大平壁非稳态导热计算，大平壁的初始温度为t0 ，两侧面向温度为tf的介质散热，表面传热系数为h。计算平壁中的温度场。-Ohira wall unsteady heat conduction calculation.Ohira initial temperature of the wall as t0, tf both sides oriented temperatures for dielectric cooling , the surface heat transfer coefficient h . Calculate the temperature field in the flat walls .