CN115077133A - Heat pump system - Google Patents
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- CN115077133A CN115077133A CN202110260225.0A CN202110260225A CN115077133A CN 115077133 A CN115077133 A CN 115077133A CN 202110260225 A CN202110260225 A CN 202110260225A CN 115077133 A CN115077133 A CN 115077133A
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- 239000003507 refrigerant Substances 0.000 claims abstract description 208
- 238000002347 injection Methods 0.000 claims abstract description 73
- 239000007924 injection Substances 0.000 claims abstract description 73
- 238000009833 condensation Methods 0.000 claims abstract description 18
- 230000005494 condensation Effects 0.000 claims abstract description 18
- 239000013589 supplement Substances 0.000 claims abstract description 13
- 238000001816 cooling Methods 0.000 claims description 23
- 239000007788 liquid Substances 0.000 claims description 12
- 238000011144 upstream manufacturing Methods 0.000 claims description 4
- 230000000052 comparative effect Effects 0.000 description 10
- 238000010586 diagram Methods 0.000 description 7
- 238000001704 evaporation Methods 0.000 description 6
- 230000008020 evaporation Effects 0.000 description 6
- 230000001603 reducing effect Effects 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 230000009471 action Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- 230000006835 compression Effects 0.000 description 2
- 238000007906 compression Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- MSSNHSVIGIHOJA-UHFFFAOYSA-N pentafluoropropane Chemical compound FC(F)CC(F)(F)F MSSNHSVIGIHOJA-UHFFFAOYSA-N 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 239000004568 cement Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000007791 dehumidification Methods 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000005485 electric heating Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 238000004781 supercooling Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B30/00—Heat pumps
- F25B30/02—Heat pumps of the compression type
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/04—Heating; Cooling; Heat insulation
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B7/00—Compression machines, plants or systems, with cascade operation, i.e. with two or more circuits, the heat from the condenser of one circuit being absorbed by the evaporator of the next circuit
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B30/00—Energy efficient heating, ventilation or air conditioning [HVAC]
- Y02B30/52—Heat recovery pumps, i.e. heat pump based systems or units able to transfer the thermal energy from one area of the premises or part of the facilities to a different one, improving the overall efficiency
Abstract
The present invention provides a heat pump system, comprising: the first-stage loop is sequentially provided with a first-stage compressor, a condensation evaporator, a first-stage main path expansion valve and a first-stage evaporator along the flowing direction of a refrigerant; a second-stage circuit on which a second-stage compressor, a second-stage condenser, an enhanced vapor injection heat exchanger, a second-stage main-path expansion valve, and a condensing evaporator are sequentially arranged along a refrigerant flow direction, wherein the condensing evaporator functions as both the condenser in the first-stage circuit and the evaporator in the second-stage circuit; and the enhanced vapor injection branch, wherein the first-stage compressor is provided with a first refrigerant supplement port, and the enhanced vapor injection branch extends from a first branch point on the first-stage circuit, which is positioned at the downstream of the condensation evaporator, passes through the enhanced vapor injection heat exchanger and is connected to the first refrigerant supplement port.
Description
Technical Field
The present invention relates to the field of heat pump systems, and more particularly to a cascade system for industrial heat pump applications.
Background
This section provides background information related to the present invention, and such information does not necessarily constitute prior art.
In industrial applications, high temperature heat sources above 100 ℃ are in great demand, such as rotary dehumidification regeneration, lithium battery drying, cement drying, and the like. At present, the high-temperature heat source is generally realized by adopting traditional modes such as electric heating, gas, fuel oil and the like, but has the problems of serious energy consumption, high pollution and the like. The heat pump system is used as a high-efficiency and environment-friendly new energy technology, and can be applied to many occasions so as to solve the problems existing in the traditional high-temperature heat source supply mode. For example, a heat pump system is used in the northern coal-to-electricity engineering, and the heat pump system absorbs heat from air and transfers the heat to hot water, so that the efficiency can reach 3.0.
Typical heat pump systems today have condensation temperatures around 65 c, however, in industrial heat pump applications the condensation temperature requirements are high, typically exceeding 100 c and even up to 135 c. On the one hand, this means that the system pressure ratio is high, and therefore is usually achieved with a cascade system. On the other hand, a high condensation temperature also leads to a high temperature resistance requirement for the expansion valve, whereas the maximum withstand temperature of a typical expansion valve is 70 ℃. If a specially made expansion valve is used, this results in an increase in cost. Therefore, the tolerance temperature of the expansion valve limits the large-scale popularization and application of the high-temperature heat pump system.
