Efficient heat exchange direct expansion air conditioning system and opening degree control method

Abstract

The invention discloses an efficient heat exchange direct expansion air conditioning system and an opening degree control method. The air conditioning system comprises a compressor, a four-way valve, a condenser, a heat exchanger, an expansion valve, a first gas-liquid separator, an evaporator and a second gas-liquid separator. The compressor is connected with the four-way valve and the second gas-liquid separator. The C end of the four-way valve is connected with the input end of the condenser, and the E end is connected with the output end of the evaporator. The output end of the condenser is connected with a liquid pipe of the heat exchanger. A liquid pipe of the heat exchanger is connected with the expansion valve, and a gas pipe is connected with the S end of the four-way valve, the first gas-liquid separator and the second gas-liquid separator. And the output end of the expansion valve is connected with the first gas-liquid separator. The gas-phase output end of the first gas-liquid separator is connected with a gas pipe of the heat exchanger, and the liquid-phase output end is connected with the evaporator. The gas-liquid separator is additionally arranged after throttling of the expansion valve, and gaseous refrigerants are prevented from entering the evaporator. The heat exchanger increases the superheat temperature of the gaseous refrigerant, reduces the supercooling degree of the liquid refrigerant, and effectively increases the proportion of the liquid refrigerant in the evaporator.

Description

Technical Field

[0001] This invention relates to a high-efficiency heat exchange direct expansion air conditioning system, and also to an opening control method for the air conditioning system, belonging to the field of air conditioning technology. Background Technology

[0002] Conventional air conditioning heat exchangers achieve subcooling and superheating of the refrigerant by utilizing the temperature of the refrigerant or air. Since subcooling and superheating of the refrigerant involve non-phase change heat transfer, the heat exchange efficiency is very low. Therefore, achieving higher levels of subcooling and superheating requires wasting a large amount of heat exchange area.

[0003] Chinese patent application No. 202210188453.6 discloses a heat pump system and a clothing processing device. The heat pump system includes a gas-liquid separator, a compressor, a condenser, a throttling device, and an evaporator connected in series in a refrigerant circuit. The gas-liquid separator is located in the refrigerant circuit between the outlet of the throttling device and the inlet of the evaporator to separate the refrigerant into gas and liquid phases before it enters the evaporator.

[0004] Furthermore, Chinese invention patent number ZL 201810528759.5 discloses an air conditioning device. This device connects a compressor, an indoor heat exchanger, a main expansion valve, an outdoor heat exchanger, and a four-way valve via piping for refrigerant flow to form a refrigeration cycle. It has a first flow path between the outlet of the indoor heat exchanger and the inlet of the outdoor heat exchanger, and a second flow path between the outlet of the outdoor heat exchanger and the inlet of the four-way valve. The main expansion valve is located in the first flow path. The device also includes a heating unit that reduces heat loss in the four-way valve by heating the two-phase refrigerant flowing from the evaporator into a single-phase gaseous phase before it reaches the valve, thereby improving the energy efficiency ratio of the air conditioning device.

[0005] Similarly, 20%–35% of the refrigerant entering the evaporator after throttling is in a gaseous state, which is a non-phase change heat transfer process with low heat exchange efficiency. Meanwhile, a certain percentage of the refrigerant at the evaporator outlet is in a liquid state, which can cause liquid slugging in the compressor. Current technologies all rely on large heat exchange areas to compensate for the low efficiency of non-phase change heat transfer and introduce external heat sources to heat the gas pipes to vaporize the refrigerant, resulting in high equipment costs and low system energy efficiency. Summary of the Invention

[0006] The primary technical problem to be solved by this invention is to provide a high-efficiency heat exchange direct expansion air conditioning system.

[0007] Another technical problem to be solved by the present invention is to provide an opening degree control method for the above-mentioned air conditioning system.

