal direction of the center
tube.
[0041] Preferably the outer tube surrounds the center tube such
that there is only a single layer wall between the first fluid flow
in the center tube and the second fluid flow in said annular
space.
[0042] As described herein, in some embodiments the inner tube ribs
have some going inward in order to agitate the waste water as it
falls along the inside of the tube wall. Other ribs on inner tube
may be pointing outward to agitate the fresh water passing over top
the external surface of the inner tube.
[0043] The protrusions on the outer tube serve to agitate the fresh
water passing over the inner surface of the tube. Together with the
outward ribs of the inner tube, the ribs work to agitate the fresh
water.
[0044] Typically the ribs of the inner tube and the ribs of the
outer tube alternate along the length of the tubes. This serves to
make sure that the entire water stream flowing between to two tubes
is agitated well. The alternating nature of the ribs may also be
replaced by ribs that are on top of each other so as to pinch the
water flow at the same point along the tubes.
[0045] The concept of water flowing between tubes, across ribs,
whereby the ribs serve to agitate the water, is not limited to
ribs. The ribs may be spirals instead, where the spirals on the
inner tube and outer tubes do not close in on each other, but
rather the water would still spill over the ribs while moving in a
somewhat spiral manner instead of a direct axial flow manner.
[0046] The heat exchanger in the preferred embodiment is single
wall, however the heat exchanger may also be constructed for form a
double inner wall between the first and second fluid flows as well.
In the instance of a double wall, the center tube may be made of
two tubes that are pressed together with or without a space between
them.
[0047] The fresh water which passes between the inner and outer
tubes preferably enters via a pipe at the bottom and leaves via a
pipe at the top of the outer tube so as to counter the flow through
the center tube.
[0048] Various embodiments of the invention will now be described
in conjunction with the accompanying drawings in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0049] FIG. 1 is a partly sectional perspective view of a first
embodiment of the heat exchanger.
[0050] FIG. 2 is an enlarged portion of the partly sectional
perspective view of the heat exchanger in FIG. 1 according to a
first variant of the first embodiment.
[0051] FIG. 3 is a sectional view of a portion of the wall of the
center tube according to a second variant of the first
embodiment.
[0052] FIG. 4 is a sectional view of a portion of the wall of the
center tube according to a third variant of the first
embodiment.
[0053] FIG. 5 is a perspective view of a second embodiment of the
heat exchanger in which the outer tube is shown to be transparent
for illustrative purposes only.
[0054] FIG. 6 is a sectional view of a connection between the
center tube and the outer tube according to a third embodiment of
the heat exchanger.
[0055] FIG. 7 is a sectional view of the connection between the
center tube and the outer tube according to a fourth embodiment of
the heat exchanger.
[0056] FIG. 8 is a sectional view of the connection between the
center tube and the outer tube according to a fifth embodiment of
the heat exchanger.
[0057] FIG. 9 is a sectional view of the connection between the
center tube and the outer tube according to a sixth embodiment of
the heat exchanger.
[0058] FIG. 10 is a sectional view of the connection between the
center tube and the outer tube according to a seventh embodiment of
the heat exchanger.
[0059] FIG. 11 is a sectional view of the connection between the
center tube and the outer tube according to an eighth and preferred
embodiment of the heat exchanger.
[0060] In the drawings like characters of reference indicate
corresponding parts in the different figures.
DETAILED DESCRIPTION
[0061] Referring to the accompanying figures, there is illustrated
a heat exchanger device generally indicated by reference numeral
10. The device 10 is particularly suited for use in heat recovery
from a drain tube of a plumbing fixture in a building for
pre-heating the water supply lines to the plumbing fixture from
which heat is recovered. For example, the device 10 is connected in
series with the drain line of a shower in close proximity to the
shower for exchanging heat with the main supply line which supplies
water to the faucets of the shower and/or the hot water tank of the
same water supply system. Although various embodiments are
described and illustrated herein, the common features of the
various embodiments will first be described.