Therefore, there is a need to provide an improved heat pump system, which can reduce the temperature of the refrigerant before the expansion valve to ensure the reliability of the system operation, and can improve the energy efficiency and controllability of the system.
Disclosure of Invention
A general summary of the invention is provided in this section, and is not a comprehensive disclosure of the full scope of the invention or all of the features of the invention.
The invention aims to provide a reliable and high-efficiency heat pump system, which adopts a cascade system design, on one hand, the heat pump system utilizes the refrigerant in the first-stage loop to cool the refrigerant in front of the expansion valve in the second-stage loop, thereby reducing the temperature in front of the valve in the second-stage loop and solving the problem of temperature resistance requirement of the expansion valve in the existing heat pump system; on the other hand, the refrigerant in the first-stage loop cools the refrigerant in the second-stage loop before the expansion valve and then is injected into the first-stage compressor as enhanced vapor injection fluid, so that the energy efficiency of the system is improved; in another aspect, the heat pump system can also be provided with a cooling branch in the second-stage loop, so that the exhaust temperature control requirement of the high-temperature compressor can be realized by using a small amount of liquid spraying, and the controllability and the efficiency of the system are improved.
According to an aspect of the present invention, there is provided a heat pump system including: the first-stage loop is sequentially provided with a first-stage compressor, a condensation evaporator, a first-stage main path expansion valve and a first-stage evaporator along the flowing direction of a refrigerant; a second-stage circuit on which a second-stage compressor, a second-stage condenser, an enhanced vapor injection heat exchanger, a second-stage main-path expansion valve, and a condensing evaporator are sequentially arranged along a refrigerant flow direction, wherein the condensing evaporator functions as both the condenser in the first-stage circuit and the evaporator in the second-stage circuit; and the enhanced vapor injection branch, wherein the first-stage compressor is provided with a first refrigerant supplement port, and the enhanced vapor injection branch extends from a first branch point on the first-stage circuit, which is positioned at the downstream of the condensation evaporator, passes through the enhanced vapor injection heat exchanger and is connected to the first refrigerant supplement port.
Optionally, the heat pump system is configured such that the first refrigerant supplied to the first refrigerant charge port via the enhanced vapor injection branch is in a pure gaseous state.
Optionally, a first branch expansion valve is arranged on the enhanced vapor injection branch between the first branch point and the enhanced vapor injection heat exchanger.
Optionally, the second stage compressor has a second refrigerant make-up port, and the heat pump system further comprises a cooling branch extending from a second branch point on the second stage circuit between the enhanced vapor injection heat exchanger and the second stage main circuit expansion valve and connected to the second refrigerant make-up port.
Optionally, the heat pump system is configured such that the second refrigerant supplied to the second refrigerant charge port via the cooling branch is in a pure liquid state.
Optionally, a throttle valve is provided in the cooling branch.
Optionally, the heat pump system is configured such that the condensing temperature of the second stage condenser is above 100 ℃ and the refrigerant temperature immediately upstream of the second stage main circuit expansion valve is below 70 ℃.
Optionally, the first refrigerant in the first stage circuit is different from the second refrigerant in the second stage circuit.
Overall, the heat pump system according to the invention brings at least the following advantages: according to the heat pump system, the enhanced vapor injection branch circuit is arranged between the first-stage loop and the second-stage loop, so that the temperature of a refrigerant in front of a main expansion valve in the second-stage loop can be effectively reduced, the system can still reliably operate under the condition that a common expansion valve is adopted, the application range of the heat pump system is expanded, and the enhanced vapor injection fluid is injected into the first-stage compressor through the enhanced vapor injection branch circuit, so that the energy efficiency of the system is improved. In addition, the heat pump system can also realize the exhaust cooling of the high-temperature compressor by a small amount of liquid spraying through arranging the cooling branch in the second-stage loop, thereby improving the controllability and the efficiency of the system.
