Flow Boiling Heat Transfer of R141b in Sintered Porous Tubes.

In this paper, the high flux tubes of 25 mm outer diameter with the content of 8% and 12% nanoparticles were experimentally studied with the refrigerant R141b under atmospheric pressure. The liquid mass flux was controlled from 128.30 to 252.03 kg/m²·s, the maximum heat flux provided by the electric heating rod was 80 kW/m², and the range of the superheated degree was from −7 to 4 °C. The results indicate that the porous media promotes the phase change at a low superheated degree, and the heat transfer capacity is 1.88 times that of the smooth tube. Additionally, the vapor quality increases significantly with the increase of nanoparticle concentration. Moreover, the heat transfer coefficient decreases as the outer wall temperature increases due to the formation of the gas film but increases with the increase of nano-powder content. Under the same superheated degree condition, the maximum heat transfer coefficient of the sintered porous tube with 12% nano-powder content is 1.3 times that of the tube with 8% nano-powder content. [ABSTRACT FROM AUTHOR]