[0062] The heat exchanger device 10 comprises a center tube 12
comprising a vertical tube arranged to be connected in series with
the drain line to receive the first fluid flow of the drain line
through the center tube 12. The center tube extends vertically in a
longitudinal direction between a top end 14 and a bottom end 16.
The top and bottom ends are configured for suitable connection to
respective portions of the drain line. The center tube comprises a
generally cylindrical tube formed of a material having a high
conductivity, such as copper for example. The inner and outer
surfaces of the center tube are accordingly similarly generally
cylindrical in shape. The diameter of the center tube corresponds
approximately to the diameter of the drain tube typically.
[0063] The device 10 further comprises an outer tube 18 similarly
extending in a longitudinal direction between a top end 20 and a
bottom end 22. The outer tube is supported about the center tube to
surround the center tube and extend along the center tube in the
longitudinal direction along the full length between the top and
bottom ends of the outer tube. The outer tube is also generally
cylindrical in shape to define respective inner and outer surfaces
which are also substantially cylindrical in shape. The outer tube
has a larger diameter than the center tube such that the center
tube is received concentrically within the outer tube while the
single wall of the outer tube remains spaced radially outward from
the single wall of the center tube about the full circumference
thereof.
[0064] The concentric configuration of the center and outer tubes
defines a space therebetween extending along the full length of the
outer tube between the top and bottom ends thereof which is
generally in the shape of an annular cylinder. End walls 24 span
the annular gap between the center tube and the outer tube at both
top and bottom ends of the outer tube so that the annular space 25
defined between the centre tube and the outer tube comprises an
enclosed volume for receiving the second fluid flow of the water
supply line therethrough.
[0065] An inlet port 26 is connected through the wall of the outer
tube adjacent the bottom end thereof which is suitably configured
for connection to the water supply line. Similarly an outlet port
28 communicates through the single wall of the outer tube adjacent
the top end thereof which is also arranged for connection to the
supply line. By connecting the bottom inlet port 26 and the upper
outlet port 28 in the appropriate configuration to the water supply
line, the flow of fluid from the supply line is directed upwardly
through the annular space from the bottom to the top of the outer
tube in a counter flow configuration with the first fluid flow of
the drain line downwardly through the center tube.
[0066] In the various embodiments of the present invention, the
annular space includes baffle portions 29 therein which having a
thickness in the radial direction of the tubes which is less than
the radial dimension of the annular space 25 between the outer
diameter of the center tube 12 and the inner diameter of the outer
tube 18. The baffle portions 29 are arranged such that the flow
through the annular space primarily or substantially remains in the
axial direction of the tubes, but the flow is turbulent as it flows
over the various baffle portions.
[0067] As described herein according to a first embodiment, the
invention relates to a tube-in-tube heat exchanger that recovers
heat from waste-water as it passes through the inner (drain) tube
to the cold, fresh water supply which flows between the inner and
outer tubes. In the first embodiment, the inner and outer tubes are
each of single wall construction and the tubes have ribbed surfaces
which cause the water to agitate or turn over, so that heat is more
effectively transferred from the warm waste-water to the copper
tube to the cold fresh-water. Copper is approximately 700 times
more heat conductive than water. Only the surface film of water
transfers its heat quickly. The water must be agitated so that the
water touching the surface of the copper changes as it moves along
the tube. The agitation of the water by the ribs greatly increases
the efficiency of this heat exchanger.
[0068] In the first embodiment, the baffle portions 29 are in the
form of various protrusions as described in the following. The
outer tube locates a plurality of outer protrusions 30 formed
thereon such that each of the protrusions protrudes inwardly from
an inner surface of the outer tube only partway across the annular
space in the radial direction towards the center tube. The radial
dimension of the protrusions 30 typically correspond to
approximately 25% to 50% of the radial dimension of the annular
space.
[0069] In the illustrated first embodiment, the outer protrusions
30 are formed by crimping the single wall of the outer tube to
define a plurality of generally circular and annular ribs at
longitudinally spaced positions along the length of the outer tube
between the top and bottom ends thereof.
