A microchannel heat exchanger heat pump system and control method thereof

Abstract

A microchannel heat exchanger heat pump system and a control method thereof, wherein the microchannel heat exchanger heat pump system includes a compressor, two indoor heat exchangers, a gas-liquid separator, a microchannel heat exchanger, five ball valves, two throttle valves, and two heat exchange tubes; when the microchannel heat exchanger operates under frosting conditions, there are problems such as a fast frosting rate and a fast attenuation of heat exchange performance; in addition, condensate will appear in the heat exchanger during the heat exchange process, and the condensate will increase the heat exchange thermal resistance; the present invention proposes a control method for a microchannel heat exchanger heat pump system, which utilizes the high-temperature refrigerant coming out of the gas-liquid separator and the second indoor heat exchanger to heat the low-temperature refrigerant in the microchannel heat exchanger, thereby increasing the evaporation temperature and delaying frosting; in addition, the heat pump system is controlled according to the operating load of the heat pump system and the surface temperature of the flat tubes, so that the heat pump system operates efficiently.

Description

Technical Field

[0001] The present invention relates to the technical field of a microchannel heat exchanger heat pump system, and in particular to a microchannel heat exchanger heat pump system and a control method thereof. Background Art

[0002] Microchannel heat exchangers have been widely used in the field of refrigeration and air conditioning due to their advantages such as high heat exchange efficiency, small size, compact structure, small refrigerant charge and low production cost. However, when microchannel heat exchangers are used as evaporators and operate under frosting conditions, there are problems such as excessively fast frosting rate and rapid degradation of heat exchange performance. In addition, condensate will appear in the condenser during the condensation process, and the condensate will form a liquid film inside the heat exchanger, increasing the heat transfer thermal resistance.

[0003] The two main factors that influence rapid frost formation on microchannel heat exchangers are air humidity and surface temperature. Changing air humidity is often costly, making it difficult to promote and apply in heat pump air conditioning. Changing the heat exchanger's surface temperature is an effective method for suppressing frost, but increasing this temperature typically requires an additional heat source to heat the refrigerant entering the evaporator. Furthermore, to improve heat pump system performance, timely separation of condensate is an effective means of enhancing heat exchange performance. Summary of the Invention

[0004] In response to the problems existing in the microchannel heat exchanger heat pump system described above, the purpose of the present invention is to provide a microchannel heat exchanger heat pump system and its control method. By installing a gas-liquid separator between the two indoor heat exchangers, the condensate is separated to improve the heat exchange performance of the heat exchanger. Secondly, the separated high-temperature condensate can also be used to heat the low-temperature refrigerant in the microchannel heat exchanger, increase the evaporation temperature of the microchannel heat exchanger, and delay frosting. The high-temperature refrigerant coming out of the second indoor heat exchanger can also be used to heat the low-temperature refrigerant in the microchannel heat exchanger. The specific control is determined by the operating load of the heat pump system and the temperature of the flat tube surface.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A microchannel heat exchanger heat pump system includes a compressor 01, a first indoor heat exchanger 02, and a gas-liquid separator 03. The exhaust port of the compressor 01 is connected to the first indoor heat exchanger 02, which is in turn connected to the gas-liquid separator inlet 301. The gas outlet 302 of the gas-liquid separator is connected to the first ball valve 04, which is in turn connected to the inlet of the second indoor heat exchanger 05. The outlet of the second indoor heat exchanger 05 is respectively connected to the fourth ball valve 08 and the fifth ball valve 09. The liquid outlet 303 of the gas-liquid separator is respectively connected to the second ball valve 06 and the third ball valve 07. The first heat exchange tube 10 is connected to the second ball valve 06, the second heat exchanger 11 is connected to the fourth ball valve 08, the first heat exchange tube 10 and the second heat exchange tube 11 are both installed in the first liquid collecting pipe 12, and the throttle valve 13 is respectively connected to the first heat exchange tube 10, the second heat exchange tube 11, and the third ball valve 0 7 is connected to the fifth ball valve 09, and the throttle valve 13 is connected to the first liquid collecting pipe 12. A plurality of flat tubes 14 are arranged between and connect the first and second liquid collecting pipes 12, 16. Fins 15 are installed between adjacent flat tubes. The second liquid collecting pipe 16 is connected to the inlet of the compressor 01. A temperature sensor T1 is arranged on the surface of the flat tube 14 to measure the surface temperature of the microchannel heat exchanger. Among them, the first heat exchange tube 10, the second heat exchange tube 11, the first liquid collecting pipe 12, the second liquid collecting pipe 16, the flat tube 14 and the fin 15 constitute the microchannel heat exchanger. The first ball valve 04, the second ball valve 06, the third ball valve 07, the fourth ball valve 08, the fifth ball valve 09 and the temperature sensor T1 are respectively connected to the control module C1. The control module C1 controls the opening and closing of each ball valve according to the workload and working conditions of the heat pump system.