[0008] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution: According to a first aspect of the present invention, a high-efficiency heat exchange direct expansion air conditioning system is provided, comprising a compressor, a four-way valve, a condenser, a heat exchanger, an expansion valve, a first gas-liquid separator, an evaporator, and a second gas-liquid separator; The output end of the compressor is connected to the compressor discharge end of the four-way valve, and the input end is connected to the output end of the second gas-liquid separator; The condenser end of the four-way valve is connected to the input end of the condenser; the evaporator end of the four-way valve is connected to the output end of the evaporator. The output end of the condenser is connected to the liquid inlet end of the heat exchanger; The liquid pipe output end of the heat exchanger is connected to the input end of the expansion valve, the gas pipe input end is connected to the compressor suction end of the four-way valve and the gas phase output end of the first gas-liquid separator, and the gas pipe output end is connected to the input end of the second gas-liquid separator. The output end of the expansion valve is connected to the input end of the first gas-liquid separator; The gas phase output end of the first gas-liquid separator is connected to the gas pipe input end of the heat exchanger, and the liquid phase output end is connected to the input end of the evaporator.

[0009] Preferably, the heat exchanger is a medium heat exchanger equipped with liquid pipes and gas pipes.

[0010] Preferably, the high-efficiency heat exchange direct expansion air conditioning system further includes a first one-way valve, a second one-way valve, a third one-way valve and a fourth one-way valve; The output end of the condenser is connected to the input end of the first one-way valve and the output end of the fourth one-way valve; the liquid inlet of the heat exchanger is connected to the output end of the first one-way valve and the output end of the third one-way valve; the liquid phase output end of the first gas-liquid separator is connected to the input end of the second one-way valve and the input end of the fourth one-way valve; the input end of the evaporator is connected to the output end of the second one-way valve and the input end of the third one-way valve.

[0011] Preferably, the high-efficiency heat exchange direct expansion air conditioning system further includes a first regulating valve and a second regulating valve; The input end of the first regulating valve is connected to the liquid inlet of the heat exchanger, and its output end is connected to the liquid outlet of the heat exchanger; the input end of the second regulating valve is connected to the gas outlet of the first gas-liquid separator, and its output end is connected to the gas inlet of the heat exchanger.

[0012] Preferably, the high-efficiency heat exchange direct expansion air conditioning system further includes a high-pressure gauge, a low-pressure gauge, an intake thermometer, and an evaporation thermometer; The high-pressure gauge is located at the output end of the compressor; the low-pressure gauge is located at the input end of the compressor; the suction thermometer is located at the input end of the second gas-liquid separator; and the evaporation thermometer is located at the gas pipe input end of the heat exchanger.

[0013] Preferably, the expansion valve is electrically connected to the low-pressure gauge and the intake thermometer; the first regulating valve is electrically connected to the intake thermometer; and the second regulating valve is electrically connected to the high-pressure gauge and the low-pressure gauge.

[0014] According to a second aspect of the present invention, a method for controlling the opening degree of the above-described air conditioning system is provided, comprising the following steps: Step S1: Obtain the low-pressure and suction temperature of the compressor, calculate the superheat of the evaporator in refrigeration mode or the condenser in heating mode, and compare it with the target superheat. If the superheat is higher than the target superheat, increase the opening of the expansion valve; otherwise, decrease the opening. Step S2: Obtain the compressor's suction temperature and compare it with the target suction temperature; if the suction temperature is higher than the target suction temperature, decrease the opening of the first regulating valve; otherwise, increase the opening. Step S3: Obtain the high pressure and low pressure of the compressor, calculate the refrigerant circulation volume, and control the opening of the second regulating valve according to the pre-programmed opening degree program of the second regulating valve corresponding to different high pressure and low pressure.

