A device and method for testing the high-altitude heat transfer capacity of an air-liquid heat exchanger

Abstract

The present invention discloses a high-altitude heat exchange test device and method for an air-liquid heat exchanger, and belongs to the field of experimental test technology. The test device includes a fixed frame, and also includes an evaporation fan, an evaporator, a compressor, a condensation fan and a condenser arranged on the fixed frame; the outlet of the compressor is connected to the inlet of the condenser; the outlet of the condenser is connected to the inlet of the expansion valve; the outlet of the expansion valve (106) is connected to the inlet of the evaporator; the outlet of the evaporator is connected to the inlet of the compressor; the air outlet of the evaporation fan faces the evaporator; the air outlet of the condensation fan faces the condenser; the evaporation fan and the evaporator and the air-liquid heat exchanger to be tested are located in the same closed loop. The present invention has the advantages of small investment, small size, compact structure, short test time, low test cost, high test accuracy, etc. It can meet the requirements of ground test of high-altitude heat exchange of air-liquid heat exchanger of small unmanned aerial vehicle pod.

Description

Technical Field

[0001] The invention relates to the field of experimental testing technology, and in particular to a high-altitude heat exchange testing device and method for an air-liquid heat exchanger. Background Art

[0002] In order to meet the heat dissipation requirements of small UAV pods, a ram air direct cooling environment control liquid supply system is often used. The environment control liquid supply system usually consists of a liquid supply component and an air-liquid heat exchanger, in which the air-liquid heat exchanger generally needs to be exposed to the atmosphere, that is, placed outside the UAV pod. When the UAV platform is flying, the ram air generated flows through the internal fins of the air-liquid heat exchanger (see Figure 1 ), taking away the heat of the coolant in the air-liquid heat exchanger and lowering the temperature of the coolant.

[0003] The amount of heat exchange at high altitude is a key indicator of the air-to-liquid heat exchanger in the drone pod. It is closely related to the actual air velocity, temperature and density flowing through the air inlet section of the heat exchanger. In order to obtain the heat exchange performance indicators of the air-to-liquid heat exchanger under certain operating conditions (a certain flight speed at a certain altitude), it is necessary to conduct a wind tunnel test of the entire drone pod. Wind tunnel tests have high test accuracy, but the construction of wind tunnel test facilities requires huge investment, large land area, and high energy consumption for a single test. In order to simulate low-density, high-speed ram air under actual conditions at high altitudes, the cost of a single operating condition performance test can reach hundreds of thousands of yuan. When more operating conditions need to be tested, huge time and economic costs will be incurred.

[0004] CFD fluid simulation software is used to create a digital wind tunnel to simulate the conditions of high-altitude flight, simulate the heat transfer performance of the air-liquid heat exchanger, and calculate the heat transfer index of the air-liquid heat exchanger. Due to the influence of factors such as the complex shape of the aircraft and the high flight speed in the heat transfer calculation of the air-liquid two-phase fluid, the simulation accuracy is low, and the error with the actual value is usually more than 25%. In order to ensure the index, it is often necessary to leave a large design margin, resulting in the air-liquid heat exchanger being too large in size and weight, resulting in reduced payload loading capacity of the airborne platform and reduced endurance, which is unacceptable for airborne products. Summary of the invention

[0005] The technical problem to be solved by the present invention is to avoid the shortcomings of the above-mentioned background technology and provide a high-altitude heat exchange test device and method for air-liquid heat exchangers, which has the advantages of small investment, small size, compact structure, short test time, low test cost, high test accuracy, etc. It can meet the requirements of ground test of high-altitude heat exchange of air-liquid heat exchangers in small UAV pods.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is:

[0007] A high-altitude heat exchange testing device for an air-liquid heat exchanger comprises a fixed frame, and also comprises an evaporation fan 103, an evaporator 102, a compressor 101, a condensation fan 105 and a condenser 104 arranged on the fixed frame;

[0008] The outlet of the compressor 101 is connected to the inlet of the condenser 104; the outlet of the condenser is connected to the inlet of the expansion valve 106; the outlet of the expansion valve 106 is connected to the inlet of the evaporator 102; the outlet of the evaporator 102 is connected to the inlet of the compressor 101;

[0009] The air outlet of the evaporation fan 103 faces the evaporator 102; the air outlet of the condensation fan faces the condenser;

[0010] The evaporation fan 103, the evaporator 102 and the air-liquid heat exchanger to be tested are located in the same closed loop.

[0011] Furthermore, it also includes an electronic control module; an electric heater is provided on the cold air outlet side of the evaporator; a temperature speed sensor is provided at the air inlet of the evaporator fan; the temperature speed sensor is used to detect the temperature and wind speed at the air inlet of the evaporator fan; the temperature speed sensor, electric heater and evaporator fan are all connected to the electronic control module.

