Heat transfer coefficient, pressure gradient, and flow patterns of R1233zd(E) and R1336mzz(Z) evaporating in a microchannel tube

This paper presents the heat transfer coefficient, pressure gradient, and flow patterns of R1233zd(E) and R1336mzz(Z) in a microchannel tube. Both heat transfer coefficient and pressure gradient are measured simultaneously and presented in the same plot in this paper. The experiment was conducted on a 24-port microchannel tube with an average hydraulic diameter of 0.643 mm. Experiment covers mass flux from 100 to 200 kg-m(-2) s(-1), heat flux from 0 to 6 kW-m(-2), vapor quality from 0 to 1. The saturation temperature of R1233zd(E) is from 30 to 50 degrees C, and R1336mzz(Z) is from 40 to 60 degrees C. The pressure gradient is a strong function of mass flux and saturation temperature (properties). Heat flux has an insignificant effect on the pressure gradient because of low accelerating pressure drop. The heat transfer coefficient is strongly affected by mass flux, heat flux, and saturation temperature. When mass flux is higher, the flow has more waves and turbulence, and the HTC and dP/dz are higher. R1233zd(E) and R1336mzz(Z) have much smaller HTC and higher dP/dz than R1234yf and R1234ze(E) under the same condition. R1234yf has almost the same HTC as R1234ze(E) at high quality (x>0.5), but higher at low quality (x<0.5). Hwang and Kim (2006) is recommended for predicting pressure gradient of the two low pressure fluids (R1233zd(E): MAE = 14.1%, ME= -3.7%, Dev= 16.8%; R1336mzz(Z): MAE= 16.7%, ME= -2.0%, Dev= 22.0%). Liu and Winterton (1991) is recommended for predicting HTC of R1336mzz(Z) (MAE=15.2%, ME=-4.6%, Dev=17.9%). None model has good agreement with the measured HTC of R1233zd(E). (c) 2021 Elsevier Ltd. All rights reserved.