U.S. patent application number 11/801188 was filed with the patent office on 2008-12-11 for refrigeration system for transcritical operation with economizer and low-pressure receiver.
Invention is credited to Dieter Mosemann, Dmytro Zaytsev.
Application Number | 20080302129 11/801188 |
Document ID | / |
Family ID | 38529098 |
Filed Date | 2008-12-11 |
United States Patent
Application |
20080302129 |
Kind Code |
A1 |
Mosemann; Dieter ; et
al. |
December 11, 2008 |
Refrigeration system for transcritical operation with economizer
and low-pressure receiver
Abstract
A refrigeration apparatus for transcritical operation includes a
gas cooler, an aftercooler, an evaporator with a low-pressure
liquid separator, a compressor, a first controllable throttling
device and interconnecting piping between the mentioned components
and in addition a second controllable throttling device and an
intercooler that comprises two flow paths separated by heat
exchanging surfaces. A first flow path inlet of the intercooler is
connected to the gas cooler outlet. A first flow path outlet of the
intercooler is connected to the aftercooler inlet. A second flow
path inlet of the intercooler is connected to the outlet of the
second throttling device. A second flow path outlet of the
intercooler is connected to the economizer port of the compressor.
The second throttling device inlet is connected to the piping
either upstream or downstream of the aftercooler. The second
throttling device outlet is connected to the second flow path inlet
of the intercooler.
Inventors: |
Mosemann; Dieter; (Schildow,
DE) ; Zaytsev; Dmytro; (Berlin, DE) |
Correspondence
Address: |
Horst M. Kasper
13 Forest Drive
Warren
NJ
07059
US
|
Family ID: |
38529098 |
Appl. No.: |
11/801188 |
Filed: |
May 9, 2007 |
Current U.S.
Class: |
62/498 ;
418/201.1 |
Current CPC
Class: |
F25B 1/04 20130101; F25B
1/10 20130101; F25B 43/006 20130101; F25B 2309/061 20130101; F25B
9/008 20130101; F25B 2400/13 20130101; F25B 2400/23 20130101; F25B
40/02 20130101 |
Class at
Publication: |
62/498 ;
418/201.1 |
International
Class: |
F25B 1/00 20060101
F25B001/00; F04C 18/08 20060101 F04C018/08 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 1, 2006 |
DE |
DE102006035784.1 |
Claims
1. A refrigeration apparatus for transcritical operation comprising
a screw compressor featuring inlet and outlet ports geometrically
controlled by rotation of male and female rotors operating at least
on three pressure levels: suction pressure on the compressor
suction side, intermediate pressure at the economizer port and
discharge pressure at the compressor discharge side, a gas cooler,
a low-pressure liquid separator, an aftercooler communicating with
said low-pressure liquid separator, a first controllable throttling
device and an evaporator, wherein there is a second controllable
throttling device and an intercooler that comprises a first and a
second flow path separated by heat-exchanging surfaces.
2. A refrigeration apparatus according to claim 1 wherein a first
flow path inlet of said intercooler is connected to the gas cooler
outlet, a first flow path outlet of said intercooler is connected
to the aftercooler inlet, a second flow pass inlet of said
intercooler is connected to the outlet of said second controllable
throttling device and a second flow pass outlet of said intercooler
is connected to the economizer port of the compressor.
3. A refrigeration apparatus according to claim 1 wherein the inlet
of said second controllable throttling device is connected to the
piping either upstream or downstream of the aftercooler and the
outlet of said second controllable throttling device is connected
to said second flow pass inlet of said intercooler.
Description
[0001] This invention relates to a refrigeration apparatus for
transcritical operation with screw compressors featuring
geometrically controlled inlet and outlet ports operating at least
on three pressure levels. The pressure levels comprise the suction
pressure prevailing on the compressor suction side and being close
to the pressure in the evaporator, the intermediate pressure
prevailing at the economizer port, and the discharge pressure
acting on the compressor discharge side and being close to the
pressure in a gas cooler. The pertinent sides of the compressor are
also designated as low-pressure side, intake side or suction side,
and as high-pressure side or discharge side respectively. The
pressure on the high-pressure side is higher than the pressure at
the critical point of the refrigerant. Therefore, this process is
designated as transcritical or overcritical refrigeration process.
