U.S. patent application number 11/914695 was filed with the patent office on 2008-09-04 for heat pump system and method for heating a fluid.
Invention is credited to Ying You.
Application Number | 20080210768 11/914695 |
Document ID | / |
Family ID | 37424908 |
Filed Date | 2008-09-04 |
United States Patent
Application |
20080210768 |
Kind Code |
A1 |
You; Ying |
September 4, 2008 |
Heat Pump System and Method For Heating a Fluid
Abstract
This invention relates to a heat pump system and in particular
to a heat pump system and method for heating a fluid. According to
one aspect of the invention, there is provided a heat pump system
for heating a fluid, said system including: an evaporator for
extracting heat from a heat source to vaporise a refrigerant; a
compressor fluidly connected to said evaporator for compressing
said refrigerant vapour; a condenser fluidly connected to said
compressor for transferring heat from said compressed refrigerant
to said fluid; a main expansion device fluidly connecting said
condenser to said evaporator for reducing the temperature of the
refrigerant; means for diverting and reducing the temperature of a
portion of said refrigerant from said condenser, and means for
fluidly injecting said temperature reduced refrigerant portion into
said compressor such that said temperature reduced refrigerant
portion mixes with said refrigerant vapour at an intermediate
pressure and induces at least quasi-two-stage compression of said
refrigerant vapour and said refrigerant portion for discharge into
said condenser. According to another aspect of the invention, there
is provided a method for heating a fluid, said method including the
steps of: extracting heat from a heat source to vaporise a
refrigerant; compressing said refrigerant vapour to increase its
temperature; transferring heat from said compressed refrigerant
vapour to said fluid; diverting and reducing the temperature of a
portion of said refrigerant after said transferring step; reducing
the temperature of said refrigerant; introducing said temperature
reduced refrigerant portion during said compressing step such that
said temperature reduced refrigerant portion mixes with said
refrigerant vapour at an intermediate pressure and induces at least
quasi-two-stage compression of said refrigerant vapour and said
refrigerant portion, and discharging said compressed refrigerant to
transfer heat to said fluid in said transferring step.
Inventors: |
You; Ying; (New South Wales,
AU) |
Correspondence
Address: |
HARRITY SNYDER, LLP
11350 Random Hills Road, SUITE 600
FAIRFAX
VA
22030
US
|
Family ID: |
37424908 |
Appl. No.: |
11/914695 |
Filed: |
May 18, 2006 |
PCT Filed: |
May 18, 2006 |
PCT NO: |
PCT/AU2006/000663 |
371 Date: |
November 16, 2007 |
Current U.S.
Class: |
237/2B ;
62/160 |
Current CPC
Class: |
F24H 4/02 20130101; F25B
2339/047 20130101; F25B 2400/052 20130101; F25B 2400/0403 20130101;
F25B 2400/13 20130101; F25B 1/10 20130101; F25B 2600/2509 20130101;
F25B 30/02 20130101 |
Class at
Publication: |
237/2.B ;
62/160 |
International
Class: |
F24H 4/02 20060101
F24H004/02 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2005 |
AU |
2005902571 |
Claims
1. A heat pump system for heating a fluid, said system including:
an evaporator for extracting heat from a heat source to vaporise a
refrigerant; a compressor fluidly connected to said evaporator for
compressing said refrigerant vapour; a condenser fluidly connected
to said compressor for transferring heat from said compressed
refrigerant to said fluid; a main expansion device fluidly
connecting said condenser to said evaporator for reducing the
temperature of the refrigerant; means for diverting and reducing
the temperature of a portion of said refrigerant from said
condenser, and means for fluidly injecting said temperature reduced
refrigerant portion into said compressor such that said temperature
reduced refrigerant portion mixes with said refrigerant vapour at
an intermediate pressure and induces at least quasi-two-stage
compression of said refrigerant vapour and said refrigerant portion
for discharge into said condenser.
2. The heat pump system of claim 1 wherein the diverting and
temperature reducing means includes an expansion device fluidly
connected to the condenser and the compressor.
3. The heat pump system of claim 2 wherein the expansion device
includes a capillary tube.
4. The heat pump system of claim 2 wherein the expansion device
includes an expansion valve.
5. The heat pump system of claim 2 wherein the expansion device
includes a heat exchanger, such as an intercooler.
