Flow boiling heat transfer and pressure drop characteristics of R1234ze(E) in metal foam filled tubes

Metal foam has large specific surface area and high thermal conductivity, and can be used to enhance heat transfer in refrigeration and air-conditioning systems by filling it in the heat exchange tube. The flow boiling heat transfer and pressure drop characteristics of R1234ze(E) in metal foam filled tubes are experimentally studied. The experimental conditions cover vapor quality of 0.1-0.9, mass flux of 90-180 kg·m-2∙s-1 and heat flux of 12.4-18.6 kW·m-2. The test samples are copper foam filled tubes with the pore density ranging from 10 PPI to 40 PPI and the porosity ranging from 90% to 95%. The experimental results show that, the heat transfer coefficient and two-phase pressure of R1234ze(E) are 2%-10% and 30%-42% lower than those of R410A, respectively. As the vapor quality increases (x>0.8), the increment in heat transfer coefficient of the metal foam filled tube is more significant under low heat flux conditions. Metal foam enhances flow boiling heat transfer at the cost of increased pressure drop, metal foam effect factor for heat transfer ranges from 1.23 to 2.90 and effect factor for pressure drop ranges from 6 to 45. New correlations for flow boiling of R1234ze(E) in metal foam filled tubes is developed. The predicted values of heat transfer coefficient and two-phase pressure drop agree with 95% of experimental data within a deviation of ±15% and ±25%, respectively. © 2021, Editorial Board of CIESC Journal. All right reserved.