CFD investigation on heat transfer improvement of subcooled flow boiling in a vertical upflow minichannel with straight and enhanced geometrical structure

•Good agreement is observed between simulation model for a subcooled flow boiling and experimental results.•The heat transfer coefficient tends to decrease with the rise of the inlet temperature.•The heat transfer coefficient varies periodically along the periodic constriction-expansion minichannel from.•The periodic constriction-expansion configuration improves the greatest enhancement in heat transfer. This paper presents the effects of minichannel geometrical configuration on flow structures, hydrodynamics, and heat transfer behavior of the subcooled flow boiling process in a cooling system with high heat flux. The two-dimensional numerical simulations are quantitatively conducted for dielectric fluid FC-72 as a working fluid in two different configurations (straight and periodic constriction-expansion) of a minichannel mounted vertically at three inlet temperatures (285.35, 304.54, and 325.35 K) at constant mass flux (836.64 kg/m2s) and input heat flux (191,553 W/m2). The predicted results are in excellent agreement with the published experimental data, which proves the efficiency of the present numerical model. In both configurations, the heat transfer coefficient increases with an increase in the inlet temperature. The results show that the periodic constriction-expansion design significantly improves the heat transfer performances of subcooled flow boiling by 21.77–36.9% for Tin = 285.35–325.35 K because the periodic constriction-expansion configuration offers good mixing between layers.