Multi-cooling source combined refrigeration system for environmental wind tunnels

Abstract

The present invention discloses a multi-cold source combined refrigeration system for an environmental wind tunnel, comprising: a main circulation pipeline, which is connected to a heat exchanger within the environmental wind tunnel and is provided with a cooling medium; multiple refrigerators, which are arranged in parallel and respectively connected to the main circulation pipeline, and each refrigerator provides cooling for different temperature ranges; and a PID control unit, which is configured to activate refrigerators in corresponding temperature ranges according to the real-time temperature of the environmental wind tunnel to cool the environmental wind tunnel until the temperature within the environmental wind tunnel reaches a set target temperature. The present invention enables the wind tunnel to have a corresponding refrigerator in each temperature range and output the maximum cooling capacity, thereby accurately matching the experimental requirements of different cooling capacities at different temperatures.

Description

Technical Field

[0001] The present invention belongs to the technical field of temperature control of low-speed environmental wind tunnels, and more particularly, relates to a multi-cold source combined refrigeration system applied to environmental wind tunnels. Background Art

[0002] One of the primary functions of a low-speed environmental wind tunnel is to provide a suitable ambient temperature for the test piece, simulating its actual environment and thereby testing its performance. Common tests include simulating the test piece's cold resistance at low temperatures and its heat dissipation at high temperatures. The simulated environment varies depending on the test piece's needs. Based on the natural environment, the typical temperature range is -30°C to 40°C, but can be expanded to -50°C to 70°C for extreme climates.

[0003] Traditional low-speed environmental wind tunnels typically employ two chillers. These chillers operate similarly to air conditioners, with their core components consisting of an evaporator, condenser, compressor, and expansion valve. Due to the pressure differential limitations of the compressor, a single chiller cannot cover the entire temperature range. Therefore, wind tunnels typically utilize one chiller for low-temperature cooling and another for ambient temperature cooling. Each chiller operates independently within its respective temperature ranges to provide cooling for the wind tunnel. These chillers are limited by their COP (Cooling Performance of Parts)—meaning that for compressors of the same power, cooling capacity decreases as temperatures drop. For example, cooling capacity at -40°C is only one-quarter of that at 0°C. This results in a nonlinear positive correlation between the cooling capacity provided by the temperature control system and the ambient temperature. For some military or specialized test pieces, maintaining maximum power load under all conditions and providing maximum cooling capacity at all temperatures is essential, something a single chiller cannot achieve. Consequently, existing refrigeration systems limit wind tunnel performance and make it impossible to precisely match cooling or heating capacity to test requirements. Summary of the Invention

[0004] The purpose of this invention is to propose a multi-cold source combined refrigeration system for environmental wind tunnels, which can ensure that the wind tunnel has a corresponding refrigerator in each temperature range and output the maximum cooling capacity, thereby accurately matching the test requirements of different cooling capacities at different temperatures and allowing the wind tunnel to quickly increase or decrease temperature.

[0005] To achieve the above objectives, the present invention proposes a multi-cold source combined refrigeration system for an environmental wind tunnel, comprising:

[0006] A main circulation pipeline, the main circulation pipeline is connected to the heat exchanger in the environmental wind tunnel, and a cooling medium is provided in the main circulation pipeline;

[0007] A plurality of refrigerators are arranged in parallel and respectively connected to the main circulation pipeline, and the plurality of refrigerators respectively perform cooling for different temperature ranges;

[0008] A PID control unit is configured to activate a refrigerator in a corresponding temperature range according to the real-time temperature of the environmental wind tunnel to cool the environmental wind tunnel until the temperature in the environmental wind tunnel reaches a set target temperature.

[0009] Optionally, a natural cooling tower is further included, wherein the main circulation pipeline includes an inlet main pipeline and a return main pipeline, one end of the inlet main pipeline is connected to the working medium inlet of a heat exchanger arranged in the environmental wind tunnel, and the other end of the inlet main pipeline is connected to the working medium outlet of the natural cooling tower; one end of the return main pipeline is connected to the working medium outlet of the heat exchanger, and the other end of the return main pipeline is connected to the working medium inlet of the natural cooling tower;

[0010] When the return temperature of the environmental wind tunnel is higher than the temperature at which the refrigerator can cool, the PID control unit controls the natural cooling tower to connect to the main circulation pipeline to cool the environmental wind tunnel;

[0011] When the return temperature of the environmental wind tunnel drops to the cooling temperature range of the refrigerator with the highest cooling temperature range among the multiple refrigerators, the PID control unit controls the natural cooling tower to be disconnected from the main circulation pipeline, and controls the refrigerator with the highest cooling temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel;

[0012] When the return temperature of the environmental wind tunnel is lower than the lower limit of the refrigeration temperature range of the refrigerator with the highest refrigeration temperature range, the PID control unit controls the refrigerator with the highest refrigeration temperature range to be disconnected from the main circulation pipeline, and controls the refrigerator with the second highest refrigeration temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel, and so on, until the environmental wind tunnel reaches the target temperature.