[0015] Compared with existing technologies, the high-efficiency direct expansion air conditioner provided by this invention adds a gas-liquid separator after the expansion valve throttling, ensuring that more liquid refrigerant enters the evaporator and improving the phase change heat transfer ratio. The separated gaseous refrigerant and the refrigerant at the evaporator outlet are heated by the heat exchanger to increase their superheat temperature, ensuring that the compressor does not experience liquid slugging. At the same time, the heat exchanger reduces the subcooling of the liquid refrigerant, increases the proportion of liquid refrigerant, and further improves the heat exchange efficiency of the evaporator. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of a high-efficiency heat exchange direct expansion air conditioning system in the first embodiment of the present invention; Figure 2 This is a schematic diagram of the cooling and heating modes of the high-efficiency heat exchange direct expansion air conditioning system in the second embodiment of the present invention. Detailed Implementation

[0017] The technical content of the present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0018] The technical concept in this invention is to increase the liquid content of the refrigerant entering the evaporator, thereby improving evaporator efficiency. Specifically, a heat exchanger and a gas-liquid separator are added between the condenser and the evaporator to further increase the subcooling of the liquid refrigerant and separate the gaseous refrigerant. The heat lost by the liquid refrigerant is used to heat the gas refrigerant after evaporation, increasing the superheat of the gas refrigerant.

[0019] First Embodiment like Figure 1 As shown, the first embodiment of the present invention provides a high-efficiency heat exchange direct expansion air conditioning system, including a compressor 1, a four-way valve 2, a condenser 3 (outdoor unit), a heat exchanger 4, an expansion valve 5, a first gas-liquid separator 6, an evaporator 7 (indoor unit), and a second gas-liquid separator 8. The pipelines transporting liquid refrigerant are collectively referred to as liquid pipes, and the pipelines transporting gaseous and gas-liquid mixed refrigerant are collectively referred to as gas pipes; this is common industry practice.

[0020] The output end of compressor 1 is connected to the D end (compressor exhaust end) of four-way valve 2, and the input end is connected to the output end of the second gas-liquid separator 8.

[0021] The four-way valve 2 has its D end connected to the output end of compressor 1, its C end (condenser end) connected to the input end of condenser 3, its E end (evaporator end) connected to the output end of evaporator 7, and its S end (compressor suction end) connected to the gas pipe input end of heat exchanger 4 (the input end of compressor 1). The structure and port numbering of the four-way valve 2 are industry standard.

[0022] The input end of condenser 3 (taking refrigeration mode as an example, the same below) is connected to the C end of four-way valve 2, and the output end is connected to the liquid pipe input end of heat exchanger 4.

[0023] Heat exchanger 4 is a heat exchanger equipped with two medium pipelines. The mediums in the two pipelines with a temperature difference can exchange heat through heat exchanger 4. In this embodiment of the invention, the medium pipelines of heat exchanger 4 are liquid pipelines and gas pipelines, with their input and output ends being liquid pipeline input, liquid pipeline output, gas pipeline input, and gas pipeline output, respectively. The liquid pipeline input end of heat exchanger 4 is connected to the output end of condenser 3, the liquid pipeline output end is connected to the input end of expansion valve 5, the gas pipeline input end is connected to the S end of four-way valve 2 and the gas phase output end of first gas-liquid separator 6, and the gas pipeline output end is connected to the input end of second gas-liquid separator 8.

[0024] The input end of the expansion valve 5 is connected to the liquid outlet end of the heat exchanger 4, and the outlet end is connected to the input end of the first gas-liquid separator 6.

[0025] The first gas-liquid separator 6 is a gas-liquid separation device, equipped with an input end, a gas phase output end, and a liquid phase output end. The input end of the first gas-liquid separator 6 is connected to the output end of the expansion valve 5, the gas phase output end is connected to the gas pipe input end of the heat exchanger 4, and the liquid phase output end is connected to the input end of the evaporator 7.

[0026] The input end of the evaporator 7 is connected to the liquid phase output end of the first gas-liquid separator 6, and the output end is connected to the E end of the four-way valve 2.

[0027] The input end of the second gas-liquid separator 8 is connected to the gas pipe output end of the heat exchanger 4, and the output end is connected to the input end of the compressor 1.

