To investigate the effects of spray cooling on air-side heat transfer and pressure drop

and to determine the water spray flow rate when spray droplets evaporate completely on the hot surface of a compact heat exchanger

we built an experimental plant to analyze the air-side heat transfer and pressure drop of an automotive compact heat exchanger with and without spray cooling. The results indicate that the j factor and f factor obtained from experiments without spray were in good agreement with those calculated from Chang’s correlations

within an error of 10%. Compared with that without spray

the j factor with spray increased significantly

but the increasing rate declined with a decrease in the spray flow rate and substrate temperature. The f factor with spray changed slightly compared with that without spray. Using the substrate temperature and air velocity as variables

we proposed a correlation of the critical value of the spray flow rate (where spray droplets can evaporate completely). Based on Chang’s correlation

the j factor with spray can be obtained using a correction factor. These results support the prediction of air-side heat transfer with spray and also facilitate future application of spray cooling in automotive air conditioners.