In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When...In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.展开更多
Stack effect is a dominant driving force for building natural ventilation.Analytical models were developed for the evaluation of stack effect in a shaft,accounting for the heat transfer from shaft interior boundaries....Stack effect is a dominant driving force for building natural ventilation.Analytical models were developed for the evaluation of stack effect in a shaft,accounting for the heat transfer from shaft interior boundaries.Both the conditions with constant heat flux from boundaries to the airflow and the ones with constant boundary temperature were considered.The prediction capabilities of these analytical models were evaluated by using large eddy simulation(LES) for a hypothetical shaft.The results show that there are fairly good agreements between the predictions of the analytical models and the LES predictions in mass flow rate,vertical temperatures profile and pressure difference as well.Both the results of analytical models and LES show that the neutral plane could locate higher than one half of the shaft height when the upper opening area is identical with the lower opening area.Further,it is also shown that the analytical models perform better than KLOTE's model does in the mass flow rate prediction.展开更多
A mathematical model based on the theory of heat and mass transfer in porous media was developed to simulate the evolution of grain temperature and moisture content in a wheat storage bin during ventilation with cooli...A mathematical model based on the theory of heat and mass transfer in porous media was developed to simulate the evolution of grain temperature and moisture content in a wheat storage bin during ventilation with cooling air at the constant temperature and humidity.Unlike the previous works on this aspect,the present work was not focused on cooling the stored grain by ventilation with ambient air,but with the refrigerated air.Validation was performed by comparing between predicted and measured grain temperature and grain moisture content for two cases.Predicted data were in reasonable good agreement with measured ones.The model and the parameter values used in the model are applicable for predicting temperature and moisture of stored grains under ventilation conditions.展开更多
基金Projects BK2007145 supported by the Jiangsu Natural Science Foundation of China NCET-04-0454 by the Program for New Century Excellent Talentsin Universities
文摘In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.
基金Project(50838009) supported by the National Natural Science Foundation of ChinaProject(2010DFA72740-03) supported by the National Key Technology Research and Development Program of China
文摘Stack effect is a dominant driving force for building natural ventilation.Analytical models were developed for the evaluation of stack effect in a shaft,accounting for the heat transfer from shaft interior boundaries.Both the conditions with constant heat flux from boundaries to the airflow and the ones with constant boundary temperature were considered.The prediction capabilities of these analytical models were evaluated by using large eddy simulation(LES) for a hypothetical shaft.The results show that there are fairly good agreements between the predictions of the analytical models and the LES predictions in mass flow rate,vertical temperatures profile and pressure difference as well.Both the results of analytical models and LES show that the neutral plane could locate higher than one half of the shaft height when the upper opening area is identical with the lower opening area.Further,it is also shown that the analytical models perform better than KLOTE's model does in the mass flow rate prediction.
文摘A mathematical model based on the theory of heat and mass transfer in porous media was developed to simulate the evolution of grain temperature and moisture content in a wheat storage bin during ventilation with cooling air at the constant temperature and humidity.Unlike the previous works on this aspect,the present work was not focused on cooling the stored grain by ventilation with ambient air,but with the refrigerated air.Validation was performed by comparing between predicted and measured grain temperature and grain moisture content for two cases.Predicted data were in reasonable good agreement with measured ones.The model and the parameter values used in the model are applicable for predicting temperature and moisture of stored grains under ventilation conditions.
