Temperature control device and temperature control method
By using a temperature control device that separates hot and cold airflows through vortex tubes and optimizes the circulation system, the problems of unstable temperature control and high energy consumption in semiconductor temperature control devices have been solved, achieving precise temperature control and energy optimization.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI SHENGJIAN SEMICONDUCTOR TECHNOLOGY CO LTD
- Filing Date
- 2023-12-20
- Publication Date
- 2026-05-12
AI Technical Summary
Existing semiconductor temperature control equipment uses an evaporator combined with an electric heater in its refrigeration system, which leads to unstable temperature control, high PID control delay, difficulty in responding to large temperature changes in real time, and high energy consumption.
By using vortex tubes to separate hot and cold airflows, and through a pre-temperature control system and a circulation system, combined with regulating components and temperature sensors, preliminary temperature control of the refrigerant is achieved, reducing the temperature fluctuation range and improving PID control accuracy. Furthermore, the flow rate is regulated through gas-water heat exchange tubes and expansion valves to optimize the power utilization of the refrigeration and heating device.
It reduces the temperature fluctuation range, improves PID control accuracy, reduces the power consumption of refrigeration and heating devices, reduces equipment size, and lowers production costs.
Smart Images
Figure CN117492489B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor technology, and more specifically, to a temperature control device and a temperature control method. Background Technology
[0002] Semiconductor temperature control equipment is used to provide fast, accurate, and stable temperature output for semiconductor integrated circuit etching process equipment to ensure the precise manufacturing of integrated circuits. It is one of the important pieces of equipment in the upstream support link of the semiconductor industry.
[0003] However, currently, the refrigeration system of the temperature control equipment used to control the process cavity of etching equipment mainly adopts the method of evaporator combined with electric heater. Temperature control is achieved by adjusting the PID (proportional-integral-derivative) parameters. On the one hand, the method of evaporator combined with electric heater will cause a certain temperature loss, thereby increasing power consumption; on the other hand, since PID control has a certain delay, the requirements for parameter adjustment are very high, and it is difficult to respond in real time to large temperature changes and ensure the stability of the supply temperature. Summary of the Invention
[0004] This invention provides a temperature control device and method that can reduce the temperature fluctuation range, improve PID control accuracy, reduce the power consumption of the refrigeration and heating devices, reduce the size of the equipment, and improve refrigeration efficiency.
[0005] The embodiments of the present invention can be implemented as follows:
[0006] An embodiment of the present invention provides a temperature control device, which includes:
[0007] A pre-temperature control system, comprising a vortex tube, a gas delivery device, a first heat exchange device, and a second heat exchange device, wherein the gas inlet of the vortex tube is connected to the gas delivery device, the first outlet of the vortex tube is connected to the heat exchanger inlet of the first heat exchange device, and the second outlet of the vortex tube is connected to the heat exchanger inlet of the second heat exchange device.
[0008] A circulation system, comprising a circulation pump and a circulation tank, wherein the outlet of the circulation pump is connected to the inlet of the first heat exchanger and the inlet of the second heat exchanger, respectively; the outlet of the circulation tank is connected to the circulation pump, and the inlet of the circulation tank is used to connect to the output end of the load device.
[0009] The processing device has its inlet connected to the outlets of the first heat exchanger and the second heat exchanger, respectively; and its outlet is connected to the input of the load device.
[0010] In the above embodiment, by setting up a pre-temperature control system, the refrigerant flowing out of the output end of the load device enters the first heat exchanger and the second heat exchanger respectively. A vortex tube is used to provide heat exchanger to the first and second heat exchangers respectively. Due to the inherent properties of the vortex tube, it can generate vortices in the high-speed airflow, separating cold and hot airflows, which flow out through two outlets respectively. The gas temperatures flowing out of the two outlets of the vortex tube are different. The cold and hot airflows, as heat exchangers, enter the first and second heat exchangers respectively. Therefore, the first and second heat exchangers have different temperature treatment effects on the refrigerant flowing out of the load device. The refrigerant flowing out of the load device first enters the first and second heat exchangers for heat exchange separately, then mixes and flows into the treatment device, and finally flows back into the load device. Therefore, the refrigerant flowing out of the load device can be initially temperature-controlled before being combined and flow into the treatment device for heating and cooling treatment to reach the temperature required by the load device. Therefore, the temperature fluctuation range of the refrigerant that the processing device needs to handle is reduced, which improves the PID control accuracy, increases the refrigeration efficiency, and also reduces the power consumption of the refrigeration and heating devices. This allows for a reduction in the size of the refrigeration and heating devices, as well as the overall size of the temperature control equipment, thus lowering production costs.
[0011] In an optional embodiment, the temperature control device further includes a gas delivery device, which includes an ejector, a gas-liquid separator, and a compressor. The outlet of the compressor is connected to the inlet of the vortex tube, the inlet of the compressor is connected to the outlet of the gas-liquid separator, the inlet of the gas-liquid separator is connected to the outlet of the ejector, and the inlet of the ejector is connected to the heat exchanger outlet of the first heat exchanger and the heat exchanger outlet of the second heat exchanger, respectively.
[0012] In the above embodiments, by adding an ejector, a gas-liquid separator, and a compressor, the heat exchange medium input into the vortex tube can be used in the first heat exchange tube and the second heat exchange tube respectively, then mixed by the ejector, condensed by the gas-liquid separator, and then pressurized by the compressor before re-entering the vortex tube for recycling. This improves efficiency and reduces energy consumption and production costs.
[0013] In an optional embodiment, the circulation system further includes a regulating component disposed on the inlet branch and the outlet branch connecting the first heat exchanger and the second heat exchanger. The regulating component is used to distribute and control the amount of liquid entering and exiting the first and second heat exchangers. By distributing the regulating component on the branch connecting the inlet and outlet of the first and second heat exchangers, respectively, the flow rates of the liquid entering and exiting the first and second heat exchangers can be adjusted, thereby regulating the temperature of the refrigerant after exiting the first and second heat exchangers.
[0014] In an optional embodiment, the regulating assembly includes a regulating valve, at least one first expansion valve, and at least one second expansion valve; the regulating valve is disposed on a branch connecting the outlet of the circulating pump to the first heat exchanger and the second heat exchanger.
