三维微肋螺旋管内流动沸腾流型与传热性能

采用三维微肋螺旋管进行了制冷剂R134a在管内的流动沸腾传热与流型可视化实验。随着流量和干度的变化,流型可划分为泡状流、塞状流、分层波状流、间歇流以及环状流。在Taitel-Dukler流型图上给出了流型的分区及其转变曲线,讨论了螺旋管内两相流动流型转变的特性。传热实验揭示了质量流量、热流密度及蒸汽干度对传热性能的影响,三维微肋螺旋管的强化因子为1.5-2.1。

FLOW BOILING HEAT TRANSFER AND FLOW PATTERNS IN THREE-DIMENSIONAL MICRO-FIN HELICALLY COILED TUBE

Three dimensional micro-fin helically coiled tube is a heat transfer enhancing component developed by the authors, which is a combination of micro-finned tube and helix tube. In this paper we focus on the flow boiling heat transfer characteristics and flow patterns of refrigerant 134a in such kind of tube. With the variation of flow rates and qualities, the flow patterns can be divided into bubbly flow, plug flow, stratified-wavy flow, intermittent flow and annular flow. The transition curves are plotted in the Taitel-Dukler flow map. And the transition from intermittent flow to annular flow of micro-fin helix tube is obviously different from that of smooth tube. The effect of mass flow rate, heat flux and vapor quality on heat transfer characteristics are discussed. And the three-dimensional micro-fin helically coiled tube can perfectly enhance the flow boiling heat transfer process inside tube. The results show that the heat transfer enhancement factor is from 1.5 to 2.1.