Heat Transfer and Pressure Drop Characteristics of R-22, R-134A and R-407C in Microchannel Tubes

摘要

A study of heat transfer and pressure drop characteristics for single-phase and twophaseflow of refrigerants in micro channel tubes was conducted. An existing facility wasmodified to perform tests on a single microchannel tube using water flowing in counterflowas the heat sink fluid. Data were collected for sub cooled liquid, superheated vapor andcondensing refrigerant for circular-port microchannel tubes at four different mass flowrates. The refrigerants tested were R-22, R-134a and R-407C. In addition to circularporttubes, square-port tubes were tested with R-22 for both single-phase and two-phaseflow. Data were also taken with water flowing inside a square-port microchannel tube.The Reynolds number for all the flows in this study ranged from 3,000 to 17,000 in theliquid phase and 30,000 to 110,000 in the vapor phase.The heat transfer coefficients and pressure drop for circular-port micro channel tubeswere compared for R-22, R-134a and R-407C. For sub cooled liquid flow, the heat transfercoefficient for R-407C was found to be greater than that for R-22 and R-134a. The heattransfer coefficient for R-22 was found to slightly lesser than the other two refrigerantsfor condensing flow.A model was built to predict the heat transfer and pressure drop in the microchanneltube. In most cases, the heat transfer and pressure drop predicted by the model agreevery well with experimental results. A sensitivity analysis revealed that the total heattransfer is not very sensitive to the refrigerant side heat transfer coefficient.