Drawings
The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description, taken in conjunction with the accompanying drawings, which are given by way of example only and which are not necessarily drawn to scale. Like reference numerals are used to indicate like parts in the accompanying drawings, in which:
fig. 1 shows a schematic view of a heat pump system according to a first embodiment of the invention;
fig. 2 and 3 show enthalpy pressure diagrams of a first-stage circuit and a second-stage circuit, respectively, of a heat pump system according to a first embodiment of the present invention;
fig. 4 shows a schematic view of a heat pump system according to a second embodiment of the present invention;
FIG. 5 illustrates an enthalpy pressure diagram of the second stage circuit of the heat pump system according to the second embodiment of the present invention;
fig. 6 shows a schematic diagram of a heat pump system according to a first comparative example;
fig. 7 and 8 show enthalpy pressure maps of the first-stage circuit and the second-stage circuit, respectively, of the heat pump system according to the first comparative example;
fig. 9 shows a schematic diagram of a high temperature circuit of a heat pump system according to a second comparative example; and
fig. 10 shows an enthalpy pressure map of the second-stage circuit of the heat pump system according to the second comparative example.
Detailed Description
Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. Corresponding components or parts are designated by the same reference numerals throughout the several views.
Fig. 1 shows a schematic diagram of a heat pump system S according to a first embodiment of the present invention, which is a cascade system comprising a first-stage circuit (low-temperature-stage circuit) and a second-stage circuit (high-temperature-stage circuit). Wherein the refrigerant in the first stage circuit is preferably different from the refrigerant in the second stage circuit to accommodate different operating conditions. For example, the first-stage circuit may employ conventional HFC, HCFC refrigerants such as R410A, R22, R134a, etc., while the second-stage circuit may employ refrigerants having a critical temperature of 100 ℃ or higher such as HFO refrigerants such as R245fa or R1233 zde.
The first-stage circuit includes a low-temperature-stage refrigerant circulation main path (in the drawing, arrows indicate the flow direction of the refrigerant) formed by connecting in sequence a first-stage compressor PL, a condenser-evaporator EC, a first-stage main-path expansion valve VL, and a first-stage evaporator EL via pipes. That is, the first-stage compressor PL, the condensing evaporator EC, the first-stage main-circuit expansion valve VL, and the first-stage evaporator EL are arranged in the first-stage circuit in this order along the flow direction of the low-temperature-stage refrigerant (first refrigerant). The second stage loop comprises a high temperature stage refrigerant circulation main path (in the figure, the arrow indicates the flow direction of the refrigerant) formed by connecting a second stage compressor PH, a condenser CH, an enhanced vapor injection heat exchanger EH, a second stage main path expansion valve VH and a condensation evaporator EC in sequence through pipelines. That is, the second-stage compressor PH, the condenser CH, the enhanced vapor injection heat exchanger EH, the second-stage main-path expansion valve VH, and the condensing evaporator EC are arranged in the second-stage circuit in this order along the flow direction of the high-temperature-stage refrigerant (second refrigerant).
The first-stage circuit and the second-stage circuit are thermally coupled by a condensing evaporator EC. That is, the condensing evaporator EC, in which the high-temperature-stage refrigerant exchanges heat with the low-temperature-stage refrigerant, includes a refrigerant evaporation passage as a part of the second-stage circuit and a refrigerant condensation passage as a part of the first-stage circuit, whereby the second refrigerant in the refrigerant evaporation passage is evaporated and the first refrigerant in the refrigerant condensation passage is condensed. In other words, the condensing evaporator EC functions as a condenser in the first-stage loop and as an evaporator in the second-stage loop.
The heat pump system S further comprises an enhanced vapor injection branch, in which a first branch expansion valve VX and an enhanced vapor injection heat exchanger EH may be arranged. The enhanced vapor injection heat exchanger EH is a refrigerant-refrigerant heat exchanger, and can be a plate heat exchanger, a sleeve type heat exchanger and the like. The enhanced vapor injection heat exchanger EH includes a second refrigerant passage as part of the second stage circuit and a first refrigerant passage as part of the enhanced vapor injection branch. In the heat pump system having the enhanced vapor injection bypass, the first-stage compressor PL is configured as an enhanced vapor injection compressor having a first refrigerant supplement port PLI in addition to a suction port and a discharge port, as compared with a general compressor. Also included in the first stage circuit is a first branch point P on the path between the condensing evaporator EC and the first stage main circuit expansion valve VL, downstream of the condensing evaporator EC. The enhanced vapor injection branch extends from the first branch point P, passes through a first refrigerant passage in the enhanced vapor injection heat exchanger EH, and is finally connected to a first refrigerant supplement port PLI of the first-stage compression PL (an arrow in the drawing indicates a flow direction of refrigerant), and the first branch expansion valve VX is disposed on a path between the first branch point P and an inlet (point c) of the first refrigerant passage.
