Influence of lubricant oil on heat transfer performance of refrigerant flow boiling inside small diameter tubes. Part II: Correlations

Measurement and Correlation of Flow-Boiling Heat Transfer of a R-410A/Oil Mixture Inside a 4.18 mm Straight Smooth Tube

“…Figures 6b, 6c, and 6d depict a comparison of the predicted values of these correlations with the present experimental data. Figure 6b shows that the Wei et al (2007b) correlation provides a poor prediction for the heat transfer coefficient of the R-410A/oil mixture, and the deviation may be larger than 80% at some experimental conditions. The poor predictability of the Wei et al (2007b) correlation may be due to the fact that the Wei et al correlation model incorrectly uses refrigerant vapor quality in the correlation instead of refrigerant-oil mixture vapor quality.…”

“…Figure 6b shows that the Wei et al (2007b) correlation provides a poor prediction for the heat transfer coefficient of the R-410A/oil mixture, and the deviation may be larger than 80% at some experimental conditions. The poor predictability of the Wei et al (2007b) correlation may be due to the fact that the Wei et al correlation model incorrectly uses refrigerant vapor quality in the correlation instead of refrigerant-oil mixture vapor quality. Figure 6c shows that the deviation of the Hambraeus (1995) correlation is within -70%-30%, so it also provides a poor prediction for the heat transfer coefficient of the R-410A/oil mixture.…”

“…The third category is different from the first two and is developed based on refrigerant-oil mixture properties (Hu et al 2008a;Wei et al 2007b;Hambraeus 1995;Zurcher et al 1998b). The mixture properties are used to replace the pure refrigerant properties to address oil influence on heat transfer.…”

“…The available experimental research shows that the flow mechanism in small-diameter tubes is different from that in conventionally-sized tubes (Wei et al 2007a;Coleman and Garimella 1999). The research on the heat transfer performance of different refrigerant-oil mixtures, such as the R-12/oil mixture (Cawte et al 1996;Tichy et al 1986;Hughes et al 1984;Worsoe-Schmidt 1960), R-22/oil mixture (Wei et al 2007a(Wei et al , 2007bCawte et al 1996;Suguru et al 1991;Schlager et al 1989aSchlager et al , 1989bSchlager et al , 1990, R-134a/oil mixture (Eckels et al 1998a(Eckels et al , 1998b(Eckels et al , 1994Hambraeus 1995;Nidegger et al 1997;Zurcher et al 1997;Fukushima and Kudou 1990), and R-407C/oil mixture (Zurcher et al 1998a(Zurcher et al , 1998b, etc., show that different refrigerant-oil mixtures in different diameter tubes have different heat transfer characteristics. However, there are no paper reports documenting the heat transfer performance of a R-410A/oil mixture flow boiling in small tubes, and the existing research results of refrigerant-oil mixture flow boiling in the normally-sized tubes may not be extended to a R-410A/oil mixture in small tubes.…”

Single-Phase Heat Transfer of R245fa + Lubricant Oil Mixtures Inside Horizontal Smooth and Microfin Tubes

“…Therefore, it is important to clarify the e®ect of oil on the heat transfer characteristics when designing heat exchangers. Wei et al 6 investigated the heat transfer characteristics of refrigerant oil mixture°ow boiling inside tubes with inner diameters of 6.34 and 2.50 mm, and found out that the detrimental e®ect of the oil on the tubes' performance was more signi¯cant in small tubes when compared to large tubes. Kedzierski 7 investigated the e®ect of additives on the boiling performance of an R134a + polyolester lubricant mixture and R123 + naphthenic mineral oil mixture on a horizontal°at surface, and concluded that the miscibility and concentration of the lubricant strongly in°uenced the refrigerant lubricant mixture's boiling heat transfer characteristics.…”