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

Giovanni A Longo,Simone Mancin,Giulia Righetti,Claudio Zilio

doi:10.1007/s00231-020-02991-x

Abstract

AbstractR134a 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. This 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 mm. Three saturation temperatures were considered for each refrigerant, from 5 °C to 20 °C. Furthermore, for each temperature studied, the heat flux was varied between 15 and 30 kW m−2 and the refrigerant mass flux from 100 to 400 kg m−2 s−1. 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.

Highlights

Following the environmental issues linked to anthropogenic greenhouse effect and the consequent increment of ambient temperatures, several HFC refrigerants, including R134a, are subjected to a progressive phase-down, depending on local legislations.In the last years, several low-GWP (Global Warming Potential) synthetic molecules, like R1234yf and R1234ze (E), have been proposed as R134a replacements in some applications like mobile air conditioning and large chillers
Since the nineties, some traditional low-GWP molecules, like R152a and isobutane (R600a) have been evaluated and in some cases already used as substitutes of R134a in applications like domestic appliances, heat pumps, cabin heating and cooling for vehicles [1,2,3]
The experimental campaign presented in this work aimed to collect new average heat transfer coefficient and frictional pressure drop data during flow boiling of two refrigerants: R600a and R152a inside the same 4 mm smooth tube

Summary

Introduction

Following the environmental issues linked to anthropogenic greenhouse effect and the consequent increment of ambient temperatures, several HFC refrigerants, including R134a, are subjected to a progressive phase-down, depending on local legislations.In the last years, several low-GWP (Global Warming Potential) synthetic molecules, like R1234yf and R1234ze (E), have been proposed (mostly HydroFluoOlefins, HFO) as R134a replacements in some applications like mobile air conditioning and large chillers. Since the nineties, some traditional low-GWP molecules, like R152a (an HFC) and isobutane (R600a) have been evaluated and in some cases already used as substitutes of R134a in applications like domestic appliances, heat pumps, cabin heating and cooling for vehicles [1,2,3]. Despite those fluids are promising alternatives to R134a and available for relatively longtime, the studies about heat transfer behavior of R152a and R600a during in-tube flow boiling are still limited. Considering horizontal smooth tubes, they found only four papers investigating R600a for a total number of 820 data points

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Conclusion