The operation of the heat pump system S will be described with reference to fig. 2 to 3. In the first-stage circuit, the first refrigerant discharged from the first-stage compressor PL is in a high-temperature and high-pressure state (corresponding to the state of point 2 in fig. 2), and at this time, the first refrigerant is a gas. The first refrigerant then enters the condensing evaporator EC via a pipe, is condensed in the condensing evaporator EC to turn into a liquid state (corresponding to the state of point 3 in fig. 2). In the present embodiment, the condensation temperature of the first-stage circuit is about 80 ℃. The condensed first refrigerant is discharged from the condensing evaporator EC. Then, a part of the first refrigerant (hereinafter referred to as a first refrigerant first part) enters the first-stage main expansion valve VL, and is converted into a low-temperature and low-pressure refrigerant (corresponding to a state of point 4 in fig. 2) by a pressure reduction action of the first-stage main expansion valve VL. Subsequently, the first portion of the first refrigerant enters the first-stage evaporator EL, is evaporated in the first-stage evaporator EL to turn into a gaseous state (corresponding to the state of point 1 in fig. 2). In the present embodiment, the evaporation temperature of the first-stage circuit is about 30 ℃. A first portion of the evaporated first refrigerant exits the first stage evaporator EL and enters the suction inlet of the first stage compressor PL.
The other part (hereinafter referred to as a second part) of the first refrigerant discharged from the condenser-evaporator EC enters the enhanced vapor injection branch from the first branch point P on the first-stage circuit, and is throttled by the first branch expansion valve VX, so that the pressure of the second part of the first refrigerant is reduced, and the second part of the first refrigerant is converted from a liquid refrigerant into a gas-liquid mixed refrigerant. At this time, the temperature of the second portion of the first refrigerant is about 53 ℃. Subsequently, the second portion of the first refrigerant enters the first refrigerant pass of the enhanced vapor injection heat exchanger EH, that is, at the point of inlet c of the first refrigerant pass of the enhanced vapor injection heat exchanger EH, the temperature of the second portion of the first refrigerant is about 53 ℃. The second portion of the first refrigerant exchanges heat with the second refrigerant in the second refrigerant passage in the first refrigerant passage, absorbs heat of the second refrigerant, and lowers the temperature of the second refrigerant. The second portion of the first refrigerant is then discharged from the first refrigerant pass of the enhanced vapor injection heat exchanger EH at point d and delivered to a first refrigerant charge port PLI of the first stage compressor PL communicating with an intermediate pressure location thereof. The second portion of the first refrigerant, which is delivered back to the first refrigerant supplementary port PLI of the first stage compressor PL, is finally mixed with the first portion of the first refrigerant, which enters from the suction port of the first stage compressor PL, in the first stage compressor PL, and is again compressed to a state of point 2 and discharged out of the first stage compressor PL. Preferably, the first refrigerant discharged from the outlet point d of the first refrigerant passage of the enhanced vapor injection heat exchanger EH and delivered to the first refrigerant supplement port PLI of the first stage compressor PL is in a pure gas state, thereby further effectively reducing the refrigerant temperature in the second stage circuit immediately upstream of the main circuit expansion valve and effectively improving the system efficiency.
In the second-stage circuit, the second refrigerant discharged from the second-stage compressor PH is in a high-temperature and high-pressure gas state (corresponding to a state of point 6 in fig. 3). The second refrigerant then enters the second-stage condenser CH via a pipe, is condensed in the second-stage condenser CH to be turned into a liquid state (corresponding to a state of point 7 in fig. 3). In the present embodiment, the condensation temperature of the second-stage circuit is about 135 ℃. The condensed second refrigerant is discharged from the condensing evaporator EC and then enters the enhanced vapor injection heat exchanger EH from the inlet a point of the second refrigerant passage of the enhanced vapor injection heat exchanger EH. In the enhanced vapor injection heat exchanger EH, heat of the second refrigerant in the second refrigerant passage is absorbed by the first refrigerant second portion in the first refrigerant passage, whereby the temperature of the second refrigerant is further lowered, and then the enhanced vapor injection heat exchanger EH is discharged from the outlet b point of the second refrigerant passage. Next, the second refrigerant enters the second-stage main circuit expansion valve VH, and is brought into a state corresponding to point 8 in fig. 3 by the pressure reducing action of the second-stage main circuit expansion valve VH. Subsequently, the second refrigerant enters the refrigerant evaporation passage of the condensation evaporator EC, in which the second refrigerant in the refrigerant evaporation passage exchanges heat with the first refrigerant in the refrigerant condensation passage, and the second refrigerant is evaporated to turn into a gaseous state (corresponding to the state of point 5 in fig. 3). In this embodiment, the evaporation temperature of the second stage circuit is 75 ℃. The evaporated second refrigerant is discharged from the condenser evaporator EC and introduced into the air inlet of the second stage compressor PH.
