Flow Boiling Pressure Drop of R134a in Microdiameter Tubes: Experimental Results and Assessment of Correlations

Abstract

The experimental results of two phase flow boiling pressure drop of R134a in vertical micro diameter stainless steel tubes are presented in this paper. The tests were conducted using four tubes; one tube with an inner diameter of 0.52 mm and 100 mm heated length and three tubes with an inner diameter of 1.1 mm and different heated lengths (150, 300 and 450 mm). Other experimental conditions include: mass flux range of 200-500 kg/m 2 s, system pressure range of 6-10 bar, inlet sub-cooling of about 5K and heat flux range of 1-140 kW/m 2. The results indicated that the total measured two phase pressure drop increases with increasing mass flux, heat flux (exit quality) and decreasing system pressure and tube inner diameter. The test section heated length was found to have a significant effect on the measured pressure drop per metre length. The total measured two phase pressure drop results were also compared with eighteen macro and micro scale models and correlations.

Flow pattern maps, pressure drop and performance assessment of horizontal tubes with coiled wire inserts during condensation of R-600a

“…Accordingly, Song et al [37] appraised twenty nine pressure drop correlations and reported that the best performing relation was able to predict the results within error band of ±30%. Similar conclusions were also drawn in other studies [38][39][40][41]. Indeed, based on the above-mentioned investigations, having the ability to predict the data in the error range of ±30% seems to be satisfactory in two-phase flow regimes.…”

Flow Boiling Pressure Drop Characteristics in a Rectangular Metallic Microchannel

“…They reported that the flow boiling pressure drop increased with increasing mass flux and heat flux. The effect of system pressure on the flow boiling pressure drop was also studied in the literature [5,9,12]. Tran et al [9] carried out sets of experiments in two microtubes (D = 2.46 mm and 2.92 mm) and one rectangular microchannel (Dh = 2.4 mm) using various working fluids (R-134a, R-113 and R-12).…”

“…They stated that the flow boiling pressure drop increased with decreasing system pressure in all experiments. In another study, Mahmoud et al [12] tested four microtubes with one tube with an inner diameter of 0.52 mm and 100 mm heated length and three tubes with an inner diameter of 1.1 mm and different heated lengths (150, 300, and 450 mm) using R-134a. They concluded that the flow boiling pressure drop increased with decreasing system pressure due to the reduction of the liquid vapour density ratio.…”