WO2022188668A1 - Heat pump system - Google Patents

Abstract

The present disclosure provides a heat pump system, comprising: a first-stage circuit, a first-stage compressor, a condenser/evaporator, a first-stage main path expansion valve, and a first-stage evaporator being sequentially arranged on the first-stage circuit along the flow direction of a refrigerant; a second-stage circuit, a second-stage compressor, a second-stage condenser, an enhanced vapor injection heat exchanger, a second-stage main path expansion valve, and a condenser/evaporator being sequentially arranged on the second-stage circuit along the flow direction of the refrigerant; the condenser/evaporator being used as a condenser in the first-stage circuit and being used as an evaporator in the second-stage circuit; and an enhanced vapor injection branch, the first-stage compressor having a first refrigerant supplementing port; the enhanced vapor injection branch extending from a first branch point on the first-stage circuit located at the downstream of the condenser/evaporator, passing through the enhanced vapor injection heat exchanger, and being connected to the first refrigerant supplementing port.

Description

heat pump system

This application claims the priority of the following Chinese patent applications: the Chinese patent application with the application number 202110260225.0 and the invention-creation name "Heat Pump System" filed with the China Patent Office on March 10, 2021; filed in China on March 10, 2021 The patent office's application number is 202120509779.5, and the Chinese patent application for the invention and creation name is "heat pump system". The entire contents of these patent applications are incorporated herein by reference.

technical field

The present disclosure relates to the field of heat pump systems, and more particularly, to a cascade system for industrial heat pump applications.

Background technique

This section provides background information related to the present disclosure that does not necessarily constitute prior art.

In industrial applications, high temperature heat sources above 100 °C are in great demand, such as regeneration of rotary dehumidification, drying of lithium batteries, and drying of cement. At present, this high-temperature heat source is usually realized by traditional methods such as electric heating, gas, and fuel, but there are problems such as serious energy consumption and high pollution. As an efficient and environmentally friendly new energy technology, the heat pump system can be applied in many occasions to improve the problems existing in the traditional high-temperature heat source supply method. For example, the heat pump system is used in the northern coal-to-electricity project, which absorbs heat from the air and transfers it to hot water, which can make the efficiency reach 3.0.

The current typical heat pump system has a condensing temperature of about 65°C. However, in industrial heat pump applications, the condensing temperature is very high, usually exceeding 100°C, and even reaching 135°C. On the one hand, this means that the system pressure ratio is very high, so it is usually achieved with a cascade system. On the other hand, the high condensing temperature also leads to high temperature resistance requirements for the expansion valve, and the maximum temperature resistance of the general expansion valve is 70 °C. If a special expansion valve is used, it will lead to an increase in cost. Therefore, the tolerance temperature of the expansion valve limits the large-scale popularization and application of high-temperature heat pump systems.

Therefore, there is a need to provide an improved heat pump system, which on the one hand can reduce the temperature of the refrigerant before the expansion valve to ensure the reliability of the system operation, and on the other hand can improve the energy efficiency and controllability of the system.

SUMMARY OF THE INVENTION

A general summary of the disclosure is provided in this section, rather than a comprehensive disclosure of its full scope or all of its features.

The purpose of the present disclosure is to provide a reliable and efficient heat pump system, which adopts a cascade system design. The refrigerant is cooled, thereby reducing the temperature before the valve in the second-stage circuit, which solves the problem of the temperature resistance requirement of the expansion valve in the existing heat pump system; The refrigerant before the expansion valve in the circuit is cooled and then injected into the first-stage compressor as an air jet enthalpy-increasing fluid, thereby improving the energy efficiency of the system; on the other hand, the heat pump system can also set a cooling branch in the second-stage circuit, Thereby, the discharge temperature control requirement of the high-temperature compressor can be achieved with a small amount of liquid injection, and the controllability and efficiency of the system can be improved.

