Heat Transfer Performance of R-1234ze(E) with the Effect of High-Viscosity POE Oil on Enhanced GEWA-B5H Tube

Abhishek Kumar,Jung-Hsien Wu,Chi-Chuan Wang,Miao-Ru Chen,Li-Kang Su,Kuo-Shu Hung

doi:10.3390/pr9122285

Abhishek Kumar, Jung-Hsien Wu + Show 4 more

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https://doi.org/10.3390/pr9122285

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Abstract

In this study, the heat transfer performance of high-viscosity polyol ester (POE) oil POEA-220 (220 cSt) with low-GWP (global warming potential) refrigerant R-1234ze(E) on enhanced GEWA-B5H tube was investigated at saturation temperatures of 10 °C, 0 °C, and −6 °C. The mass fraction of oil varied from 0.25% to 10%, and all the nucleate pool boiling data were measured at heat fluxes ranging from 10 kW/m2 to 90 kW/m2. The experimental results showed that the heat transfer performance of the R-1234ze(E)/POEA-220 mixtures were superior to the R-1234ze(E)/POEA-68 mixtures. At saturation temperatures of 0 °C and −6 °C, even a 10% mass fraction of the POEA-220 oil showed an enhancement in the HTC (heat transfer coefficient) compared to the pure refrigerant in the moderate heat flux range. On the other hand, for the R-1234ze(E)/POEA-68 mixtures, a 5% mass fraction of oil showed no enhancement in the HTC compared to pure refrigerant at the same saturation temperature. Moreover, at low saturation temperatures (0 °C and −6 °C), the enhancement in the HTC decreased with increasing mass fraction of low-viscosity oil POEA-68, whereas high-viscosity oil POEA-220 showed the highest enhancement in the HTC for a 5% mass fraction of oil at −6 °C saturation temperature compared to the pure refrigerant. The results indicate that for nucleate boiling, the effect of oil viscosity on heat transfer performance is negligible if it contains comparatively high thermal conductivity and low surface tension. In addition, the effect of surface aging on heat transfer performance for the GEAW-B5H tube with pure refrigerant was also reported.

Highlights

Specific refrigerant-oil pairs are required for the efficient operation of the compressor and refrigeration system
The maximum mass fraction of oil was increased from 5% to 10%, and the heat transfer performances of seven refrigerant-oil mixtures (R-1234ze(E)/POEA220) were tested on the same tube at the saturation temperatures of 10 ◦ C, 0 ◦ C, and
The nucleate pool boiling experiments were performed with low-GWP refrigerant R1234ze(E)

Summary

Introduction

Specific refrigerant-oil pairs are required for the efficient operation of the compressor and refrigeration system. The oil miscibility, lubricity, solubility, and viscosity are essential parameters to characterize the suitability when mixing with refrigerant. An era of third- generation HFC (hydrofluorocarbon) refrigerants face an uncertain future due to their high GWP. Several low-GWP refrigerants have been developed by several manufactures and recognized by the ASHRAE Refrigerating and Air-Conditioning Engineers), which are termed as fourth-generation. R-1234ze(E) is one of the ultra-low-GWP refrigerant (GWP < 1) alternatives to R-134a that has been tested by several researchers in the past decades, and detailed summaries are available in References [1,2,3].

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