The subway operation generates a large amount of waste heat,which will lead to a disruption of the underground thermal balance.To remove the heat,a ground source heat pump system adopting capillary net as the front-en...The subway operation generates a large amount of waste heat,which will lead to a disruption of the underground thermal balance.To remove the heat,a ground source heat pump system adopting capillary net as the front-end heat exchanger can be built in the tunnels to recycle the waste heat and use it for building heating.Different simulation method was used to analyze the heat transfer process in the tunnel and the surrounding rock.The existing simulation method usually takes a long time for calculation and can not be used for a real-time regulation of the system.Based on the concept of thermoelectric analogy,a resistance-capacitance(RC)model was proposed for rapid prediction and analysis on the heat transfer of the capillary net in subway tunnel.The annual thermal response in the tunnel was analyzed,and the influence of the tunnel air temperature and the capillary inlet water temperature was examined using this model.The maximum heat transfer flux of the capillary in summer(release heat)and in winter(extract heat)was 55.27 W/m 2 and 38.33 W/m 2,respectively.The effect of capillary inlet water temperature was more remarkable than that of the tunnel air temperature on the capillary heat exchange process.展开更多
A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle's energy consumption. Heat exchangers, such as a charged air ...A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle's energy consumption. Heat exchangers, such as a charged air cooler (CAC), radiator, oil cooler, or condenser have different structures and can be arranged in various orders, and each combination may produce different effects because of interactions among them. In this study, we aimed to explore the principles governing interactions among adjacent heat exchangers in a cooling system, using numerical simulation and experimental technology. 3D models with different combinations were developed, compared, and analyzed comprehensively. A wind tunnel test platform was constructed to validate the computational results. We found that the heat dissipation of the modules was affected slightly by their relative position (the rules basically comply with the field synergy principle), but was independent of the modules' spacing within a certain distance range. The heat dissipation of one module could be effectively improved by restructuring, but with a penalty of higher resistance. However, the negative effect on the downstream module was much less than expected. The results indicated that the intensity of heat transfer depends not only on the average temperature difference between cold and hot mediums, but also on the temperature distribution.展开更多
In low-temperature processes, there are interactions between heat exchanger network(HEN) and refrigeration system. The modification on HEN of the chilling train for increasing energy recovery does not always coordinat...In low-temperature processes, there are interactions between heat exchanger network(HEN) and refrigeration system. The modification on HEN of the chilling train for increasing energy recovery does not always coordinate with the minimum shaft work consumption of the corresponding refrigeration system. In this paper, a systematic approach for optimizing low-temperature system is presented through mathematical method and exergy analysis. The possibility of "pockets", which appears as right nose section in the grand composite curve(EGCC) of the process, is first optimized. The EGCC with the pockets cutting down is designed as a separate part. A case study is used to illustrate the application of the approach for a HEN of a chilling train with propylene and ethylene refrigerant system in an ethylene production process.展开更多
During the operation of the capillary heat exchange system in the metro tunnel,the pipe length,pipe spacing and air velocity have different effects on the heat transfer effect and show certain rules.Taking Kunming as ...During the operation of the capillary heat exchange system in the metro tunnel,the pipe length,pipe spacing and air velocity have different effects on the heat transfer effect and show certain rules.Taking Kunming as an example,a single-factor analysis method was used to establish multiple-capillary model,and the variation of different influencing factors in the heat transfer process was obtained.On this basis,a single-capillary model was established to analyze the thermal interference variation of the pipe spacing between the two models.Under the condition of ensuring the capillary outlet water temperature and heat flux,the relevant parameters of the capillary heat exchanger were optimized.The results show that the pipe length of the capillary heat exchanger should be kept within 3-5 m,the pipe spacing is maintained at 20-30 mm,and the capillary heat exchanger of each set can be operated in parallel to ensure that heat exchanger have better heat transfer performance.During the system stop running,the air velocity in winter and summer has different effects on the recovery of surrounding rock.展开更多
基金the National Natural Sci-ence Foundation of China(No.52108079).
文摘The subway operation generates a large amount of waste heat,which will lead to a disruption of the underground thermal balance.To remove the heat,a ground source heat pump system adopting capillary net as the front-end heat exchanger can be built in the tunnels to recycle the waste heat and use it for building heating.Different simulation method was used to analyze the heat transfer process in the tunnel and the surrounding rock.The existing simulation method usually takes a long time for calculation and can not be used for a real-time regulation of the system.Based on the concept of thermoelectric analogy,a resistance-capacitance(RC)model was proposed for rapid prediction and analysis on the heat transfer of the capillary net in subway tunnel.The annual thermal response in the tunnel was analyzed,and the influence of the tunnel air temperature and the capillary inlet water temperature was examined using this model.The maximum heat transfer flux of the capillary in summer(release heat)and in winter(extract heat)was 55.27 W/m 2 and 38.33 W/m 2,respectively.The effect of capillary inlet water temperature was more remarkable than that of the tunnel air temperature on the capillary heat exchange process.
基金Project (No. 51206141) supported by the National Natural Science Foundation of China
文摘A cooling system consisting of several heat exchange modules is a necessary part of an automobile, and its performance has a direct effect on a vehicle's energy consumption. Heat exchangers, such as a charged air cooler (CAC), radiator, oil cooler, or condenser have different structures and can be arranged in various orders, and each combination may produce different effects because of interactions among them. In this study, we aimed to explore the principles governing interactions among adjacent heat exchangers in a cooling system, using numerical simulation and experimental technology. 3D models with different combinations were developed, compared, and analyzed comprehensively. A wind tunnel test platform was constructed to validate the computational results. We found that the heat dissipation of the modules was affected slightly by their relative position (the rules basically comply with the field synergy principle), but was independent of the modules' spacing within a certain distance range. The heat dissipation of one module could be effectively improved by restructuring, but with a penalty of higher resistance. However, the negative effect on the downstream module was much less than expected. The results indicated that the intensity of heat transfer depends not only on the average temperature difference between cold and hot mediums, but also on the temperature distribution.
基金Supported by the National Basic Research Program of China(2010CB720500)the National Natural Science Foundation(21176178)
文摘In low-temperature processes, there are interactions between heat exchanger network(HEN) and refrigeration system. The modification on HEN of the chilling train for increasing energy recovery does not always coordinate with the minimum shaft work consumption of the corresponding refrigeration system. In this paper, a systematic approach for optimizing low-temperature system is presented through mathematical method and exergy analysis. The possibility of "pockets", which appears as right nose section in the grand composite curve(EGCC) of the process, is first optimized. The EGCC with the pockets cutting down is designed as a separate part. A case study is used to illustrate the application of the approach for a HEN of a chilling train with propylene and ethylene refrigerant system in an ethylene production process.
基金This work was supported by the Natural Science Foundation of China(Grant No.51678488).
文摘During the operation of the capillary heat exchange system in the metro tunnel,the pipe length,pipe spacing and air velocity have different effects on the heat transfer effect and show certain rules.Taking Kunming as an example,a single-factor analysis method was used to establish multiple-capillary model,and the variation of different influencing factors in the heat transfer process was obtained.On this basis,a single-capillary model was established to analyze the thermal interference variation of the pipe spacing between the two models.Under the condition of ensuring the capillary outlet water temperature and heat flux,the relevant parameters of the capillary heat exchanger were optimized.The results show that the pipe length of the capillary heat exchanger should be kept within 3-5 m,the pipe spacing is maintained at 20-30 mm,and the capillary heat exchanger of each set can be operated in parallel to ensure that heat exchanger have better heat transfer performance.During the system stop running,the air velocity in winter and summer has different effects on the recovery of surrounding rock.