[0007] A gas-liquid separator 03 is installed between the first indoor heat exchanger 02 and the second indoor heat exchanger 05. When the heat pump system is working at full load, condensate will appear during the condensation process. The condensate will form a liquid film on the inner wall of the first indoor heat exchanger 02, which is not conducive to heat exchange of the heat exchanger. The gas-liquid separator 03 can separate the condensate, so that the refrigerant entering the second indoor heat exchanger 05 is gas, thereby improving the heat exchange performance of the second indoor heat exchanger 05; when the heat pump system is working under low load, only one indoor heat exchanger is needed to meet the heat exchange demand. At this time, the control module C1 closes the first ball valve 04 and only uses the first indoor heat exchanger 02 to heat the room, reducing the pressure drop of the first indoor heat exchanger and improving the performance of the heat pump system.

[0008] The control module C1 detects the surface temperature change of the flat tube 14 based on the temperature sensor T1 and determines whether the microchannel heat exchanger is in a frosted state. When the microchannel heat exchanger is in a frosted state, the high-temperature condensate separated by the gas-liquid separator 03 and the high-temperature refrigerant from the second indoor heat exchanger 05 are respectively introduced into the first heat exchange tube 10 and the second heat exchange tube 11 to heat the low-temperature refrigerant in the first liquid collecting pipe 12, thereby increasing the surface temperature of the flat tube 14, suppressing the growth of the frost layer, extending the operating time of the heat pump system, and improving the operating performance of the heat pump system under frosting conditions.

[0009] In the control method of the microchannel heat exchanger heat pump system, the control module C1 collects signals of the heat pump system workload and working conditions, and controls the opening and closing of the first ball valve 04, the second ball valve 06, the third ball valve 07, the fourth ball valve 08, and the fifth ball valve 09. The specific control method is as follows:

[0010] When the heat pump system is operating under non-frosting conditions:

[0011] When the heat pump system is operating at full load, the control module C1 controls the first ball valve 04, the third ball valve 07, and the fifth ball valve 09 to open, and the second ball valve 06 and the fourth ball valve 08 to close. At this time, the gas-liquid separator 03 separates the condensate, and the high-temperature condensate enters the second indoor heat exchange pipe 05. When the heat pump system is operating at low load, the control module C1 controls the third ball valve 07 to open, and the first ball valve 04, the second ball valve 06, the fourth ball valve 08, and the fifth ball valve 09 to close. At this time, the refrigerant flow is small, and gas-liquid separation is not required. The refrigerant only flows through the first indoor heat exchanger 02, reducing the pressure drop and improving the performance of the heat pump system.

[0012] When the heat pump system operates under frosting conditions:

[0013] When the heat pump system is working at full load, the control module C1 controls the amount of high-temperature refrigerant entering the first heat exchange tube 10 and the second heat exchange tube 11 according to the surface temperature of the flat tube 14. When the temperature T1 of the microchannel heat exchanger surface tested by the temperature sensor T1 is greater than or equal to -2°C, the frost on the microchannel heat exchanger surface is not serious, and the demand can be met by only requiring the high-temperature condensate separated by the gas-liquid separator 03 to enter the first heat exchange tube 10 to heat the low-temperature refrigerant in the first liquid collecting pipe 12. At this time, the control module C1 controls the first ball valve 04, the second ball valve 06 and the fifth ball valve 09 to open, and the third ball valve 07 and the fourth ball valve 08 to close. When T1 < -2 ℃, the surface of the microchannel heat exchanger is severely frosted, and the high-temperature condensate separated by the gas-liquid separator 03 needs to enter the first heat exchange tube 10 and the high-temperature refrigerant coming out of the second indoor heat exchanger 05 needs to enter the second heat exchange tube 10 to heat the low-temperature refrigerant in the first collecting pipe 12. At this time, the control module C1 controls the first ball valve 04, the second ball valve 06 and the fourth ball valve 08 to open, and the third ball valve 07 and the fifth ball valve 09 to close; when the heat pump system is working at a low load, only the first indoor heat exchanger 02 is needed to exchange heat to meet the heating needs, and the control module C1 controls the first ball valve 04, the third ball valve 07, the fourth ball valve 08 and the fifth ball valve 09 to close.

