| The first lab module of China Space Station,the Wentian lab module,is mainly focused on space life science research.The variable gravity science experiment rack inside the module uses a centrifuge to simulate gravity,supporting life science research under Lunar gravity of 1/6g and Martian gravity of 1/3g,requiring the centrifuge to provide a long-term stable thermal environment.The special structure of the centrifuge system makes the thermal control,mechanical,and electronic interfaces of the original standard experiment rack no longer compatible,requiring personalized thermal control design specifically for the centrifuge payload.This thesis is based on the Manned Space National Science and Technology Major Project and focuses on the heat dissipation issue from the science payload of the space centrifuge.By adopting an iterative design approach and integrating numerical simulation and experimental research,this thesis breaks through the multiple constraints of the complex rotation structure of the centrifuge,the low aircooling capacity of the experiment rack,and the high temperature of the liquid supply on the space station platform.The special thermal control system with long-life,highreliability is developed,and in-orbit condition prediction and validation are realized.The main parts of this article are as follow:In order to solve the problem of the high-power heat dissipation during the rotation of the centrifuge payload,it is necessary to design and optimize the overall layout of air cooling thermal control system.Combined with the constraints of the space station platform for cooling(air,liquid),power supply,volume,weight,etc.,the thesis conducts research on the heat exchange constraints analysis between the experiment rack and the module,the performance characteristics analysis of the variable gravity rack science payload,and the adaptability analysis of the centrifuge thermal control system in space application.A basic scheme based on the air-liquid heat exchanger for the centrifuge air-cooling thermal control and key technical requirement are proposed.Furthermore,to solve the problems of the low air-cooling capacity of the experiment rack and the high temperature of the platform liquid supply,a two-stage air-cooling thermal control scheme combining thermoelectric cooler module and air-liquid heat exchanger is proposed.Through the optimization analysis of the cooling efficiency of the thermoelectric cooler module in the air and liquid loop,the overall layout of the two-stage air-cooling thermal control system is determined,and the detailed designs of the air-liquid heat exchanger and air-cooling heat exchanger are completed.The centrifuge thermal control system consists of the centrifuge rotating experiment area and the air-cooling loop(including air ducts,air-cooling heat exchanger,and air-liquid heat exchanger).Mastering the heat transfer characteristics of the air-solid coupling in the experiment area,as well as the temperature and flow resistance characteristics of the air-cooling loop,is crucial for verifying the system design,guiding the operation parameters setting,and predicting in-orbit conditions.In order to realize the numerical simulation of the thermal/flow characteristics of the system of centrifuge thermal control,a calculation model is established based on the one and three-dimensional coupling.The full three-dimensional air-solid coupling model is used for the experiment area,while the heat exchangers are modeled in one dimension,which is equivalent to the porous media.By fitting the pressure drop-flow velocity(P-v)relationship curve of the heat exchanger through experiment,the resistance characterization parameter is obtained.The numerical simulation reveals the air-solid coupling heat transfer characteristics of the science payload in the experiment area under extreme condition and predicts the air resistance and air temperature of the air-cooling loop.The numerical study shows that under extreme conditions,the air-cooling loop can provide a low-temperature coolant with a temperature of 12℃ to meet the temperature requirements of the scientce payload.To reduce the inlet air temperature of the thermal control system,it is necessary to develop a thermoelectric cooling module for secondary air cooling.The maximum heat dissipation of the science experiment payload on the centrifuge is 600 W.To match the continuous heat dissipation requirements of the cooling load,a step control method of thermoelectric cooling module under variable load is proposed.A "four in series and eight in parallel" grouping control strategy is selected considering factors such as cooling efficiency,series and parallel grouping control,and structural layout.This strategy achieves stepwise control of cooling capacity,and a prototype thermoelectric cooler module is developed and tested for its cooling and heat dissipation capabilities.In order to determine the operating parameters of the thermoelectric cooler module and guide the development of the space station user manual,experiments are conducted to test the heat transfer performance of the module under different conditions such as different stepwise startup modes,air flow rate(on the cold side),and cooling liquid temperature(on the hot side).The mapping relationship between input working conditions and cooling temperature difference is established to verify the in-orbit availability of the module.To solve the problem of fluid stagnation caused by the mismatch between the flow resistance of the air-cooling loop and the driving static pressure,optimization design was carried out on the air loop.By changing the core and interface sizes of the air-cooling heat exchanger,the flow resistance was effectively reduced from 1.5kPa to 0.5kPa.By matching the flow resistance of each resistance load with the driving component,the maximum air supply volume of the system was determined to be 83 cfm.The airflow of the fan can be adjusted within the range of 0～83cfm to adapt to the heat dissipation conditions of different science payloads.The centrifuge thermal control system is undergoing its first flight.In order to ensure its effective operation in orbit,it is necessary to realize the in orbit operation condition prediction and real-time simulation based on ground mirror experiment.Comprehensive thermal performance experiments were conducted under extreme conditions to obtain the system’s maximum heat dissipation capacity.According to the operating conditions on the space station platform,the thermal control system’s operation in orbit was simulated by changing the heat load of the science payload,the platform’s liquid supply temperature,and the voltage of the thermoelectric cooler.In order to match the upcoming science payload to be launched and anticipate the thermal control system’s state parameters during in-orbit operation,and to prepare in advance for parameter limit plans,it requires to be able to predict the thermal performance of the system parameters under changing conditions,meanwhile acquire the internal correlation between primary thermal control and secondary thermoelectric cooler module and the correlation between various levels of thermal control cooling capacity and boundary conditions,as well as the balance relationship between power supply resources and temperature requirements of the payload.After the system was launched,a comparison between the ground and in-orbit experiment was conducted with the support of a mirror-image experiment.The results showed that the temperature difference between the ground and in-orbit was only 0.4℃ when TEC module 1/2 was started,effectively demonstrating the normal working performance of the thermal control system in orbit and completing the in-orbit application verification. |
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