[0013] Optionally, a first circulation pump and a first throttle valve are provided at one end of the return main line close to the natural cooling tower; a second throttle valve is provided at one end of the inlet main line close to the natural cooling tower;

[0014] A first temperature sensor is provided in the environmental wind tunnel;

[0015] A first three-way valve is provided at one end of the return main line close to the environmental wind tunnel, wherein a first end of the first three-way valve is in communication with the heat exchanger in the environmental wind tunnel, a second end of the first three-way valve is in communication with the return main line, and a third end of the first three-way valve is in communication with the inlet main line;

[0016] When the first three-way valve is opened, the first end and the second end of the first three-way valve are connected, and the environmental wind tunnel is connected to the main circulation pipeline. When the first three-way valve is closed, the second end and the third end of the first three-way valve are connected, and the environmental wind tunnel is disconnected from the main circulation pipeline.

[0017] The PID control unit obtains the temperature in the environmental wind tunnel according to the first temperature sensor, and opens the first three-way valve when the temperature in the environmental wind tunnel is greater than a target temperature to cool the environmental wind tunnel.

[0018] Optionally, the working medium inlet of each refrigerator is connected to the reflux main line through a cooling reflux branch line, and the working medium outlet of each refrigerator is connected to the inlet main line through a cooling inlet branch line;

[0019] A second circulation pump is provided on the cooling inlet branch pipe;

[0020] A one-way valve and a second three-way valve are provided on the cooling return branch pipeline, a first end of the second three-way valve is communicated with the return main pipeline, a second port of the second three-way valve is communicated with the working medium inlet of the refrigerator, and a third port of the second three-way valve is communicated with the cooling inlet branch pipeline located between the second circulation pump and the inlet main pipeline;

[0021] When the second three-way valve is opened, the first end and the second end of the second three-way valve are connected, and the refrigerator is connected to the main circulation pipeline. When the second three-way valve is closed, the second end and the third end of the first three-way valve are connected, the refrigerator is disconnected from the main circulation pipeline, and the refrigerator enters a self-circulation state.

[0022] Optionally, a second temperature sensor is provided at one end of the return main line close to the environmental wind tunnel, and the second temperature sensor is used to monitor the return temperature of the environmental wind tunnel;

[0023] A third temperature sensor is provided at one end of the main inlet pipe close to the environmental wind tunnel, and the third temperature sensor is used to monitor the inlet temperature of the environmental wind tunnel;

[0024] A fourth temperature sensor is provided at one end of the cooling refrigeration branch pipe close to the working medium inlet of the refrigerator, and the fourth temperature sensor is used to monitor the refrigeration temperature of the refrigerator;

[0025] The PID control unit obtains the return water temperature of the environmental wind tunnel according to the second temperature sensor, and controls the natural cooling tower or the refrigerator in the corresponding temperature range to connect to the main circulation pipeline for cooling according to the temperature range to which the return water temperature belongs;

[0026] When the natural cooling tower is connected to the main circulation pipeline, the PID control unit controls the first throttle valve and the second throttle valve to open, and controls the plurality of second three-way valves to close, and causes the refrigerator to enter a self-circulation state;

[0027] When the refrigerator in the corresponding temperature range is connected to the main circulation pipeline, the PID control unit controls the first throttle valve and the second throttle valve to close, controls the second three-way valve of the refrigerator in the corresponding temperature range to open, and controls the second three-way valves of the remaining refrigerators to close, and makes the remaining refrigerators enter the self-circulation state.

[0028] Optionally, an electric heater is further included, wherein the working medium inlet of the electric heater is connected to the reflux main line through a heating reflux branch line, and the working medium outlet of the electric heater is connected to the inlet main line through a heating inlet branch line;

[0029] A one-way valve and a third three-way valve are provided on the heating reflux branch pipeline, a first end of the third three-way valve is connected to the reflux main pipeline, a second end of the third three-way valve is connected to the working medium inlet of the electric heater, and a third end of the third three-way valve is connected to the heating inlet branch pipeline;

[0030] When the third three-way valve is opened, the first end and the second end of the third three-way valve are connected, and the electric heater is connected to the main circulation pipeline; when the third three-way valve is closed, the second end and the third end of the third three-way valve are connected, and the electric heater is disconnected from the main circulation pipeline;

[0031] A third circulation pump is provided on the heating inlet branch pipe;

[0032] When the temperature in the environmental wind tunnel is lower than the target temperature, the PID control unit controls the first three-way valve and the second three-way valve to close, and controls the third three-way valve to open, and the electric heater is started to heat the environmental wind tunnel.

[0033] Optionally, it further comprises a main buffer tank and a cold buffer tank, wherein the main buffer tank is arranged on the reflux main line and located between the first three-way valve and the second temperature sensor;

[0034] The cold buffer tank is arranged on the cooling reflux branch line and is located between the second three-way valve and the fourth temperature sensor.

[0035] Optionally, a thermal buffer tank is further included, which is arranged on the heating inlet branch pipeline and located between the third three-way valve and the electric heater.

[0036] Optionally, the first three-way valve and the third three-way valve are both pneumatic three-way valves, and the second three-way valve is an electric three-way valve.

[0037] Optionally, filters are provided upstream of the first circulation pump, the second circulation pump and the third circulation pump.

