Experimental study on heat transfer condensation of R1234ze(E) and R134a inside a 4.0 mm OD horizontal microfin tube

Small sized microfin tubes are a smart option to keep the refrigerant charge under the stricter and stricter values depicted by the new environmental laws. Despite of the large number of papers dedicated to phase change phenomena inside traditional microfin tubes with diameters larger than 5 mm, small sized micro-fin tubes are still a topic which deserves further studies. In this context, this paper proposes experimental results of heat transfer coefficients and frictional pressure drops collected during condensation of R1234ze(E) and R134a inside a small sized microfin tube with an outer diameter of 4.0 mm. Experimental tests were carried out for mass velocities from 100 to 1000 kg m(-2) s(-1), vapor qualities from 0.1 to 0.99, at saturation temperatures at the inlet of the test section of 30 degrees C and 40 degrees C. The range of working conditions permitted to better understand how each operative parameter affects the thermal and hydraulic behavior of the microfin tube during condensation heat transfer. The experimental results of heat transfer coefficient and frictional pressure drop were finally compared against values predicted by empirical correlations available in the open literature. (C) 2018 Elsevier Ltd. All rights reserved.