[0028] In refrigeration mode, the high-pressure, high-temperature refrigerant output from compressor 1 enters condenser 3 through four-way valve 2 and is condensed, transforming into medium-pressure, medium-temperature liquid refrigerant. The refrigerant then passes through the liquid line of heat exchanger 4 and expansion valve 5, transforming into gaseous or gas-liquid mixed refrigerant. The refrigerant enters the first gas-liquid separator 6 for separation. The separated liquid refrigerant enters evaporator 7 for evaporation and heat absorption, transforming into low-pressure, low-temperature gaseous or gas-liquid mixed refrigerant. This liquid refrigerant then passes through four-way valve 2 and, together with the gaseous refrigerant separated from the first gas-liquid separator 6, enters the gas line of heat exchanger 4. The refrigerant output from the gas line of heat exchanger 4 enters the compressor through the second gas-liquid separator 8 to continue the next cycle.

[0029] The medium-pressure, medium-temperature refrigerant in the liquid pipe of heat exchanger 4 exchanges heat fully with the low-pressure, low-temperature refrigerant in the gas pipe, resulting in the following advantages.

[0030] On the one hand, it lowers the refrigerant temperature before expansion valve 5, increasing the subcooling of the refrigerant in the liquid line. This causes more gaseous refrigerant to condense into liquid, increasing the proportion of liquid refrigerant before expansion valve 5. Consequently, while maintaining the same liquid line flow rate, it increases the flow rate of liquid refrigerant obtained by evaporator 7. With more liquid refrigerant participating in phase change evaporation, the efficiency of evaporator 7 is improved.

[0031] On the other hand, the refrigerant temperature before the second gas-liquid separator 8 is increased, raising the superheat of the refrigerant in the gas pipe. This causes more liquid refrigerant to evaporate into gas, increasing the proportion of gaseous refrigerant before the second gas-liquid separator 8. Consequently, while maintaining the same gas pipe flow rate, the flow rate of gaseous refrigerant obtained by compressor 1 is increased. More gaseous refrigerant is then compressed again, thus improving the efficiency of compressor 1 and preventing liquid refrigerant slugging that could damage compressor 1.

[0032] It is worth noting that heat exchanger 4 exchanges heat between the liquid pipe and the gas pipe without introducing external energy, thus improving the subcooling of the refrigerant in the liquid pipe and the superheating of the refrigerant in the gas pipe, saving external energy for heating the gas pipe. This ensures that the majority of the refrigerant entering evaporator 7 is liquid, improving evaporation efficiency. It also prevents a large amount of liquid refrigerant from entering compressor 1 under specific operating conditions (such as during startup or after defrosting), which could cause liquid slugging and damage compressor 1.

[0033] A first gas-liquid separator 6 is installed between the expansion valve 5 and the evaporator 7, allowing the gas-liquid two-phase refrigerant, after being throttled by the expansion valve 5, to undergo gas-liquid separation before entering the evaporator 7. This ensures that only liquid refrigerant flows to the evaporator 7, preventing gaseous refrigerant from doing so. This allows the liquid refrigerant to maintain better contact with the evaporator 7 wall, improving the heat exchange efficiency of the evaporator 7. It is worth noting that because flash evaporation is prone to occur after throttling, in existing technologies, a significant proportion of gaseous refrigerant enters the evaporator 7, occupying heat exchange area and reducing heat exchange efficiency.

[0034] Second Embodiment Unlike the above embodiments, the second embodiment of the present invention provides a high-efficiency heat exchange direct expansion air conditioning system, which further includes a first one-way valve 11, a second one-way valve 12, a third one-way valve 13, a fourth one-way valve 14, a first three-way pipe 31, a second three-way pipe 32, a third three-way pipe 33, and a fourth three-way pipe 34.

