Semi-Analytical Correlation for Pool Boiling Heat Transfer Using Nanofluids Based on Fractal Theory

Abstract

On the basis of fractal dispersion of active nucleation sites on boiling surface, a revised fractal model for nucleate pool boiling of nanofluids was established incorporating microlayer evaporation, nature convection and transient conduction. It has fewer empirical constants than that of traditional ones. Results of model using pure fluids and nanofluids conform to data from previous investigations. Thus, accuracy of model is verified. Effects of liquid properties and contact angle on pool boiling heat transfer coefficient (HTC) using nanofluids are discussed according to the present model. It is found that the HTC of nanofluid and the fractal dimension of nucleation sites decrease with the decreasing contact angle. The effect of liquid properties enhancement due to the presence of nanoparticles, has ignorable influence on HTC of dilute nanofluids while the decreased contact angle plays a more important role. It is also found that the surface with lower contact angle had a higher natural convection component.