[0070] The inner tube includes a plurality of inner protrusions 32
formed on the outer surface thereof which similarly protrude in a
generally radial direction partway across the annular space in an
outward direction towards the outer tube. Each inner protrusion is
generally centered in a longitudinal direction between an adjacent
pair of the outer protrusions on the outer tube. In this manner,
the protrusions within the annular space alternate between a
protrusion supported on the outer tube and a protrusion supported
on the inner tube along the full length of the annular space in the
longitudinal direction.
[0071] In the illustrated first embodiment, the inner protrusions
also comprise generally circular or annular ribs which are spaced
apart in a longitudinal direction from one another along the length
of the annular space.
[0072] The inner tube may also support a plurality of central
protrusions 34 on the inner surface thereof at longitudinally
spaced positions similar to the spacing of the inner protrusions
such that each central protrusion 34 is associated with a
respective one of the inner protrusions 32. The central protrusions
34 also comprise generally circular or annular ribs projecting
generally in a radial direction inwardly towards a center of the
inner tube.
[0073] Turning now to a first variant of the first embodiment of
FIGS. 1 and 2, the inner protrusions 32 in this instance comprise
crimped formations in the single wall of the inner tube such that
each inner protrusion forms a corresponding annular grove 36 on the
inner surface of the center tube opposite the protrusion on the
outer surface. Accordingly, the grooves 36 formed in the inner
surface of the center tube are similarly generally circular or
annular in shape at longitudinally spaced positions.
[0074] The central protrusions 34 in this instance also comprise a
corresponding groove 38 when formed of a similar crimping process
such that the grooves are located on the outer surface of the
center tube opposite the respective protrusions on the inner
surface.
[0075] As shown in FIGS. 1 and 2 along both the inner and outer
surfaces of the center tube, each protrusion on that surface is
associated with an adjacent groove with the grooves being ahead of
the protrusions in the flow direction. In this manner, as the first
or second flows extend generally longitudinally in respective flow
directions, the flows each engage a groove followed by a protrusion
along the respective surface of the center tube to induce a
considerable turbulence into the respective fluid flow. In the
annular space the fluid flow is caused further turbulence by the
protrusions on the outer tube at spaced positions between the
groove and protrusion pairs on the center tube. Along each surface
of the center tube in FIGS. 1 and 2, each groove is located
directly adjacent a corresponding protrusion.
[0076] Turning now to FIG. 3, according to a further variation of
the first embodiment, the protrusions on the inner tube may be
formed similarly to the previous embodiment to define corresponding
grooves on the opposing sides of each protrusion; however, the
protrusions on the inner surface in this instance are spaced from
the protrusions on the outer surface of the center tube such that
along each surface of the tube, each protrusion is spaced apart
from its corresponding groove instead of being located directly
adjacent one another.
[0077] In yet a further variation to the first embodiment as shown
in FIG. 4, each inner protrusion on the outer surface of the inner
tube may be aligned in the longitudinal direction with a
corresponding one of the central protrusions on the inner surface
of the inner tube by forming a rib in the single wall where the
single wall has an increased overall thickness such that there are
no corresponding grooves on either surface of the central inner
tube in this instance.
[0078] When the heat exchanger device is connected to respective
drain and supply lines as described above, the first fluid flow of
the drain line directed through the center tube comes into contact
with a greater surface area due to the central protrusions 34 along
the inner surface while also increasing the turbulence of the flow
for optimal mixing and ensuring a greater volume of the fluid flow
comes into direct heat exchanging contact with the single wall
between the first and second fluid flows. Similarly the alternating
protrusions in the annular space receiving the second fluid flow of
the supply line also cause considerable turbulence in the second
flow to disrupt the boundary layer and ensure mixing and greater
contact of a greater volume of fluid with the heat exchanging
surface of the single wall center tube between the first and second
fluid flows.
