Two-phase Closed Thermosyphon Enhancement Of Heat Transfer Experiments

The heat pipe(HP) is applied widely in the recent years. The study on heat pipe is emphasized and concerned very much. The demand for heat pipe is much more higher than before. Many ways are thought out in order to improve the heat transfer efficiency of heat pipe. For example, adding ribs on the outside of the heat pipe, adding vertical grooves on the inside of the heat pipe and so on. But in some special cases, the traditional heat pipe cannot satisfy the demand of the application. So the special heat pipe is produced.A new kind of efficiency heat pipe for the spirally grooves situation is put forward. And that is the spirally corrugated two-phase closed thermosyphon. The experimental investigation of the traditional thermosyphon and the new kind of heat pipe with three different geometries, called H1,H2 and H3 tube respectively, are done in the present paper. The refrigerant used in this heat transfer performance experiment of heat pipe is water.To compare more scientifically the merit of heat transfer characteristics of heat pipes, the equivalent coefficient of convective heat transfer is proposed in this paper as a new criterion of evaluation of the performance of heat pipes. Therefore, the formula of the equivalent coefficient of convective heat transfer is introduced. In order to measure the equivalent coefficient of convective heat transfer, experimental apparatus was set up.The heat pipe is heated by the resistance wire and cooled by water through a water jacket. The wall temperature can be measured by the 8 thermocouples buried in the wall. The heating rate can be measured by the voltmeter and amperemeter. And the cooling rate is calculated by the water flux and temperature difference between inlet and outlet. The equivalent coefficient of convective heat transfer is achieved by process of the data.The experimental results indicate that the filling ratio can influence the equivalent heat transfer coefficient significantly and that the optimal filling ratio is between 55% and 65%. That is to say, heat pipe can possess higher equivalent heat transfer coefficient with the optimal filling ratio. From the experimental investigation of the spirally corrugated thermosyphon, compares with the traditional thermosyphon in this experimental conditions, it shows that the equivalent heat transfer coefficient of H1 tube (groove depth 1mm, pitch 74mm, number of spiral grooves 4)can increase 10%—16%, the equivalent heat transfer coefficient of H2 tube (groove depth 0.75mm, pitch 86mm, number of spiral grooves 4)can increase 14%～18%, the equivalent heat transfer coefficient of H3 tube (groove depth 0.5mm, pitch 102mm, number of spiral grooves 4)can increase 15%～23%. The spirally grooved structure is a viable way to improve the heat transfer characteristics of heat pipe.