The advantageous effects of the heat pump system according to the first embodiment of the present invention will be described below with reference to the heat pump systems of the first comparative examples shown in fig. 6 to 8.
Fig. 6 shows a schematic diagram of a heat pump system S' according to a first comparative example, which is also a cascade system including a first-stage circuit and a second-stage circuit, similarly to the first embodiment of the present invention. Here, the main constituent devices, arrangements, connection manners, choices of refrigerants, and the like of the first-stage circuit and the second-stage circuit are the same as those of the first embodiment of the present invention, for example, the first-stage circuit is formed by connecting a first-stage compressor PL, a condensing evaporator EC, a first-stage main expansion valve VL, and a first-stage evaporator EL in this order along the flow direction of a low-temperature-stage refrigerant (first refrigerant), the second-stage circuit is formed by connecting a second-stage compressor PH, a second-stage condenser CH, an enhanced vapor injection heat exchanger EH, a second-stage main expansion valve VH, and a condensing evaporator EC in this order along the flow direction of a high-temperature-stage refrigerant (second refrigerant), and the first-stage circuit and the second-stage circuit are thermally coupled by the condensing evaporator EC.
Unlike the first embodiment, in this heat pump system S', the second-stage compressor PH is configured as an enhanced vapor injection compressor having a gas supplement port, and the enhanced vapor injection branch extends from a branch point Q downstream of the enhanced vapor injection heat exchanger EH in the second-stage circuit and between the enhanced vapor injection heat exchanger EH and the second-stage main-circuit expansion valve VH, passes through the second-branch expansion valve VX and the enhanced vapor injection heat exchanger EH, and is connected to the gas supplement port of the second-stage compressor PH. Referring to fig. 7 and 8, a portion of the second refrigerant (hereinafter, referred to as a second refrigerant first portion) discharged from the outlet b point of the second refrigerant passage of the enhanced vapor injection heat exchanger EH enters the second-stage main circuit expansion valve VH, and is changed to a state corresponding to point 8 in fig. 8 by the pressure reducing action of the first-stage main circuit expansion valve VH. Subsequently, the second refrigerant first portion enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to turn into a gaseous state (corresponding to the state of point 5 in fig. 8), and then is discharged from the condensing evaporator EC to enter the air intake of the second-stage compressor PL. Another portion of the second refrigerant (hereinafter, referred to as a second refrigerant second portion) discharged from the outlet b point of the second refrigerant passage of the enhanced vapor injection heat exchanger EH enters the enhanced vapor injection branch circuit from the branch point Q on the second-stage circuit, and is throttled by the second branch expansion valve VX', and the pressure of the second portion of the second refrigerant is reduced. At this time, the temperature of the second portion of the second refrigerant is a saturation temperature corresponding to the injection pressure, i.e., about 103 ℃. Subsequently, the second portion of the second refrigerant enters the first refrigerant pass of the enhanced vapor injection heat exchanger EH, that is, at the point of inlet c of the first refrigerant pass of the enhanced vapor injection heat exchanger EH, the temperature of the second portion of the second refrigerant is about 103 ℃. The second refrigerant second portion exchanges heat with the second refrigerant in the second refrigerant passage in the first refrigerant passage, absorbs heat of the second refrigerant to lower the temperature of the second refrigerant, thereby lowering the temperature of the second refrigerant before the second-stage main circuit expansion valve VH. A second portion of the second refrigerant is then discharged from the first refrigerant pass of the enhanced vapor injection heat exchanger EH at point d and delivered to the makeup port of the second stage compressor PH in communication with the intermediate pressure location thereof. The second portion of the second refrigerant delivered back to the suction port of the second stage compressor PH is finally mixed with the first portion of the second refrigerant entering the second stage compressor PH from the suction port of the second stage compressor PH, and is again compressed to a high temperature and high pressure gas (corresponding to a state of point 6) and discharged out of the second stage compressor PH. As can be seen from fig. 8, the condensation temperature of the second-stage circuit is about 135 deg.c, and the second refrigerant temperature after being throttled by the second branch expansion valve VX' (i.e., at point c) is about 103 deg.c, and the pre-valve temperature of the second-stage main expansion valve VH (corresponding to the temperature at point b) is about 108 deg.c, assuming a heat exchange temperature difference of 5 deg.c. The temperature far exceeds the long-term use tolerance temperature (about 70 ℃) of most electronic expansion valves, so that a proper electronic expansion valve product is difficult to find in the market, and the reliability of a valve part and even a system is influenced.