[0079] Turning now more particularly to the embodiment of FIG. 5,
the baffle portions 29 in this instance comprise a plurality of
wire members 50. The wires are made of a heat conductive material
having a thickness or diameter arranged to only span partway in the
radial direction of the annular space 25 between the outer diameter
of the center tube and the inner diameter of the outer tube. In
this instance, the flow through the annular space remains primarily
and substantially in the axial direction while the baffle portions
ensure that the flow is turbulent.
[0080] Although the baffle portions may comprise any suitable
structure for partially obstructing the flow in the axial
direction, in the preferred embodiment of FIG. 5 the baffle
portions are defined by a first wire member and a second wire
member which are helically wound about the center tube in opposing
directions from one another such that the wires cross over one
another in a crosswise intersecting manner at several axially
spaced positions along the length of the annular space. The baffle
portions are assembled by initially winding the first wire member
helically upward in a first circumferential direction substantially
along the full length of the annular space between the top and
bottom ends. Subsequently, the second wire member is wound about
the first wire member to extend helically upward in the opposing
circumferential direction. When the wire members have a diameter
corresponding to approximately half of the radial dimension of the
annular space as in the illustrated embodiment, at each
intersecting cross over of a second wire member extending overtop
of a first wire member, the combined thickness in the radial
direction may substantially fill the radial dimension of the
annular space at the cross over point to further obstruct the flow
and encourage turbulent flow in the axial direction.
[0081] In other embodiments, various heat conductive materials can
be used which have a thickness which is less than the radial
dimension of the annular space such as mesh materials (or strand
materials like steel wool) comprised of many individual wire
members in crosswise intersecting configurations relative to one
another to ensure a turbulent flow around the wire members in the
axial direction.
[0082] In yet further embodiments, the baffle portions 29 may be
formed by various forms of textured surfaces on the outer surface
of the center tube or the inner surface of the outer tube such as
protrusions defining the baffle portions or recesses defining
baffle portions therebetween which encourage turbulent flow.
[0083] As described above with regard to FIG. 5, the gap between
the inner and outer tubes has spiral wrapped wires. One wire or set
of wires fills approximately half the gap thickness and is wound in
one direction. The other wire or set of wires is wrapped on top of
the first wire and fills approximately the other half of the gap
space. This wires force the water to agitate, turn over as it flows
along the length of the tube space. The gap space may be filled
with any other obstacles which cause the laminar flow to be
disrupted, and the water is constantly `turned over` so that heat
transfer from the inner tube surface contacts a new surface film of
cooler water. Like making scrambled eggs, turning over the surface
film of water touching the inner tube continuously puts previously
non-contacted water against the inner wall. This process rapidly
transfers more heat into the water in the gap space. Gap space may
have spirals of wire or any other material that is wire-like in
shape. Gap may have non-spiral wound wire. Gap may have any
obstruction method which serves to disrupt laminar flow and agitate
the water flow so as to break the surface film with a new film to
transfer more heat to the water occupying the entire gap space.
[0084] Turning now to FIGS. 6 through 11, various embodiments of
the connection of the ends of the outer tube to the center tube
will now be described. The embodiments of FIGS. 6 through 11
include the baffle portions of FIG. 5.
[0085] In each instance of FIGS. 6 through 11, a double wall
portion is defined on the center tube which can be used with any of
the embodiments of the baffle portions described above. As in
previous embodiments, a main portion of both the center tube and
the outer tube remains single wall in construction, however in the
new embodiments, a pair of auxiliary sleeves 60 are supported at
respective axially opposed ends of the outer tube for defining a
respective pair of double wall portions 67 on the center tube. In
further arrangements, a double wall portion 67 may be defined at
only one end of the main single wall portion by only using one
auxiliary sleeve 60 mounted at that end.
[0086] In each instance, when used at one or both ends of the
central single wall portion, the auxiliary sleeve 60 is mounted in
close fit arrangement with the center tube such that the inner
diameter of the auxiliary sleeve substantially corresponds with the
outer diameter of the portion of the center tube upon which it is
received. When two sleeves 60 are used, the sleeve portions are
axially spaced apart along the center tube with the inner ends 62
being closest to one another and the outer ends 64 being opposite
one another at the opposing top and bottom ends of the outer tube
18 respectively.
