U.S. patent application number 11/992034 was filed with the patent office on 2009-10-29 for heat exchanger element and a water heater and heat pump utilizing same.
Invention is credited to Patrick Pussell.
Application Number | 20090266509 11/992034 |
Document ID | / |
Family ID | 37864541 |
Filed Date | 2009-10-29 |
United States Patent
Application |
20090266509 |
Kind Code |
A1 |
Pussell; Patrick |
October 29, 2009 |
Heat Exchanger Element and a Water Heater and Heat Pump Utilizing
Same
Abstract
A heat exchanger element (30) formed from an inner copper tube
(32) and an outer copper tube (34). The entire outer surface of the
inner tube (32) is substantially in contact with the entire inner
surface of the outer tube (34).
Inventors: |
Pussell; Patrick; (New South
Wales, AU) |
Correspondence
Address: |
PATENT GROUP;C/O DLA PIPER US LLP
203 N. LASALLE ST., SUITE 1900
CHICAGO
IL
60601
US
|
Family ID: |
37864541 |
Appl. No.: |
11/992034 |
Filed: |
August 1, 2006 |
PCT Filed: |
August 1, 2006 |
PCT NO: |
PCT/AU2006/001086 |
371 Date: |
April 2, 2009 |
Current U.S.
Class: |
165/47 ; 165/156;
29/890.03; 62/498 |
Current CPC
Class: |
Y10T 29/4935 20150115;
F25B 39/04 20130101; Y02E 60/14 20130101; F28D 7/024 20130101; F28F
1/003 20130101; F28D 20/0034 20130101; F28F 21/085 20130101; F25B
2339/047 20130101; Y02E 60/142 20130101; F24D 3/082 20130101; F24H
9/0021 20130101 |
Class at
Publication: |
165/47 ;
29/890.03; 62/498; 165/156 |
International
Class: |
F24H 4/02 20060101
F24H004/02; B21D 53/02 20060101 B21D053/02; F25B 1/00 20060101
F25B001/00; F28D 7/10 20060101 F28D007/10 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 16, 2005 |
AU |
2005905136 |
Dec 13, 2005 |
AU |
2005906999 |
Claims
1. A method of forming a heat exchanger element, the method
comprising the following steps: a. drawing a first and a second
copper tube, the first tube having an outer diameter less than the
internal diameter of the second tube; b. inserting the first tube
into the second tube; c. passing the tubes through a roll former
adapted to crush the second tube onto the first tube, such that the
entire outer surface of the first tube is substantially in contact
with the entire inner surface of the second tube. d. annealing the
crushed tubes; e. bending the tubes into a desired configuration;
and f. annealing the bent tubes.
2. The method as claimed in claim 1, wherein step e. includes
bending the tubes into a generally cylindrical shape.
3. The method as claimed in claim 2, including the step of forming
the cylindrical walls from spiraled tubes.
4. The method as claimed in claim 1, wherein step a. includes
drawing the second tube with internal rifling or grooves.
5. A heat exchanger clement formed by the method as defined in
claim 1.
6. A water heater including a tank and a heat exchanger element
according to claim 5.
7. A heat pump circuit comprising an evaporator coil; a compressor,
a condenser coil in a heat exchanging relationship with a body of
water, and a thermostatic expansion valve (TX valve), the circuit
adapted to hold a charge of refrigerant, wherein the condenser coil
is in the form of a heat exchanger element according to claim 5.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a heat exchanger element
and a water heater and a heat pump utilising same.
[0002] The invention has been primarily developed for use in
domestic hot water heaters and will be described hereinafter with
reference to this application. However, the invention is not
limited to this particular use and is also suitable for heating
fluid other than water in numerous heat exchanger applications.
BACKGROUND OF THE INVENTION
[0003] Regulatory authorities in many jurisdictions, including
Australia, Europe and the United States of America, require heat
exchanger elements used in domestic hot water heaters to have two
layers of metal separating the heated fluids circulating through
the heat exchanger and the water being heated in the hot water
tank. This is to ensure that even if one of the layers is
compromised, there will be no mixing between the heat exchanger
fluid and the water supplied to user.
