Boiling Characteristics for Water and Nanofluid on Copper Finned Surface

Abstract

This study presents an experimental and computational study performed to investigate the changes in boiling characteristics of various working fluids. Boiling characteristics of a working fluid is determined by bubble diameter and bubble frequency. These characteristics changes in a fluid with the change of different parameters such as the heating surface, fluid in use, heat flux etc. In this study 5 different working fluids, 4 of which are nano-fluids, were used to compare their changes in these boiling characteristics and to find the best one among them. As for the heating surface, finned surface was chosen. Finned surface shows a better heating value compared to plane surface because of its increased surface area. Quantitative measurements are obtained from high speed visualizations of nucleate pool boiling at atmospheric pressure on finned surface using water and 1% and 6% of -Water and CuO-Water as working fluid. Theoretical studies of these working fluids are also done using correlations such as Rohsenow’s correlation, Cole correlation, Peebles and Garber Correlation. For computational analysis a modelling of boiling of working fluids is done. Results are compared to predictions from existing model of bubble nucleation behaviour. Graphs are plotted to show variation of bubble diameter and frequency against heat flux while variation of surface and saturation temperature with variation of heat flux determines which working fluid is more efficient. This study will help to understand the behaviour of nano-fluids as compared to normal fluids used in heat transfer applications. The study shows that experimental values of bubble frequency have variations compared to predicted values. In case of bubble diameter the experimental values are found to be higher. Again comparing experimental bubble diameter, bubble frequency and heat flux results the most preferable choice among these fluids from our study is 1% CuO-Water.