[0014] Compared with the prior art, the present invention has the following advantages

[0015] 1. The present invention proposes a microchannel heat exchanger heat pump system and a control method thereof, which fully utilizes the high-temperature refrigeration from the gas-liquid separator and the second indoor heat exchanger to heat the low-temperature refrigerant in the microchannel heat exchanger, thereby increasing the evaporation temperature and delaying frosting.

[0016] 2. The present invention proposes a microchannel heat exchanger heat pump system and a control method thereof, which can control the efficient operation of the heat pump system according to the operating load of the heat pump system and the temperature of the flat tube surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The figure is a schematic diagram of the refrigerant flow of a microchannel heat exchanger heat pump system according to the present invention under full load and frosting conditions.

[0018] Figure 2 The figure is a schematic diagram of the refrigerant flow of a microchannel heat exchanger heat pump system according to the present invention under low-load operation and frosting conditions. DETAILED DESCRIPTION

[0019] The specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0020] like Figure 1 and Figure 2As shown, the present invention provides a microchannel heat exchanger heat pump system, including a compressor 01, a first indoor heat exchanger 02, and a gas-liquid separator 03. The exhaust port of the compressor 01 is connected to the first indoor heat exchanger 02, and the first indoor heat exchanger 02 is connected to the gas-liquid separator inlet 301. The gas outlet 302 of the gas-liquid separator is connected to the first ball valve 04, and the first ball valve 04 is connected to the inlet of the second indoor heat exchanger 05. The outlet of the second indoor heat exchanger 05 is respectively connected to the fourth ball valve 08 and the fifth ball valve 09. The liquid outlet 303 of the gas-liquid separator is respectively connected to the second ball valve 06 and the third ball valve 07. The first heat exchange tube 10 is connected to the second ball valve 06, and the second heat exchanger 11 is connected to the fourth ball valve 08. The first heat exchange tube 10 and the second heat exchange tube 11 are both installed in the first liquid collecting pipe 12. The throttle valve 13 is respectively connected to the first heat exchange tube 10, the second heat exchange tube 11, and the third Ball valve 07 is connected to the fifth ball valve 09, and the throttle valve 13 is connected to the first manifold 12. Multiple flat tubes 14 are arranged between and connect the first and second manifolds 12, 16. Fins 15 are installed between adjacent flat tubes. The second manifold 16 is connected to the inlet of the compressor 01. A temperature sensor T1 is arranged on the surface of the flat tube 14 to measure the surface temperature of the microchannel heat exchanger. Among them, the first heat exchange tube 10, the second heat exchange tube 11, the first manifold 12, the second manifold 16, the flat tube 14 and the fin 15 constitute the microchannel heat exchanger. The first ball valve 04, the second ball valve 06, the third ball valve 07, the fourth ball valve 08, the fifth ball valve 09 and the temperature sensor T1 are respectively connected to the control module C1. The control module C1 controls the opening and closing of each ball valve according to the workload and working conditions of the heat pump system.

[0021] The heat pump system of the present invention is equipped with a gas-liquid separator 03 between the first indoor heat exchanger 02 and the second indoor heat exchanger 05. When the heat pump system is operating at full load, condensate will appear during the condensation process. The condensate will form a liquid film on the inner wall of the first indoor heat exchanger 02, which is not conducive to heat exchange of the heat exchanger. The gas-liquid separator 03 can separate the condensate, allowing the refrigerant entering the second indoor heat exchanger 05 to be gas, thereby improving the heat exchange performance of the second indoor heat exchanger 05; when the heat pump system is operating under low load, only one indoor heat exchanger is needed to meet the heat exchange demand. At this time, the control module C1 closes the first ball valve 04 and only uses the first indoor heat exchanger 02 to heat the indoor space, reducing the pressure drop of the first indoor heat exchanger and improving the performance of the heat pump system.

[0022] The control module C1 detects the surface temperature change of the flat tube 14 based on the temperature sensor T1 and determines whether the microchannel heat exchanger is in a frosted state. When the microchannel heat exchanger is in a frosted state, the high-temperature condensate separated by the gas-liquid separator 03 and the high-temperature refrigerant from the second indoor heat exchanger 05 are respectively introduced into the first heat exchange tube 10 and the second heat exchange tube 11 to heat the low-temperature refrigerant in the first liquid collecting pipe 12, thereby increasing the surface temperature of the flat tube 14, suppressing the growth of the frost layer, extending the operating time of the heat pump system, and improving the operating performance of the heat pump system under frosting conditions.