The economizer port is arranged between suction- and discharge side
of the compressor. At the economizer port, the inlet process to the
working cavity starts when there is no more flow connection of this
working cavity to the compressor suction side. In this phase, the
geometric volume of the working cavity considered has reached its
maximum. Depending on the wrap angle of the rotor profile of the
male rotor, number of lobes of both rotors, the geometric volume of
the working cavity considered can be constant (transfer phase) or
can decrease due to rotation of rotors.
[0002] The invention relates to a refrigeration apparatus featuring
a heat exchanger, a so-called aftercooler, arranged in or at the
low-pressure liquid separator and communicating with the liquid
separator, and in this aftercooler the refrigerant--the working
fluid--being under discharge pressure is subcooled prior to its
expansion nearly to evaporation temperature, thus changing from the
vaporous phase to the liquid phase, before it is expanded into the
evaporators at the throttling device of the refrigeration
apparatus.
[0003] The pressure upstream of this throttling device is kept
constant by opening or closing it more or less respectively
enabling the compressor to operate at constant discharge pressure.
The refrigerating capacity of the refrigeration apparatus changes
depending on the temperature to which the refrigerant was cooled
down in the gas cooler. It will be reduced as a result of higher
outlet temperatures at the gas cooler, because at higher gas cooler
outlet temperatures more working fluid will evaporate in the
low-pressure liquid separator for cooling-down the working fluid in
the aftercooler prior to expansion than at lower gas cooler outlet
temperatures. Therefore, the efficiency of the refrigeration
apparatus will decrease with increasing temperature at the gas
cooler.
[0004] The object of the invention is to improve the process and to
increase the efficiency of the refrigeration apparatus.
[0005] According to the invention the refrigeration apparatus for
transcritical operation comprises in addition to the components gas
cooler, aftercooler, evaporator with low-pressure liquid separator,
compressor, first controllable throttling device and
interconnecting piping between the mentioned components a second
controllable throttling device and an intercooler that comprises
two flow paths separated by heat-exchanging surfaces, wherein a
first flow path inlet of the intercooler is connected to the gas
cooler outlet, a first flow path outlet of the intercooler is
connected to the aftercooler inlet, a second flow pass inlet of the
intercooler is connected to the outlet of the second throttling
device and a second flow pass outlet of the intercooler is
connected to the economizer port of the compressor, and the second
throttling device inlet is connected to the piping either upstream
or downstream of the aftercooler and the second throttling device
outlet is connected to the second flow pass inlet of the
intercooler.
[0006] According to the invention, a part of the refrigerant is
taken from the main flow either upstream or downstream of the
aftercooler and led via the second controllable throttling device,
where the refrigerant pressure decreases from discharge pressure to
intermediate pressure and the temperature drops, to the second flow
path of the intercooler to cool down the working fluid in the first
flow path of the intercooler. In this way, the refrigerant being
under discharge pressure is cooled down on one side of the
heat-exchanging surfaces of the intercooler, while the refrigerant
on the other side of the heat-exchanging surfaces of the
intercooler evaporates being under intermediate pressure. The
refrigerant evaporated is led to the economizer port of the
compressor.
[0007] Due to this operation of the intercooler, the aftercooler is
unloaded. As a result of the unloading, less amount of vapor is
created in the aftercooler on the side of the low-pressure liquid
separator. Thus, with the same compressor size, more vapor can be
taken from the evaporator. Therefore, the refrigerating capacity of
the refrigeration apparatus and its efficiency will increase.
[0008] In the following, the invention is explained in detail by an
example of embodiment.
[0009] The accompanying drawings show in:
[0010] FIG. 1 a simplified schematic for arrangement of compressor
and heat exchangers with pertinent interconnecting piping and
control devices of the refrigeration apparatus according to the
invention.
[0011] FIG. 2 a Pressure-Enthalpy diagram for a refrigeration- or
air conditioning apparatus according to the invention.
[0012] FIG. 3 a simplified schematic for arrangement of compressor
and heat exchangers with pertinent interconnecting piping and
control devices for another arrangement example of a refrigeration
apparatus according to the invention.
[0013] FIG. 4 a Pressure-Enthalpy diagram for the arrangement
according to the invention in compliance with FIG. 3.
[0014] The refrigeration apparatus for transcritical operation
according to FIG. 1 comprises a gas cooler 23, an intercooler 24,
an evaporator 30, a low-pressure liquid separator 25 communicating
with an aftercooler 27, a screw compressor 21 having geometrically
controlled inlet and outlet ports, a first controllable throttling
device 28, a second controllable throttling device 26 and
interconnecting piping between the components mentioned. When
compressor 21 is in operation, suction pressure 11 prevails on its
suction side 29, while discharge pressure 12 prevails on its
discharge side 22 with the pressure on the discharge side 22 being
higher than the pressure at the critical point of the refrigerant.
