Heat transfer performance enhancement in compact heat exchangers by using shallow square dimples in flat tubes

Abstract The use of a passive method to enhance heat transfer performance based on the application of shallow square dimples on the walls of flat tubes in compact heat exchangers for vehicular applications has been experimentally investigated through tests in a calorimeter and validated through predictions performed using recent literature. The measurements performed with uncertainties in 95% confidence level showed that the correlation ratio between the experimental heat transfer data and the predicted heat transfer was about 97%–106% for the water side and about 90%–100% for the air side, therefore validating the results. It was found that the use of shallow square dimples in flat tubes promoted an increase in the heat transfer augmentation factor between 1.37 and 2.28. It means that the increase of heat transfer performance promoted by the use of shallow square dimples compensates the increase in the water-side friction factor at fixed pumping power and ideal fan power consumption.