According to one aspect of the present disclosure, a heat pump system is provided, the heat pump system includes: a first-stage circuit, on which a first-stage compressor, a condensing evaporator, a first-stage compressor, a condensing evaporator, a The first-stage main circuit expansion valve and the first-stage evaporator; the second-stage loop, the second-stage compressor, the second-stage condenser, and the air jet enthalpy heat exchange are arranged in sequence along the refrigerant flow direction on the second-stage loop. a condenser, a second-stage main circuit expansion valve and a condensing evaporator, wherein the condensing evaporator is used both as a condenser in the first-stage loop and as an evaporator in the second-stage loop; and a jet enthalpy increasing branch, Wherein, the first stage compressor has a first refrigerant replenishment port, and the jet enthalpy increasing branch extends from the first branch point on the first stage loop located downstream of the condensation evaporator and passes through the jet enthalpy increasing heat exchanger , and is connected to the first refrigerant replenishment port.

Optionally, the heat pump system is configured such that the first refrigerant supplied to the first refrigerant replenishment port via the gas injection enthalpy branch is in a pure gaseous state.

Optionally, on the jetting enthalpy increasing branch, a first branch expansion valve is provided between the first branch point and the jetting enthalpy increasing heat exchanger.

Optionally, the second-stage compressor has a second refrigerant supplementary port, and the heat pump system further includes a cooling branch, and the cooling branch is connected from the jet enthalpy heat exchanger on the second-stage circuit and the second-stage main circuit expansion valve. A second branch point between starts to extend and connects to the second refrigerant replenishment port.

Optionally, the heat pump system is configured such that the second refrigerant supplied to the second refrigerant replenishment port via the cooling branch is in a pure liquid state.

Optionally, a throttle valve is provided on the cooling branch.

Optionally, the heat pump system is configured such that the condensing temperature of the second stage condenser is higher than 100°C and the refrigerant temperature immediately upstream of the second stage main circuit expansion valve is lower than 70°C.

Optionally, the first refrigerant in the first stage circuit is different from the second refrigerant in the second stage loop.

In general, the heat pump system according to the present disclosure brings at least the following beneficial effects: the heat pump system according to the present disclosure can not only effectively reduce the second stage by means of the jet enthalpy increasing branch provided between the first stage circuit and the second stage loop The temperature of the refrigerant before the expansion valve in the main circuit in the circuit ensures that the system can still operate reliably even when a common expansion valve is used, which expands the application range of the heat pump system. Injection into the first stage compressor, thereby increasing the energy efficiency of the system. In addition, the heat pump system according to the present disclosure can also provide a cooling branch in the second-stage circuit, so as to realize the cooling of the exhaust gas of the high-temperature compressor with a small amount of liquid injection, thereby improving the controllability and efficiency of the system.

Description of drawings

The foregoing and additional features and characteristics of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings, which are by way of example only and are not necessarily drawn to scale. The same reference numerals are used to designate the same parts in the drawings, in which:

FIG. 1 shows a schematic diagram of a heat pump system according to a first embodiment of the present disclosure;

2 and 3 show enthalpy-pressure diagrams of a first-stage loop and a second-stage loop, respectively, of the heat pump system according to the first embodiment of the present disclosure;

4 shows a schematic diagram of a heat pump system according to a second embodiment of the present disclosure;

5 shows an enthalpy-pressure diagram of a second stage loop of a heat pump system according to a second embodiment of the present disclosure;

FIG. 6 shows a schematic diagram of a heat pump system according to a first comparative example;

7 and 8 show enthalpy-pressure diagrams of the first-stage loop and the second-stage loop of the heat pump system according to the first comparative example, respectively;

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 diagram of the second-stage loop of the heat pump system according to the second comparative example.

Detailed ways

Preferred embodiments of the present disclosure 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 and its application or uses. In the various views, corresponding components or parts are given the same reference numerals.

1 shows a schematic diagram of a heat pump system S according to a first embodiment of the present disclosure, the heat pump system S being a cascade system including a first stage circuit (low temperature stage loop) and a second stage loop (high temperature stage loop). Wherein, preferably, the refrigerant in the first-stage loop is different from the refrigerant in the second-stage loop, so as to be suitable for different working conditions. For example, the first-stage loop can use conventional HFC, HCFC refrigerants, such as R410A, R22, R134a, etc., while the second-stage loop can use refrigerants with a critical temperature above 100 °C, such as R245fa or R1233zde and other HFO-based refrigerants .