6. The heat pump system of claim 2 wherein the diverting and
temperature reducing means includes a bypass passage fluidly
connecting the condenser and the expansion device.
7. The heat pump system of claim 2 wherein the fluid injecting
means includes a fluid injection valve for controlling the flow of
the refrigerant portion into the expansion device.
8. The heat pump system of claim 1 wherein the compressor includes
a fluid injection port connected to the fluid injection means.
9. The heat pump system of claim 8 wherein the fluid injection
means includes a check valve connected to the fluid injection
port.
10. The heat pump system of claim 1 wherein the main expansion
device is fluidly connected to the condenser by a first pipe.
11. The heat pump system of claim 10 wherein the capillary tube is
in close proximity with the first pipe to cool the refrigerant
passing through the first pipe to the main expansion device.
12. The heat pump system of claim 11 wherein the capillary tube is
helically wound around the first pipe.
13. The heat pump system of claim 1 wherein the temperature
reducing means includes an expansion device and an intercooler,
said intercooler fluidly connected to the condenser and the main
expansion device such that refrigerant passes through the
intercooler to the main expansion device and exchanges heat with
the refrigerant portion passing through the intercooler.
14. A method for heating a fluid, said method including: extracting
heat from a heat source to vaporise a refrigerant; compressing said
refrigerant vapour to increase its temperature; transferring heat
from said compressed refrigerant vapour to said fluid; diverting
and reducing the temperature of a portion of said refrigerant after
said transferring; reducing the temperature of said refrigerant;
introducing said temperature reduced refrigerant portion during
said compressing such that said temperature reduced refrigerant
portion mixes with said refrigerant vapour at an intermediate
pressure and induces at least quasi-two-stage compression of said
refrigerant vapour and said refrigerant portion, and discharging
said compressed refrigerant to transfer heat to said fluid in said
transferring.
15. The heat pump system of claim 14 wherein said method includes
the step of returning said refrigerant from said temperature
reducing step to said vaporising step.
16. The heat pump system of claim 14 wherein fluid to be heated is
water.
17. The method of claim 14 wherein the heat source is ambient air.
Description
FIELD OF THE INVENTION
[0001] This present invention relates to a heat pump system and in
particular to a heat pump system and method for heating a
fluid.
[0002] The invention has been developed primarily for use as a heat
pump system and a method for water heating in a cold environment or
an environment with large variations in ambient temperature and
will be described hereinafter with reference to this application.
However, it will be appreciated that the invention is not limited
to this particular field of use.
BACKGROUND OF THE INVENTION
[0003] Any discussion of the prior art throughout the specification
should in no way be considered as an admission that such prior art
is widely known or forms part of the common general knowledge in
the field.
[0004] Sanitary water needs to be heated to a temperature at or
above 60.degree. C. Quite often the water for building heating also
needs to be heated to this temperature. An air sourced heat pump
system has been used for this type of water heating and
conventionally uses an air conditioning compressor. However, owing
to the narrow operational temperature range of the air conditioning
compressor, the conventional heat pump system cannot work in
environments with a wide ambient temperature range, such as an
environment where it is very hot in summer but very cold in winter.
Similarly, the conventional system cannot work where there is a
relatively large temperature difference between the water and the
heat source. For example, where the ambient temperature is
constantly low, such as a cold environment.
[0005] An approach to overcome this problem is to use a two-stage
compression system, a multi-stage compression system, or a cascade
system. However, such systems require two or more compressors,
making the heat pump system complicated, expensive, and difficult
to make suitable for large variations in ambient temperatures. The
compression system also becomes unnecessary when the ambient
temperature is warm.
[0006] In cold environments, fossil fuel burning boilers are
frequently used to heat water with high running costs and adverse
effects on the environment.
OBJECTS OF THE INVENTION
[0007] It is an object of the present invention to overcome or
ameliorate at least one of the disadvantages of the prior art, or
to provide a useful alternative.
[0008] It is an object of the invention in its preferred form to
provide a heat pump system with a compressor which can perform
quasi-two-stage compression to allow operation in cold environments
or environments with large variations in ambient temperature and
which is simple and inexpensive.
