Abstract: Compared to the channel with uniform section area,those with various section areas are much similar to the internal cooling structure of the turbine blade.In this thesis,a 180°turn over channel with various sectional areas and 90° parallel ribs is studied of its characteristic of heat transfer.The channel is divided into some heat transfer elements each with one,single rib as the basic character.The influences of every characteristic non dimensional geometric parameter and Reynolds number on the heat transfer of the ribbed walls are studied on the premise that the channel area changes continually.At the same channel inlet Reynolds number,the average Nusselt number of the test model's rib walls is 74%～128% larger compared with Dittus Boelter formula and much larger at smaller Reynolds number.