The first-stage circuit includes a low-temperature refrigerant circulation main path formed by connecting the first-stage compressor PL, the condensing evaporator EC, the first-stage main circuit expansion valve VL and the first-stage evaporator EL through pipes in sequence (in the accompanying drawings). The arrow in the middle indicates the flow direction of the refrigerant). 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 sequentially arranged at the first stage along the flow direction of the low-temperature stage refrigerant (the first refrigerant). in the primary loop. The second-stage circuit includes a high-temperature-grade refrigerant cycle formed by connecting the second-stage compressor PH, condenser CH, jet enthalpy heat exchanger EH, second-stage main circuit expansion valve VH and condensing evaporator EC in sequence through pipes The main path (the arrow in the drawing indicates the flow direction of the refrigerant). That is, the second stage compressor PH, condenser CH, jet enthalpy heat exchanger EH, second stage main circuit expansion valve VH and condensing evaporator EC flow along the flow of the high temperature stage refrigerant (second refrigerant). The directions are sequentially arranged in the second-level loop.

The primary circuit and the secondary circuit are thermally coupled by the condensing evaporator EC. That is, the condensing evaporator EC includes a refrigerant evaporation passage as part of a second-stage circuit and a refrigerant condensation passage as part of a first-stage circuit, in which the high temperature stage refrigerant and the low temperature stage refrigerant are condensed Heat exchange is performed, 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 acts as a condenser in the first stage circuit and as an evaporator in the second stage loop.

The heat pump system S further includes a jetting enthalpy increasing branch, and the jetting enthalpy increasing branch may be arranged with a first branch expansion valve VX and a jetting enthalpy increasing heat exchanger EH. The jet enthalpy heat exchanger EH is a refrigerant-refrigerant heat exchanger, which can be a plate heat exchanger, a casing heat exchanger, and the like. The jet enthalpy heat exchanger EH includes a second refrigerant passage as part of the second stage circuit and a first refrigerant passage as part of the jet enthalpy branch. In the heat pump system with the jet enthalpy branch, the first stage compressor PL is configured as a jet enthalpy compressor. Compared with the ordinary compressor, the jet enthalpy compressor has a suction port and an exhaust port, There is also a first refrigerant replenishment port PLI. The first-stage circuit also includes a first branch point P on the path downstream of the condensing evaporator EC and between the condensing evaporator EC and the first-stage main circuit expansion valve VL. The jet enthalpy increase branch extends from the first branch point P, passes through the first refrigerant passage in the jet enthalpy heat exchanger EH, and is finally connected to the first refrigerant replenishment port PLI of the first stage compression PL (in the appendix). The arrow in the figure indicates the flow direction of the refrigerant), and the first branch expansion valve VX is provided on the path between the first branch point P and the inlet (point c) of the first refrigerant passage.

The working process of the heat pump system S will be described below with reference to FIGS. 2 to 3 . In the first-stage circuit, the first refrigerant discharged from the first-stage compressor PL is in a state of high temperature and high pressure (corresponding to the state of point 2 in FIG. 2 ), and the first refrigerant is a gas at this time. Then the first refrigerant enters the condensing evaporator EC through the pipeline, and is condensed in the condensing evaporator EC to be converted into a liquid state (corresponding to the state of point 3 in FIG. 2 ). In this embodiment, the condensation temperature of the first-stage circuit is about 80°C. The condensed first refrigerant is discharged from the condensing evaporator EC. Next, a part of the first refrigerant (hereinafter referred to as the first part of the first refrigerant) enters the first-stage main circuit expansion valve VL, and is converted into a low temperature and low pressure through the depressurization effect of the first-stage main circuit expansion valve VL refrigerant (corresponding to the state of point 4 in Figure 2). Subsequently, the first portion of the first refrigerant enters the first-stage evaporator EL, where it is evaporated and transformed into a gaseous state (corresponding to the state of point 1 in FIG. 2 ). In this embodiment, the evaporation temperature of the first-stage circuit is about 30°C. The first part of the evaporated first refrigerant is discharged from the first-stage evaporator EL, and then enters the intake port of the first-stage compressor PL.

