Heat transfer and pressure drop model of in-tube condensation in a vapor-compression system

摘要

A typical “3-zone” models assume uniform temperature in the cross section of the tube duringcondensation. The first droplet occurs when the bulk quality is 1. However, as soon as walltemperature drops to the saturation, condensation begins regardless of what the bulk temperatureis.The new heat transfer and pressure drop models use “5-zone” approach, seeking to capture thetwo-phase mechanisms in the condensing superheated (CSH) and condensing subcooled (CSC)regions.Heat transfer coefficient and pressure drop measured in 4 and 6 mm tubes are used to validate thenew approach in the range: mass flux from 50 to 400 kg m~(-2) s~(-1); heat flux 5 to 15 kW m~(-2);condensing temperatures 30 and 50°C. The refrigerants explored are R744, R32, R410A, R134a,and R1233zd(E).The new models are more physical and better fit the experimental data than the conventionalmodels, especially in the CSH region. This is because the latent heat and vapor-liquid interactionare present even though the bulk temperature indicates otherwise.