Heat transfer enhancement in pool boiling of liquid nitrogen using a low thermal conductive layer with openings

A method of enhancing the heat transfer of a metal surface in pool boiling of liquid nitrogen by attaching a low thermal conductive layer with openings was proposed and evaluated. This method was proposed to improve a previously investigated method that used a layer without openings and had a low heat flux in a smaller degree of superheat range. Five surfaces of a copper plate, 6 mm in thickness and 50 mm in width and depth, were covered with polystyrene foam. The copper plate was soaked in liquid nitrogen, and its temperature variation was observed. The results indicate that the temperature of the plate with a layer having openings decreased three times faster than that of the plate without a layer. Furthermore, the temperature of the plate with a layer having openings decreased faster than that of the plate with a layer not having any openings. The heat flux of the plate with a layer having openings increased in both low and high degree of superheat ranges.