Another part of the first refrigerant discharged from the condensing evaporator EC (hereinafter referred to as the second part of the first refrigerant) enters the gas injection enthalpy increasing branch from the first branch point P on the first stage circuit, and passes through the first branch After the expansion valve VX is throttled, the pressure of the second part of the first refrigerant is reduced, and the refrigerant is changed from a liquid refrigerant to a gas-liquid mixed refrigerant. At this time, the temperature of the second part of the first refrigerant is about 53°C. Subsequently, the second part of the first refrigerant enters the first refrigerant passage in the jet enthalpy heat exchanger EH, that is, at the inlet point c of the first refrigerant passage of the jet enthalpy heat exchanger EH, the The temperature of the second portion of a refrigerant is about 53°C. The second part of the first refrigerant exchanges heat with the second refrigerant in the second refrigerant passage in the first refrigerant passage, absorbs the heat of the second refrigerant, and reduces the temperature of the second refrigerant. Then the second part of the first refrigerant is discharged from the outlet point d of the first refrigerant passage of the jet enthalpy heat exchanger EH, and sent to the first refrigerant supplement of the first stage compressor PL, which is communicated with the middle pressure part port PLI. The second part of the first refrigerant sent back to the first refrigerant replenishment port PLI of the first stage compressor PL ends up in the first stage with the first part of the first refrigerant entering from the intake port of the first stage compressor PL The mixture is mixed in the compressor PL, compressed to the state of point 2 again, and discharged from the first-stage compressor PL. Preferably, the first refrigerant discharged from the outlet d point of the first refrigerant passage of the jet enthalpy heat exchanger EH and delivered to the first refrigerant replenishment port PLI of the first stage compressor PL is in a pure gas state, so that It further effectively reduces the refrigerant temperature immediately upstream of the main circuit expansion valve in the second stage circuit and effectively improves 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 the state at point 6 in FIG. 3 ). Then, the second refrigerant enters the second-stage condenser CH through the pipeline, and is condensed in the second-stage condenser CH to be converted into a liquid state (corresponding to the state of point 7 in FIG. 3 ). In this embodiment, the condensation temperature of the second-stage circuit is about 135°C. The condensed second refrigerant is discharged from the condensing evaporator EC, and then enters the jet enthalpy heat exchanger EH from the inlet point a of the second refrigerant passage of the jet enthalpy heat exchanger EH. In the jet enthalpy heat exchanger EH, the heat of the second refrigerant in the second refrigerant passage is absorbed by the second part of the first refrigerant in the first refrigerant passage, whereby the temperature of the second refrigerant is further reduced , and then the air jet enthalpy heat exchanger EH is discharged from the outlet b of the second refrigerant passage. Next, the second refrigerant enters the second-stage main circuit expansion valve VH, and changes to a state corresponding to point 8 in FIG. 3 through the depressurization action of the second-stage main circuit expansion valve VH. Subsequently, the second refrigerant enters the refrigerant evaporation channel of the condensation evaporator EC, and in the condensation evaporator EC, the second refrigerant in the refrigerant evaporation channel exchanges heat with the first refrigerant in the refrigerant condensation channel, The second refrigerant is evaporated and transformed into a gaseous state (corresponding to the state at point 5 in FIG. 3 ). In this embodiment, the evaporation temperature of the second-stage circuit is 75°C. The evaporated second refrigerant is discharged from the condensing evaporator EC and then enters the intake port of the second stage compressor PH.

The beneficial effects of the heat pump system according to the first embodiment of the present disclosure will be described below with reference to the heat pump system of the first comparative example shown in FIGS. 6 to 8 .