[0035] like Figure 2 As shown, the first three-way pipe 31 is connected to the output end of the condenser 3, the input end of the first one-way valve 11, and the output end of the fourth one-way valve 14; the second three-way pipe 32 is connected to the output end of the first one-way valve 11, the output end of the third one-way valve 13, and the liquid inlet of the heat exchanger 4; the third three-way valve 33 is connected to the liquid phase output end of the first gas-liquid separator 6, the input end of the second one-way valve 12, and the input end of the fourth one-way valve 14; and the fourth three-way pipe 34 is connected to the input end of the evaporator 7, the output end of the second one-way valve 12, and the input end of the third one-way valve 13.

[0036] In refrigeration mode, the medium-pressure, medium-temperature liquid refrigerant output from condenser 3 passes sequentially through the first three-way pipe 31, the first one-way valve 11, the second three-way pipe 32, the liquid pipe of heat exchanger 4, expansion valve 5, the first gas-liquid separator 6, the third three-way pipe 33, the second one-way valve 12, and the fourth three-way pipe 34 before entering evaporator 7. The gaseous refrigerant separated by the first gas-liquid separator 6 and the gaseous refrigerant output from expansion valve 7 are then fed into the gas pipe of heat exchanger 4 for heat exchange. The operating logic under this mode is the same as in the first embodiment and will not be repeated here.

[0037] In heating mode, the high-pressure, high-temperature refrigerant output from compressor 1 enters evaporator 7 through four-way valve 2 and condenses, transforming into medium-pressure, medium-temperature liquid refrigerant. The refrigerant then sequentially passes through fourth three-way pipe 34, third one-way valve 13, second three-way pipe 32, liquid pipe of heat exchanger 4, and expansion valve 5, transforming into gaseous or gas-liquid mixed refrigerant. The refrigerant enters first gas-liquid separator 6 for separation. The separated liquid refrigerant sequentially passes through third three-way pipe 33, fourth one-way valve 14, and first three-way pipe 31, then enters condenser 3 for evaporation and heat absorption, transforming into low-pressure, low-temperature gaseous or gas-liquid mixed refrigerant. This liquid refrigerant then passes through four-way valve 2 and, together with the gaseous refrigerant separated from first gas-liquid separator 6, enters the gas pipe of heat exchanger 4. The refrigerant output from the gas pipe of heat exchanger 4 enters compressor through second gas-liquid separator 8 to continue the next cycle.

[0038] The cooling and heating modes provided in this embodiment are achieved through the same heat exchanger 4 and the first gas-liquid separator 6. By making reasonable use of the one-way characteristic of the check valve and optimizing the pipeline design, countercurrent heat exchange of the refrigerant is achieved in both cooling and heating modes, thereby improving the subcooling degree of the refrigerant in the liquid pipe and the superheating degree of the refrigerant in the gas pipe.

[0039] Third Embodiment Unlike the above embodiments, the third embodiment of the present invention provides a high-efficiency heat exchange direct expansion air conditioning system, which further includes a first regulating valve 15, a second regulating valve 16, a high-pressure gauge 21, a low-pressure gauge 22, an intake thermometer 23, and an evaporation thermometer 24.

[0040] like Figure 2 As shown, the input end of the first regulating valve 15 is connected to the liquid pipe input end of the heat exchanger 4, and its output end is connected to the liquid pipe output end of the heat exchanger 4. In other words, the first regulating valve 15 is connected in parallel (short-circuited) with the liquid pipe of the heat exchanger 4, which allows all or part of the liquid refrigerant to bypass the heat exchanger 4.

[0041] The input end of the second regulating valve 16 is connected to the gas phase output end of the first gas-liquid separator 6, and its output end is connected to the gas pipe input end of the heat exchanger 4. In other words, the gas phase output end of the first gas-liquid separator 6 is connected to the gas pipe input end of the heat exchanger 4 through the second regulating valve 16.

