Abstract:
An experimental study of flow resistance characteristics of R410Aoil mixture during evaporation inside a 5 mm internally spiral grooved enhanced tube was performed. The test results show that the frictional pressured drop of R410A initially increases with vapor quality and then decreases, presenting a local maximum in the vapor quality range between 0.7 and 0.8; the frictional pressure drop of R410Aoil mixture increases with increasing nominal oil concentration, vapor quality and mass flux; the presence of oil enhances frictional pressure drop maximum by 120% as the oil concentration increases from 0 to 5% at a vapor quality of 0.9. The frictional pressure drop of R410Aoil mixture in 5 mm enhanced tube is about 10% to 30% higher than that in 7 mm enhanced tube. The deviations of the prediction of existing correlation for 7 mm enhanced tube to the pressure drop characteristics of R410Aoil mixture in 5 mm enhanced tube are within ±40%. Based on the experimental data of R410Aoil mixture in 7 mm and 5 mm enhanced tubes, a new correlation of frictional pressure drop was developed by considering the mixture properties, which agreed with 95% of the experimental data within the deviation of ±20%.