Ernest Gyan Bediako, Petra Dancova, Anas F. A. Elbarghthi, Tomas Vit

Abstract: This study presents an experimental analysis of flow boiling heat transfer of R134a refrigerant in a smooth horizontal stainless-steel tube with the goal of investigating the effect of heat flux on heat transfer coefficient and dry-out characteristics. The experiment was performed for heat fluxes ranging from 7.2 kW/m2 to 47.4 kW/m2, mass flux of 300 kg/m2s and saturation pressure of 460 kPa. The results showed that at low heat fluxes, the heat transfer is predominantly controlled by convective boiling with a higher slope of heat transfer coefficient. As heat flux increases, nucleate boiling begins to predominate the heat transfer. The predominance of nucleate boiling is strongly experienced at low vapor quality when the higher slope in convective boiling begins to disappear as nucleate boiling dominates. Dry-out vapor quality incipience ( ) is not affected appreciably by heat flux. All the dry-out vapor quality incipience correlations investigated predicted well the vapor quality for which dry-out begins and ends.

Keywords: heat transfer coefficient, mass flux, heat flux, vapor quality, dry-out, R134a, convective boiling, nucleate boiling.

Date Published: August 18, 2023
DOI: 10.11159/jffhmt.2023.007

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