[0012] A method for testing the high-altitude heat transfer capacity of an air-liquid heat exchanger is implemented by the above-mentioned air-liquid heat exchanger. The specific process is as follows:

[0013] The air-liquid heat exchanger to be tested is installed in the closed loop of the evaporating fan 103 and the evaporator 102;

[0014] after,

[0015] Taking the standard atmosphere as an example, assuming that the altitude of the test site is 0m, the UAV flight Mach number M, the UAV flight altitude h, and the exhaust safety factor λ are known parameters, query the physical parameters of the standard atmosphere to obtain the air pressure P at the test site 空 , atmospheric temperature t at height h 空 、Air density at height h ρ 空 、Local ground air density ρ 地 ;

[0016] First, follow P 总 =P 空 ×(1+0.2M 2 ) 3.5 Calculate the total ram air pressure P 总 ,

[0017] △t r =0.2M 2 t 空

[0018] t总 =t 空 +△t r

[0019] Calculate the total ram air temperature t 总 ; where △t r is the ram air temperature rise, t 总 is the total temperature of the ram air;

[0020] In the CFD software, the air-liquid heat exchanger is modeled according to its actual structure, and the air pressure at the inlet of the air-liquid heat exchanger is set to P. 总 , the inlet air temperature is t 总 , the air density is ρ 空 , outlet pressure is λP 空 , the volume flow rate V through the air-liquid heat exchanger is obtained through simulation 空 ;pass

[0021] q m空 =V 空 ×ρ 空

[0022] Calculate the air mass flow rate q at height h m空 ;

[0023] The convective heat transfer effect is proportional to the mass flow rate of air, so

[0024] q m空 =q m地 =V 地 ×ρ 地

[0025]

[0026] Calculate the surface equivalent mass flow V 地 ; where q m地 is the surface air mass flow rate, V 地 is the air volume flow rate passing through the heat exchanger when it is on the ground, ρ 地 is the local ground air density;

[0027] The air supply temperature and air supply flow rate of the ram air simulation device are set to t 总 and V 地 , the liquid side inlet of the air-liquid heat exchanger is fed with a temperature of t L入 , flow rate is V 液 The high temperature coolant is measured at the coolant outlet temperature t L出 ;pass

[0028] Q=V 液 ×ρ 液 ×C P液 (t L入 -t L出)

[0029] where ρ 液 is the coolant density, C P液 is the constant-pressure specific heat capacity of the coolant, that is, the high-altitude heat transfer capacity Q of the air-liquid heat exchanger is calculated.

[0030] Compared with the background technology, the present invention has the following beneficial effects:

[0031] 1. Compared with the wind tunnel test scheme, this test device is small in size, low in power consumption, and has low equipment loss during the test, and the cost of a single test can be reduced by more than 90%;

[0032] 2. Compared with the solution of using CFD to create digital wind tunnel simulation, this test method only uses CFD to calculate the ventilation volume of the air-liquid heat exchanger, which has higher accuracy and avoids the disadvantages of low accuracy in simulating complex aircraft models and two-phase fluid heat exchange calculations. The test error can be controlled within 10%, which can meet engineering requirements, is conducive to the refined design of the air-liquid heat exchanger, and reduces the size and weight of the product, thereby increasing the endurance performance of the carrier platform;

[0033] 3. This test device and method have the advantages of wide adaptability and strong scalability. By adjusting the indicators of ram air, it can simulate the ram air intake conditions of the air-to-liquid heat exchanger during high-altitude flight of various small UAV platforms such as Wing Loong and Rainbow. By replacing the air duct and wind cover, it can adapt to air-to-liquid heat exchangers with various structural forms. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of the structure of the air-liquid heat exchanger in the embodiment of the present invention.

[0035] Figure 2 It is a schematic diagram of the external structure of an embodiment of the present invention.

[0036] Figure 3 Schematic diagram of the position of the electronic control module according to an embodiment of the present invention.

[0037] Figure 4 It is an internal structure diagram of an embodiment of the present invention.

[0038] Figure 5 It is a schematic diagram of the internal structure of an embodiment of the present invention.

[0039] Figure 6 It is a flow chart of a method according to an embodiment of the present invention.

[0040] In the figure: a ram air simulation device 10, an air supply duct 50, an air hood 30, an air-liquid heat exchanger 40, and a return air duct 20.

[0041] Frame 100, compressor 101, evaporator 102, evaporation fan 103, condenser 104, condensation fan 105, expansion valve 106, air collecting cover 107, power supply interface 108. Air supply duct 110, return air duct 109.