[0015] At least one first expansion valve is provided between the liquid outlet of the first heat exchange device and the liquid inlet of the processing device, and at least one second expansion valve is provided between the liquid outlet of the second heat exchange device and the liquid inlet of the processing device.
[0016] In the above embodiment, by setting a regulating valve, the refrigerant flowing from the outlet of the circulating pump can be divided into two controllable flow paths. One path enters the first heat exchanger, and the other enters the second heat exchanger, where they undergo heat exchange at different temperatures, resulting in two refrigerant streams with different temperatures. Furthermore, a first expansion valve is installed between the outlet of the first heat exchanger and the inlet of the processing device, and a second expansion valve is installed between the outlet of the second heat exchanger and the inlet of the processing device. This allows for easy adjustment of the temperature of the mixed liquid entering the processing device by regulating the opening of the first and second expansion valves, thus reducing the temperature fluctuation range of the refrigerant. This reduces the power consumption of the processing device during operation, specifically reducing the power required to reach the inlet temperature range of the load equipment.
[0017] In an optional embodiment, the temperature control device further includes a plurality of temperature sensors, including a first temperature sensor, a second temperature sensor, a third temperature sensor, a fourth temperature sensor, and a fifth temperature sensor. At least one first temperature sensor is provided at the output end of the load device, at least one second temperature sensor is provided between the liquid outlet of the first heat exchange device and the first expansion valve, and at least one third temperature sensor is provided between the liquid outlet of the second heat exchange device and the second expansion valve.
[0018] In the above embodiments, adding a temperature sensor before the expansion valve and setting a temperature sensor at the output end of the load device makes it easier to obtain the required temperature value. This facilitates adjusting the opening of the expansion valve and the opening of the regulating valve at different locations based on the obtained temperature values, thereby obtaining the required temperature value of the load device.
[0019] In an optional embodiment, the outlet of the first heat exchange device is connected to the outlet of the circulating pump and the first expansion valve, respectively, and the outlet of the second heat exchange device is connected to the outlet of the circulating pump and the second expansion valve, respectively.
[0020] In the above embodiment, by connecting the inlet and outlet of the first heat exchange device and the inlet and outlet of the second heat exchange device, during the adjustment of the first expansion valve and the second expansion valve, the liquid that failed to flow into the refrigeration device from the first heat exchange device and the second heat exchange device can flow back to the outlet of the circulating pump, be redistributed, and then enter the first heat exchange device and the second heat exchange device for recycling, thereby reducing energy consumption.
[0021] In an optional embodiment, the first heat exchange device and / or the second heat exchange device is a gas-water heat exchange tube. Using a gas-water heat exchange tube allows for the introduction of liquids at different temperatures into the inner and outer tubes of the tube according to heat exchange requirements, thereby achieving heat exchange. Gas-water heat exchange tubes have a simple structure and are easy to use.
[0022] In an optional embodiment, the temperature control device further includes at least one third expansion valve and at least one fourth expansion valve, with at least one third expansion valve provided between the load device and the circulating water tank, and at least one fourth expansion valve provided between the processing device and the load device.
[0023] In the above embodiments, by setting a third expansion valve between the load device and the circulating water tank, and a fourth expansion valve between the refrigeration device and the load device, the temperature difference between the liquid inlet and the liquid outlet of the load device can be adjusted by adjusting the opening degree of the third expansion valve and the fourth expansion valve.
[0024] Embodiments of the present invention also provide a temperature control method, applied to the temperature control device described in any of the above embodiments, the temperature control method comprising:
[0025] Determine the first preset temperature and the first preset range;
[0026] Obtain the first temperature of the liquid inlet of the load device;
[0027] Compare the first temperature with the first preset temperature;
[0028] If the difference between the first preset temperature and the first temperature is greater than the maximum value of the first preset range, then the output power of the heating device is reduced.
[0029] If the difference between the first preset temperature and the first temperature is less than the minimum value of the first preset range, then the output power of the heating device is increased.
[0030] If the difference between the first preset temperature and the first temperature is within the first preset range, then the heating device is controlled to maintain its current state.
[0031] In the above embodiments, the temperature control method further includes a plurality of expansion valves, the expansion valves including at least one first expansion valve and at least one second expansion valve; at least one first expansion valve is provided between the liquid outlet of the first heat exchange device and the liquid inlet of the refrigeration device, and at least one second expansion valve is provided between the liquid outlet of the second heat exchange device and the liquid inlet of the refrigeration device.
[0032] Prior to the step of obtaining the temperature of the liquid inlet of the load device, the temperature control method further includes:
[0033] Determine the second preset temperature and the second preset range;
[0034] Obtain the second temperature at the liquid inlet of the processing device;
[0035] Compare the second temperature with the second preset temperature;
[0036] If the difference between the second preset temperature and the second temperature is greater than the maximum value of the second preset range, then the opening of the first expansion valve is increased and the opening of the second expansion valve is decreased.
[0037] If the difference between the second preset temperature and the second temperature is less than the minimum value of the second preset range, then the opening of the first expansion valve is reduced and the opening of the second expansion valve is increased.
[0038] If the difference between the second preset temperature and the second temperature is within the second preset range, then the first expansion valve and the second expansion valve are controlled to remain in their current state.
[0039] In the above embodiments, by adjusting the opening degree of the first expansion valve and the second expansion valve, the temperature of the liquid entering the refrigeration unit can be adjusted, thereby reducing the temperature fluctuation of the liquid to be processed by the refrigeration unit, improving the PID control accuracy, and reducing the power consumed by the refrigeration unit when it is working.