SUMMARY OF THE INVENTION
[0009] According to one aspect of the invention, there is provided
a heat pump system for heating a fluid, said system including:
[0010] an evaporator for extracting heat from a heat source to
vaporise a refrigerant;
[0011] a compressor fluidly connected to said evaporator for
compressing said refrigerant vapour;
[0012] a condenser fluidly connected to said compressor for
transferring heat from said compressed refrigerant to said
fluid;
[0013] a main expansion device fluidly connecting said condenser to
said evaporator for reducing the temperature of the
refrigerant;
[0014] means for diverting and reducing the temperature of a
portion of said refrigerant from said condenser, and
[0015] means for fluidly injecting said temperature reduced
refrigerant portion into said compressor such that said temperature
reduced refrigerant portion mixes with said refrigerant vapour at
an intermediate pressure and induces at least quasi-two-stage
compression of said refrigerant vapour and said refrigerant portion
for discharge into said condenser.
[0016] According to another aspect of the invention, there is
provided a method for heating a fluid, said method including the
steps of:
[0017] extracting heat from a heat source to vaporise a
refrigerant;
[0018] compressing said refrigerant vapour to increase its
temperature;
[0019] transferring heat from said compressed refrigerant vapour to
said fluid;
[0020] diverting and reducing the temperature of a portion of said
refrigerant after said transferring step;
[0021] reducing the temperature of said refrigerant;
[0022] introducing said temperature reduced refrigerant portion
during said compressing step such that said temperature reduced
refrigerant portion mixes with said refrigerant vapour at an
intermediate pressure and induces at least quasi-two-stage
compression of said refrigerant vapour and said refrigerant
portion, and
[0023] discharging said compressed refrigerant to transfer heat to
said fluid in said transferring step.
[0024] Preferably, the diverting and temperature reducing means
includes an expansion device fluidly connected to the condenser and
the compressor. The expansion device preferably includes a
capillary tube or an expansion valve. The expansion device may
further include a heat exchanger, such as an intercooler.
[0025] It is preferred that the diverting and temperature reducing
means includes a bypass passage fluidly connecting the condenser
and the expansion device.
[0026] The fluid injecting means preferably includes a fluid
injection valve for controlling the flow of the refrigerant portion
into the expansion device. The compressor preferably includes a
fluid injection port connected to the fluid injection means. It is
preferred that the fluid injection means includes a check valve
connected to the fluid injection port.
[0027] The method preferably includes the step of returning said
refrigerant from said temperature reducing step to said vaporising
step.
[0028] The main expansion device is preferably fluidly connected to
the condenser by a first pipe. The first pipe is preferably
connected to the bypass passage. The main expansion device may be
an expansion valve.
[0029] The capillary tube is preferably in close proximity with the
first pipe to cool the refrigerant passing through the first pipe
to the main expansion device. In one preferred form, the capillary
tube is helically wound around the first pipe. A downstream end of
the capillary tube may be connected to a section of pipe. The pipe
section is preferably in contact with the first pipe to transfer
heat between the first pipe and the pipe section. The pipe section
may lie substantially parallel to the first pipe and may be fixed
to the first pipe by metal clamps or other suitable fastening
means. Heat transfer paste is preferably interposed between the
pipe section and the first pipe to facilitate heat transfer. The
pipe section is also preferably deformed to conform to the first
pipe.
[0030] Where the temperature reducing means includes an expansion
device and an intercooler, it is preferred that the intercooler is
fluidly connected to the condenser and the main expansion device so
that refrigerant passes through the intercooler to the main
expansion device and exchanges heat with the refrigerant portion
passing through the intercooler.
[0031] The fluid that is to be heated is preferably water. The heat
source may be ambient air.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] A preferred embodiment of the invention will now be
described, by way of example only, with reference to the
accompanying drawing, in which:
[0033] FIG. 1 is a schematic diagram of a heat pump system for
heating water according to the invention; and
[0034] FIG. 2 is a schematic diagram of another embodiment of the
invention.
PREFERRED EMBODIMENT OF THE INVENTION
[0035] Referring to FIG. 1, the heat pump system for heating water
includes an evaporator 1 for vaporising a refrigerant by
transferring heat from an ambient heat source 3, a compressor 4
fluidly connected to the evaporator 1 for compressing the
refrigerant vapour and a condenser 5 fluidly connected to the
compressor 4 for transferring heat from the compressed refrigerant
to the water 6. The heat source 3 is the ambient air of a cold
environment and the compressor 4 is a conventional compressor for
low temperature refrigeration with a liquid injection port 7.