[0042] Electronic control module 120 , touch screen 121 , temperature and speed sensor 122 . DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings.

[0044] The ram air simulation device is connected to the air supply duct, and the air supply duct, the return air duct and the air-liquid heat exchanger are connected through the air hood. Figure 2 .

[0045] Ram air simulator Figures 3 to 5 The outlet of the compressor 101 of the ram air simulation device of this embodiment is connected to the inlet of the condenser 104; the outlet of the condenser is connected to the inlet of the expansion valve 106; the outlet of the expansion valve 106 is connected to the inlet of the evaporator 102; the outlet of the evaporator 102 is connected to the inlet of the compressor 101;

[0046] The air outlet of the evaporation fan 103 faces the evaporator 102; the air outlet of the condensation fan faces the condenser;

[0047] The evaporation fan 103, the evaporator 102 and the air-liquid heat exchanger to be tested are located in the same closed loop.

[0048] It also includes an electronic control module; a temperature speed sensor and an electric heater are provided on the cold air outlet side of the evaporator; the temperature speed sensor is used to detect the temperature and wind speed at the cold air outlet of the evaporator; the temperature speed sensor, electric heater and evaporating fan are all connected to the electronic control module.

[0049] The low-temperature and low-pressure refrigerant gas is sucked into the compressor and compressed into high-temperature and high-pressure gas. The gas is cooled into high-pressure saturated liquid in the air-cooled condenser. The liquid enters the evaporator. The liquid refrigerant evaporates and absorbs heat in the evaporator, which reduces the surface temperature of the evaporator. The air in the cabin is cooled by the evaporator under the action of the centrifugal fan. The water vapor in the air is cooled on the surface of the evaporator to produce condensed water. The liquid refrigerant evaporates and absorbs heat to become superheated gas, which is sucked into the compressor again through the pipeline, and the cycle repeats.

[0050] The evaporation fan uses a high-pressure centrifugal fan to simulate and provide high-speed air. 2. The evaporation fan is controlled by a frequency converter to adjust the air pressure and air volume through frequency changes, with a control accuracy of 0.1Hz. 3. A temperature speed sensor is set at the air supply port of the evaporation fan, and the electronic control module collects the collected data to perform PID control on the air supply flow and air supply temperature.

[0051] Taking the standard atmosphere as an example, assuming that the altitude of the test site is 0m, the UAV flight Mach number M, the UAV flight altitude h, and the exhaust safety factor λ are known parameters, query the physical parameters of the standard atmosphere to obtain the air pressure P at the test site 空 , atmospheric temperature t at height h 空 、Air density at height h ρ 空 、Local ground air density ρ 地 ;

[0052] First, follow P 总 =P 空 ×(1+0.2M 2 ) 3.5 Calculate the total ram air pressure P 总 ,

[0053] △t r =0.2M 2 t 空

[0054] t 总 =t 空 +△t r

[0055] Calculate the total ram air temperature t 总 ; where △t r is the ram air temperature rise, t 总 is the total temperature of the ram air;

[0056] In the CFD software, the air-liquid heat exchanger is modeled according to its actual structure, and the air pressure at the inlet of the air-liquid heat exchanger is set to P. 总 , the inlet air temperature is t 总 , the air density is ρ 空 , outlet pressure is λP 空 , the volume flow rate V through the air-liquid heat exchanger is obtained through simulation 空 ;pass

[0057] q m空 =V 空 ×ρ 空

[0058] Calculate the air mass flow rate q at height h m空 ;

[0059] The convective heat transfer effect is proportional to the mass flow rate of air, so

[0060] q m空 =q m地 =V 地 ×ρ 地

[0061]

[0062] Calculate the surface equivalent mass flow V 地 ; where q m地 is the surface air mass flow rate, V 地 is the air volume flow rate passing through the heat exchanger when it is on the ground, ρ 地 is the local ground air density;

[0063] The air supply temperature and air supply flow rate of the ram air simulation device are set to t 总 and V 地 , the liquid side inlet of the air-liquid heat exchanger is fed with a temperature of t L入 , flow rate is V 液 The high temperature coolant is measured at the coolant outlet temperature t L出 ;pass

[0064] Q=V 液 ×ρ 液 ×C P液 (t L入 -t L出 )

[0065] where ρ 液 is the coolant density, C P液 is the constant-pressure specific heat capacity of the coolant, that is, the high-altitude heat transfer capacity Q of the air-liquid heat exchanger is calculated.