[0038] The beneficial effects of the present invention are:

[0039] The multi-cold source combined refrigeration system applied to the environmental wind tunnel of the present invention adopts a parallel connection method, and connects each refrigerator device to the main circulation pipeline of the environmental wind tunnel at the same time. A plurality of refrigerators are used to perform refrigeration for different temperature ranges respectively. According to the real-time temperature of the environmental wind tunnel, refrigerators in corresponding temperature ranges are turned on to cool the environmental wind tunnel, so that the wind tunnel can be connected to any number of refrigerators, and there is a corresponding refrigerator with a maximum cooling capacity output in each temperature range, which can accurately match the required cooling capacity in different temperature ranges.

[0040] The system of the present invention has other features and advantages that will be apparent from or will be described in detail in the accompanying drawings and subsequent detailed description incorporated herein, which together serve to explain the specific principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The above and other objects, features and advantages of the present invention will become more apparent through a more detailed description of exemplary embodiments of the present invention with reference to the accompanying drawings, in which like reference numerals generally represent like components.

[0042] Figure 1 A schematic structural diagram of a multi-cold source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0043] Figure 2 A schematic diagram showing the operating principle of a three-way valve in a multi-cold source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0044] Figure 3 A schematic diagram of the PID control principle of a multi-cold source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0045] Figure 4 A schematic diagram of low-temperature steady-state refrigeration in a multi-cold-source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0046] Figure 5A schematic diagram illustrating the principle of self-circulation operation of a heater and a refrigerator in a multi-cold source combined refrigeration system according to an embodiment of the present invention when a three-way valve is closed is shown.

[0047] Figure 6 A schematic diagram of high-temperature steady-state cooling in a multi-cold-source combined cooling system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0048] Figure 7 A schematic diagram showing the simultaneous operation of multiple refrigerators in a multi-cold source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0049] Figure 8 A schematic diagram of a multi-cold source combined refrigeration system for heating in an environmental wind tunnel according to an embodiment of the present invention is shown.

[0050] Figure 9 A schematic diagram of rapid cooling of a multi-cold source combined cooling system applied to an environmental wind tunnel according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0051] In order to accurately match the experimental requirements of different cooling capacities at different temperatures, the present invention provides a multi-cold source joint operation refrigeration system and design method for low-speed environmental wind tunnels. The system is mainly in the form of multiple cold sources in parallel, connecting a heater, several refrigerators and a natural cooling tower, and adjusting the connection between each module through the different openings of each valve to make it suitable for the steady-state and dynamic temperature requirements in the wind tunnel.

[0052] The present invention will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention may be implemented in various forms and is not limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present invention more thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0053] Example

[0054] Figure 1 A schematic structural diagram of a multi-cold source combined refrigeration system applied to an environmental wind tunnel according to an embodiment of the present invention is shown.

[0055] A multi-cold source combined refrigeration system for an environmental wind tunnel, comprising:

[0056] The main circulation pipeline is connected to the heat exchanger in the environmental wind tunnel and is provided with a cooling medium;

[0057] Multiple refrigerators 6 are arranged in parallel and are respectively connected to the main circulation pipeline, and the multiple refrigerators 6 are respectively used for cooling in different temperature ranges;

[0058] The PID control unit is used to start the refrigerator 6 in the corresponding temperature range according to the real-time temperature of the environmental wind tunnel to cool the environmental wind tunnel until the temperature in the environmental wind tunnel reaches the set target temperature.

[0059] Specifically, the system adopts a parallel connection mode, connecting each refrigeration device into the pipeline at the same time, so that the wind tunnel can be connected to any number of refrigerators 6, and there is a corresponding refrigerator 6 that outputs the maximum cooling capacity in each temperature range.

[0060] The refrigerator 6 used in this embodiment is a refrigeration device for a specific temperature range. It can output sufficient cooling capacity within the design temperature range. However, the cooling capacity output is small outside the design temperature range, and even pressure difference alarms may occur, or the refrigerator 6 inlet water temperature is too high and cannot be started. Therefore, by connecting multiple refrigerators 6 in parallel, it can be ensured that there is a corresponding refrigerator 6 for each small temperature range, and all of them can output sufficient cooling capacity. Due to its own characteristics, the refrigerator 6 should not be turned on and off frequently. Even after being turned off, it needs to maintain long-term unloading, and the flow of pipeline working fluid cannot be stopped during unloading. Therefore, in this system, when the second three-way valve Vm (m=1 / 2 / … / n) is opened, the refrigerator 6 is connected to the main line. When disconnected, the refrigerator 6 will not be shut down, but will enter self-circulation and maintain a low-power standby state.

[0061] In this embodiment, the system further includes a natural cooling tower 5, and the main circulation pipeline includes an inlet main line 2 and a return main line 1. One end of the inlet main line 2 is connected to the working medium inlet of the heat exchanger arranged in the environmental wind tunnel, and the other end of the inlet main line 2 is connected to the working medium outlet of the natural cooling tower 5; one end of the return main line 1 is connected to the working medium outlet of the heat exchanger, and the other end of the return main line 1 is connected to the working medium inlet of the natural cooling tower 5;

[0062] When the return temperature of the environmental wind tunnel is higher than the temperature that the refrigerator 6 can cool, the PID control unit controls the natural cooling tower 5 to connect to the main circulation pipeline to cool the environmental wind tunnel;

[0063] When the return temperature of the environmental wind tunnel drops to the cooling temperature range of the refrigerator 6 with the highest cooling temperature range among the multiple refrigerators 6, the PID control unit controls the natural cooling tower 5 to be disconnected from the main circulation pipeline, and controls the refrigerator 6 with the highest cooling temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel;

[0064] When the return temperature of the environmental wind tunnel is lower than the lower limit of the refrigeration temperature range of the refrigerator 6 with the highest refrigeration temperature range, the PID control unit controls the refrigerator 6 with the highest refrigeration temperature range to be disconnected from the main circulation pipeline, and controls the refrigerator 6 with the second highest refrigeration temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel, and so on, until the environmental wind tunnel reaches the target temperature.