[0004] One known `double walled` hot water heater utilises a copper
tube wrapped around the outside of a cylindrical steel water tank.
Heat exchanger fluid is pumped through the copper tube. However,
this arrangement is difficult and thus relatively expensive to
produce, particularly the step of rolling the tube around the
approximately 600 mm diameter tank. This arrangement also has
relatively poor heat exchanging efficiency, as steel is almost 30
times less effective as a conductor than copper.
[0005] Another known `double walled` hot water heater utilises a
coil of copper tube positioned inside a tube within a water tank.
This arrangement is also difficult and thus relatively expensive to
produce. It is difficult to ensure the copper tube makes good
surface to surface contact with the tube interior, which is
required for good heat exchanging efficiency.
OBJECT OF THE INVENTION
[0006] It is the object of the present invention to overcome or
substantially ameliorate at least one or more of the above prior
art deficiencies.
SUMMARY OF THE INVENTION
[0007] Accordingly, in a first aspect, the present invention
provides a heat exchanger element formed from an inner copper tube
and an outer copper tube, wherein the entire outer surface of the
inner tube is substantially in contact with the entire inner
surface of the outer tube.
[0008] In one form, the inner diameter of the outer tube is
substantially equal to the outer diameter of the inner tube, such
that approximately 100% of the inner surface of the outer tube is
in contact with the outer surface of the inner tube.
[0009] In another form, the inner surface of the outer tube
includes rifling or grooves having a minimum diameter substantially
equal to the outer diameter of the inner tube, such that
approximately 80% of the inner surface of the outer tube is in
contact with the outer surface of the inner tube.
[0010] In an embodiment, the element is preferably substantially
cylindrical in shape, and most preferably with cylindrical walls
formed from spiralled inner and outer tubes.
[0011] In another embodiment, the element is preferably
substantially cylindrical in shape, with cylindrical walls formed
from spiralled inner and outer tubes, and includes an outer
cylindrical wall attached to the exterior of the spiralled outer
tubes.
[0012] In yet another embodiment, the element is preferably
substantially cylindrical in shape, with cylindrical walls formed
from spiralled inner and outer tubes, and includes an inner
cylindrical wall attached to the interior of the spiralled outer
tubes.
[0013] In yet another embodiment, the element is preferably
substantially cylindrical in shape, with cylindrical walls formed
from spiralled inner and outer tubes, and includes inner and outer
cylindrical walls respectively attached to the interior and
exterior of the spiralled outer tubes.
[0014] The element preferably has two substantially longitudinal
inlet and outlet portions, one extending from a first end of the
cylinder and the other extending from the second end of the
cylinder through the cylinder interior to the first end of the
cylinder.
[0015] In a second aspect, the present invention provides a water
heater including a tank and a heat exchanger element according to
the first aspect.
[0016] In a third aspect, the present invention provides a method
of forming a heat exchanger element, the method comprising the
following steps: [0017] a. drawing a first and a second copper
tube, the first tube having an outer diameter less than the
internal diameter of the second tube; [0018] b. inserting the first
tube into the second tube; [0019] c. passing the tubes through a
roll former adapted to crush the second tube onto the first tube,
such that the entire outer surface of the first tube is
substantially in contact with the entire inner surface of the
second tube. [0020] d. annealing the crushed tubes; [0021] e.
bending the tubes into a desired configuration; and [0022] f.
annealing the bent tubes.
[0023] Step e. preferably includes bending the tubes into a
generally cylindrical shape, most preferably with the cylindrical
walls being formed from spiralled tubes.
[0024] Step a. preferably includes drawing the second tube with
internal rifling or grooves.
