A theoretical study was conducted to investigate the effects of mass transfer on heat transfer in the process of moisture exchange across a membrane and a mathematical model describing the heat transfer with considera...A theoretical study was conducted to investigate the effects of mass transfer on heat transfer in the process of moisture exchange across a membrane and a mathematical model describing the heat transfer with consideration of the effect of mass transfer was developed.A dimensionless variable,ψi,which presents the degree to which the mass transfer affects the heat transfer,was proposed through theoretical analysis.With calculating of this dimensionless variable,the heat transfer coupled with mass transfer can be converted into a conventional heat transfer,making the heat transfer calculation simpler and more easily to understand.On the basis of theoretical analysis,the effects of mass transfer on heat transfer were numerically studied.The results show that,in the case that the temperature gradient and mass transfer are in the same direction,ψi is greater than unity,and the mass transfer acts to enhance the heat transfer;in the case that the temperature gradient and mass transfer are in opposite directions,ψi is less than unity,and the mass transfer works to hinder the heat transfer.When the mass flux is small,the effect of the mass transfer is weak.When the mass flux is large,the heat flux carried by the mass flux has a considerable impact on the heat flux,and ψi,deviates from unity significantly.展开更多
通过引入脉冲函数将流量边界条件转化为源(汇)项,冻结锋面处的假想泵从未冻土中抽吸水分并储存在冻结锋面附近的狭窄区域.将水分扩散方程在整体求解域上等效分解为两个方程,避免了处理移动冻融边界的难题.在一个分解方程中引入汇项以表...通过引入脉冲函数将流量边界条件转化为源(汇)项,冻结锋面处的假想泵从未冻土中抽吸水分并储存在冻结锋面附近的狭窄区域.将水分扩散方程在整体求解域上等效分解为两个方程,避免了处理移动冻融边界的难题.在一个分解方程中引入汇项以表达未冻区水分的流出,在另一个分解方程中引入相同大小的源项以表达冻土中水分的聚集.将移动泵模型相关场方程和变量输入COMSOL M ultiphysics模拟软件的数学模块中,对一个封闭系统非饱和土冻结过程中水分和温度的变化过程进行了数值模拟,将模拟结果与前人试验和模拟结果进行了对比.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 50576040)
文摘A theoretical study was conducted to investigate the effects of mass transfer on heat transfer in the process of moisture exchange across a membrane and a mathematical model describing the heat transfer with consideration of the effect of mass transfer was developed.A dimensionless variable,ψi,which presents the degree to which the mass transfer affects the heat transfer,was proposed through theoretical analysis.With calculating of this dimensionless variable,the heat transfer coupled with mass transfer can be converted into a conventional heat transfer,making the heat transfer calculation simpler and more easily to understand.On the basis of theoretical analysis,the effects of mass transfer on heat transfer were numerically studied.The results show that,in the case that the temperature gradient and mass transfer are in the same direction,ψi is greater than unity,and the mass transfer acts to enhance the heat transfer;in the case that the temperature gradient and mass transfer are in opposite directions,ψi is less than unity,and the mass transfer works to hinder the heat transfer.When the mass flux is small,the effect of the mass transfer is weak.When the mass flux is large,the heat flux carried by the mass flux has a considerable impact on the heat flux,and ψi,deviates from unity significantly.
文摘通过引入脉冲函数将流量边界条件转化为源(汇)项,冻结锋面处的假想泵从未冻土中抽吸水分并储存在冻结锋面附近的狭窄区域.将水分扩散方程在整体求解域上等效分解为两个方程,避免了处理移动冻融边界的难题.在一个分解方程中引入汇项以表达未冻区水分的流出,在另一个分解方程中引入相同大小的源项以表达冻土中水分的聚集.将移动泵模型相关场方程和变量输入COMSOL M ultiphysics模拟软件的数学模块中,对一个封闭系统非饱和土冻结过程中水分和温度的变化过程进行了数值模拟,将模拟结果与前人试验和模拟结果进行了对比.
