ENC-2020-0358 EXPERIMENTAL EVALUATION OF THE FLOW BOILING HEAT TRANSFER COEFFICIENT OF R600A AND R134A INSIDE A 9.43 MM INNER DIAMETER TUBE.

摘要: This paper concerns an experimental investigation of the heat transfer coefficient during flow boiling of R134a and R600a inside a horizontal smooth circular tube with inner diameter of 9.43 mm. Experiments were performed for mass velocities ranging from 100 to 200 kg/m2s, heat fluxes from 10 to 30 kW/m2, vapor qualities up to the unity, and saturation temperature of 5oC. Generally, an increase of the heat transfer coefficient was observed with increasing heat flux and mass velocity. The heat transfer coefficient increases with increasing vapor quality until dryout conditions are reached. Any additional vapor quality increment beyond dryout causes a decrease in the heat transfer coefficient. In general, higher heat transfer coefficients were noticed for R600a compared to R134a under similar experimental conditions. Unsatisfactory predictions were provided for both fluids by the prediction methods from literature at high vapor qualities corresponding to conditions close to the surface dryout, while predictions for lower vapor qualities performed better.