[0042] A high-pressure gauge 21 is located at the output end of compressor 1, a low-pressure gauge 22 is located at the input end of compressor 1 (output end of the second gas-liquid separator 8), a suction thermometer 23 is located at the input end of the second gas-liquid separator 8 (outlet of the gas pipe of heat exchanger 4), and an evaporation thermometer 24 is located at the inlet of the gas pipe of heat exchanger 4. In cooling mode, the evaporation thermometer 24 is connected to the output end of evaporator 7, and its measured value is the refrigerant temperature after passing through evaporator 7. In heating mode, the evaporation thermometer 24 is connected to the output end of condenser 3, and its measured value is the refrigerant temperature after passing through condenser 3.

[0043] The readings from high-pressure gauge 21 and low-pressure gauge 22 represent the refrigerant output and input pressures of compressor 1, respectively. The reading from suction thermometer 23 represents the refrigerant suction temperature of compressor 1.

[0044] Expansion valve 5 is electrically connected to low-pressure gauge 22 and suction thermometer 23. Using the low-pressure and suction temperature of compressor 1, the superheat of evaporator 7 in refrigeration mode and condenser 3 in heating mode is calculated and compared with the target superheat to control the opening of expansion valve 5. For example, if the superheat is higher than the target superheat, the opening of expansion valve 5 is increased, and vice versa.

[0045] The first regulating valve 15 is electrically connected to the suction thermometer 23. The opening degree of the first regulating valve 15 is controlled by comparing the suction temperature of the compressor 1 with the target suction temperature. For example, if the suction temperature is higher than the target suction temperature, the opening degree of the first regulating valve is reduced, and vice versa.

[0046] The second regulating valve 16 is electrically connected to the high-pressure gauge 21 and the low-pressure gauge 22. Using the high and low pressures of the compressor 1, the refrigerant circulation volume is calculated. Based on a pre-programmed opening sequence for the second regulating valve 16 corresponding to different high and low pressures, the opening degree of the second regulating valve 16 is controlled, as shown in Table 1.

[0047] Table 1. Opening degree of the second regulating valve This invention further provides an opening degree control method for the above-mentioned high-efficiency heat exchange direct expansion air conditioning system, which includes at least the following steps.

[0048] Step S1: Obtain the low-pressure and suction temperature of compressor 1, calculate the superheat of evaporator 7 in refrigeration mode and condenser 3 in heating mode, and compare it with the target superheat. If the superheat is higher than the target superheat, increase the opening of expansion valve 5, and vice versa.

[0049] Step S2: Obtain the suction temperature of compressor 1 and compare it with the target suction temperature; if the suction temperature is higher than the target suction temperature, reduce the opening of the first regulating valve, and vice versa.

[0050] Step S3: Obtain the high pressure and low pressure of compressor 1, calculate the refrigerant circulation volume, and control the opening of the second regulating valve 16 according to the pre-programmed opening degree program of the second regulating valve 16 corresponding to different high pressure and low pressure.

[0051] In summary, the high-efficiency direct expansion air conditioning system and opening control method provided by this invention, by adding a gas-liquid separator after the expansion valve throttling, ensures that more liquid refrigerant enters the evaporator, thereby increasing the phase change heat transfer ratio. The separated gaseous refrigerant and the refrigerant at the evaporator outlet are heated by a heat exchanger to increase their superheat temperature, ensuring that the compressor does not experience liquid slugging. Simultaneously, the heat exchanger reduces the subcooling of the liquid refrigerant, increases the proportion of liquid refrigerant, and further improves the evaporator's heat exchange efficiency.

[0052] It should be noted that the above embodiments are merely illustrative examples. The technical solutions of each embodiment can be combined, and all are within the protection scope of this invention.

[0053] The order of steps in this invention can be changed according to actual needs. The order between steps can be changed, and serial processing can be changed to parallel processing. It is not limited to the order of steps listed in the embodiments.

[0054] The terms “upper,” “lower,” “horizontal,” “vertical,” “top,” “bottom,” etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0055] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0056] The above provides a detailed description of the efficient heat exchange direct expansion air conditioning system and opening degree control method provided by this invention. Any obvious modifications made by those skilled in the art without departing from the essence of this invention will constitute an infringement of the patent rights of this invention and will incur corresponding legal liability.