[0087] The inner ends 62 in each instance are joined to the center
tube by brazing or other suitable joining means such that each
auxiliary sleeve defines the respective double wall portion 67 of
the center tube at the respective sleeve and a single wall portion
66 is defined on the center tube between the auxiliary sleeves.
More particularly, the single wall portion 66 is the portion of the
center tube 12 surrounded by the outer tube 18, but not overlapped
or surrounded by one of the auxiliary sleeves 60.
[0088] The outer tube is joined at the opposing top and bottom ends
thereof to respective ones or the outer ends 64 of the two
auxiliary sleeves 60 in the preferred embodiments. Alternatively,
when an auxiliary sleeve 60 is only provided at one end, the
opposing end of the outer tube is joined to the center tube.
[0089] In either instance the annular space remains defined between
the single wall portion of the center tube and the outer tube along
the central portion, as well as between the outer diameter of the
auxiliary sleeves and the inner diameter of the outer tube at the
double wall portions where auxiliary sleeves 60 are provided. The
opposing top and bottom ends of the outer tube may be joined to the
respective sleeves or the center tube either by tapering inwardly
or by use of end walls 24 as described above with regard to the
previous embodiment.
[0090] The inlet and outlet ports 26 and 28 remain located adjacent
the opposing top and bottom ends of the outer tube as described
above such that each port is aligned with a respective one of the
double wall portions in the axial direction.
[0091] Each auxiliary sleeve defines a portion of the inner
boundary wall of the annular space towards the respective end of
the annular space while the single wall portion 66 of the center
tube defines the inner boundary of the annular space along a
central portion thereof. The outer tube defines the outer boundary
of the annular space along the full length of the annular space in
the axial direction.
[0092] The auxiliary sleeve 60 is formed of material having a
radial wall thickness which is thinner than the single wall portion
of the center tube such that any erosion at the inner boundary at
the annular space is likely to occur in the auxiliary sleeve
forming the double wall portion before any failure of the single
wall portion. A failure at the auxiliary sleeve would result in
leakage within the double wall structure between the center tube
and the annular sleeve 60 surrounding the center tube at a location
outward from the brazing connection between the two components such
that the leakage is directed axially outward towards the top or
bottom end of the outer tube where it can be discovered prior to
any contamination between the flow through the center tube and the
flow through the annular space.
[0093] The auxiliary sleeves are much shorter than the central
portion of the center tube therebetween in the axial direction such
that the area of the single wall portion of the center tube is much
larger than the area of the double wall portion defined by the
auxiliary sleeves.
[0094] The outer tube which defines the outer boundary of the
annular space along the full length thereof is typically formed of
material that has a thickness in the radial direction which is
thicker than the center tube and more particularly the single wall
portion of the center tube because larger diameter tubes require
thicker walls in order to maintain the same psi rating.
[0095] In alternative embodiments however the outer tube may
optionally be thinner than the center tube. In this instance, any
failure due to erosion of the boundary surfaces of the annular
space is more likely to occur at the outer tube where it is visible
and does not cause contamination between the first and second
flows.
[0096] In each instance in the embodiments of FIGS. 6 through 11,
both outer ends of the outer tube are joined to the center tube by
an auxiliary sleeve 60 supported about the center tube so as to
define the double wall portion of the center tube at the auxiliary
sleeve and the single wall portion of the center tube at an
intermediate location between opposing ends of the outer tube which
is not overlapped by the auxiliary sleeve. The single wall portion
is longer in an axial direction than the double wall portion.
[0097] Furthermore in the embodiments of FIGS. 6 through 11, the
auxiliary sleeve is joined to the outer tube at a location which is
spaced axially outward in relation to a connection between the
between the auxiliary sleeve and the center tube. More
particularly, the auxiliary sleeve is typically connected to the
center tube at the inner end of the sleeve and to the outer tube at
the outer end of the sleeve. The annular spaces between the center
tube and the auxiliary sleeves at the double wall portions are open
axially outwardly and externally of the center tube at the outer
ends of the outer tube. When the auxiliary sleeve portion and the
double wall portion of the center tube are both thinner in radial
thickness than the single wall portion of the center tube any leaks
are more likely to occur at the double wall portion and be detected
at the open end of the annular space of the double wall
portion.
