Proposed Correlation for Forced Convection Boiling Heat Transfer in Mini and Micro Channels With CO₂ as a Fluid

After reviewing the available literature on flow boiling heat transfer in mini/micro tubes and channels, it is felt that there is need for predictive correlations which is applicable over wide range of parameters. In present work a new correlation for two-phase flow boiling heat transfer coefficient is developed, which has considered nucleate boiling and convective boiling heat transfer effect. To develop this correlation we have considered total 651 data points, which have been collected from the open available literature covering different operational conditions and different dimensions of channels. We have selected CO₂ as a working fluid because it does not contain chlorine, hence an efficient and environmentally safe refrigerant and would be potential replacement for R-22. CO₂ has unusual heat transfer and two-phase flow characteristics, and is very different from those of conventional refrigerant. Also a comparison of present correlation with the best published correlation for CO₂ is done. The results of this comparison indicate that the new developed correlation is superior to published best correlation for CO₂. Present correlation is also compared with best published correlation for all fluids and with the correlation developed by using CO₂ data. The results of these both case, indicate that the present correlation is superior.