[0065] Specifically, this system incorporates a natural cooling tower 5, which can cool the wind tunnel when the ambient wind tunnel temperature is high and the chiller is unable to refrigerate it. Natural Cooling Tower 5, similar to an air conditioner's outdoor unit, reduces the internal working fluid temperature to a temperature close to that of the natural environment, with a typical upper temperature limit of 32°C or less. This makes it suitable for cooling wind tunnels above 40°C. Due to its inherent characteristics, Natural Cooling Tower 5 can maintain standby mode without entering a self-circulating cycle, and does not require unloading after shutdown. Therefore, it only requires a shutoff valve to control its connection and disconnection with the main line.

[0066] In this embodiment, the return main line 1 is provided with a first circulation pump 8 and a first throttle valve Vf1 at one end close to the natural cooling tower 5, and a fourth circulation pump 18 is provided at the other end close to the environmental wind tunnel; the inlet main line 2 is provided with a second throttle valve Vf2 at one end close to the natural cooling tower 5;

[0067] Specifically, the natural cooling tower is connected to the main circulation pipeline via a first throttle valve Vf1 and a second throttle valve Vf2. These valves, Vf1 and Vf2, have only two states: fully open and closed. While isolating the working fluid from flowing, they also prevent "temperature crossover" within the pipeline, protecting downstream equipment from damage caused by this "temperature crossover." (Temperature crossover: When the working fluid in a pipeline is not flowing, if one end of the pipeline contains hot working fluid and the other end contains cold working fluid, natural convection heat transfer occurs, causing the working fluid and temperature at both ends to gradually balance.) This system uses multiple circulating pumps to balance the pressure within the pipeline, ensuring appropriate flow and pressure within the pipeline. Preferably, the multiple circulating pumps (including the first circulating pump 8, the second circulating pump 16, the third circulating pump 17, and the fourth circulating pump 18) are all water pumps equipped with frequency converters. The water pump pressure head and flow rate can be calculated based on factors such as the friction resistance of the actual pipe layout, height difference, and working fluid viscosity. The water pump power needs to be adjusted by the frequency converter to compensate for the increased viscous flow resistance of the pipeline working fluid due to the decrease in temperature.

[0068] In this embodiment, a first temperature sensor Tt is provided in the environmental wind tunnel; a first three-way valve V0 is provided at one end of the return main line 1 close to the environmental wind tunnel; a first end of the first three-way valve V0 is connected to the heat exchanger in the environmental wind tunnel, a second end of the first three-way valve V0 is connected to the return main line 1, and a third end of the first three-way valve V0 is connected to the inlet main line 2;

[0069] When the first three-way valve V0 is opened, the first end and the second end of the first three-way valve V0 are connected, and the environmental wind tunnel is connected to the main circulation pipeline. When the first three-way valve V0 is closed, the second end and the third end of the first three-way valve V0 are connected, and the environmental wind tunnel is disconnected from the main circulation pipeline.

[0070] The PID control unit obtains the temperature in the environmental wind tunnel according to the first temperature sensor Tt, and opens the first three-way valve V0 when the temperature in the environmental wind tunnel is greater than the target temperature to cool the environmental wind tunnel.

[0071] In this embodiment, the working medium inlet of each refrigerator 6 is connected to the reflux main line 1 through the cooling reflux branch line 3, and the working medium outlet of each refrigerator 6 is connected to the inlet main line 2 through the cooling inlet branch line 4;

[0072] A second circulation pump 16 is provided on the cooling inlet branch pipe 4;

[0073] A one-way valve 12 and a second three-way valve Vm (m=1 / 2 / … / n) are provided on the cooling reflux branch pipeline 3. The first end of the second three-way valve Vm is connected to the reflux main pipeline 1, the second port of the second three-way valve Vm is connected to the working medium inlet of the refrigerator 6, and the third port of the second three-way valve Vm is connected to the cooling inlet branch pipeline 4 located between the second circulation pump 16 and the inlet main pipeline 2; wherein, the one-way valve 12 is used to allow the pipeline working medium to flow in the designed direction.

[0074] When the second three-way valve Vm is opened, the first end and the second end of the second three-way valve Vm are connected, and the refrigerator 6 is connected to the main circulation pipeline. When the second three-way valve Vm is closed, the second end and the third end of the first three-way valve V0 are connected, the refrigerator 6 is disconnected from the main circulation pipeline, and the refrigerator 6 enters the self-circulation state.

[0075] In this embodiment, a second temperature sensor Th is provided at one end of the return main line 1 close to the environmental wind tunnel. The second temperature sensor Th is used to monitor the return temperature of the environmental wind tunnel.

[0076] A third temperature sensor Tc is provided at one end of the inlet main line 2 close to the environmental wind tunnel. The third temperature sensor Tc is used to monitor the inlet temperature of the environmental wind tunnel.