In contrast, in the first embodiment according to the present invention, the condensation temperature of the second stage circuit may be higher than 100 ℃, for example, about 135 ℃, while the temperature of the first refrigerant after throttling in the enhanced vapor injection branch via the first branch expansion valve VX is about 53 ℃ (i.e. the first refrigerant temperature at point c), so that the first refrigerant is able to cool the second refrigerant sufficiently in the enhanced vapor injection heat exchanger such that the second refrigerant reaches a sufficiently low pre-valve temperature (i.e. the second refrigerant temperature at point b), i.e. below 70 ℃. For example, if the heat exchange temperature difference is 5 ℃, the pre-valve temperature of the second-stage main expansion valve VH (i.e., the second refrigerant temperature at the point b) is 58 ℃, and a common electronic expansion valve can meet the temperature resistance requirement, so that the cost of the system is reduced, and the reliable operation of the system is ensured.
Therefore, in the heat pump system according to the first embodiment of the present invention, on the one hand, by introducing a part of the first refrigerant condensed by the condensing evaporator EC in the first-stage circuit into the enhanced vapor injection branch, throttling the first refrigerant by the first branch expansion valve VX, and sufficiently cooling the condensed second refrigerant in the second-stage circuit by the first refrigerant having a lower temperature in the enhanced vapor injection heat exchanger EH, the temperature in the second-stage circuit before the second-stage main expansion valve VH can be significantly reduced, so that the system can employ a common electronic expansion valve, the cost of the system is reduced, and the reliable operation of the system is ensured.
On the other hand, the first refrigerant discharged from the enhanced vapor injection heat exchanger EH (point d) is delivered to the first refrigerant supplement port PLI of the first stage compressor PL at an appropriate intermediate temperature and pressure, and compared to the related scheme in which the intermediate temperature and pressure first refrigerant is delivered back to or before the intake port of the first stage compressor PL, the system efficiency is improved because the intermediate temperature and pressure first refrigerant is directly supplied to the intermediate pressure chamber of the first stage compressor PL for further compression.
The second embodiment of the present invention is a modification made on the basis of the first embodiment of the present invention. A second embodiment of the present invention will be described with reference to fig. 4 and 5.
Like the first embodiment of the present invention, the heat pump system S according to the second embodiment of the present invention is also a cascade system including a first-stage circuit and a second-stage circuit. The main components, arrangement, connection mode, selection of refrigerant, etc. of the first-stage circuit, the second-stage circuit and the enhanced vapor injection branch are the same as those of the first embodiment of the present invention, and are not described herein again.
Unlike the first embodiment of the present invention, the second embodiment of the present invention is different from the heat pump system according to the first embodiment of the present invention in that a cooling branch is further provided. The cooling branch extends from downstream of the enhanced vapor injection heat exchanger EH of the second-stage circuit, passes through the throttle valve VY, and is finally connected to a second refrigerant charge port PHI of the second-stage compressor PH, which communicates with the intermediate pressure chamber thereof. Preferably, the cooling branch extends from a second branch point R between the enhanced vapor injection heat exchanger EH and the second stage main circuit expansion valve VH, so that the refrigerant supplied to the second refrigerant charge port PHI has a suitable temperature and pressure. Referring to fig. 4, a part of the second refrigerant (hereinafter, referred to as a second refrigerant first part) discharged from the outlet b point of the second refrigerant passage of the enhanced vapor injection heat exchanger EH enters the second-stage main path expansion valve VH, and is changed to a state corresponding to a point 8 in fig. 5 by a pressure reduction action of the second-stage main path expansion valve VH. Subsequently, the second refrigerant first portion enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to turn into a gaseous state (corresponding to a state of point 5 in fig. 5), and then is discharged from the condensing evaporator EC to enter the air intake of the second-stage compressor PL. Another part (hereinafter, referred to as a second refrigerant second part) of the second refrigerant discharged from the outlet b point of the second refrigerant passage of the enhanced vapor injection heat exchanger EH enters the cooling branch circuit from a second branch point R on the second-stage circuit, and after being throttled by the throttle valve VY, the pressure of the second portion of the second refrigerant is reduced, and then the second portion of the second refrigerant is injected into the middle pressure chamber of the second stage compressor PH at a lower temperature and a suitable pressure, and the high-temperature gas in the intermediate pressure chamber (the high-temperature gas is a portion of the second refrigerant sucked from the inlet port of the second stage compressor PH and compressed into the intermediate pressure chamber, which is in a state corresponding to a point g in fig. 5) is mixed to reach a state corresponding to a point e in fig. 5, and is compressed together to a state corresponding to a point 6 in fig. 5 and then discharged from the second stage compressor PH.
