Immersion cooling effect of dielectric liquid and self-rewetting fluid on smooth and porous surface

Dielectric liquid Novec 7300 and 5% 1-butanol aqueous solution are applied for immersion cooling of heater in order to investigate effect of nucleate boiling and self-rewetting on heat transfer. Experimental results are compared with water as common liquid for immersion cooling. In first part of study, bare heater is heated until temperature arrives at certain levels (from 100 degrees C to 500 degrees C), and then immersed in liquid for observing rapid cooling performance of these three solutions. In 5% 1-butanol binary solution, heater temperature decreases the fastest and stabilizes at the lowest level. Inversed thermal Marangoni flow induced by vertical temperature difference along heat surface is supposed to assist vapor bubbles separation and improve convective heat dissipation. From 200 degrees C, vapor film appears on the surface of heater immersed in Novec 7300 and water, whose thickness is dependent of surface temperature but independent of heat flux. In second part of study, immersion cooling performances of three testing liquids on heater with or without porous shells of different porosity are explored with increasing heating power. At different heat flux input, shell porosity, capillary effect, inverse thermal Marangoni effect and pool boiling stages influence heat transfer efficiency of each fluid-heater combination. A curve of optimal heat transfer coefficient is established, which is beneficial for selection of suitable fluid-heater combination.