三维内微肋管内凝结流型分区及分层波状流换热关联式

引　言水平管内的受迫对流膜状凝结广泛用于化学工业及制冷与空调的冷凝设备中 .对于冷凝器的设计 ,确定管内膜状凝结换热系数是至关重要的 .众所周知 ,水平管内受迫对流凝结在流动方向汽液两相流动会出现不同的流型 ,对于不同的流型 ,对应的换热机理和换热系数也各不相同 .因此 ,首先需要区分管内受迫对流换热的流型 ,在此基础上再针对不同的流型对其凝结换热过程进行研究 .对于整个凝结换热过程 ,通常是根据汽液两相流在不同流型时的流动及换热特征将凝结过程划分为不同的流型区域 ,并得到相应的流型转变的判据 ,然后通过实验对不同的流型…

FLOW REGIMES AND STRATIFIED-WAVY FLOW EXPERIMENTAL CORRELATION OF CONDENSATION HEAT TRANSFER IN THREE-DIMENSIONAL MICROFIN TUBE

Studies of two-phase flow patterns and their transitions during condensation have gained increasing interest because heat transfer characteristics are strongly dependent on flow patterns.Therefore,it is very important to know flow pattern inside a condenser at certain flow conditions and hence to develop heat transfer correlations consistent with the prevailing heat transfer mechanism in each flow pattern. The condensation heat transfer for R134a in two kinds of in-tube three-dimensional (3-D) microfin tubes with different geometries is investigated experimentally.In the range of experimental conditions,six distinguishable flow patterns (annular flow,semi-annular flow,stratified flow,wavy flow,slug flow and plug flow) are recorded by a video camera.The obtained results show that the flow regime transition criterion between annular flow and stratified-wavy flow decreases from Fr equal to 7 to Fr equal to 2 in the Soliman flow regime map.In stratified-wavy flow regime,the average heat transfer coefficients h of the two kinds of in-tube 3-D microfin tubes increase as mass flux increases and the number of microfins in 3-D microfin tube is not the controlling factor of condensation heat transfer performance.The regressed condensation heat transfer correlation from the experimental data of stratified-wavy flow regime is obtained.The disparity of the experimental data is within the limits of ±22%.Combined with the criteria of flow pattern transitions,the correlations can be used for the design of condenser of 3-D microfin tubes.