Compared with the first embodiment, the cooling branch circuit added in the second embodiment can provide refrigerant with lower temperature to the supplement port PHI of the second stage compressor PH, so as to achieve the purpose of preventing the second stage compressor from exhausting and overheating, thereby improving the controllability and efficiency of the system. Preferably, the second portion of the second refrigerant throttled by the throttle valve VY to be supplied to the second refrigerant make-up port PHI is in a pure liquid state, thereby providing a sufficient cooling effect with as little refrigerant as possible, and also contributing to a reduction in the temperature of the refrigerant in the second-stage circuit immediately upstream of the main circuit expansion valve.
On the other hand, as can be seen from fig. 5, the condensation temperature of the second stage loop is about 135 ℃, and since the first refrigerant in the enhanced vapor injection heat exchanger can sufficiently cool the second refrigerant, so that the temperature at the point b of the outlet of the second refrigerant channel of the enhanced vapor injection heat exchanger is as low as 58 ℃, the temperature of the second portion of the second refrigerant entering the cooling branch is also low enough that only a small amount of liquid spray is required to meet the requirements for second stage compressor discharge temperature control. In the second comparative example shown in fig. 9 and 10, since there is no enhanced vapor injection branch introduced from the first-stage circuit, sufficient cooling cannot be provided to the second refrigerant in the second-stage circuit, which has a high temperature, resulting in a large amount of liquid spray required to be able to meet the requirement for controlling the discharge temperature of the second-stage compressor.
Fig. 9 shows a schematic diagram of the second-stage circuit of the second comparative example. In the second comparative example, the cooling branch line extends from a second branch point R downstream of the second-stage condenser CH of the second-stage circuit between the second-stage condenser CH and the second-stage main-path expansion valve VH, passes through the throttle valve VY, and is finally connected to a second refrigerant supplement port PHI' of the second-stage compressor PH communicating with the intermediate pressure chamber thereof. A part of the second refrigerant discharged from the second-stage condenser CH and in a state corresponding to point 7 in fig. 10 (hereinafter, referred to as a second refrigerant first part) enters the second-stage main circuit expansion valve VH, and is shifted to a state corresponding to point 8 in fig. 10 by the pressure reduction action of the second-stage main circuit expansion valve VH. Subsequently, the second refrigerant first portion enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to be changed into a gaseous state (corresponding to a state of point 5 in fig. 10), and then is discharged from the condensing evaporator EC to enter the suction port of the second-stage compressor PL. The other part of the second refrigerant discharged from the condenser CH (hereinafter referred to as a second refrigerant second part) enters the cooling branch from the second branch point R on the second-stage circuit, is throttled by the throttle valve VY, the pressure of the second refrigerant second part is reduced to change to a state corresponding to a point f ' in fig. 10, and then the second refrigerant second part is injected into the intermediate pressure chamber of the second-stage compressor PH through the second refrigerant charge port PHI ', is mixed with the high-temperature gas in the intermediate pressure chamber (the high-temperature gas is a part of the second refrigerant sucked from the intake port of the second-stage compressor PH and compressed to the intermediate pressure chamber, which is in a state corresponding to a point g ' in fig. 10) to a state corresponding to a point e in fig. 10, and is compressed together to a state corresponding to a point 6 in fig. 10 and then discharged from the second-stage compressor PH.