[0025] In a fourth aspect, the present invention provides a hot
water heat pump comprising: [0026] a heat pump circuit comprising
an evaporator coil; a compressor, a condenser coil in a heat
exchanging relationship with a body of water, and a thermostatic
expansion valve (TX valve), the circuit adapted to hold a charge of
refrigerant, [0027] wherein the condenser coil is in the form of a
heat exchanger element according to the first aspect.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Preferred embodiments of the present invention will now be
described, by way of examples only, with reference to the
accompanying drawings, wherein:
[0029] FIG. 1A is a schematic cross-sectional side view of a first
embodiment of a water heater according to the invention, the water
heater having a first embodiment of a heat exchanger element
according to the invention;
[0030] FIG. 1B is a cross-sectional end view of the heat exchanger
element shown in FIG. 1A;
[0031] FIG. 2 is a schematic cross-sectional side view of a second
embodiment of a water heater according to the invention
[0032] FIG. 3 is a schematic cross-sectional side view of a third
embodiment of a water heater according to the invention;
[0033] FIG. 4 is a schematic cross-sectional side view, of a fourth
embodiment of a water heater according to the invention;
[0034] FIG. 5 is a cross-sectional end view of a second embodiment
of a heat exchanger element according to the invention; and
[0035] FIG. 6 is a schematic view of an embodiment of a hot water
heat pump according to the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0036] FIG. 1A shows a first embodiment of a domestic hot water
heater 10 according to the present invention. The water heater 10
includes a 250 litre volume, insulated steel cylindrical tank 12
with upper and lower domed ends 14 and 16 respectively. The tank 12
is mounted with its longitudinal axis substantially vertical. The
upper domed end 14 has a central necked opening 18 with an external
flange 20. In use, the tank 12 is almost completely filled with
water.
[0037] The tank 12 also has a first hot water outlet 22 within the
upper domed end 14 and a first cold water inlet 24 in the lower
domed end 16. The outlet 22 is, in operation, connected to
household plumbing. The inlet 24 is, in operation, connected to
mains water supply. The tank 12 also has a second hot water outlet
26 and a second cold water inlet 20 which, for example, can be used
to connect to the tank 12 in parallel to a solar hot water
heater.
[0038] A first embodiment of a heat exchanger element 30 is
inserted into the tank interior through the opening 18. As best
shown FIG. 1B, the element 30 is formed from inner and outer copper
tubes 32 and 34 respectively. The outer diameter of the inner tube
32 is substantially equal to the inner diameter of the outer tube
34, such that the entire outer surface of the inner tube 32 is
substantially in contact with the entire surface of the outer tube
34. The inner and outer surfaces being in substantial contact
maximises the transfer of heat from hot refrigerant fluid (e.g.
water or glycol or a mixture thereof) 36 pumped through the
interior of the inner tube 32 to the water in the tank 12. The heat
exchanger element 30 also has an inlet portion 38 and an outlet
portion 40. The circulation of the water in the tank 12 caused by
the energised heating element 30 is indicated by the arrows. One
advantage of the water heater 10 is it relatively inexpensive and
simple to manufacture due to the introduction of the element 30
into the tank 12 via the opening 18. Another advantage is
relatively high efficiency due to the direct refrigerant fluid to
water heat transfer via the copper tubes 32 and 34, which have
relatively high conductivity.
[0039] The construction of the heating element 30 involves the
following steps. Firstly, two copper tubes are drawn to
approximately 19 metres in length. The smaller diameter tube 32 has
an internal diameter of 5.0 mm and an external diameter of 5.5 mm.
The large diameter outer tube 34 has an internal diameter of 5.7 mm
and an external diameter of 6.3 mm. The difference between the
outer diameter of the inner tube 32 and the inner diameter of the
outer tube 34 allows the inner tube 32 to be inserted within the
outer tube 34. At this stage, there is a small gap between the
outer surface of the inner tube 32 and the inner surface of the
outer tube 34. The two tubes 42 and 34 are then fed through a roll
former which crushes the outer tube 34 into contact with the inner
tube 32 to eliminate the gap. The roll forming also slightly
extends the length of the outer tube 34 and, if desired, it can
initially be made slightly shorter than the inner tube 32 so that
it expands to a common length. Alternatively, the excess of the
outer tube 34 can be trimmed. The roll forming also hardens the
tubes 32 and 34. The (roll formed/crushed) tubes 32 and 34 are then
annealed for softening, so they can then be bent and spiral wound
into the shape shown in FIG. 1. The (bent/spiralled) tubes 32 and
34 are then annealed again. Finally, appropriate connection
fittings (e.g. brass) and then attached to the inlet portion 38 and
outlet portion 40.
