Experimental Study of Critical Heat Flux During Pool Boiling on Mini Tubes: Effect of Subcooling, Orientation, and Dimensions

Pool boiling is cost-effective, simple and prevalent amongst all available cooling schemes. The lack of quantitative data, qualitative theories and explanations in the area of critical heat flux (CHF) in mini tubes makes it an interesting domain of research. This paper discusses the effect of heater length, diameter, orientation and subcooling on CHF. There is the scarcity of literature that considers all the effects altogether. This paper analyses the effect of all the parameters together in a single study. SS304 mini tubes of 2.5- and 1.2-mm diameters with various lengths are used as a heater in horizontal and vertical orientations. The water pool is kept at 30, 50, 75 degrees C and saturation temperature. The study is performed at atmospheric pressure. It has been observed that with the increase in pool temperature, the magnitude of CHF decreases. The shortest length has a higher magnitude of CHF corresponding to a given pool temperature. The values of CHF decrease with an increase in tube diameter. The CHF value is higher for horizontal as compared to vertical orientation. An empirical correlation, including the effect of subcooling, orientation and tube dimensions is derived from the CHF data. The experimental data is presented in a tabulated form to contribute to pool boiling CHF databank.