[0098] Turning now more particularly to the embodiment of FIG. 6, a
center tube has a constant thickness and constant diameter along
the length thereof from the single wall portion to the double wall
portion in this instance. The continuous nature of the center tube
permits the auxiliary sleeve members 60 to be secured thereabout
only by a single brazing seam extending about the full
circumference of the tube at the inner end thereof with the entire
double wall structure between the sleeve and the center tube being
arranged to drain axially outward through the respective top or
bottom end of the outer tube.
[0099] Alternatively, in the embodiment of FIG. 7, the center tube
includes a central portion 68 having a first thickness and two end
portions 70 abutted at opposing ends of the central portion having
a second thickness which is thinner than the central portion. The
central portion 68 defines the single wall portion of the center
tube while the overlap of the sleeves 60 with the respective end
portions 70 substantially define the double wall portions.
[0100] In the instance of FIG. 7, the sleeve structures 60 are
again joined to the center tube at the inner ends which overlap
opposing ends of the central portion 68 such that the inner ends
are brazed to a portion of the center tube having the thicker first
dimension. The second smaller dimension at the end portions 70 of
the center tube thus only communicate with the double wall
structure formed by the sleeve 60. In this instance, the thinner
section of the center tube is arranged to fail by erosion prior to
the thicker central portion which would result in leakage into the
double wall section which would in turn be visible as leakage
through the outer end of the double wall structure instead of
contaminating the flow in the annular space.
[0101] The single wall portion or central portion 68 of the center
tube may be near the combined thickness of the center tube portion
and sleeve 60 portion of the double wall but, is preferably thinner
than the combined thickness at the double wall sections as the
thinner material has a greater heat transfer efficiency.
[0102] The embodiment of FIG. 7 is further distinguished from the
embodiment of FIG. 6 by arranging the outer diameter of the center
tube to be recessed inwardly at the end portions 70 relative to the
central portion 68 by a radial dimension corresponding to the
thickness of the sleeves. In this instance, when the outer tube has
a continuous internal diameter, the radial dimension of the annular
space 25 remains constant across the single wall portion and both
double wall portions of the center tube.
[0103] In the embodiment of FIG. 7, the central portion 68 and end
portions 70 of the center tube and the auxiliary sleeves 60 may be
joined to one another by various means. In one instance, the
central portion and end portions of the center tube may be joined
by a first braze 80 at the internal surfaces thereof with the
sleeve structure then being brazed at its inner end to the central
portion 68 at a location axially inward relative to the first braze
80.
[0104] According to a second configuration, the inner end 62 of the
sleeve 60 may be joined by a large continuous solder 82 which joins
the inner end 62 to both the end of the central portion 68 and the
end of the respective end portion 70 in one step.
[0105] In another embodiment, a first braze 80 joins the inner end
of the respective end portion 70 to the sleeve at a location spaced
outward from the inner end 62 of the sleeve 60. Subsequently, the
inner end 62 of each sleeve 60 may be joined to the central portion
68 at a location spaced axially inward from the end portion 70 by a
second braze 86. In this instance, both the central portion 68 and
the respective end portion 70 are joined to the sleeve by a
respective brazing such that the end portions 70 substantially abut
the opposing ends of the central portion 68.
[0106] Turning now to the embodiment of FIG. 8, the center tube 12,
the auxiliary sleeve 60, and the outer tube 18 are arranged
substantially as in FIG. 6 described above, with the exception of
the outer diameter of the center tube 12 at the double wall
portion. In this instance, the outer diameter of the center tube is
reduced at the double wall portion so that the thickness of the
double wall portion of the center tube is thinner than at the
single wall portion. This has the same advantages as described
above with regard to FIG. 7 by ensuring that any leaking of the
center tube due to erosion from the central flow would be apparent
at the double wall section prior to any contaminating leakage
through the single wall portion. The auxiliary sleeve 60 is joined
to the center tube by a single brazing at the inner end 62 in this
instance.