[0077] A fourth temperature sensor Tm (m=1 / 2 / … / n) is provided at one end of the cooling return branch pipe 3 close to the working medium inlet of the refrigerator 6. The fourth temperature sensor Tm is used to monitor the return temperature of the refrigerator 6.

[0078] The PID control unit obtains the return water temperature of the environmental wind tunnel according to the second temperature sensor Th, and controls the natural cooling tower 5 or the refrigerator 6 of the corresponding temperature range to connect to the main circulation pipeline for cooling according to the temperature range of the return water temperature;

[0079] When the natural cooling tower 5 is connected to the main circulation pipeline, the PID control unit controls the first throttle valve Vf1 and the second throttle valve Vf2 to open, and controls the multiple second three-way valves Vm to close, and puts the refrigerator 6 into a self-circulation state;

[0080] When the refrigerator 6 in the corresponding temperature range is connected to the main circulation pipeline, the PID control unit controls the first throttle valve Vf1 and the second throttle valve Vf2 to close, controls the second three-way valve of the refrigerator in the corresponding temperature range to open, and controls the second three-way valves of the remaining refrigerators to close, and makes the remaining refrigerators 6 enter the self-circulation state.

[0081] Specifically, the system detects the temperature of the corresponding pipelines through multiple temperature sensors and provides signals for opening / closing each valve or heating / cooling device. The three-way valves in the system (including the first three-way valve V0, the second three-way valve Vm (m = 1 / 2 / ... / n) and the third three-way valve Vh) only connect two of the interfaces when the opening is 0% and 100%. The specific interface connection and opening correspond to the following: Figure 2 As shown, when the opening is between 0% and 100%, all three interfaces are connected. However, the degree of connection varies depending on the opening. Therefore, the three-way valve can flexibly control the flow rate and the mixing of working fluids of different temperatures. When the three-way valve is open, each device can be connected to the main line, and the operating state of the device can be adjusted by adjusting the opening. When the three-way valve is closed, each device can be disconnected from the main line, entering a self-circulating state.

[0082] Three-way valves respond quickly when pneumatically actuated and are generally used for precise flow and temperature regulation. Electric motors respond slowly and are generally used to connect and disconnect pipe interfaces. In this system, the first three-way valve V0 and the third three-way valve Vh are preferably pneumatic three-way valves, while the second three-way valve Vm (m = 1 / 2 / … / n) is an electric three-way valve.

[0083] In this embodiment, the system further includes a main buffer tank 9 and a cold buffer tank 10. The main buffer tank 9 is provided on the reflux main line 1 and is located between the first three-way valve V0 and the second temperature sensor Th.

[0084] The cold buffer tank 10 is disposed on the cooling reflux branch line 3 and is located between the second three-way valve Vm and the fourth temperature sensor Tm.

[0085] Specifically, the buffer tanks (including the main buffer tank 9, multiple cold buffer tanks 10 and hot buffer tanks 11) added to this system have two functions. First, before the working fluid flows into each heat source or each cold source, it is mixed with the original working fluid in the buffer tank to ensure that the working fluid flowing into the refrigerator 6 is within the reasonable operating temperature range of the refrigerator 6; second, the working fluid in the tank body can store cold or heat, reducing the temperature fluctuation of the working fluid flowing into the cold source or heat source equipment, so that the cold source or heat source equipment outputs stable power.

[0086] In this embodiment, the system further includes an electric heater 7, the working medium inlet of the electric heater 7 is connected to the reflux main line 1 through a heating reflux branch line 14, and the working medium outlet of the electric heater 7 is connected to the inlet main line 2 through a heating inlet branch line 15;

[0087] A one-way valve 12 and a third three-way valve Vh are provided on the heating reflux branch line 14. The first end of the third three-way valve Vh is connected to the reflux main line 1, the second end of the third three-way valve Vh is connected to the working medium inlet of the electric heater 7, and the third end of the third three-way valve Vh is connected to the heating inlet branch line 15.

[0088] When the third three-way valve Vh is opened, the first end and the second end of the third three-way valve Vh are connected, and the electric heater 7 is connected to the main circulation pipeline. When the third three-way valve Vh is closed, the second end and the third end of the third three-way valve Vh are connected, and the electric heater 7 is disconnected from the main circulation pipeline.

[0089] A third circulation pump 17 is provided on the heating inlet branch pipe 15;

[0090] When the temperature in the environmental wind tunnel is lower than the target temperature, the PID control unit controls the first three-way valve V0 and the second three-way valve Vm to close, and controls the third three-way valve Vh to open, and the electric heater 7 is started to heat the environmental wind tunnel.

[0091] In this embodiment, a thermal buffer tank 11 is further included. The thermal buffer tank 11 is disposed on the heating inlet branch pipeline 15 and is located between the third three-way valve Vh and the electric heater 7 .

[0092] Specifically, by adding an electric heater 7 to provide a heat source for the system, the working fluid can be heated when the ambient wind tunnel temperature is too low. The electric heater 7 in this system includes an electric heating rod, which is inserted into the electric heating rod to directly heat the working fluid. Since there is less working fluid flowing in the pipeline, the electric heating rod will quickly heat the working fluid to the upper temperature limit when it is powered on. Then, when the electric heating rod is powered off, the working fluid temperature in the water tank quickly drops to the lower temperature limit, causing the electric heating rod to be turned on again. As a result, the output temperature and power of the electric heater 7 fluctuate significantly, making it difficult to stably control the temperature. Therefore, this system adopts the method of adding a heat buffer tank 11 upstream of the electric heater 7 to reduce the amplitude and frequency of the temperature fluctuation of the working fluid flowing into the electric heater 7, thereby slowing down the output fluctuation of the electric heater 7 and making the temperature control more stable.

