New Experimental Data and Flow Boiling Heat Transfer Analysis of CO₂ at Low Temperatures

ABSTRACT

There is a growing use of CO₂ cascade refrigeration systems to achieve low temperatures, particularly in food and refrigeration industries, where understanding of the flow boiling heat transfer mechanisms is essential for heat exchanger design. Although considerable information is available in the open literature on the flow boiling heat transfer of CO₂ at relatively high saturation temperatures, very limited information is available for flow boiling heat transfer of CO₂ at low saturation temperatures below −30°C. This paper presents an overview and analysis of the new experimental data on flow boiling heat transfer of CO2 at low saturation temperatures (between −30°C and −40°C in the subcooled boiling, saturated boiling and dryout regions, along with the effects of saturation temperatures, and heat and mass fluxes. It is expected that new experimental data and analysis would be useful in the design of new heat exchangers for CO₂ cascade refrigeration systems at low temperatures.

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