[0040] The beneficial effects of the temperature control device and temperature control method according to the embodiments of the present invention include:
[0041] By setting up a pre-temperature control system, the refrigerant flowing from the output end of the load equipment enters the first and second heat exchangers respectively. A vortex tube is used to supply heat exchanger to the first and second heat exchangers respectively. Due to the inherent properties of the vortex tube, it can generate vortices in the high-speed airflow, separating cold and hot airflows, which flow out through two separate outlets. The gas temperatures exiting from the two outlets of the vortex tube are different. The cold and hot airflows, as heat exchangers, enter the first and second heat exchangers respectively. The temperature of the heat exchanger flowing out of the inner tube is higher than that of the heat exchanger flowing out of the outer tube. Therefore, the first and second heat exchangers have different temperature treatment effects on the refrigerant flowing from the load equipment. The refrigerant flowing from the load equipment first undergoes heat exchange in the first and second heat exchangers, then mixes and flows into the treatment device, and finally flows back into the load equipment. Therefore, the refrigerant flowing from the load equipment can be initially temperature-controlled before being combined and flow into the treatment device for heating and cooling treatment to reach the required temperature of the load equipment, thus reducing temperature fluctuations. Then, after the refrigerant undergoes heat exchange treatment through the first and second heat exchange devices, it flows into the refrigeration and heating devices. As a result, the temperature fluctuation range of the refrigerant that the processing devices need to handle is reduced, thus improving the PID control accuracy and refrigeration efficiency. At the same time, it also reduces the power consumption of the refrigeration and heating devices, thereby reducing the size of the refrigeration and heating devices, reducing the overall size of the temperature control equipment, and lowering production costs. Attached Figure Description
[0042] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0043] Figure 1 This is a schematic diagram of the temperature control device provided in an embodiment of the present invention;
[0044] Figure 2 This is a schematic diagram of the heat exchanger flow path of the temperature control device provided in an embodiment of the present invention;
[0045] Figure 3 This is a schematic diagram of the refrigerant flow path of the temperature control device provided in an embodiment of the present invention;
[0046] Figure 4 This is a schematic diagram of a gas-water heat exchange tube provided in an embodiment of the present invention from a first perspective.
[0047] Figure 5 This is a schematic diagram from a second perspective of the gas-water heat exchange tube provided in an embodiment of the present invention.
[0048] Icons: 1000 - Temperature control equipment; 100 - Pre-temperature control system; 110 - Vortex tube; 120 - First heat exchanger; 130 - Second heat exchanger; 140 - Gas delivery device; 141 - Ejector; 142 - Gas-liquid separator; 143 - Compressor; 200 - Circulation system; 210 - Circulation pump; 220 - Circulation water tank; 300 - Processing device; 310 - Refrigeration device; 320 - Heating device; 400 - Regulating component; 410 - Regulating valve; 500 - Load device; 600 - Expansion valve; 610 - First expansion valve; 620 - Second expansion valve; 630 - Third expansion valve; 640 - Fourth expansion valve; 700 - Temperature sensor; 710 - First temperature sensor; 720 - Second temperature sensor; 730 - Third temperature sensor; 740 - Fourth temperature sensor; 750 - Fifth temperature sensor; 800 - Gas-water heat exchange tube; 810 - Inner tube; 820 - Outer tube; 830 - Insulation layer. Detailed Implementation
[0049] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.
[0050] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.
[0051] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.
[0052] In the description of this invention, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed, they are only for the convenience of describing this 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, and therefore should not be construed as a limitation of this invention.
[0053] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.
[0054] It should be noted that, where there is no conflict, the features in the embodiments of the present invention can be combined with each other.
[0055] Semiconductor temperature control equipment provides rapid, accurate, and stable temperature output for semiconductor integrated circuit etching process equipment, ensuring the precise manufacturing of integrated circuits. It is one of the important pieces of equipment in the upstream support link of the semiconductor industry. However, currently, the refrigeration system of the temperature control equipment used to control the process chamber of etching equipment mainly adopts the method of evaporator combined with electric heater, and temperature control is achieved by adjusting PID parameters. On the one hand, the evaporator combined with electric heater method will cause a certain temperature loss, thereby increasing power consumption; on the other hand, because PID control has a certain delay, the requirements for parameter adjustment are very high, and it is difficult to respond in real time to large temperature changes and ensure the stability of the supply temperature.
[0056] Based on this, please refer to Figure 1 The temperature control device 1000 provided in the embodiments of the present invention can effectively improve the aforementioned technical problems. This temperature control device 1000 is applied in the semiconductor manufacturing field. It can reduce temperature fluctuation range, improve PID control accuracy, reduce the power consumption of the processing device 300, reduce equipment size, and improve cooling efficiency.
[0057] Figure 1 This is a schematic diagram of a temperature control device 1000 provided in an embodiment of the present invention. Figure 2 This is a schematic diagram of the heat exchanger flow path of the temperature control device provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the refrigerant flow path of the temperature control device provided in an embodiment of the present invention. To reduce the temperature fluctuation range of the semiconductor temperature control device 1000 and improve the PID control accuracy, such as... Figure 1 , Figure 2 and Figure 3As shown, the temperature control device 1000 provided in this embodiment of the present invention includes a pre-temperature control system 100, a circulation system 200, and a processing device 300. The pre-temperature control system 100 includes a vortex tube 110, a gas delivery device 140, a first heat exchange device 120, and a second heat exchange device 130. The gas inlet of the vortex tube 110 is connected to the gas delivery device 140, the first outlet of the vortex tube 110 is connected to the heat exchanger inlet of the first heat exchange device 120, and the second outlet of the vortex tube 110 is connected to the heat exchanger inlet of the second heat exchange device 130. The circulation system 200 includes a circulation pump 210 and a circulation water tank 220. The liquid outlet of the circulation pump 210 is connected to the liquid inlet of the first heat exchange device 120 and the liquid inlet of the second heat exchange device 130, respectively. The liquid outlet of the circulation water tank 220 is connected to the circulation pump 210, and the liquid inlet of the circulation water tank 220 is used to connect to the output end of the load device 500. The inlet of the processing device 300 is connected to the outlet of the first heat exchanger 120 and the outlet of the second heat exchanger 130, respectively; the outlet of the processing device 300 is connected to the input terminal of the load device 500. The processing device 300 is used to heat and / or cool the mixed refrigerant after heat exchange by the first heat exchanger 120 and the second heat exchanger 130, so that the mixed refrigerant meets the temperature required by the load device 500.