[0023] In the control method of the microchannel heat exchanger heat pump system, the control module C1 collects signals of the heat pump system workload and working conditions, and controls the opening and closing of the first ball valve 04, the second ball valve 06, the third ball valve 07, the fourth ball valve 08, and the fifth ball valve 09. The specific control method is as follows:

[0024] When the heat pump system is operating under non-frosting conditions:

[0025] When the heat pump system is working at full load, the control module C1 controls the first ball valve 04, the third ball valve 07 and the fifth ball valve 09 to open, and the second ball valve 06 and the fourth ball valve 08 to close. At this time, the high-temperature exhaust gas of the compressor 01 enters the first indoor heat exchanger 02 for condensation and heat exchange, and then enters the gas-liquid separator 03 to separate the condensate, and the high-temperature condensate enters the second indoor heat exchange pipe 05. When the heat pump system is working at low load, the control module C1 controls the third ball valve 07 to open, and the first ball valve 04, the second ball valve 06, the fourth ball valve 08 and the fifth ball valve 09 to close. At this time, the refrigerant flow is small, and gas-liquid separation is not required. The refrigerant only flows through the first indoor heat exchanger 02, reducing the pressure drop and improving the performance of the heat pump system.

[0026] When the heat pump system operates under frosting conditions:

[0027] When the heat pump system is working at full load, the control module C1 controls the amount of high-temperature refrigerant entering the first heat exchange tube 10 and the second heat exchange tube 11 according to the surface temperature of the flat tube 14. When the temperature T1 of the microchannel heat exchanger surface tested by the temperature sensor T1 is greater than or equal to -2°C, the frost on the microchannel heat exchanger surface is not serious, and the high-temperature condensate separated by the gas-liquid separator 03 only needs to enter the first heat exchange tube 10 to heat the low-temperature refrigerant in the first collecting pipe 12 to meet the demand. At this time, the control module C1 controls the first ball valve 04, the second ball valve 06 and the fifth ball valve 09 to open, and the third ball valve 07 and the fourth ball valve 08 to close. When T1 is less than -2°C, the microchannel heat exchanger surface is seriously frosted, and the high-temperature condensate separated by the gas-liquid separator 03 is required. The high-temperature refrigerant entering the first heat exchange tube 10 and the second indoor heat exchanger 05 enters the second heat exchange tube 10 to heat the low-temperature refrigerant in the first liquid collecting pipe 12. After passing through the first liquid collecting pipe 12, the refrigerant enters the flat tube 14 for evaporation and heat exchange, and then enters the second liquid collecting pipe 16. The refrigerant coming out of the second liquid collecting pipe 16 enters the compressor 01 for compression. At this time, the control module C1 controls the first ball valve 04, the second ball valve 06 and the fourth ball valve 08 to open, and the third ball valve 07 and the fifth ball valve 09 to close; when the heat pump system is working at low load, only the first indoor heat exchanger 02 is needed for heat exchange to meet the heating needs, and the control module C1 controls the first ball valve 04, the third ball valve 07, the fourth ball valve 08 and the fifth ball valve 09 to close.