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 loop and a second-stage loop, similar to the first embodiment of the present disclosure. The main components, arrangement, connection, refrigerant selection, etc. of the first-stage circuit and the second-stage circuit are the same as those in the first embodiment of the present disclosure. For example, the first-stage circuit is composed of the first-stage compressor PL. , the condensing evaporator EC, the first-stage main circuit expansion valve VL and the first-stage evaporator EL are connected in sequence along the flow direction of the low-temperature stage refrigerant (first refrigerant), and the second-stage loop is formed by the second-stage compression The machine PH, the second stage condenser CH, the jet enthalpy heat exchanger EH, the second stage main circuit expansion valve VH and the condensing evaporator EC are connected in sequence along the flow direction of the high temperature stage refrigerant (second refrigerant), And the first stage loop and the second stage loop are thermally coupled through the condensing evaporator EC.

Different from the first embodiment, in this heat pump system S', the second stage compressor PH is configured as a jet enthalpy compressor with a supplementary air port, and the jet enthalpy increase branch is derived from the jet enthalpy increase in the second stage circuit. Downstream of the heat exchanger EH, the branch point Q between the jet enthalpy heat exchanger EH and the second-stage main circuit expansion valve VH begins to extend, and is connected through the second branch expansion valve VX and the jet enthalpy heat exchanger EH To the air supply port of the second stage compressor PH. Referring to FIG. 7 and FIG. 8, a part of the second refrigerant (hereinafter referred to as the first part of the second refrigerant) discharged from the outlet b of the second refrigerant passage of the jet enthalpy heat exchanger EH enters the second stage main The expansion valve VH of the main circuit is converted into a state corresponding to the point 8 in FIG. Subsequently, the first part of the second refrigerant enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to be transformed into a gaseous state (corresponding to the state at point 5 in FIG. 8 ), and is then discharged from the condensing evaporator EC and enters The intake port of the second stage compressor PL. Another part of the second refrigerant (hereinafter referred to as the second part of the second refrigerant) discharged from the outlet b point of the second refrigerant passage of the jet enthalpy heat exchanger EH passes from the branch point Q on the second stage circuit The pressure of the second part of the second refrigerant decreases after entering the gas injection enthalpy increasing branch and being throttled by the expansion valve VX' of the second branch. At this time, the temperature of the second part of the second refrigerant is the saturation temperature corresponding to the injection pressure, that is, about 103°C. Subsequently, the second part of the second refrigerant enters the first refrigerant passage in the jet enthalpy heat exchanger EH, that is, at the inlet point c of the first refrigerant passage of the jet enthalpy heat exchanger EH, the The temperature of the second part of the secondary refrigerant is about 103°C. The second part of the second refrigerant exchanges heat with the second refrigerant in the second refrigerant passage in the first refrigerant passage, absorbs the heat of the second refrigerant and reduces the temperature of the second refrigerant, thereby reducing the temperature of the second refrigerant. The temperature of the second refrigerant before the second-stage main circuit expansion valve VH. Then the second part of the second refrigerant is discharged from the outlet point d of the first refrigerant passage of the jet enthalpy heat exchanger EH, and sent to the supplementary air port of the second stage compressor PH which is communicated with the middle pressure part. The second part of the second refrigerant sent back to the make-up port of the second stage compressor PH eventually mixes with the first part of the second refrigerant entering the second stage compressor PH from the intake port of the second stage compressor PH, and The gas that is recompressed to high temperature and high pressure (corresponding to the state of point 6) is discharged from the second stage compressor PH. It can be seen from Figure 8 that the condensing temperature of the second-stage loop is about 135°C, and the temperature of the second refrigerant after being throttled by the second branch expansion valve VX' (ie at point c) is about 103°C, Assuming that the heat exchange temperature difference is 5°C, the pre-valve temperature of the second-stage main circuit expansion valve VH (corresponding to the temperature at point b) is about 108°C. This temperature far exceeds the long-term use tolerance temperature of most electronic expansion valves (about 70°C), so it is difficult to find suitable electronic expansion valve products on the market, which affects the reliability of valve parts and even the system.