[0058] The processing device 300 in this embodiment includes a refrigeration device 310 and a heating device 320. The inlet of the refrigeration device 310 is connected to the outlet of the first heat exchanger 120 and the outlet of the second heat exchanger 130, respectively. The inlet of the heating device 320 is connected to the outlet of the refrigeration device 310, and the outlet of the heating device 320 is connected to the input terminal of the load. Alternatively, depending on the specific application scenario, both the refrigeration device 310 and the heating device 320 can be configured. If the temperature of the mixed refrigerant is lower than the temperature requirement of the load device 500, only the heating device 320 needs to be configured; if the temperature of the mixed refrigerant is higher than the temperature requirement of the load device 500, only the refrigeration device 310 needs to be configured. Simultaneously configuring both the refrigeration device 310 and the heating device 320 facilitates adjustments based on the temperature of the refrigerant flowing out after heat exchange through the first heat exchanger 120 and the second heat exchanger 130, reducing the temperature fluctuation range of the refrigerant and improving the accuracy of PID control.
[0059] Specifically, in this embodiment, the refrigeration device 310 includes an evaporator, and the heating device 320 is an electric heater. The low-temperature condensed liquid passes through the evaporator, exchanges heat with the outside air, vaporizes, and absorbs heat, achieving a cooling effect. The evaporator mainly consists of a heating chamber and an evaporation chamber. The heating chamber provides the heat required for evaporation to the liquid, causing it to boil and vaporize; the evaporation chamber completely separates the gas and liquid phases. The heating device 320 uses an electric heater for easy power adjustment. Of course, the refrigeration device 310 may also include other related refrigeration equipment, such as a condenser or compressor, which is not limited here. The heating device 320 may also use other heating equipment, such as an electromagnetic heater or a heating rod, as long as it can heat the liquid entering the load device 500; this is not limited here.
[0060] It should be noted that the gas circulating inside the vortex tube 110 enters the first heat exchanger 120 and the second heat exchanger 130 and only exchanges heat with the liquid in the first heat exchanger 120 and the second heat exchanger 130. It does not come into direct contact with the liquid in the heat exchanger and the gas-liquid pipelines are not interconnected.
[0061] By setting up a pre-temperature control system 100, the refrigerant flowing out of the output end of the load device 500 enters the first heat exchanger 120 and the second heat exchanger 130 respectively. A vortex tube 110 is used to supply heat exchanger to the first heat exchanger 120 and the second heat exchanger 130 respectively. Due to the inherent properties of the vortex tube 110, it can generate vortices in the high-speed airflow, separating cold and hot airflows, which flow out through two outlets respectively. The gases flowing out of the two outlets of the vortex tube 110 have different temperatures. Since the cold and hot airflows act as heat exchangers entering the first heat exchanger 120 and the second heat exchanger 130 respectively, the first heat exchanger 120 and the second heat exchanger 130 have different temperature treatment effects on the refrigerant flowing out of the load device 500. The refrigerant flowing out of the load device 500 first enters the first heat exchanger 120 and the second heat exchanger 130 for heat exchange, then mixes and flows into the processing device 300, and finally flows back into the load device 500. Therefore, the refrigerant flowing out of the load device 500 can be initially temperature-controlled before being combined and flow into the processing device 300 for heating and cooling to reach the temperature required by the load device 500. This reduces the temperature fluctuation range of the refrigerant that the processing device 300 needs to handle, thus improving PID control accuracy, increasing cooling efficiency, and reducing the power consumption of the processing device 300. Consequently, the size of the processing device 300 (i.e., the cooling device 310 and the heating device 320) can be reduced, as can the overall size of the temperature control device 1000, thereby lowering production costs.
[0062] To achieve the recycling of the heat exchange medium within the vortex tube 110, please refer to [further details needed]. Figure 1 and combined Figure 2The gas delivery device 140 includes an ejector 141, a gas-liquid separator 142, and a compressor 143. The outlet of the compressor 143 is connected to the inlet of the vortex tube 110, the inlet of the compressor 143 is connected to the outlet of the gas-liquid separator 142, the inlet of the gas-liquid separator 142 is connected to the outlet of the ejector 141, and the inlet of the ejector 141 is connected to the heat exchanger outlet of the first heat exchanger 120 and the heat exchanger outlet of the second heat exchanger 130.
[0063] The vortex tube 110 is a simple, fast-responding, and low-cost refrigeration device. During operation, compressed gas enters the vortex chamber through a nozzle, generating a temperature separation effect that separates it into two streams of gas, one cold and one hot. These streams are discharged from the cold and hot ports respectively. The ratio of the cold and hot streams can be adjusted by a regulating valve to obtain the optimal cooling or heating effect. Its inlet pressure is typically between 0.5 and 1 MPa.
[0064] Specifically, in this embodiment, the vortex tube 110 is a Nex vortex tube 110, the working gas is room temperature air, the inlet pressure is set to 0.7 MPa, and the ratio of cold to hot air flow is 30%. At this time, the cold end temperature of the vortex tube 110 can be reduced by about 65°C, and the hot end temperature can be increased by about 25°C. In addition, the inlet pressure and the ratio of cold to hot air flow can be adjusted according to actual production needs to achieve the required temperature rise or fall values, which are not limited here. The two ends of the vortex tube 110 are respectively connected to the first heat exchange device 120 and the second heat exchange device 130, and exchange heat with the two streams of refrigerant fluid to form two liquid streams, cold and hot. After heat exchange, the gas is mixed by the ejector 141 to form an intermediate pressure gas, and then the condensate is filtered out by the gas-liquid separator 142 before being repressurized by the compressor 143 and entering the inlet of the vortex tube 110. By adding an ejector 141, a gas-liquid separator 142, and a compressor 143, the heat exchange medium input into the vortex tube 110 can be used in the first heat exchange tube and the second heat exchange tube, mixed by the ejector 141, condensed by the gas-liquid separator 142, and then pressurized by the compressor 143 before re-entering the vortex tube 110 for recycling. This improves efficiency and reduces energy consumption and production costs.