Claims

1. A control method for a microchannel heat exchanger heat pump system, characterized in that: The microchannel heat exchanger heat pump system comprises a compressor (01), a first indoor heat exchanger (02), and a gas-liquid separator (03). The exhaust port of the compressor (01) is connected to the first indoor heat exchanger (02), which is in turn connected to the gas-liquid separator inlet (301). The gas outlet (302) of the gas-liquid separator is connected to the first ball valve (04), which is in turn connected to the inlet of the second indoor heat exchanger (05). The outlet of the second indoor heat exchanger (05) is respectively connected to the fourth ball valve (08) and the fifth ball valve (09). The liquid outlet (303) of the gas-liquid separator is respectively connected to the second ball valve (06) and the third ball valve (07). The first heat exchange pipe (10) is connected to the second ball valve (06), and the second heat exchange pipe (11) is connected to the second ball valve (06). The heat exchanger (11) is connected to the fourth ball valve (08), the first heat exchange tube (10) and the second heat exchange tube (11) are both installed in the first collecting pipe (12), the throttle valve (13) is respectively connected to the first heat exchange tube (10), the second heat exchange tube (11), the third ball valve (07) and the fifth ball valve (09), the throttle valve (13) is connected to the first collecting pipe (12), a plurality of flat tubes (14) are arranged between the first collecting pipe (12) and the second collecting pipe (16) and are connected to the first collecting pipe (12) and the second collecting pipe (16), fins (15) are installed between adjacent flat tubes, the second collecting pipe (16) is connected to the inlet of the compressor (01), and a temperature sensor is arranged on the surface of the flat tube (14) for testing the surface temperature of the microchannel heat exchanger. T 1; wherein the first heat exchange tube (10), the second heat exchange tube (11), the first liquid collecting tube (12), the second liquid collecting tube (16), the flat tube (14) and the fin (15) constitute a microchannel heat exchanger, and the first ball valve (04), the second ball valve (06), the third ball valve (07), the fourth ball valve (08), the fifth ball valve (09) and the temperature sensor are respectively connected to the control module (C1), and the control module (C1) controls the opening and closing of each ball valve according to the working load and working condition of the heat pump system; A gas-liquid separator (03) is installed between the first indoor heat exchanger (02) and the second indoor heat exchanger (05). When the heat pump system is working at full load, condensate will appear during the condensation process. The condensate will form a liquid film on the inner wall of the first indoor heat exchanger (02), which is not conducive to heat exchange of the heat exchanger. The gas-liquid separator (03) can separate the condensate, so that the refrigerant entering the second indoor heat exchanger (05) is gas, thereby improving the heat exchange performance of the second indoor heat exchanger (05); when the heat pump system is working at low load, only one indoor heat exchanger is needed to meet the heat exchange demand. At this time, the control module (C1) closes the first ball valve (04) and only uses the first indoor heat exchanger (02) to heat the room, reducing the pressure drop of the first indoor heat exchanger and improving the performance of the heat pump system; The control module (C1) detects the surface temperature change of the flat tube (14) based on the temperature sensor and determines whether the microchannel heat exchanger is in a frosting state. When the microchannel heat exchanger is in a frosting state, the high-temperature condensate separated by the gas-liquid separator (03) and the high-temperature refrigerant from the second indoor heat exchanger (05) are respectively introduced into the first heat exchange tube (10) and the second heat exchange tube (11) to heat the low-temperature refrigerant in the first collecting pipe (12), thereby increasing the surface temperature of the flat tube (14), inhibiting the growth of the frost layer, extending the operating time of the heat pump system, and improving the operating performance of the heat pump system under frosting conditions; The control method is as follows: the control module (C1) collects signals of the heat pump system's workload and working conditions, and controls the opening and closing of the first ball valve (04), the second ball valve (06), the third ball valve (07), the fourth ball valve (08), and the fifth ball valve (09). The specific control method is as follows: When the heat pump system is operating under non-frosting conditions: When the heat pump system is operating at full load, the control module (C1) controls the first ball valve (04), the third ball valve (07) and the fifth ball valve (09) to open, and the second ball valve (06) and the fourth ball valve (08) to close. At this time, the gas-liquid separator (03) separates the condensate, and the high-temperature condensate enters the second indoor heat exchange pipe (05). When the heat pump system is operating at low load, the control module (C1) controls the third ball valve (07) to open, and the first ball valve (04), the second ball valve (06), the fourth ball valve (08) and the fifth ball valve (09) to close. At this time, the refrigerant flow rate is small, and gas-liquid separation is not required. Moreover, the refrigerant only flows through the first indoor heat exchanger (02), thereby reducing the pressure drop and improving the performance of the heat pump system. When the heat pump system operates under frosting conditions: When the heat pump system is operating at full load, the control module (C1) controls the amount of high-temperature refrigerant entering the first heat exchange tube (10) and the second heat exchange tube (11) according to the surface temperature of the flat tube (14). When the surface temperature of the microchannel heat exchanger tested by the temperature sensor is T 1≥-2℃, the frost on the surface of the microchannel heat exchanger is not serious, and the demand can be met by only allowing the high-temperature condensate separated by the gas-liquid separator (03) to enter the first heat exchange tube (10) to heat the low-temperature refrigerant in the first collecting tube (12). At this time, the control module (C1) controls the first ball valve (04), the second ball valve (06) and the fifth ball valve (09) to open, and the third ball valve (07) and the fourth ball valve (08) to close. T 1<-2℃, the surface of the microchannel heat exchanger is severely frosted, and the high-temperature condensate separated by the gas-liquid separator (03) needs to enter the first heat exchange tube (10) and the high-temperature refrigerant from the second indoor heat exchanger (05) needs to enter the second heat exchange tube (10) to heat the low-temperature refrigerant in the first collecting pipe (12). At this time, the control module (C1) controls the first ball valve (04), the second ball valve (06) and the fourth ball valve (08) to open, and the third ball valve (07) and the fifth ball valve (09) to close; when the heat pump system is working at a low load, only the first indoor heat exchanger (02) is needed to exchange heat to meet the heating needs, and the control module (C1) controls the first ball valve (04), the third ball valve (07), the fourth ball valve (08) and the fifth ball valve (09) to close.

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