Effects of the surfactant solution on the performance of the pulsating heat pipe

The startup, operation and dry-out characteristics of pulsating heat pipes (PHPs) are influenced by many parameters, and researches on improving its performance by optimizing the parameters, especially the thermalphysical properties of working fluids, have drawn wide attention. In this paper, the effects of deionized water (DI water) and the surfactant solution on the startup, operation and dry-out characteristics of the PHP were experimentally investigated at the charge ratios of (30.9-67.9)% and the heat fluxes of (637-21,083) W/m(2). Sodium stearate was used as the surfactant, and three different concentrations of the surfactant solutions (10 ppm, 20 ppm and 40 ppm) were prepared. The experimental results indicated that the PHP with the surfactant solutions could start at a lower heat flux, compared with the DI water-PHP. When the concentration of the solution was 20 ppm, the PHP had the lowest thermal resistance within the tested conditions. Compared with that of the DI water-PHP, the thermal resistance of the PHP with 20 ppm surfactant solution decreased by 27.8% at the charge ratio of 56.7% and the heat flux of 3503 W/m(2). The results also suggested that the PHP with the surfactant solutions presented higher dry-out heat fluxes, and showed relatively stable temperature oscillation characteristics. At the charge ratio of 67.9%, the dry-out heat flux of the PHP with the surfactant solutions increased by 17.80% compared with that of the DI water-PHP.