Flow boiling heat transfer, dry-out vapor quality and pressure drop of propane (R290): Experiments and assessment of predictive methods

This paper presents two-phase flow boiling heat transfer coefficient, pressure drop and dry-out incipience vapor quality data for refrigerant R290 (propane) in a circular channel. The test section consists of a single, horizontal, circular stainless steel tube whose internal and external diameters are 6.0 mm and 8.0 mm, respectively, whereas its heated length is 193.7 mm and the heat is provided through Joule effect with DC current directly applied to the tube. The experiments are performed by changing the mass flux from 150 to 500 kg/m2 s, the heat flux from 2.5 to 40.0 kW/m2 and the saturation temperature, which has been fixed to 25, 30 and 35 C. The effect of all the operating parameters on the experimental data is investigated and discussed. An assessment of predictive methods concerning two-phase heat transfer coefficient, pressure drop and dry-out vapor quality is then performed. The correlation of Bertsch et al. (2009) better fits the heat transfer coefficient data, with a Mean Absolute Error of 30%. The experimental dry-out vapor qualities are fairly fitted with the predictive methods of Kim and Mudawar (2013), with a Mean Absolute Error of 5.7%, whereas the separated flow method of Friedel (1979) returns the best predictions for the frictional pressure gradient, with a calculated Mean Absolute Error of 0.8%. Finally, a new flow boiling heat transfer coefficient prediction tool is proposed by modifying the correlation of Wojtan et al. (2005) to match with the present experimental database, obtaining a calculated Mean Absolute Error of 8.2% and a Mean Relative Error of 6.0%