层流传热中有效传热温差的改善及复合强化传热

从层流流体有效传热温差的新视角出发,分析与探讨了换热器层流传热的强化理论。首先对层流流体有效传热温差的现象、细节及其变化规律进行了分析,揭示了采用插入物强化层流传热的内在强化机理,探讨了有效传热温差缓变特性的合理利用方法,提出了改善层流有效传热温差的寻优途径;其次,分析研究了缩放管粗糙传热肋面与插入物相配合的协同传热强化机理,揭示了粗糙肋面协助改善层流有效传热温差的作用与规律。

IMPINGEMENT HEAT TRANSFER FROM RIB ROUGHENED SURFACE WITHIN ARRAYS OF CIRCULAR JET Part I:The Effect of the Initial Crossflow

Impingement heat transfer from the rib roughened surface within 2 dimensional arrays of circular jet has been experimentally investigated.This investigation is intended here to include the flow and the heat transfer characteristics of the jet impinging on the rib roughened surface with initial crossflow for simulating the impingement cooling midchord region of the gas turbine aerofoils in case where an initial crossflow is presented.The study covered the ranges of crossflow G_(c)/G_(j)=0~0.55 under the conditions of Re_(j)=8000~11000 and Z/d=1.5~3.0 for smooth and rib roughened surfaces.The test results show that the impingement heat transfer from the rib roughened surface is considerably affected by the initial crossflow rate.The existence of the initial crossflow will improve the efficiency of the impingement heat transfer from the rib roughened surface within arrays of circular jet compared with that from the smooth surface.