[0065] Please continue reading. Figure 1 and combined Figure 3To control the temperature of the liquid entering the processing device 300 and reduce the power and energy consumption of the processing device during operation, the circulation system 200 in this embodiment further includes an adjustment component 400. The adjustment component 400 is disposed on the inlet branch and outlet branch connecting the first heat exchange device 120 and the second heat exchange device 130. The adjustment component 400 is used to distribute and control the amount of liquid entering and exiting the first heat exchange device 120 and the second heat exchange device 130. By setting the adjustment component 400 on the branch connecting the inlet of the first heat exchange device 120 and the inlet of the second heat exchange device 130, and on the branch connecting the outlet of the first heat exchange device 120 and the outlet of the second heat exchange device 130, the flow rates of the liquid entering and exiting the first heat exchange device 120 and the second heat exchange device 130 can be adjusted, thereby adjusting the temperature of the refrigerant after exiting the first heat exchange device 120 and the second heat exchange device 130.
[0066] Specifically, at least a portion of the regulating component 400 is disposed between the first heat exchanger 120 and the circulating pump 210, and at least a portion of the regulating component 400 is disposed between the first heat exchanger 120 and the processing device 300; and / or, at least a portion of the regulating component 400 is disposed between the second heat exchanger 130 and the circulating pump 210, and at least a portion of the regulating component 400 is disposed between the second heat exchanger 130 and the processing device 300. Furthermore, a portion of the regulating component 400 may also be disposed in the flow path where the first heat exchanger 120 and the second heat exchanger 130 are both connected to the circulating pump 210, thereby regulating the proportional distribution of the liquid flowing out of the circulating pump 210 into the first heat exchanger 120 and the second heat exchanger 130. Alternatively, a portion of the regulating component 400 may also be disposed in the flow path where the first heat exchanger 120 and the second heat exchanger 130 are both connected to the processing device 300, thereby regulating the liquid flow ratio of the first heat exchanger 120 and the second heat exchanger 130 entering the processing device 300. The inlet and outlet liquid flow rate ratio of either the first heat exchanger 120 or the second heat exchanger 130 can be adjusted, or the inlet and outlet liquid flow rates of both the first heat exchanger 120 and the second heat exchanger 130 can be adjusted simultaneously to pre-treat the temperature of the liquid entering the processing device 300.
[0067] Specifically, in this embodiment, the regulating component 400 includes a regulating valve 410, at least one first expansion valve 610, and at least one second expansion valve 620. The regulating valve 410 is disposed on a branch connecting the outlet of the circulating pump 210 to the first heat exchanger 120 and the second heat exchanger 130. At least one first expansion valve 610 is disposed between the outlet of the first heat exchanger 120 and the inlet of the refrigeration device 310 of the processing device 300, and at least one second expansion valve 620 is disposed between the outlet of the second heat exchanger 130 and the inlet of the refrigeration device 310 of the processing device 300.
[0068] To control the amount of liquid entering the first heat exchanger 120 and the second heat exchanger 130 respectively, and to control the temperature of the mixed liquid after heat exchange, thereby adjusting the temperature fluctuation range of the liquid entering the cooling device and improving the PID control accuracy, a regulating valve 410 is installed between the circulating pump 210 and the first heat exchanger 120 and the second heat exchanger 130. Specifically, the regulating valve 410 in this embodiment is a manual regulating valve 410, but an electric regulating valve 410, a pneumatic regulating valve 410, a hydraulic regulating valve 410, etc., can also be used, and this is not limited here. By setting the regulating valve 410, the refrigerant flowing out of the outlet of the circulating pump 210 can be divided into two controllable flow paths, one entering the first heat exchanger 120 and the other entering the second heat exchanger 130. Heat exchange at different temperatures is performed separately to obtain two refrigerant streams at different temperatures. By controlling the flow ratio of the two streams, the temperature of the mixed refrigerant streams can be controlled.
[0069] By setting a regulating valve 410, the refrigerant flowing from the outlet of the circulating pump 210 can be divided into two controllable flow paths. One path enters the first heat exchanger 120, and the other enters the second heat exchanger 130, where they undergo heat exchange at different temperatures, resulting in two refrigerant streams with different temperatures. Furthermore, a first expansion valve 610 is installed between the outlet of the first heat exchanger 120 and the inlet of the processing device 300, and a second expansion valve 620 is installed between the outlet of the second heat exchanger 130 and the inlet of the processing device 300. This allows for easy adjustment of the temperature of the mixed liquid entering the processing device 300 by regulating the opening of the first expansion valve 610 and the second expansion valve 620, thereby reducing the temperature fluctuation range of the refrigerant. This reduces the power consumption of the refrigeration device 310 when the processing device 300 is operating, i.e., reduces the inlet temperature range required by the load device 500.
[0070] To further control the temperature at the input and output terminals of the load device 500, please refer to [link / reference needed]. Figure 1In this embodiment, the expansion valve 600 further includes at least one third expansion valve 630 and at least one fourth expansion valve 640. At least one third expansion valve 630 is provided between the load device 500 and the circulating water tank 220, and at least one fourth expansion valve 640 is provided between the refrigeration device 310 and the load device 500. By providing the third expansion valve 630 between the load device 500 and the circulating water tank 220, and the fourth expansion valve 640 between the refrigeration device 310 and the load device 500, the temperature difference between the inlet and outlet of the load device 500 can be adjusted by regulating the opening of the third expansion valve 630 and the fourth expansion valve 640. Furthermore, the third expansion valve 630 can cooperate with the regulating valve 410, the first expansion valve 610, and the second expansion valve 620 to regulate the flow rate of the refrigerant entering and exiting the first heat exchange device 120 and the second heat exchange device 130, thereby pre-treating the temperature of the liquid entering the processing device 300, regulating the temperature value of the mixed liquid entering the processing device 300, and reducing the temperature fluctuation range of the refrigerant. The third expansion valve 630 controls the total flow rate of the refrigerant entering and exiting the first heat exchanger 120 and the second heat exchanger 130.
[0071] Specifically, for ease of control and improved control precision, the expansion valves 600 in this embodiment are all electronic expansion valves 600. Alternatively, manual expansion valves 600, thermal expansion valves 600, etc., may also be used; this is not limited here. Of course, the number of expansion valves 600 used each time can be set according to specific needs; this is not limited here.