In contrast, in the first embodiment according to the present disclosure, the condensing temperature of the second-stage loop may be higher than 100° C., for example, about 135° C., and the gas injection enthalpy increasing branch passes through the first branch expansion valve VX The temperature of the first refrigerant after throttling is about 53°C (that is, the temperature of the first refrigerant at point c), so the first refrigerant can sufficiently cool the second refrigerant in the jet enthalpy heat exchanger, so that The second refrigerant reaches a sufficiently low pre-valve temperature (ie the second refrigerant temperature at point b), ie below 70°C. For example, assuming that the heat exchange temperature difference is 5°C, the pre-valve temperature of the second-stage main circuit expansion valve VH (that is, the temperature of the second refrigerant at point b) is 58°C, and an ordinary electronic expansion valve can meet the temperature resistance requirements. requirements, so that the cost of the system is reduced and the reliable operation of the system is guaranteed.

Therefore, in the heat pump system according to the first embodiment of the present disclosure, on the one hand, by introducing a part of the first refrigerant after being condensed by the condensing evaporator EC in the first stage circuit into the gas injection enthalpy increasing branch, the first refrigerant is passed through the first stage circuit. After the branch expansion valve VX is throttled, the first refrigerant with a lower temperature is used to fully cool the condensed second refrigerant in the second-stage circuit in the jet enthalpy heat exchanger EH, so that the second refrigerant can be fully cooled. The temperature before the second-stage main circuit expansion valve VH in the first-stage circuit is significantly reduced, so that the system can use a common electronic expansion valve, which reduces the cost of the system and ensures the reliable operation of the system.

On the other hand, the first refrigerant discharged from the jet enthalpy heat exchanger EH (at point d) is delivered to the first refrigerant replenishment port PLI of the first stage compressor PL at a suitable medium temperature and pressure, compared to The related scheme of transporting the medium temperature and medium pressure first refrigerant back to the air inlet of the first stage compressor PL or on the path before the air inlet is because the medium temperature and medium pressure first refrigerant is directly supplied to the first stage compressor PL. The intermediate pressure chamber of the stage compressor PL performs further compression, thus increasing the system efficiency.

The second embodiment of the present disclosure is a modification of the first embodiment of the present disclosure. The second embodiment of the present disclosure will be described below with reference to FIGS. 4 and 5 .

Similar to the first embodiment of the present disclosure, the heat pump system S according to the second embodiment of the present disclosure is also a cascade system including a first-stage loop and a second-stage loop. The main components, arrangement, connection method, refrigerant selection, etc. of the first-stage loop, the second-stage loop, and the jet enthalpy-increasing branch are the same as those in the first embodiment of the present disclosure, and will not be repeated here.

Different from the first embodiment of the present disclosure, the second embodiment of the present disclosure is further provided with a cooling branch on the basis of the heat pump system shown in the first embodiment of the present disclosure. The cooling branch extends from the downstream of the jet enthalpy heat exchanger EH of the second-stage circuit, passes through the throttle valve VY, and is finally connected to the second refrigerant replenishment port of the second-stage compressor PH, which communicates with the pressure chamber therein. PHI. Preferably, the cooling branch extends from the second branch point R between the jet enthalpy heat exchanger EH and the second-stage main circuit expansion valve VH, so that the refrigerant supplied to the second refrigerant supplementary port PHI has suitable temperature and pressure. Referring to FIG. 4 , a part of the second refrigerant (hereinafter referred to as the first part of the second refrigerant) discharged from the outlet b of the second refrigerant passage of the jet enthalpy heat exchanger EH enters the second-stage main circuit expansion valve VH is transformed into a state corresponding to point 8 in FIG. 5 through the depressurization action of the second-stage main circuit expansion valve VH. Subsequently, the first part of the second refrigerant enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to be transformed into a gaseous state (corresponding to the state at point 5 in FIG. 5 ), and is then discharged from the condensing evaporator EC into the intake of the second stage compressor PL. Another part of the second refrigerant (hereinafter referred to as the second part of the second refrigerant) discharged from the outlet b of the second refrigerant passage of the jet enthalpy heat exchanger EH is branched from the second branch on the second stage circuit Point R enters the cooling branch, after being throttled by the throttle valve VY, the pressure of the second part of the second refrigerant is reduced, and then the second part of the second refrigerant is injected to the second stage with a lower temperature and a suitable pressure In the middle-pressure chamber of the compressor PH, and the high-temperature gas in the middle-pressure chamber (the high-temperature gas is the part of the second refrigerant sucked in from the air inlet of the second-stage compressor PH that is compressed to the middle-pressure chamber , which is in the state corresponding to point g in FIG. 5 ) mixed to reach the state corresponding to point e in FIG. 5 , and then compressed together to the state corresponding to point 6 in FIG. Stage compressor PH discharge.

