The loop heat pipe(LHP)is an advanced,efficient two-phase heat transfer unit,whose operational performance may be affected by microgravity conditions in contrast to ground-based applications.The performance of on-orbi...The loop heat pipe(LHP)is an advanced,efficient two-phase heat transfer unit,whose operational performance may be affected by microgravity conditions in contrast to ground-based applications.The performance of on-orbit temperature data and ground test of a copper-propylene LHP with a condenser temperature range of 243.15 K to 303.15 K were employed to compared and analyzed.The LHP has successfully started up for more than 193 times with a good heat transfer performance and a stable start-up stabilization on-orbit under a complex orbital heating environment for more than eight months.With a small heat load(10.0W),the average start-up time is 110.0 s while the start-up temperature ranges from 5.71 K-12.78 K.The start-up time at large temperature differences in the high temperature zone will be higher than the time required for start-up at smaller temperature differences in the low one.When the condenser temperature is 250.0 K,the stable temperature difference on orbit is 3.83 K,which is generally consistent in heat transfer compared to 2.20 K in the ground test.In this paper,we can conclude that the on-orbit flight data up to now can provide a reference to the design of subsequent LHP space applications.展开更多
At present,the structural design of a loop heat pipe(LHP)condenser mostly relies on experience.To analyze the condensation flow pattern in an LHP and to find a more accurate empirical correlation that can better guide...At present,the structural design of a loop heat pipe(LHP)condenser mostly relies on experience.To analyze the condensation flow pattern in an LHP and to find a more accurate empirical correlation that can better guide condenser design in existing empirical correlations,a test system was designed and fabricated to observe the condensation phenomenon in the condenser and to evaluate the LHP’s heat transfer performance.Since propylene has a wide temperature range to different temperature control requirements,it was chosen as the working fluid.In this paper,the condensation process in the condenser was observed,and the operating parameters of a propylene LHP were measured at 283 K.The condensation flow patterns in the 2.5 mm×2.5 mm channel mainly included stratified flow,wavy flow and intermittent flow.By comparing the experimental results with four typical condensation flow regime maps,it was found that the Breber and Cavallini flow regime maps can successfully predict most of the condensation flow patterns of the LHP even with ultra-small mass flux.In addition,four condensation heat transfer coefficient correlations were selected to compare the predicted values of heat transfer coefficient with the experimental results.The study showed that the predicted values from the correlation by Cavallini et al.matched 90%of the experimental values well with an error of less than 20%,and this correlation is recommended for highly accurate LHP design.展开更多
For quantum communications,single-photon detection,millimeter wave detection and other space projects,all of them need to work at liquid helium temperatures to achieve excellent performance.The closed-cycle helium Jou...For quantum communications,single-photon detection,millimeter wave detection and other space projects,all of them need to work at liquid helium temperatures to achieve excellent performance.The closed-cycle helium Joule-Thomson cryocooler(JTC)is currently one of the mainstream solutions to realize the liquid helium temperature.While realizing the liquid helium temperature,the detector has strict requirements on the temperature fluctuation of the JTC,because the thermal noise caused by the JTC temperature fluctuation will have a critical impact on the detection performance.The typical closed-cycle helium JTC is precooling by a two-stage precooler.When the operating parameters of the JTC compressor remain unchanged,the change of the precooler is the main factor that affects the temperature fluctuation of the JTC.To explore the influence mechanism of JTC temperature fluctuations,experimental and theoretical studies are carried out.Based on the real gas equation of state,the influence of various parameters on the evaporator temperature fluctuations is explained.Research results show that the increase in temperature of each stage will cause the temperature of the JTC to increase.Especially,the change of the secondary precooling temperature(T_(pre2))has the most obvious influence on JTC temperature.Furthermore,the influence of the JT compressor’s buffer tank volume Vb on temperature fluctuation is studied.By increasing the Vb,the JTC temperature fluctuation caused by the temperature change of the precooler can be effectively reduced.展开更多
文摘The loop heat pipe(LHP)is an advanced,efficient two-phase heat transfer unit,whose operational performance may be affected by microgravity conditions in contrast to ground-based applications.The performance of on-orbit temperature data and ground test of a copper-propylene LHP with a condenser temperature range of 243.15 K to 303.15 K were employed to compared and analyzed.The LHP has successfully started up for more than 193 times with a good heat transfer performance and a stable start-up stabilization on-orbit under a complex orbital heating environment for more than eight months.With a small heat load(10.0W),the average start-up time is 110.0 s while the start-up temperature ranges from 5.71 K-12.78 K.The start-up time at large temperature differences in the high temperature zone will be higher than the time required for start-up at smaller temperature differences in the low one.When the condenser temperature is 250.0 K,the stable temperature difference on orbit is 3.83 K,which is generally consistent in heat transfer compared to 2.20 K in the ground test.In this paper,we can conclude that the on-orbit flight data up to now can provide a reference to the design of subsequent LHP space applications.
基金The work is supported by the National Natural Science Foundation of China(No.51776121).
文摘At present,the structural design of a loop heat pipe(LHP)condenser mostly relies on experience.To analyze the condensation flow pattern in an LHP and to find a more accurate empirical correlation that can better guide condenser design in existing empirical correlations,a test system was designed and fabricated to observe the condensation phenomenon in the condenser and to evaluate the LHP’s heat transfer performance.Since propylene has a wide temperature range to different temperature control requirements,it was chosen as the working fluid.In this paper,the condensation process in the condenser was observed,and the operating parameters of a propylene LHP were measured at 283 K.The condensation flow patterns in the 2.5 mm×2.5 mm channel mainly included stratified flow,wavy flow and intermittent flow.By comparing the experimental results with four typical condensation flow regime maps,it was found that the Breber and Cavallini flow regime maps can successfully predict most of the condensation flow patterns of the LHP even with ultra-small mass flux.In addition,four condensation heat transfer coefficient correlations were selected to compare the predicted values of heat transfer coefficient with the experimental results.The study showed that the predicted values from the correlation by Cavallini et al.matched 90%of the experimental values well with an error of less than 20%,and this correlation is recommended for highly accurate LHP design.
基金This study is financially supported by the Hundred Talents Program of the Chinese Academy of Sciences,the National Natural Science Foundation of China(No.51806231)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB35000000)+1 种基金the Natural Science Foundation of Shanghai(No.18ZR1445600)the China Postdoctoral Science Foundation(2018M630476).
文摘For quantum communications,single-photon detection,millimeter wave detection and other space projects,all of them need to work at liquid helium temperatures to achieve excellent performance.The closed-cycle helium Joule-Thomson cryocooler(JTC)is currently one of the mainstream solutions to realize the liquid helium temperature.While realizing the liquid helium temperature,the detector has strict requirements on the temperature fluctuation of the JTC,because the thermal noise caused by the JTC temperature fluctuation will have a critical impact on the detection performance.The typical closed-cycle helium JTC is precooling by a two-stage precooler.When the operating parameters of the JTC compressor remain unchanged,the change of the precooler is the main factor that affects the temperature fluctuation of the JTC.To explore the influence mechanism of JTC temperature fluctuations,experimental and theoretical studies are carried out.Based on the real gas equation of state,the influence of various parameters on the evaporator temperature fluctuations is explained.Research results show that the increase in temperature of each stage will cause the temperature of the JTC to increase.Especially,the change of the secondary precooling temperature(T_(pre2))has the most obvious influence on JTC temperature.Furthermore,the influence of the JT compressor’s buffer tank volume Vb on temperature fluctuation is studied.By increasing the Vb,the JTC temperature fluctuation caused by the temperature change of the precooler can be effectively reduced.