[0093] In this embodiment, preferably, a filter 13 is provided upstream of the first circulation pump 8, the second circulation pump 16, and the third circulation pump 17. By disposing a filter 13 upstream of each water pump, impurities can be prevented from entering the pump and causing it to become stuck. The main source of impurities is iron filings and sand that have not been blown away from the fine tubes in the heat exchanger or cold / heat source upstream of the water pump.

[0094] The control method of the multi-cold source combined refrigeration system of this embodiment adopts PID control. The PID control principle diagram is as follows: Figure 3 As shown, the dotted line is the control line, and the PID control method is as follows:

[0095] When the system is in steady state, it is required to provide cooling to the ambient wind tunnel. At this time, the PID control unit controls the opening of the first three-way valve V0 according to the temperature value inside the ambient wind tunnel detected by the first temperature sensor Tt. When the temperature detected by the first temperature sensor Tt is higher than the wind tunnel target temperature, the first three-way valve V0 is opened, and vice versa.

[0096] When the wind tunnel maintains a stable temperature, the temperature detected by the first temperature sensor Tt is also stable. If the cooling capacity carried by the refrigerant is too large, when the first three-way valve V0 is closed to the minimum, the temperature in the wind tunnel is still lower than the required temperature, then the third three-way valve Vh needs to be opened appropriately to add a small amount of heat to the ambient wind tunnel through the heater 7 to raise the wind tunnel back to the required temperature.

[0097] The return water temperature of the environmental wind tunnel is monitored by the second temperature sensor Th, and the PID control unit determines whether other devices have the conditions for starting based on the return water temperature measured by the second temperature sensor Th. When the return water temperature exceeds 40°C, the first throttle valve Vf1 and the second throttle valve Vf2 can be opened to allow the natural cooling tower 5 to input cooling energy into the wind tunnel. When the temperature is between 25 and 40°C, the third three-way valve Vn can be opened, and the first and second throttle valves Vf1 and Vf2 can be closed to allow the n# refrigerator 6 to input cooling energy into the wind tunnel. When the temperature is between 10 and 25°C, the third three-way valve Vn-1 can be opened and the third three-way valve Vn can be closed to allow the n-1# refrigerator 6 to input cooling energy into the wind tunnel. Subsequent refrigerators 6 and their corresponding third three-way valves are opened or closed in sequence according to this rule until the temperature is approximately -45°C, at which point the third three-way valve V1 can be opened and the third three-way valves V2 to Vn can be closed to allow the 1# refrigerator 6 to input cooling energy into the wind tunnel. The size of each temperature range and the corresponding refrigerator 6 can be selected based on the actual performance of the refrigerator 6 and test needs. The previous design results are only given here as an example.

[0098] The various operating modes of the system of this embodiment are as follows:

[0099] Figure 4 It is a typical low-temperature steady-state refrigeration state. Within a certain temperature range, the m# refrigerator 6 is turned on, and the corresponding third three-way valve Vm performs PID adjustment according to the temperature sensor Tm to ensure that the m# refrigerator 6 is in normal working condition and maintains refrigeration. The heater pipeline maintains self-circulation, which is used to add heat to the main pipeline when the temperature is too low to maintain stable temperature control. At this time, the other refrigerators 6 are in a self-circulation state because their corresponding three-way valves are closed, maintaining low-power operation. At this time, the temperature of the working fluid in the circulation pipeline will decrease at a slow rate. When the self-circulation time is too long, the self-circulation pipeline needs to be connected to the main pipeline with a small opening (about 3 to 5% according to the test debugging results) to raise the temperature of the working fluid flowing in the circulation pipeline back to the normal temperature range. The self-circulation of refrigerator 6 is as follows Figure 5 shown.

[0100] Figure 6 This is a typical high-temperature steady-state refrigeration state. At this time, due to the high temperature, the refrigerator 6 cannot be started, and the natural cooling tower 5 is used for cooling. The first throttle valve Vf1 and the second throttle valve Vf2 are opened. The electric heater pipeline maintains self-circulation, which is used to add heat to the main pipeline when the temperature is too low to maintain stable temperature control. When the electric heater pipeline is circulating, although the electric heater 7 itself is closed, the pipeline itself has insulation, and the pump in the pipeline will continue to work on the working fluid. As a result, after a long time, the temperature of the working fluid in the self-circulation pipeline will gradually rise to above the tolerance range of the equipment. Therefore, it is necessary to connect the self-circulation pipeline to the main circulation pipeline with a small opening (about 1-2% according to the test debugging results) to reduce the temperature of the working fluid flowing in the circulation pipeline back to the normal temperature range. The principle of heater self-circulation is as follows Figure 5 shown.

