Experimental investigation of heat transfer of hydrocarbons and their mixtures in pool boiling on steel tubes.

Due to high energy demand required for chemical processes, refrigeration and process industries, increasing the efficiency and performance of thermal systems especially evaporators is indispensable. One of the possibilities are investigations in enhancement of the heat transfer in nucleate boiling where high heat fluxes at low superheat are transferred. In the present work, the heat transfer in pool boiling is investigated with hydrocarbons over wide ranges of reduced pressures and heat fluxes. The working fluids investigated are pure n-pentane, and a mixture of n-pentane and iso-octane. The heating material of the test tubes is stainless steel. Furthermore, the influence of the microstructure on the heat transfer coefficients is also analysed by variation of the surface roughness between polished and sandblasted surfaces. The heat transfer coefficients increases with increasing surface roughness and reduced pressures. The experimental results show a large degradation of the heat transfer coefficients between pure fluids and their corresponding mixtures. The correlation of the VDI Heat-Atlas predicts the experimental results well for the pure fluid, but do not accurately consider the stainless steel material reference properties and the mixture effects.