Compared with the first embodiment, the cooling branch added in the second embodiment can provide refrigerant with a lower temperature to the supplementary port PHI of the second-stage compressor PH, so as to prevent the discharge of the second-stage compressor from overheating. purpose, thereby improving the controllability and efficiency of the system. Preferably, the second part of the second refrigerant supplied to the second refrigerant replenishment port PHI after being throttled by the throttle valve VY is in pure liquid state, so as to provide sufficient cooling effect with as little refrigerant as possible, and also It is beneficial to reduce the refrigerant temperature immediately upstream of the main circuit expansion valve in the second-stage circuit.

On the other hand, it can be seen from Fig. 5 that the condensing temperature of the second-stage circuit is about 135°C. Since the first refrigerant in the air-jet enthalpy-enhancing heat exchanger can sufficiently cool the second refrigerant, the air-jet increasing The temperature at the outlet b of the second refrigerant passage of the enthalpy heat exchanger is as low as 58°C, so the temperature of the second part of the second refrigerant entering the cooling branch is also low enough, and only a small amount of liquid injection is needed to meet the requirements of the first refrigerant. Requirements for secondary compressor discharge temperature control. However, in the second comparative example shown in Figures 9 and 10, since there is no gas injection enthalpy-increasing branch introduced from the first-stage circuit, sufficient cooling cannot be provided for the second refrigerant in the second-stage circuit, The temperature of the second refrigerant is relatively high, so that a large amount of liquid injection is required to meet the requirements for controlling the discharge temperature of the second-stage compressor.

FIG. 9 shows a schematic diagram of the second stage loop of the second comparative example. In the second comparative example, the cooling branch extends from the 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 circuit expansion valve VH , passes through the throttle valve VY, and is finally connected to the second refrigerant supplementary port PHI' of the second stage compressor PH that communicates with the pressure chamber therein. A part of the second refrigerant in the state corresponding to point 7 in FIG. 10 (hereinafter referred to as the first part of the second refrigerant) discharged from the second-stage condenser CH enters the second-stage main circuit expansion valve VH, And the state corresponding to the point 8 in FIG. 10 is changed to the state corresponding to the point 8 in FIG. Subsequently, the first part of the second refrigerant enters the condensing evaporator EC, is evaporated in the condensing evaporator EC to be transformed into a gaseous state (corresponding to the state at point 5 in FIG. 10 ), and is then discharged from the condensing evaporator EC into the intake of the second stage compressor PL. Another part of the second refrigerant discharged from the condenser CH (hereinafter referred to as the second part of the second refrigerant) enters the cooling branch from the second branch point R on the second stage circuit, and is throttled through the throttle valve VY After that, the pressure of the second part of the second refrigerant decreases to change to a state corresponding to point f' in FIG. 10 , and then the second part of the second refrigerant is injected into the second refrigerant through the second refrigerant supplementary port PHI' In the middle pressure chamber of the first stage compressor PH, and the high temperature gas in the middle pressure chamber (the high temperature gas is the part of the second refrigerant sucked in from the air inlet of the second stage compressor PH that is compressed to the middle pressure chamber, which In the state corresponding to point g' in Figure 10), it is mixed to reach the state corresponding to point e in Figure 10, and then compressed together to the state corresponding to point 6 in Figure 10. Compressor PH discharge.

