Two-phase frictional pressure drop in horizontal micro-scale channels: experimental data analysis and prediction method development

An investigation was conducted on the effects of fluid refrigerant and channel geometry on the frictional pressure drop during two-phase flow inside microchannels. Experimental results for two-phase frictional pressure drop were obtained for the refrigerants R134a, R1234ze(E), R1234yf and R600a in a circular channel and for R134a in square and triangular channels. The experiments were performed for mass velocities from 100 to 1600 kg m-2 s-1, saturation temperatures of 31 and 41°C, and vapor qualities from 0.05 to 0.95. The experimental data have been analyzed focusing on the effects of the geometry and fluid on the two-phase pressure drop. Then, the data were compared with the most quoted predictive methods from literature. Based on the broad database obtained, a new method for prediction of the two-phase frictional pressure drop was proposed. The new method provided accurate predictions of the database, predicting 89% of the results within an error band ±20%.The authors gratefully acknowledge FAPESP (The State of São Paulo Research Foundation, Brazil) for the financial support under contract numbers 2010/17605-4 and 2011/50176-2 and CNPq (The National Council for Scientific and Technological Development, Brazil) for the financial support under Contract Numbers nº476763/2013- 4 and 303852/2013-5. The technical support given to this investigation by Mr. José Roberto Bogni is also appreciated and deeply recognized. The authors also thank Prof. Renato Goulart Jasinevicius for the support in obtaining the profiles of the test sections and measuring the surface roughness. The authors are also grateful to Honeywell for supplying the low GWP refrigerants R1234ze(E) and R1234yf