Flow boiling heat transfer capabilities of R134a low GWP substitutes inside a 4\ua0mm id horizontal smooth tube: R600a and R152a

R134a was recognized as probably one of the most important refrigerants of the two past decades. Among the proposed alternative fluids, there are certainly isobutane (R600a) and R152a.\ua0This article presents about 200 new heat transfer coefficient and pressure drop data obtained during flow boiling of R152a and R600a inside a smooth copper tube having an internal diameter of 4\ua0mm.\ua0Three saturation temperatures were considered for each refrigerant, from 5\ua0\ub0C to 20\ua0\ub0C. Furthermore, for each temperature studied, the heat flux was varied between 15 and 30\ua0kW\ua0m 122 and the refrigerant mass flux from 100 to 400\ua0kg\ua0m 122\ua0s 121. After presenting the new data, a critical comparison was proposed between the performance of these refrigerants and R134a. Finally, some classic correlations available in the literature have been implemented. The deviations between the calculated and experimental values were reported and commented