[0107] Turning now to the embodiment of FIG. 9, the centre tube 12,
the auxiliary sleeve 60, and the outer tube 18 are again arranged
substantially as in FIG. 6 described above, with the exception of
the outer diameter of the center tube at the double wall portion.
In this instance, the outer diameter of the center tube at the
double wall portion is provided with scored annular grooves 90 at a
plurality of axially spaced apart positions to reduce the wall
thickness of the center tube at the grooves 90. This has the same
advantages as described above with regard to FIGS. 7 and 8 by
ensuring that any leaking of the center tube due to erosion from
the central flow would occur at the grooves 90 and be apparent at
the double wall section prior to any contaminating leakage through
the single wall portion. The auxiliary sleeve 60 is joined to the
center tube by a single brazing at the inner end 62 in this
instance.
[0108] Turning now to the embodiment of FIG. 10, the centre tube is
similar to FIG. 7 in this instance in that there is provided a
central portion 68 substantially forming the single wall portion
and an end portion 70 defining the double wall portion. As in the
previous embodiment, the end portion 70 is reduced in wall
thickness relative to the central portion so that leakage would
more likely occur through the double wall portion than the single
wall portion. Furthermore, the outer diameter of the end portion 70
is reduced relative to the central portion 68 such that the end
portion 70 can be snugly received within the inner diameter of the
central portion. The auxiliary sleeve 60 can thus overlap the end
portion 70 of the center tube at the double wall portion with the
outer diameter of the auxiliary sleeve being substantially
identical to the outer diameter of the single wall central portion
68. This has the advantage of a constant radial gap dimension in
the annular spaced when the outer tube has a constant inner
diameter. Furthermore, a single braze or solder 92 at the inner end
62 of the sleeve should be sufficient to simultaneously join the
outer end portion 70 of the center tube to the end of the central
portion 68 of the center tube and join the inner end 62 of the
sleeve 60 to the center tube.
[0109] Turning now to the embodiment of FIG. 11, heat exchanger is
substantially identical to the embodiment of FIG. 8 except for the
configuration of the outer ends of the double wall portions of the
center tube 12, the outer ends 64 of the sleeves 60 and the outer
ends of the outer tube 18. The auxiliary sleeve 60 protrudes
axially outward to the outer end 64 beyond the respective outer end
of the outer tube. A braze connection 100 is located at the outer
end of the outer tube 18 adjacent the outer end of the sleeve, but
with a portion of the sleeve protruding beyond the braze connection
to join the sleeve to the outer tube 18 about the full
circumferences thereof. Similarly, the center tube protrudes
axially outward beyond the outer end 64 of the auxiliary sleeve 60
to a respective bottom end 16. The annular space between the double
wall portion of the centre tube and the auxiliary sleeve 60 remains
open externally at the outer end for leak detection.
[0110] Furthermore, as shown in the embodiment of FIG. 11, the
center tube includes an end portion 102 associated with the
auxiliary sleeve 60 at each end of the outer tube. The end portion
102 is aligned with and overlapped by a corresponding end portion
104 of the auxiliary sleeve such that both the end portions 102 and
104 are aligned with and overlapped by the respective outer end of
the outer tube in the axial direction. The end portions 102 and 104
are both enlarged in diameter by expanding the tube after the
sleeve 60 is mounted on the center tube. The end portions are
expanded such that the outer diameter of the sleeve at the end
portion is approximately equal to the inner diameter of the outer
tube which is a constant diameter tube between opposing top and
bottom ends in this instance. The stepped diameter at the outer end
of the sleeve and center tube thus provides the function of an end
wall to the annular space receiving the second fluid flow of the
supply line therethrough when a connection is made by the braze
connection 100. The resulting inner diameter at the end portion of
the center tube is also arranged such that the end portion is
arranged to receive a portion 106 of a drain line therein having an
outer diameter which is substantially equal to an outer diameter of
the single wall portion. The inner diameter of the expanded end
portion is such as to receive the end piece 106 with its outer
diameter equal to the outer diameter of the single wall portion of
the inner tube which permits different wall thicknesses of piece
106, given that the outer diameter is the constant dimension for
different wall gauges. An additional braze 108 can thus be located
about the full circumference of the center tube at the outer end
thereof for connection between the center tube and the adjacent
portion 106 of drain line without interfering with the open end of
the annular leak detection space. As in previous embodiments, a
braze connection 110 is also provided at the inner end 62 of the
sleeve for connecting the sleeve to the center tube about the full
circumferences thereof.