[0072] To facilitate obtaining the temperature values required for PID control, please refer to [link / reference]. Figure 1 In this embodiment, the temperature control device 1000 also includes multiple temperature sensors 700. The temperature sensors 700 include a first temperature sensor 710, a second temperature sensor 720, and a third temperature sensor 730. At least one first temperature sensor 710 is provided at the output end of the load device 500. At least one second temperature sensor 720 is provided between the liquid outlet of the first heat exchange device 120 and the first expansion valve 610. At least one third temperature sensor 730 is provided between the liquid outlet of the second heat exchange device 130 and the second expansion valve 620.
[0073] Furthermore, to facilitate the adjustment of multiple expansion valves 600 based on the temperature values at different inlet and outlet ports to obtain the required temperature for the load device 500, the temperature sensor 700 in this embodiment also includes a fourth temperature sensor 740 and a fifth temperature sensor 750. At least one fourth temperature sensor 740 is provided at the inlet of the refrigeration device 310, and a fifth temperature sensor 750 is provided between the outlet of the refrigeration device 310 and the fourth expansion valve 640. Adding temperature sensors 700 before the expansion valve 600, at the inlet of the refrigeration device 310, and at the outlet of the heating device 320 facilitates the acquisition of the required temperature value. This allows for the adjustment of the opening of the expansion valves 600 at different locations based on the acquired temperature values to obtain the required temperature value for the load device 500.
[0074] Specifically, the second temperature sensor 720 detects the temperature of the hot fluid, the third temperature sensor 730 detects the temperature of the cold fluid, and the fourth temperature sensor 740 detects the temperature of the mixed liquid. The three temperature sensors 700, along with the first expansion valve 610 and the second expansion valve 620, are connected to the first controller. PID parameters are used to control the opening of the first and second expansion valves 610 and 620 to adjust the ratio of the cold and hot fluids, thereby bringing the mixed liquid as close as possible to the target load temperature, achieving initial temperature control. After initial temperature control, the refrigerant temperature fluctuation decreases, entering the secondary temperature control process. First, the evaporator in the refrigeration unit 310 provides cooling, and then the electric heater provides real-time heating. The electric heater, the first temperature sensor 710, the fifth temperature sensor 750, the third electronic expansion valve 600, and the fourth electronic expansion valve 600 are connected to the second controller. PID parameters are used to adjust the output power of the electric heater to achieve precise temperature control.
[0075] Please continue reading. Figure 1 and combined Figure 3To allow excess liquid in the first heat exchanger 120 and the second heat exchanger 130 to circulate and participate in the heat exchange process, thereby reducing the temperature fluctuation range of the liquid flowing out of the load device 500, in this embodiment, the outlet of the first heat exchanger 120 is connected to the outlet of the circulating pump 210 and the first expansion valve 610, respectively, and the outlet of the second heat exchanger 130 is connected to the outlet of the circulating pump 210 and the second expansion valve 620, respectively. Specifically, the liquid in the first heat exchanger 120 and the second heat exchanger 130 that fails to flow into the refrigeration device 310 flows back to the outlet of the circulating pump 210, where it merges with the liquid flowing out of the load device 500 via the circulating water tank 220 and the circulating pump 210. After the three streams of liquid merge, they are redistributed and enter the first heat exchanger 120 and the second heat exchanger 130. This allows for the recycling of the liquid after heat exchange, reducing energy consumption, and also pre-treats the temperature of the liquid flowing out of the load device 500.
[0076] Figure 4 5 is a schematic diagram of the gas-water heat exchange tube 800 provided in an embodiment of the present invention from a first-view perspective; 5 is... Figure 4 For another perspective illustration, please refer to [link / reference]. Figure 4 and Figure 5 To facilitate preliminary temperature control of the refrigerant flowing out of the load device 500, the first heat exchange device 120 and / or the second heat exchange device 130 in this embodiment are gas-water heat exchange tubes 800. The gas-water heat exchange tube 800 is a double-layered tube used for heat exchange between the outlet gas of the vortex tube 110 and the refrigerant fluid. The inner layer is axially continuous, and the outer layer tightly wraps around the inner layer for heat exchange. There is a protruding section at each end, and the outer tube is separated from the outer tube, thus connecting the double-layered tube to the two separate pipes. In the gas-water heat exchange tube 800 of the first heat exchange device 120, the inner tube 810 is used to supply the hot-end outlet gas of the vortex tube 110, and the outer tube 820 is used to supply the refrigerant fluid. In the second heat exchanger 130, a refrigerant fluid is introduced into the inner tube 810 of the gas-water heat exchanger tube 800, and the gas from the cold end outlet of the vortex tube 110 is introduced into the outer tube 820. Therefore, the liquid temperature entering the first heat exchanger 120 is increased, while the liquid temperature entering the second heat exchanger 130 is decreased. To reduce safety hazards, an insulation layer 830 is also provided on the outermost layer of the gas-water heat exchanger tube 800 in this embodiment. The gas-water heat exchanger tube 800 allows for the introduction of liquids of different temperatures into the inner tube 810 and outer tube 820 respectively, according to heat exchange requirements, to achieve heat exchange. Furthermore, the gas-water heat exchanger tube 800 has a simple structure and is easy to use. Alternatively, heat exchangers with the same function can be used, and this is not limited here.
[0077] To facilitate observation of the amount of circulating liquid inside the circulating water tank 220, a level gauge is provided in the circulating water tank 220 in this embodiment.
[0078] The following is based on Figure 1 Taking the temperature control device 1000 shown as an example, the temperature control method provided by the embodiment of the present invention will be described by way of example. Specifically, the temperature control method includes:
[0079] Determine the first preset temperature and the first preset range;
[0080] In this embodiment, the first preset range is ±0.1℃. Of course, the first preset range can also be adjusted according to the specific processing accuracy requirements, which is not limited here.
[0081] Obtain the first temperature at the 500 liquid inlet of the load device;
[0082] The first temperature of the liquid inlet of the load device 500 is obtained by temperature sensor 700.
[0083] Compare the first temperature with the first preset temperature;
[0084] The first temperature at the inlet of the load device 500 is compared with the temperature required for the load device 500 to operate normally, and the difference between the first temperature and the first preset temperature is obtained. The first preset temperature is determined according to actual production needs and is not limited here.
[0085] If the difference between the first preset temperature and the first temperature is greater than the maximum of the first preset range, the output power of the control processing device 300 is reduced.
