A REVIEW ON CARBON DIOXIDE HEAT TRANSFER CHARACTERISTICS DURING FLOW BOILING

摘要

An original review on carbon dioxide (CO_2) flow boiling characteristics is proposed through a wide range ofrndiameters and temperatures representing promising applications such as mobile air-conditioning, heat pumprnwater heater and cascade commercial refrigeration. Although there is a consensus that CO_2 outperformsrnconventional refrigerants due to its nucleate boiling dominated heat transfer, it is still not clear whichrnphenomenon induces the decrease of the heat transfer coefficient at moderate to high vapour quality. Basedrnon the open literature, a heat transfer database was built from flow boiling experiments in circular tubesrnincluding 216 test conditions. Cross-references among the data and comparisons at varying diameters allowrnto better discriminate the contribution of nucleate boiling suppression, partial dryout and distributionrnproblems.