INFLUENCE OF WORKING FLUID TO HEAT TRANSFER CHARACTERISTICS OF OSCILLATING HEAT PIPE FOR LOW TEMPERATURE

摘要

The heat transfer characteristics of the non-loop type oscillating heat pipe for low temperature are investigated experimentally. The oscillating heat pipe is made of capillary copper tube bundles with 105 m length and 70 turns, having a 2.6 mm in outside diameter and 1.4 mm in inside diameter. It has the capacity of 1 kW; the properties depending on working fluid, inclination angle and the analysis of its performance are speculated, R-22, R-142b, and R-290 are used as the working fluid, and the charging ratio of working fluid is 40 and 50 % respectively. Water is used as secondary fluid, inlet temperature of heating & cooling water are 298 K & 280 K, mass flux is varied from 9 to 27 kg/m~2s, respectively. From the experimental results, the oscillating heat pipe shows the maximum performance when the inclination angle 90° (bottom heating mode), and optimum charging ratio or the working fluid is 40% in volumetric. The working fluid R-22, which has the high value in the Figure of Merit for thermosyphon, is better in the performance when compared with the R-142b and R-290. By converting the heat transfer rate to heat flux, it is found that the performance of oscillating heat pipe is superior when compare with correlations for maximum heat flux in two-phase closed thermosyphon. Experimental results are compared with nucleate boiling and condensing heat transfer coefficient correlations, which are suggested by Foster and Zuber, Rohsenow, Mostinski, Copper, Bier et al., Nusselt, and Chato.