[0036] An expansion device 8 in the form of a capillary tube is
fluidly connected to the condenser 5 and the compressor 4 to divert
a small portion of the condensed refrigerant and reduce its
temperature. A fluid injection means 9 fluidly injects the
temperature reduced refrigerant portion into the compressor 4 from
the capillary tube 8. The temperature reduced refrigerant portion
mixes with the refrigerant vapour that has been compressed to an
intermediate pressure in the compressor 4 and induces at least
quasi-two-stage compression. The combined refrigerant (the
refrigerant vapour and the refrigerant portion) is then further
compressed and discharged into the condenser 5.
[0037] A main expansion valve 10 is fluidly connected to the
condenser 5 by a pipe 11 and to the evaporator 1. A bypass passage
12 diverts the refrigerant portion from the pipe 11 to the
capillary tube 8.
[0038] The fluid injection means 9 includes a fluid injection
solenoid valve 13 for turning liquid injection of the refrigerant
portion on and off, and a pipe section 15 for delivering the
temperature reduced refrigerant portion through a check valve 17 to
the injection port 7 at the compressor 4. The check valve 17
ensures that only the temperature reduced refrigerant portion
enters the compressor 4 and prevents any backflow of refrigerant
from the compressor 4 through pipe section 15 to the capillary tube
8 and the fluid injection solenoid valve 13.
[0039] The capillary tube 8 is helically wound around the pipe 11
to cool down the refrigerant passing through the pipe 11 as it
flows towards the main expansion valve 10. The pipe section 15 is
also fixed to a portion 21 of the pipe 11 by metal clamps and lies
substantial parallel to and in contact with the pipe portion 21 to
facilitate heat transfer between the pipe section 15 and the pipe
portion 21. Heat transfer paste is also applied between the pipe
section 15 and the pipe portion 21. The pipe section 15 can be
deformed to conform to the pipe portion 21 to improve heat
transfer.
[0040] Other elements of the heat pump system include a liquid
solenoid valve 23 for turning the flow of condensed refrigerant on
and off and a filter/drier 25 located between the condenser 5 and
the capillary tube 8. A sight glass 27 is provided on the pipe 11
for observing the refrigerant prior to entering the main expansion
valve 10. A de-ice solenoid valve 29 is also provided in a
subsidiary line 31.
[0041] The operation of the heat pump system will now be described.
Refrigerant in the evaporator 1 is vaporised using heat extracted
from the ambient air 3. The compressor 4 draws the refrigerant
vapour from the evaporator 1 and compresses it from a low pressure,
low temperature vapour state to a high pressure, high temperature
vapour state. The high pressure, high temperature refrigerant
vapour is then exhausted to the condenser 5, which acts as a heat
exchanger to pass heat from the refrigerant vapour to the water 6.
As a result of this process, the refrigerant is condensed into a
liquid and subcooled.
[0042] The liquid refrigerant then passes through the liquid
solenoid valve 23 and filter/drier 25 to remove moisture and
contaminants from the refrigerant. After passing through the
filter/drier 25, the majority of the liquid refrigerant flows
through the pipe 11 to the main expansion valve 10. The liquid
refrigerant expands through the main expansion valve 10, causing
its pressure and temperature to drop. The temperature of the
refrigerant is now below the temperature of the ambient air 3. The
refrigerant then enters the evaporator 1 where heat is again
transferred from the ambient air 3 to the refrigerant. The
vaporised refrigerant is subsequently drawn into the compressor 4
and the cycle repeats.
[0043] While most of the liquid refrigerant enters the main
expansion valve 10, a small portion of the liquid refrigerant
(which may be about 10% of the total refrigerant) enters the bypass
passage 12 from the pipe 11 and passes through the liquid injection
solenoid valve 13 to capillary tube 8. The capillary tube 8 expands
the refrigerant portion, causing its pressure and temperature to
drop. The temperature reduced refrigerant portion then passes
through the pipe section 15 and the check valve 17 to the injection
port 7. The refrigerant portion in liquid/vapour form is then
injected to the compressor 4 to mix with, and cool down, the
superheated refrigerant vapour in the compressor 4 after
quasi-first-stage compression (that is, the refrigerant portion is
injected into the compressor after the refrigerant vapour has been
compressed to an intermediate pressure). As a result, quasi-second
stage compression takes place and the combined refrigerant vapour
and refrigerant portion is compressed to a final pressure. The
compressed refrigerant is then discharged into condenser 5.