[0086] If the difference between the first preset temperature and the first temperature is greater than the maximum value of the first preset range, it indicates that the temperature of the circulating liquid entering the inlet of the load device 500 is too high. Therefore, by reducing the output power of the processing device 300, the temperature of the circulating liquid entering the inlet of the load device 500 can be reduced.
[0087] If the difference between the first preset temperature and the temperature is less than the minimum value of the first preset range, the output power of the control processing device 300 increases.
[0088] If the difference between the first preset temperature and the first temperature is less than the minimum value of the first preset range, it indicates that the temperature of the circulating liquid entering the inlet of the load device 500 is too low. Therefore, by increasing the output power of the processing device 300, the temperature of the circulating liquid entering the inlet of the load device 500 can be increased.
[0089] If the difference between the first preset temperature and the temperature is within the first preset range, the control processing device 300 maintains the status quo.
[0090] The temperature control method in this embodiment further includes a plurality of expansion valves 600 in the temperature control device 1000. Each expansion valve 600 includes at least one first expansion valve 610 and at least one second expansion valve 620. At least one first expansion valve 610 is provided between the liquid outlet of the first heat exchange device 120 and the liquid inlet of the processing device 300, and at least one second expansion valve 620 is provided between the liquid outlet of the second heat exchange device 130 and the liquid inlet of the processing device 300.
[0091] Prior to the step of obtaining the temperature of the liquid inlet of the load device 500, the temperature control method further includes:
[0092] Determine the second preset temperature and the second preset range;
[0093] In this embodiment, the second preset range is ±3℃. Of course, the second preset range can also be adjusted according to the specific processing accuracy requirements, which is not limited here.
[0094] The second temperature at the liquid inlet of the processing device 300 is obtained;
[0095] The second temperature of the liquid inlet of the processing device 300 is obtained by temperature sensor 700.
[0096] Compare the second temperature with the second preset temperature;
[0097] The second temperature at the inlet of the processing device 300 is compared with the temperature required for normal operation of the load device 500 to obtain the difference between the second temperature and the second preset temperature. The second preset temperature is determined according to actual production needs and is not limited here.
[0098] If the difference between the second preset temperature and the second temperature is greater than the maximum value of the second preset range, then the opening of the first expansion valve 610 is increased and the opening of the second expansion valve 620 is decreased.
[0099] If the difference between the second preset temperature and the second temperature is greater than the maximum value of the second preset range, it indicates that the temperature of the circulating liquid entering the cooling device inlet is too high. Therefore, increasing the opening of the first expansion valve 610 and decreasing the opening of the second expansion valve 620 can reduce the temperature of the circulating liquid entering the cooling device inlet.
[0100] If the difference between the second preset temperature and the second temperature is less than the minimum value of the second preset range, then the opening of the first expansion valve 610 is reduced and the opening of the second expansion valve 620 is increased.
[0101] If the difference between the second preset temperature and the temperature is less than the minimum value of the second preset range, it indicates that the temperature of the circulating liquid entering the cooling device inlet is too low. Therefore, reducing the opening of the first expansion valve 610 and increasing the opening of the second expansion valve 620 can raise the temperature of the circulating liquid entering the cooling device inlet.
[0102] If the difference between the second preset temperature and the second temperature is within the second preset range, then the first expansion valve 610 and the second expansion valve 620 are controlled to remain in their current state.
[0103] In summary, the temperature control device 1000 includes a pre-temperature control system 100, a circulation system 200, and a processing device 300. The pre-temperature control system 100 includes a vortex tube 110, a gas delivery device 140, a first heat exchange device 120, and a second heat exchange device 130. The gas inlet of the vortex tube 110 is connected to the gas delivery device 140, the first outlet of the vortex tube 110 is connected to the heat exchanger inlet of the first heat exchange device 120, and the second outlet of the vortex tube 110 is connected to the heat exchanger inlet of the second heat exchange device 130. The circulation system 200 includes a circulation pump 210 and a circulation water tank 220. The outlet of the circulation pump 210 is connected to the inlet of the first heat exchange device 120 and the inlet of the second heat exchange device 130, respectively. The outlet of the circulation water tank 220 is connected to the circulation pump 210, and the inlet of the circulation water tank 220 is used to connect to the output end of the load device 500. The inlet of the processing device 300 is connected to the outlet of the first heat exchanger 120 and the outlet of the second heat exchanger 130, respectively; the outlet of the processing device 300 is connected to the input terminal of the load device 500. The processing device 300 is used to heat and / or cool the mixed refrigerant after heat exchange by the first heat exchanger 120 and the second heat exchanger 130, so that the mixed refrigerant meets the temperature required by the load device 500.
[0104] By setting up a pre-temperature control system 100, the refrigerant flowing out of the output end of the load device 500 enters the first heat exchanger 120 and the second heat exchanger 130 respectively. A vortex tube 110 is used to supply heat exchanger to the first heat exchanger 120 and the second heat exchanger 130 respectively. Due to the inherent properties of the vortex tube 110, it can generate vortices in the high-speed airflow, separating cold and hot airflows, which flow out through two outlets respectively. The gas temperatures flowing out of the two outlets of the vortex tube 110 are different. The cold and hot airflows, as heat exchangers, enter the first heat exchanger 120 and the second heat exchanger 130 respectively. The temperature of the heat exchanger flowing out of the inner tube 810 is higher than the temperature of the heat exchanger flowing out of the outer tube 820 of the vortex tube 110. Therefore, the first heat exchanger 120 and the second heat exchanger 130 have different temperature treatment effects on the refrigerant flowing out of the load device 500. The refrigerant flowing out of the load device 500 first enters the first heat exchanger 120 and the second heat exchanger 130 for heat exchange, then mixes and flows into the processing device 300, and finally flows back into the load device 500. Therefore, the refrigerant flowing out of the load device 500 can undergo preliminary temperature control before being combined and flow into the processing device 300 for heating and cooling to reach the required temperature of the load device 500, thus reducing temperature fluctuations. After heat exchange in the first heat exchanger 120 and the second heat exchanger 130, the refrigerant flows into the refrigeration device 310 and the heating device 320. Therefore, the temperature fluctuation range of the refrigerant that the processing device 300 needs to handle is reduced, thereby improving PID control accuracy and refrigeration efficiency. It also reduces the power consumption of the refrigeration device 310 and the heating device 320, which in turn reduces the size of the refrigeration device 310 and the heating device 320, thus reducing the overall size of the temperature control device 1000 and lowering production costs. The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.