[0101] When the corresponding refrigerators 6 within each temperature range operate individually, although the other refrigerators 6 have not reached the specified operating temperature range, under the joint action of the third three-way valve Vm and the cold buffer tank 10, by slightly opening the corresponding third three-way valve Vm, a small amount of low-temperature working fluid can be mixed with the working fluid in the cold buffer tank 10 and flow into the downstream refrigerator 6 at a suitable temperature, so that the refrigerator 6 can operate under temperature conditions outside the specified temperature range.

[0102] Figure 7 This is a typical multi-refrigeration unit 6 combined cooling state. At this point, the temperature range corresponds to the m# chiller 6. The third three-way valve Vm is fully opened, and the m# chiller 6 enters the full-load cooling state. The natural cooling tower 5 and the m+1 to n# chillers 6 cannot be opened because their outlet water temperatures are higher than that of the m# chiller 6. Meanwhile, the k# to m-1# chillers 6, protected by their respective upstream cold buffer tanks 10, can also connect to the main line for cooling. However, their corresponding third three-way valves Vk to Vm-1 cannot be fully opened. Instead, their openings are adjusted based on their respective fourth temperature sensors Tk to Tm-1, allowing the k# to m-1# chillers 6 to partially connect for cooling.

[0103] Figure 8 This is a typical heating state. All cold sources do not participate in cooling. Therefore, the valves corresponding to the refrigerator 6 and the natural cooling tower 5 are also closed, leaving only the third three-way valve Vh to maintain the maximum opening, so that the electric heater 7 heats the main line at full load.

[0104] Figure 9This is a typical rapid cooling state, with no heat source involved in heating. All refrigeration equipment operates within its temperature range. Starting from the highest wind tunnel temperature, the natural cooling tower 5 begins cooling. At this point, chillers #m through #n can also connect to the system due to buffer tank protection. However, chillers #1 through #m-1 cannot be turned on due to high inlet water temperatures and low outlet water temperatures. As the wind tunnel temperature decreases, chillers #6 with high outlet water temperatures gradually shut down, while chillers #6 with low outlet water temperatures can be turned on.

[0105] In summary, the combined refrigeration system of the present invention has the following advantages:

[0106] 1. This system adopts a parallel connection method, connecting various heating and cooling equipment into the pipeline at the same time, so that the wind tunnel can be connected to any number of refrigerators, and there is a corresponding refrigerator outputting the maximum cooling capacity in each temperature range.

[0107] 2. All heating / cooling equipment incorporated into this system are connected through a three-way valve, which can put the refrigerator in a low-load standby self-circulation state when it is not needed, without the need to shut down, thereby increasing the service life of the equipment.

[0108] 3. Each heating / cooling device incorporated into this system is equipped with its own buffer tank, which can reduce the temperature fluctuation of the input and output working fluids of the refrigerator and improve the temperature control stability (tests have shown that the fluctuation can be reduced from ±6°C to about ±2°C).

[0109] 4. With the combined action of the three-way valve and the buffer tank, the refrigerator that originally could only operate at low temperatures can now operate at higher temperature conditions, expanding the operating temperature range of the refrigerator and allowing multiple refrigerators to operate simultaneously without interfering with each other. This also enables the wind tunnel to obtain greater cooling capacity than when a single refrigerator is operating, withstand greater test loads, and have a faster cooling rate.

[0110] While various embodiments of the present invention have been described above, the above description is intended to be illustrative, not exhaustive, and not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A multi-cold source combined refrigeration system applied to an environmental wind tunnel, characterized in that: include: A main circulation pipeline, the main circulation pipeline is connected to the heat exchanger in the environmental wind tunnel, and a cooling medium is provided in the main circulation pipeline; A plurality of refrigerators are arranged in parallel and respectively connected to the main circulation pipeline, and the plurality of refrigerators respectively perform cooling for different temperature ranges; A PID control unit is configured to activate a refrigerator in a corresponding temperature range according to the real-time temperature of the environmental wind tunnel to cool the environmental wind tunnel until the temperature in the environmental wind tunnel reaches a set target temperature.

2. The refrigeration system according to claim 1, characterized in that The system further comprises a natural cooling tower, wherein the main circulation pipeline comprises an inlet main pipeline and a return main pipeline, wherein one end of the inlet main pipeline is connected to the working medium inlet of a heat exchanger disposed in the environmental wind tunnel, and the other end of the inlet main pipeline is connected to the working medium outlet of the natural cooling tower; one end of the return main pipeline is connected to the working medium outlet of the heat exchanger, and the other end of the return main pipeline is connected to the working medium inlet of the natural cooling tower; When the return temperature of the environmental wind tunnel is higher than the temperature at which the refrigerator can cool, the PID control unit controls the natural cooling tower to connect to the main circulation pipeline to cool the environmental wind tunnel; When the return temperature of the environmental wind tunnel drops to the cooling temperature range of the refrigerator with the highest cooling temperature range among the multiple refrigerators, the PID control unit controls the natural cooling tower to be disconnected from the main circulation pipeline, and controls the refrigerator with the highest cooling temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel; When the return temperature of the environmental wind tunnel is lower than the lower limit of the refrigeration temperature range of the refrigerator with the highest refrigeration temperature range, the PID control unit controls the refrigerator with the highest refrigeration temperature range to be disconnected from the main circulation pipeline, and controls the refrigerator with the second highest refrigeration temperature range to be connected to the main circulation pipeline to cool the environmental wind tunnel, and so on, until the environmental wind tunnel reaches the target temperature.