[0044] Since the refrigerant in the compressor 4 has undergone at
least quasi-first-stage compression, introducing the temperature
reduced refrigeration portion into the compressor 4 to mix with the
superheated refrigerant reduces the temperature of the refrigerant
prior to the next stage of compression and thus reduces the
temperature in the compressor for subsequent compressions. This
results in the pressure ratio for each stage of compression being
reduced to the desired level for quasi-two-stage compression, and
thus improves the efficiencies for each compression.
Quasi-two-stage compression, combined with intercooling in the
compressor due to fluid injection of the refrigerant portion, also
reduces the power drawn by the heat pump system (compared to
single-stage compression). The fluid injection valve 13 and the
check valve 17 controls the timing and direction of the temperature
reduced refrigerant portion that is injected into the compressor 4.
Thus, at least quasi-two-stage compression can be controllably
achieved by a single compressor. Consequently, there is a
significant increase in the difference between the condensing
temperature and the evaporating temperature, increasing the
operating ambient temperature range of the heat pump system.
[0045] In its preferred form, the expansion device 8 is a capillary
tube to simplify the heat pump system. The capillary tube 8 also
permits the temperature reduced refrigerant portion to be used
simply after expansion to absorb heat from the liquid refrigerant
in the pipe 11 before it enters the main expansion valve 10. As
described above, the capillary tube 8 is helically wound around the
pipe 11 and the pipe section 15 located substantially parallel to
and in contact with the pipe 11. In this way, additional subcooling
of the refrigerant in the pipe 11 takes place, which reduces the
risk of the liquid refrigerant flashing prior to entry into the
main expansion valve 10.
[0046] While an approximate amount of 10% of the total refrigerant
is diverted to the capillary tube 8 in the embodiment, the amount
of the refrigerant portion that is diverted depends on the
temperature of the ambient heat source and the water temperature
that is required.
[0047] While the above description represents a preferred
configuration of the invention, it will be appreciated that
components of the system can be varied in other embodiments.
[0048] A second embodiment is illustrated in FIG. 2, where
corresponding features have been given the same reference numerals.
In the second embodiment, the expansion device 8 is an expansion
valve 33 with an intercooler 35. The intercooler 35 is fluidly
connected to the condenser 5 and the main expansion valve 10. The
bypass passage 12 is located downstream of the intercooler 35.
Liquid refrigerant from the condenser 5 enters the intercooler 35.
The intercooler 35 initially cools down the liquid refrigerant
before the refrigerant portion is extracted via the bypass passage
12 to the liquid injection valve 13. The refrigerant portion passes
through expansion valve 33 to further reduce its temperature and
pressure. The temperature reduced refrigerant portion is then
returned to the intercooler 35 to exchange heat with the liquid
refrigerant from the condenser 5 passing through the intercooler 35
before being delivered to the compressor 4. As in the first
embodiment, the refrigerant portion mixes with the refrigerant
vapour in the compressor to induce at least quasi-two-stage
compression. The liquid refrigerant portion is extracted after the
intercooler 35 so that the probability of flashing of the
refrigerant in both the expansion valve 33 and the main expansion
valve 9 will be reduced.
[0049] In other embodiments, multi-stage compression can be induced
if required by injecting additional temperature reduced refrigerant
portion(s) after quasi-second stage compression.
[0050] The compressor may be a refrigeration compressor with one or
more liquid injection ports built in, or any compressor modified to
be equipped with liquid injection port(s).
[0051] The description of the heat pump system has been simplified
to assist understanding of the invention. It will be appreciated
that there are other parts and control and safety mechanisms in the
heat pump system which have been omitted from the description but
do not affect the basic operation of the system in its preferred
form.
[0052] The invention in its preferred form as described above
provides an energy efficient and practical system of water heating,
particularly for an air sourced heat pump system delivering heat
from a cold temperature environment. The invention in its preferred
form replaces current fossil fuel burning boilers, thereby reducing
any adverse impact on the environment.
[0053] Although the invention has been described with reference to
a specific example it will be appreciated by those skilled in the
art that the invention may be embodied in many other forms.
* * * * *