[0066] M: UAV flight Mach number;

[0067] h: UAV flight altitude, m;

[0068] P 空 : atmospheric pressure at height h, Pa;

[0069] t 空 : atmospheric temperature at height h, °C;

[0070] P 总 : total pressure of ram air, Pa;

[0071] △t r : Ram air temperature rise, K;

[0072] t 总 : total temperature of ram air, °C;

[0073] V 空 : Volume flow rate of air passing through the heat exchanger at height h, m 3 / s;

[0074] V 地 : The air volume flow rate through the heat exchanger at ground level, m 3 / s

[0075] ρ 空 : Air density at height h, kg / m 3 ;

[0076] ρ 地 : Local ground air density, kg / m 3 ;

[0077] λ: Exhaust safety factor, generally 1.1;

[0078] q m空 : Air mass flow rate at height h, kg / s;

[0079] q m地 : Ground air mass flow rate, kg / s;

[0080] V 液 : Coolant volume flow, m 3 / s;

[0081] ρ 液 : Coolant density, kg / m 3 ;

[0082] t L入 : Coolant inlet temperature, °C;

[0083] t L出 : Coolant outlet temperature, °C;

[0084] C P液 : Specific heat capacity of coolant at constant pressure, J / (kg·K);

[0085] Q: The heat exchange capacity of the heat exchanger at high altitude, W.

[0086] Table 1 Physical parameters of standard atmosphere

[0087]

[0088]

Claims

1. A method for testing the high-altitude heat transfer capacity of an air-liquid heat exchanger. It is characterized in that This is achieved through an air-liquid heat exchanger. The specific process is as follows: The air-liquid heat exchanger to be tested is installed in a closed circuit between an evaporating fan (103) and an evaporator (102); after, Taking the standard atmosphere as an example, assuming that the altitude of the test site is 0m, the UAV flight Mach number M, the UAV flight altitude h, and the exhaust safety factor λ are known parameters, query the physical parameters of the standard atmosphere to obtain the air pressure P at the test site 空 , atmospheric temperature t at height h 空 、Air density ρ at height h 空 、Local ground air density ρ 地 ; First, follow P 总 =P 空 ×(1+0.2M 2 ) 3.5 Calculate the total ram air pressure P 总 , △t r =0.2M 2 t 空 t 总 =t 空 +△t r Calculate the total ram air temperature t 总 ; where △t r is the ram air temperature rise, t 总 is the total temperature of the ram air; In the CFD software, the air-liquid heat exchanger is modeled according to its actual structure, and the air pressure at the inlet of the air-liquid heat exchanger is set to P. 总 , the inlet air temperature is t 总 , the air density is ρ 空 , outlet pressure is λP 空 , the volume flow rate V of the air-liquid heat exchanger is obtained through simulation 空 ;pass q m空 =V 空 ×ρ 空 Calculate the air mass flow rate q at height h m空 ; The convective heat transfer effect is proportional to the mass flow rate of air, so q m空 =q m地 =V 地 ×ρ 地 Calculate the surface equivalent mass flow V 地 ; where q m地 is the surface air mass flow rate, V 地 is the air volume flow rate passing through the heat exchanger when it is on the ground, ρ 地 is the local ground air density; The air supply temperature and air supply flow rate of the ram air simulation device are set to t 总 and V 地 , the liquid side inlet of the air-liquid heat exchanger is fed with a temperature of t L入 , flow rate is V 液 The high temperature coolant is measured at the coolant outlet temperature t L出 ;pass Q=V 液 ×ρ 液 ×C P液 (t L入 -t L出 ) where ρ 液 is the coolant density, C P液 is the constant pressure specific heat capacity of the coolant, that is, the high altitude heat transfer capacity Q of the air-liquid heat exchanger is calculated; The air-liquid heat exchanger comprises a fixed frame, on which an evaporation fan (103), an evaporator (102), a compressor (101), a condensation fan (105) and a condenser (104) are arranged; The outlet of the compressor (101) is connected to the inlet of the condenser (104); the outlet of the condenser is connected to the inlet of the expansion valve (106); the outlet of the expansion valve (106) is connected to the inlet of the evaporator (102); the outlet of the evaporator (102) is connected to the inlet of the compressor (101); The air outlet of the evaporating fan (103) faces the evaporator (102); the air outlet of the condensing fan faces the condenser; The evaporation fan (103), the evaporator (102) and the air-liquid heat exchanger to be tested are located in the same closed loop; An electric heater is provided on the cold air outlet side of the evaporator; a temperature speed sensor is provided at the air inlet of the evaporator fan; the temperature speed sensor is used to detect the temperature and wind speed at the air inlet of the evaporator fan; the temperature speed sensor, electric heater and evaporator fan are all connected to the electronic control module.

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