Claims

1. A high-efficiency heat exchange direct expansion air conditioning system, characterized in that... It includes a compressor, a four-way valve, a condenser, a heat exchanger, an expansion valve, a first gas-liquid separator, an evaporator, and a second gas-liquid separator; The output end of the compressor is connected to the compressor discharge end of the four-way valve, and the input end is connected to the output end of the second gas-liquid separator; The condenser end of the four-way valve is connected to the input end of the condenser; the evaporator end of the four-way valve is connected to the output end of the evaporator. The output end of the condenser is connected to the liquid inlet end of the heat exchanger; The liquid pipe output end of the heat exchanger is connected to the input end of the expansion valve, the gas pipe input end is connected to the compressor suction end of the four-way valve and the gas phase output end of the first gas-liquid separator, and the gas pipe output end is connected to the input end of the second gas-liquid separator. The output end of the expansion valve is connected to the input end of the first gas-liquid separator; The gas phase output end of the first gas-liquid separator is connected to the gas pipe input end of the heat exchanger, and the liquid phase output end is connected to the input end of the evaporator.

2. The high-efficiency heat exchange direct expansion air conditioning system as described in claim 1, characterized in that: The heat exchanger is a medium heat exchanger equipped with liquid pipes and gas pipes.

3. The high-efficiency heat exchange direct expansion air conditioning system as described in claim 2, characterized in that... It also includes a first check valve, a second check valve, a third check valve, and a fourth check valve; The output end of the condenser is connected to the input end of the first one-way valve and the output end of the fourth one-way valve; the liquid inlet of the heat exchanger is connected to the output end of the first one-way valve and the output end of the third one-way valve; the liquid phase output end of the first gas-liquid separator is connected to the input end of the second one-way valve and the input end of the fourth one-way valve; the input end of the evaporator is connected to the output end of the second one-way valve and the input end of the third one-way valve.

4. The high-efficiency heat exchange direct expansion air conditioning system as described in claim 3, characterized in that... It also includes a first regulating valve and a second regulating valve; The input end of the first regulating valve is connected to the liquid inlet of the heat exchanger 4, and its output end is connected to the liquid outlet of the heat exchanger; the input end of the second regulating valve is connected to the gas outlet of the first gas-liquid separator, and its output end is connected to the gas inlet of the heat exchanger.

5. The high-efficiency heat exchange direct expansion air conditioning system as described in claim 4, characterized in that... It also includes high-pressure gauges, low-pressure gauges, intake thermometers, and evaporation thermometers; The high-pressure gauge is located at the output end of the compressor; the low-pressure gauge is located at the input end of the compressor 1; the suction thermometer is located at the input end of the second gas-liquid separator; and the evaporation thermometer is located at the gas pipe input end of the heat exchanger.

6. The high-efficiency heat exchange direct expansion air conditioning system as described in claim 5, characterized in that: The expansion valve is electrically connected to the low-pressure gauge and the intake thermometer; the first regulating valve is electrically connected to the intake thermometer; and the second regulating valve is electrically connected to the high-pressure gauge and the low-pressure gauge.

7. A method for controlling the opening degree of a high-efficiency heat exchange direct expansion air conditioning system according to any one of claims 1 to 6, characterized in that... Includes the following steps: Step S1: Obtain the low-pressure and suction temperature of the compressor, calculate the superheat of the evaporator in refrigeration mode or the condenser in heating mode, and compare it with the target superheat; if the superheat is higher than the target superheat, increase the opening of the expansion valve. Conversely, reduce the opening. Step S2: Obtain the compressor's suction temperature and compare it with the target suction temperature; if the suction temperature is higher than the target suction temperature, decrease the opening of the first regulating valve; otherwise, increase the opening. Step S3: Obtain the high pressure and low pressure of the compressor, calculate the refrigerant circulation volume, and control the opening of the second regulating valve according to the pre-programmed opening degree program of the second regulating valve corresponding to different high pressure and low pressure.

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