说明：  常物性流体在带直肋的环形通道内作充分发展层流对流换热，内表面为均匀壁温（周向），轴向则呈线性变化，外表面绝热。求：截面上速度分布、温度分布
(Constant physical properties of fluid in the annular channel with a straight rib for fully developed laminar flow within the convective heat transfer, uniform wall temperature of the inner surface (circumferential) and axial variation is linear, the outer surface of insulation. Requirements: section on the velocity distribution, temperature distribution)