The compressor has an economizer port 31 at the housing enabling a
flow connection to intercooler 24, and the pressure in this pipe
section lies between discharge pressure and suction pressure.
[0015] In the Pressure-Enthalpy diagram according to FIG. 2, point
1 describes the condition on the suction side of compressor 21. The
outlet condition of the refrigerant after compressor 21, point 2,
is the inlet condition into gas cooler 23. The refrigerant passes
gas cooler 23 which is fed by a cooling medium, e.g. cooling water,
for cooling the refrigerant vapor. When leaving said gas cooler 23,
the refrigerant has the condition at point 3. In intercooler 24
through which two refrigerant flows of the refrigeration apparatus
are led, the refrigerant is cooled from point 3 to point 4. For
this purpose, the partial refrigerant flow expanded to intermediate
pressure level 10 will be evaporated and superfed via economizer
port 31 into the compressor without considerably influencing the
suction volume flow. The refrigerant flow is further cooled from
point 4 to point 5 in aftercooler 27 wherein liquid evaporates in
aftercooler 27 communicating with low-pressure liquid separator 25,
and hence reducing the available volumetric refrigerating capacity
by the enthalpy difference from point 1 to point 9. Point 9
corresponds to the condition of the refrigerant at the evaporator
outlet 35 characterized by a two-phase mixture. The intermediate
pressure level 10 can be used for changing the refrigerating
capacity by way of rising the intermediate pressure, and hence
changing the intermediate cooling effect.
[0016] Due to cooling the refrigerant vapor in intercooler 24,
there will be created less vapor in aftercooler 27 on the side of
low-pressure liquid separator 25. Thus, with the same compressor
size, more vapor can be taken from the evaporator. Therefore, the
refrigerating capacity of the refrigeration apparatus and its
efficiency will increase.
[0017] The refrigeration apparatus for transcritical operation
according to FIG. 3 is configured similarly to FIG. 1 with the
distinguishing feature that the second flow path of intercooler 24
on its inlet side is connected via piping and second controllable
throttling device 32 to the outlet of an intermediate-pressure
aftercooler 34. The inlet of the intermediate-pressure aftercooler
34 is connected to the outlet of the first flow path of intercooler
24. The outlet side of the second flow path of intercooler 24 is
connected to economizer port 31 of compressor 21 via an
intermediate-pressure liquid separator 33. Intermediate-pressure
aftercooler 34 communicates with intermediate-pressure liquid
separator 33.
[0018] In the Pressure-Enthalpy diagram according to FIG. 4, point
4' describes the outlet condition from intermediate-pressure
aftercooler 34, point 13 describes the inlet condition into
intercooler 24 and point 17 describes the outlet condition from
intercooler 24.
LIST OF REFERENCE NUMERALS USED
[0019] 1. Point [0020] 2. Point [0021] 3. Point [0022] 4. Point
[0023] 4'. Point [0024] 5. Point [0025] 9. Point [0026] 10.
Intermediate-pressure level [0027] 11. Suction pressure [0028] 12.
Discharge pressure [0029] 13. Point [0030] 17. Point [0031] 21.
Screw compressor [0032] 22. Compressor discharge side [0033] 23.
Gas cooler [0034] 24. Intercooler [0035] 25. Low-pressure liquid
separator [0036] 26. Second controllable throttling device [0037]
27. Aftercooler [0038] 28. First controllable throttling device
[0039] 29. Compressor suction side [0040] 30. Evaporator [0041] 31.
Economizer port [0042] 32. Second controllable throttling device
[0043] 33. Intermediate-pressure liquid separator [0044] 34.
Intermediate-pressure aftercooler [0045] 35. Evaporator outlet
[0046] 36. First flow path [0047] 37. Second flow path [0048] 38.
First flow path inlet/Gas cooler outlet [0049] 39. First flow path
outlet [0050] 40. Second flow path inlet [0051] 41. Second flow
path outlet [0052] 42. Inlet of the second controllable throttling
device [0053] 43. Outlet of the second controllable throttling
device [0054] 44. Aftercooler inlet [0055] 45. Piping
* * * * *