Claims
1. A temperature control device, characterized in that, include: A pre-temperature control system (100) includes a vortex tube (110), a gas delivery device (140), a first heat exchange device (120), and a second heat exchange device (130). The inlet of the vortex tube (110) is connected to the gas delivery device (140), the first outlet of the vortex tube (110) is connected to the heat exchanger inlet of the first heat exchange device (120), and the second outlet of the vortex tube (110) is connected to the heat exchanger inlet of the second heat exchange device (130). A circulation system (200) includes a circulation pump (210) and a circulation tank (220). The outlet of the circulation pump (210) is connected to the inlet of the first heat exchange device (120) and the inlet of the second heat exchange device (130), respectively. The outlet of the circulation tank (220) is connected to the circulation pump (210), and the inlet of the circulation tank (220) is used to connect to the output end of the load device (500). The processing device (300) has its inlet connected to the outlet of the first heat exchanger (120) and the outlet of the second heat exchanger (130), respectively; and its outlet is connected to the input of the load device (500).
2. The temperature control device according to claim 1, characterized in that, The gas delivery device (140) includes an ejector (141), a gas-liquid separator (142), and a compressor (143). The outlet of the compressor (143) is connected to the inlet of the vortex tube (110), the inlet of the compressor (143) is connected to the outlet of the gas-liquid separator (142), the inlet of the gas-liquid separator (142) is connected to the outlet of the ejector (141), and the inlet and outlet of the ejector (141) are connected to the heat exchanger outlet of the first heat exchange device (120) and the heat exchanger outlet of the second heat exchange device (130), respectively.
3. The temperature control device according to claim 1, characterized in that, The circulation system (200) further includes an adjustment component (400), which is disposed on the inlet branch and outlet branch connecting the first heat exchange device (120) and the second heat exchange device (130). The adjustment component (400) is used to distribute and control the amount of liquid entering and leaving the first heat exchange device (120) and the second heat exchange device (130).
4. The temperature control device according to claim 3, characterized in that, The regulating assembly (400) includes a regulating valve (410), at least one first expansion valve (610) and at least one second expansion valve (620). The regulating valve (410) is disposed on a branch in which the outlet of the circulating pump (210) communicates with the first heat exchange device (120) and the second heat exchange device (130). At least one first expansion valve (610) is provided between the liquid outlet of the first heat exchange device (120) of the temperature control device and the liquid inlet of the refrigeration device (310) of the processing device (300), and at least one second expansion valve (620) is provided between the liquid outlet of the second heat exchange device (130) and the liquid inlet of the refrigeration device (310) of the processing device (300).
5. The temperature control device according to claim 4, characterized in that, The temperature control device (1000) also includes a plurality of temperature sensors (700), including a first temperature sensor (710), a second temperature sensor (720) and a third temperature sensor (730). At least one first temperature sensor (710) is provided at the output end of the load device (500). At least one second temperature sensor (720) is provided between the liquid outlet of the first heat exchange device (120) and the first expansion valve (610). At least one third temperature sensor (730) is provided between the liquid outlet of the second heat exchange device (130) and the second expansion valve (620).
6. The temperature control device according to claim 4, characterized in that, The outlet of the first heat exchange device (120) is connected to the outlet of the circulating pump (210) and the first expansion valve (610), respectively. The outlet of the second heat exchange device (130) is connected to the outlet of the circulating pump (210) and the second expansion valve (620), respectively.
7. The temperature control device according to claim 1, characterized in that, The temperature control device (1000) further includes at least one third expansion valve (630) and at least one fourth expansion valve (640). At least one third expansion valve (630) is provided between the load device (500) and the circulating water tank (220), and at least one fourth expansion valve (640) is provided between the processing device (300) and the load device (500).
8. The temperature control device according to claim 1, characterized in that, The first heat exchange device (120) and / or the second heat exchange device (130) is a gas-water heat exchange tube (800).
9. A temperature control method, applied to the temperature control device (1000) according to any one of claims 1-8, characterized in that, The temperature control method includes: Determine the first preset temperature and the first preset range; Obtain the first temperature of the liquid inlet of the load device (500); Compare the first temperature with the first preset temperature; If the difference between the first preset temperature and the first temperature is greater than the maximum value of the first preset range, then the output power of the heating device (320) of the processing device (300) is reduced. If the difference between the first preset temperature and the first temperature is less than the minimum value of the first preset range, then the output power of the heating device (320) of the processing device (300) is increased. If the difference between the first preset temperature and the first temperature is within the first preset range, then the heating device (320) of the processing device (300) is controlled to remain unchanged.
10. The temperature control method according to claim 9, characterized in that, The temperature control device (1000) further includes a plurality of expansion valves (600), the plurality of expansion valves (600) including at least one first expansion valve (610) and at least one second expansion valve (620); at least one first expansion valve (610) is provided between the liquid outlet of the first heat exchange device (120) and the liquid inlet of the refrigeration device (310) of the processing device (300), and at least one second expansion valve (620) is provided between the liquid outlet of the second heat exchange device (130) and the liquid inlet of the refrigeration device (310) of the processing device (300); Prior to the step of obtaining the temperature of the liquid inlet of the load device (500), the temperature control method further includes: Determine the second preset temperature and the second preset range; Obtain the second temperature of the liquid inlet of the processing device (300); Compare the second temperature with the second preset temperature; If the difference between the second preset temperature and the second temperature is greater than the maximum value of the second preset range, then the opening of the first expansion valve (610) is increased and the opening of the second expansion valve (620) is decreased. If the difference between the second preset temperature and the second temperature is less than the minimum value of the second preset range, then the opening of the first expansion valve (610) is reduced and the opening of the second expansion valve (620) is increased. If the difference between the second preset temperature and the second temperature is within the second preset range, then the first expansion valve (610) and the second expansion valve (620) are controlled to remain in their current state.