[0040] FIG. 2 shows a second embodiment of a water heater 210. Like
features to those used to describe the first embodiment are
indicated using like reference numerals. The water heater 210 is
very similar in construction and operation to the water heater 10
shown in FIG. 1, except the heating element 30 is enclosed by an
external cylinder or tube 42 which serves to increase the
conduction area of the heat exchanger element 30 and thus increase
the heat transfer from heated fluid 36 to the water in the tank
12.
[0041] FIG. 3 shows a third embodiment of a water heater 310. Like
features to those used to describe earlier embodiments are
indicated using like reference numerals. The water heater 310 is
also very similar in construction and operation to the water heater
10 shown in FIG. 1, except the heat exchanger element 30 has an
internal cylinder or tube 44 to increase its conduction area.
[0042] FIG. 4 shows a fourth embodiment of a water heater 410. Like
features to those used to describe earlier embodiments are
indicated using like reference numerals. The water heater 410 is
also very similar in construction and operation to the water heater
10 shown in FIG. 1, except the heater exchanger element 30 has
external and internal tubes 42 and 44 respectively, to increase its
conduction area.
[0043] FIG. 5 shows a second embodiment of a heat exchanger element
130 formed from inner and outer copper tubes 132 and 134
respectively. The element 130 is constructed in a similar manner as
that described previously in relation to the element 30, except the
inner surface of the outer tube 134 is initially provided with
internal rifling or grooves 136. After roll forming, only
approximately 80% of the inner surface of the outer tube 134 is in
contact with the outer surface of the inner tube 132 due to the
gaps left by the rifling/grooves 136. This slightly reduces the
conductivity/heat exchanging efficiency of the element 130.
However, the air gaps are required to meet safety regulations in
some jurisdictions.
[0044] FIG. 6 shows an embodiment of a hot water heat pump 140
according to the invention. The heat pump 140 has a heat pump
circuit comprising an evaporator coil 142, a compressor 144, a
condenser coil 146, and a thermostatic expansion valve (TX valve)
148. The circuit is configured with an outlet of the compressor 144
connected to an inlet of the condenser coil 146, an outlet of the
condenser coil 146 connected to an inlet of the TX valve 148, an
outlet of the TX valve 148 connected to an inlet of the evaporator
coil 142 and an outlet of the evaporator coil 142 connected to an
inlet of the compressor 144. The circuit is adapted to hold a
charge of refrigerant. The components of the heat pump 140 operate
to produce a refrigeration cycle, as is well known to persons
skilled in the art. The condenser coil 146 is positioned in a heat
exchanging relationship with a body of water contained by a tank
150. The condenser coil 146 is in the form of a double walled heat
exchanger element as previously described with reference to FIGS. 1
to 5.
[0045] The advantage of the double walled heat exchanger element as
the condenser coil 146 in the heat pump application is it provides
the most direct, and thus efficient, transfer path of energy by
conduction into the water. More particularly, as the condenser coil
146 is suspended in the water, there is no air gap around it. This
results in a minimum coefficient of heat transfer from the
refrigerant to the water.
[0046] This is in contrast to existing refrigerant systems which
use copper piping systems to contain the refrigerant, such as
existing heat pump configurations in which the copper pipe is wound
on an external face of the water tank.
[0047] Further, the double walled construction of the condenser
coil 146 provides a safety feature (being an internal refrigerant
escape path between the inner and the outer tubes) that is only
actuated when there is a failure in the inner tube. This safety
feature is only possible due to the nature of the manufacturing
process and the suspension of the condenser coil in water contained
within a tank at a lower pressure than the refrigerant in the
condenser coil.
[0048] Normal "tube in tube" designs have this safety feature
permanently in place in the form of an air gap between the tubes,
which results in poor heat transfer.
[0049] Although the invention has been described with reference to
preferred embodiments, it would be appreciated by those persons
skilled in the art that the invention may be embodied in many other
forms.
* * * * *