Review of low-GWP refrigerant pool boiling heat transfer on enhanced surfaces

Global warming mitigation efforts have stimulated investigations of a new generation of low-GWP refrigerants. Because some of the proposed low-GWP refrigerants have unfavorable characteristics (e.g., flammability and toxicity), a small refrigerant charge is desirable. Compact heat exchangers with enhanced surfaces facilitate small refrigerant charge by having a large heat exchanger surface area to heat exchanger volume ratio. This paper reviews the current state-of-the-art for pool boiling heat transfer of low-GWP refrigerants on enhanced surfaces. An overview for the enhanced surface manufacturing technique is given along with detailed reviews of the heat transfer measurements and predictions for many of the low-GWP refrigerants, including the hydrofluoroolefin (HFO) class, the hydrocarbon (HC) class, carbon dioxide (CO₂), and ammonia (NH₃). The overview of the predictive methods includes mechanistic models and correlations for pool boiling on enhanced surfaces. Based on the surveyed literature, existing shortfalls are identified and suggestions for future studies are proposed.