非均匀加热条件下微矩形槽道内的滑移流动换热特性

利用正交函数法对定热流密度加热、壁面温度在周向可任意变化条件下，气体在微矩形槽道内的热充分发展滑移流动的换热特性进行理论分析，获得相应条件下的Nu数计算方法及换热特性，并与大尺度槽道的换热特性进行比较，探讨了Kn数、槽道高宽比及不同加热条件对微矩形槽道内滑移流动换热性能的影响。结果表明，在任何加热条件下，微矩形槽道内的平均Nu数均低于相同加热条件下大尺度矩形槽道中的Nu数，且随Kn数的增加而减小。高宽比越小，平均Nu数下降越大。在相同的高宽比和Kn数下，单边加热条件下的换热性能相比相同加热条件的常规大槽道内的换热性能下降最小。

HEAT TRANSFER CHARACTERISTICS OF GAS SLIP FLOWING IN UNSYMMETRICALLY HEATED RECTANGULAR MICROCHANNELS

The heat transfer characteristics of gas slip flowing in the rectangular microchannels heated unsymmetrically with constant axial heat flux are analyzed theoretically for the slip flow regime. The energy equation with temperature jump boundary conditions in slip flow regime is solved by a computation-oriented method of the orthonormal function analysis. The dim-ensionless temperature profiles and the average Nusselt numbers for various thermal boundary conditions are obtained and compared with those in macrochannel under the same conditions. The effects of Knudsen number, aspect ratio, and thermal boundary conditions on the heat transfer characteristics in slip flow regime are discussed, respectively. The calculated results show that the average Nusselt numbers in rectangular microchannels is lower for slip flow than for no-slip flow under any heating condition, and decreases with increasing Knudsen number. The smaller the aspect ratio is, the more the decrease of the average Nusselt number is. The decrease of the average Nusselt number in rectangular microchannel compared with the macrochannel for the condition of only one wall heated is the smallest at the same Knudsen number and aspect ratio compared with others heating conditions.