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

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.

A Comprehensive Review on the Nucleate/Convective Boiling of Low-GWP Refrigerants: Alternatives to HFC Refrigerants

“…For nucleate boiling subject to a high-viscosity polyol-ester oil (POEA)-220, with a LGWP refrigerant (R-1234ze(E)), Kumar et al [21] conducted nucleate pool boiling tests on a GEWA-B5H tube at −6, 0, and 10 • C saturation temperatures, with an oil mass fraction ranging from 0.25 to 10% with heat fluxes ranging between 10 and 90 kW/m 2 . The results were compared to earlier research [19] and the experimental results are shown in Figure 4.…”

“…On the other hand, the HTC degrades due to the creation of a micro-sized bubble fog directly above the test surface, which is connected to a higher oil mass fraction at a high heat flux. Furthermore, Kumar et al [21] also presented HTCs against applied heat fluxes in association with new and aged surfaces at varying saturation temperatures. These experiments were conducted in 4-month gaps.…”

Special Issue: “Emerging Technologies in Heating, Ventilation, Air Conditioning and Refrigeration (HVAC&R) Systems”

“…Kumar et al [2] investigated the nucleate pool boiling heat transfer of low-globalwarming-potential (GWP) refrigerant R-1234ze(E) on enhanced GEWA-B5H tube with the addition of a highly viscous oil, POEA-220, at saturation temperatures of 10 • C, 0 • C and −6 • C. It was found that compared to the pure R-1234ze(E) in the moderate heat flux range, an enhancement in the heat transfer coefficient at saturation temperatures of 0 • C and −6 • C can be achieved with the addition of 10% mass fraction of the POEA-220 oil into R-1234ze(E). Moreover, for the R-1234ze(E)/POEA-68 mixtures, a 5% mass fraction of oil showed no enhancement in the heat transfer coefficient compared to pure refrigerant at the same saturation temperature.…”