It can be seen from FIG. 10 that the condensation temperature of the second-stage loop is about 135°C. Assuming that the subcooling degree of the condenser CH is 5°C, the second-stage liquid discharged from the condenser CH in the state corresponding to point 7 The refrigerant temperature is about 130°C, which is significantly higher than the temperature of the second refrigerant at point b shown in FIG. 5 (58°C). Assuming that the refrigerant is R245fa, and the saturation temperature corresponding to the injection pressure is about 103°C, it is assumed that the pressure of the refrigerant injected into the medium-pressure chamber for cooling and the refrigerant in the state of g/g' in the medium-pressure chamber remains unchanged after mixing, Other parameters regarding the refrigerant in state f/f' and state g/g' are shown in the following table (Table 1).

Table 1

According to the above parameters, assuming that the mass of the refrigerant in the intermediate pressure chamber of the second-stage compressor PH (that is, the refrigerant in the state corresponding to point g or point g') is 0.1 kg, the target temperature of the mixed state e is 110°C, then it can be calculated that the mass of the cooling refrigerant that needs to be injected according to the second embodiment of the present disclosure is about 0.015kg, while the mass of the cooling refrigerant that needs to be injected for the second comparative example is about 0.033 kg. Therefore, the heat pump system according to the second embodiment of the present disclosure can achieve the purpose of controlling the exhaust gas temperature of the second-stage compressor with a small amount of liquid injection, which further improves the system efficiency.

The high temperature heat pump system according to the preferred embodiment of the present disclosure is described above in conjunction with the specific embodiments. It is to be understood that the above description is illustrative only and not restrictive, and that various variations and modifications may occur to those skilled in the art with reference to the above description without departing from the scope of the present disclosure. These variations and modifications are also included within the scope of protection of the present disclosure.

Claims (8)

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 circuit expansion valve (VL), and a first-stage main circuit expansion valve (VL) are sequentially arranged along the refrigerant flow direction. Primary Evaporator (EL); A second-stage circuit, on which a second-stage compressor (PH), a second-stage condenser (CH), a jet enthalpy heat exchanger (EH), The second stage main circuit expansion valve (VH) and the condensing evaporator (EC), wherein the condensing evaporator (EC) is used both as a condenser in the first stage loop and in the second used as an evaporator in a stage circuit; and jet enthalpy branch, It is characterized in that the first stage compressor has a first refrigerant replenishment port (PLI), and the gas injection enthalpy branch is located downstream from the condensing evaporator (EC) on the first stage circuit The first branch point (P) of , begins to extend, passes through the jet enthalpy heat exchanger (EH), and is connected to the first refrigerant replenishment port (PLI). The heat pump system (S) according to claim 1, characterized in that it is configured such that the first refrigerant is supplied to the first refrigerant replenishment port (PLI) via the gas injection enthalpy branch for pure gaseous state. The heat pump system (S) according to claim 1, characterized in that, on the jetting enthalpy increasing branch, between the first branch point (P) and the jetting enthalpy increasing heat exchanger (EH) A first branch expansion valve (VX) is provided. The 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 replenishment port (PHI), the heat pump system further Including a cooling branch from a second branch on the second stage circuit between the jet enthalpy heat exchanger (EH) and the second stage main circuit expansion valve (VH) Point (R) begins to extend and connects to the second refrigerant replenishment port (PHI). The heat pump system (S) according to claim 4, characterized in that the heat pump system is configured such that the second refrigerant supplied to the second refrigerant replenishment port (PHI) via the cooling branch is pure liquid. The heat pump system (S) according to claim 4, characterized in that a throttle valve (VY) is provided on the cooling branch. The heat pump system (S) according to any one of claims 1 to 3, characterized in that the heat pump system is configured such that the condensing temperature of the second stage condenser (CH) is higher than 100° C. The temperature of the refrigerant immediately upstream of the second-stage main circuit expansion valve (VH) is lower than 70°C. The heat pump system (S) according to any one of claims 1 to 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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