[0111] In all instances, the inlet and outlet ports are aligned
with the sleeve structure at a location which overlaps the end
portion 70 of the center tube by locating the inlet and outlet
ports outward in the axial direction of the tubes in relation to
any brazing connection of the sleeve 60 to the center tube. As the
directional flow change resulting from the inlet and outlet ports
increases the likelihood of erosion to take place at a location in
alignment with the port, overlapping the port with the end portions
70 ensures that any leakage resulting from erosion at that location
aligns with a portion of the double wall structure which is open to
the top or bottom ends of the outer tube for leak detection and
prevention of contamination between the first and second flows.
[0112] As described above with regard to FIGS. 6 through 11, the
major portion of the heat exchanger is the single wall, as
described earlier, with all its variations of ribs and/or spiral
internal water baffles. A smaller portion of the heat exchanger is
double wall. The double wall is designed to fail before the single
wall portion, so that leak detection is possible. The double wall
consists of a double inner wall. The fresh water wall and the
drainwater wall. The fresh water wall is thinner gauge than the
inner wall of the single wall portion. This is so that in the event
of wall thinning over time due to water erosion of the copper pipe,
this wall will fail first. This leak causes the fresh water to exit
between the double walls and out the end of the heat exchanger,
visible and thus prompting the device to be replaced. The
drainwater wall is also a thinner gauge than the inner wall of the
single wall portion in the embodiment of FIGS. 7 and 11. This is so
that in the event of drain wall thinning over time, the drain wall
will fail in the double wall portion of the heat exchanger. This
will cause the leak in drainwater to be detected and the device
will be replaced. The single wall portion need not be the sum
thickness of the two double wall portions. Or they may be depending
on the local municipality approving the device for use. The thicker
the single wall, the less the efficiency, so something less than
double is preferred in general. The single inner wall portion may
or may not be formed to a narrower diameter at the end where it
mates with the double wall portion. A narrower diameter allows the
gap between inner and outer walls not to be reduced much or at all,
thus not creating a water pressure drop in the double wall
portion.
[0113] In some instances, more than one heat exchanger device may
be provided in parallel with one another with the corresponding
pipe joining the center tubes being branched into parallel
branches. Similarly any tubing flowing through the annular space is
similarly branched into multiple parallel lines in which each
parallel line is connected in series from the inlet port to the
outlet port of a respective one of the heat exchanger devices.
[0114] Paralleling of two or more heat exchanger devices (either
single or hybrid or any other style) may be used to increase
efficiency. Since heat transfer efficiency is improved with thinner
wall thicknesses, there is an advantage to keeping the overall
diameter of the heat exchanger pipes small. Larger pipes require
thicker walls in order to handle water pressure and to meet minimum
acceptable tested PSI values. A single heat exchanger has a flow
rate above which the efficiency drops significantly. In order to
efficiently capture drainwater heat at higher flow rates than a
single heat exchanger can efficiently handle, it may be practical
to parallel two or more of these single devices. Again, as opposed
to making a single larger diameter heat exchanger with thicker
walls which reduce efficiency.
[0115] Since various modifications can be made in my invention as
herein above described, and many apparently widely different
embodiments of same made within the spirit and scope of the claims
without department from such spirit and scope, it is intended that
all matter contained in the accompanying specification shall be
interpreted as illustrative only and not in a limiting sense.
* * * * *