As can be seen from fig. 10, the condensing temperature of the second-stage circuit is about 135 c, and assuming that the supercooling degree of the condenser CH is 5 c, the temperature of the second refrigerant discharged from the condenser CH in a state corresponding to point 7 is about 130 c, which is significantly higher than the temperature (58 c) of the second refrigerant at point b shown in fig. 5. Assuming that the refrigerant is R245fa and the saturation temperature corresponding to the injection pressure is about 103 ℃, the pressure of the refrigerant for cooling injected into the intermediate-pressure chamber is not changed after mixing with the refrigerant in the state of g/g ' in the intermediate-pressure chamber, and other parameters related to the refrigerant in the states of f/f ' and g/g ' are shown in the following table (table 1).
TABLE 1
From the above parameters, assuming that the mass of the refrigerant (i.e., the refrigerant in the state corresponding to the point g or the point g') in the middle pressure chamber of the second stage compressor PH is 0.1kg, and the target temperature of the mixed state e is 110 ℃, it can be calculated that the mass of the refrigerant for cooling to be injected according to the second embodiment of the present invention is about 0.015kg, and the mass of the refrigerant for cooling to be injected according to the second comparative example is about 0.033 kg. Therefore, the heat pump system according to the second embodiment of the present invention can achieve the purpose of controlling the discharge temperature of the second stage compressor with a small amount of liquid injection, further improving the system efficiency.
The high temperature heat pump system according to the preferred embodiment of the present invention has been described above with reference to the specific embodiments. It will be understood that the above description is intended to be illustrative and not restrictive, and that various changes and modifications may be suggested to one skilled in the art in view of the above description without departing from the scope of the invention. Such variations and modifications are also included in the scope of the present invention.
Claims (8)
1. A heat pump system (S), comprising:
a first-stage circuit on which a first-stage compressor (PL), a condensing Evaporator (EC), a first-stage main-path expansion Valve (VL), and a first-stage Evaporator (EL) are arranged in this order along a refrigerant flow direction;
a second-stage circuit on which a second-stage compressor (PH), a second-stage Condenser (CH), an enhanced vapor injection heat Exchanger (EH), a second-stage main-path expansion Valve (VH), and the condensing Evaporator (EC) are arranged in this order in a refrigerant flow direction, wherein the condensing Evaporator (EC) functions as both a condenser in the first-stage circuit and an evaporator in the second-stage circuit; and
an enhanced vapor injection branch is arranged on the gas injection branch,
characterized in that the first stage compressor has a first refrigerant makeup Port (PLI) and in that the enhanced vapor injection branch extends from a first branch point (P) on the first stage circuit downstream of the condenser Evaporator (EC), through the enhanced vapor injection heat Exchanger (EH) and is connected to the first refrigerant makeup Port (PLI).
2. The heat pump system (S) according to claim 1, characterized in that it is configured so that the first refrigerant supplied to the first refrigerant supplement Port (PLI) via the enhanced vapor injection branch is in a pure gaseous state.
3. Heat pump system (S) according to claim 1, characterized in that on the enhanced vapor injection branch a first branch expansion Valve (VX) is arranged between the first branch point (P) and the enhanced vapor injection heat Exchanger (EH).
4. A heat pump system (S) according to any one of claims 1 to 3, characterized in that the second stage compressor (PH) has a second refrigerant charge Port (PHI), the heat pump system further comprising a cooling branch extending from a second branch point (R) on the second stage circuit between the enhanced vapor injection heat Exchanger (EH) and the second stage main circuit expansion Valve (VH) and connected to the second refrigerant charge Port (PHI).
5. The heat pump system (S) according to claim 4, characterized in that it is configured such that the second refrigerant supplied to the second refrigerant charge Port (PHI) via the cooling branch is in a pure liquid state.
6. Heat pump system (S) according to claim 4, characterized in that a throttle Valve (VY) is provided on the cooling branch.
7. A heat pump system (S) according to any of claims 1-3, characterized in that it is configured such that the condensation temperature of the second stage Condenser (CH) is higher than 100 ℃ and the refrigerant temperature immediately upstream of the second stage main circuit expansion Valve (VH) is lower than 70 ℃.
8. A heat pump system (S) according to any of claims 1-3, characterized in that the first refrigerant in the first stage circuit is different from the second refrigerant in the second stage circuit.
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| PCT/CN2022/078712 WO2022188668A1 (en) | 2021-03-10 | 2022-03-02 | Heat pump system |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108692475A (en) * | 2018-06-08 | 2018-10-23 | 贺吉军 | A kind of air injection enthalpy-increasing refrigeration machine |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108692475A (en) * | 2018-06-08 | 2018-10-23 | 贺吉军 | A kind of air injection enthalpy-increasing refrigeration machine |
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