3. The refrigeration system according to claim 2, characterized in that The return main line is provided with a first circulation pump and a first throttle valve at one end close to the natural cooling tower; the inlet main line is provided with a second throttle valve at one end close to the natural cooling tower; A first temperature sensor is provided in the environmental wind tunnel; A first three-way valve is provided at one end of the return main line close to the environmental wind tunnel, wherein a first end of the first three-way valve is in communication with the heat exchanger in the environmental wind tunnel, a second end of the first three-way valve is in communication with the return main line, and a third end of the first three-way valve is in communication with the inlet main line; When the first three-way valve is opened, the first end and the second end of the first three-way valve are connected, and the environmental wind tunnel is connected to the main circulation pipeline. When the first three-way valve is closed, the second end and the third end of the first three-way valve are connected, and the environmental wind tunnel is disconnected from the main circulation pipeline. The PID control unit obtains the temperature in the environmental wind tunnel according to the first temperature sensor, and opens the first three-way valve when the temperature in the environmental wind tunnel is greater than a target temperature to cool the environmental wind tunnel.

4. The refrigeration system according to claim 3, characterized in that The working medium inlet of each refrigerator is connected to the refrigeration main line through a cooling refrigeration branch line, and the working medium outlet of each refrigerator is connected to the inlet main line through a cooling inlet branch line; A second circulation pump is provided on the cooling inlet branch pipe; A one-way valve and a second three-way valve are provided on the cooling return branch pipeline, a first end of the second three-way valve is communicated with the return main pipeline, a second port of the second three-way valve is communicated with the working medium inlet of the refrigerator, and a third port of the second three-way valve is communicated with the cooling inlet branch pipeline located between the second circulation pump and the inlet main pipeline; When the second three-way valve is opened, the first end and the second end of the second three-way valve are connected, and the refrigerator is connected to the main circulation pipeline. When the second three-way valve is closed, the second end and the third end of the first three-way valve are connected, the refrigerator is disconnected from the main circulation pipeline, and the refrigerator enters a self-circulation state.

5. The refrigeration system according to claim 4, characterized in that A second temperature sensor is provided at one end of the return main line close to the environmental wind tunnel, and the second temperature sensor is used to monitor the return temperature of the environmental wind tunnel; A third temperature sensor is provided at one end of the main inlet pipe close to the environmental wind tunnel, and the third temperature sensor is used to monitor the inlet temperature of the environmental wind tunnel; A fourth temperature sensor is provided at one end of the cooling refrigeration branch pipe close to the working medium inlet of the refrigerator, and the fourth temperature sensor is used to monitor the refrigeration temperature of the refrigerator; The PID control unit obtains the return water temperature of the environmental wind tunnel according to the second temperature sensor, and controls the natural cooling tower or the refrigerator in the corresponding temperature range to connect to the main circulation pipeline for cooling according to the temperature range to which the return water temperature belongs; When the natural cooling tower is connected to the main circulation pipeline, the PID control unit controls the first throttle valve and the second throttle valve to open, and controls the plurality of second three-way valves to close, and causes the refrigerator to enter a self-circulation state; When the refrigerator in the corresponding temperature range is connected to the main circulation pipeline, the PID control unit controls the first throttle valve and the second throttle valve to close, controls the second three-way valve of the refrigerator in the corresponding temperature range to open, and controls the second three-way valves of the remaining refrigerators to close, and makes the remaining refrigerators enter the self-circulation state.

6. The refrigeration system according to claim 5, characterized in that It also includes an electric heater, the working medium inlet of the electric heater is connected to the reflux main line through a heating reflux branch line, and the working medium outlet of the electric heater is connected to the inlet main line through a heating inlet branch line; A one-way valve and a third three-way valve are provided on the heating reflux branch pipeline, a first end of the third three-way valve is connected to the reflux main pipeline, a second end of the third three-way valve is connected to the working medium inlet of the electric heater, and a third end of the third three-way valve is connected to the heating inlet branch pipeline; When the third three-way valve is opened, the first end and the second end of the third three-way valve are connected, and the electric heater is connected to the main circulation pipeline; when the third three-way valve is closed, the second end and the third end of the third three-way valve are connected, and the electric heater is disconnected from the main circulation pipeline; A third circulation pump is provided on the heating inlet branch pipe; When the temperature in the environmental wind tunnel is lower than the target temperature, the PID control unit controls the first three-way valve and the second three-way valve to close, and controls the third three-way valve to open, and the electric heater is started to heat the environmental wind tunnel.

7. The refrigeration system according to claim 5, characterized in that It also includes a main buffer tank and a cold buffer tank, wherein the main buffer tank is arranged on the reflux main line and is located between the first three-way valve and the second temperature sensor; The cold buffer tank is arranged on the cooling reflux branch line and is located between the second three-way valve and the fourth temperature sensor.

8. The refrigeration system according to claim 6, wherein: It also includes a thermal buffer tank, which is arranged on the heating inlet branch pipeline and located between the third three-way valve and the electric heater.

9. The refrigeration system according to claim 6, wherein: The first three-way valve and the third three-way valve are both pneumatic three-way valves, and the second three-way valve is an electric three-way valve.

10. The refrigeration system according to claim 6, wherein: Filters are provided upstream of the first circulation pump, the second circulation pump, and the third circulation pump.

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