Flow Boiling Heat Transfer Of R134a In A 500 Mu M Id Tube

The present paper presents experimental results for the heat transfer coefficient during flow boiling of refrigerant R134a in a circular channel with internal diameter of 500 mu m. The experimental database covers mass velocities ranging from 200 to 800 kg/m(2) s, heat fluxes up to 100 kW/m(2) and vapor qualities from 0.02 to 0.75 for a saturation temperature of 40 degrees C. The experimental data were parametrically analyzed and the effects of the experimental parameters (heat flux, mass velocity and vapor quality) identified. Additionally, images of two-phase flow were obtained through a high-speed camera and employed to identify the flow patterns. A flow pattern map was built and compared to prediction methods from the literature. In general, the heat transfer coefficient increased with increasing mass velocity and heat flux. The experimental data were compared against seven flow boiling predictive methods from the literature. Sun and Mishima (Int J Heat Mass Transf 52(23):5323-5329, 2009. 10.1016/j.ijheatmasstransfer.2009.06.041) and Kanizawa et al. (Int J Heat Mass Transf 93:566-583, 2016. 10.1016/j.ijheatmasstransfer.2015.09.083) methods provided the best prediction of the experimental results with only Kanizawa et al. (2016) capturing the experimental heat transfer trends.