Experiment for Drop-wise Condensation Heat Transfer by Infrared Thermal Imager

T-type thermocouples and an IR (Infrared) thermal imager are used to observe the generation, growth, coalescence and roll off from the cooling surface of the droplets. Results have been found that the surface temperature varies sharply during the drop-wise condensation, which is not the same to the literature assumption of keeping constant at saturate temperature. The temperature of droplets surface increases sharply and decreases gradually during condensation, though the condensation surface keeps at constant temperature. Through analysis, studies have been presented that the small diameter droplets are critical to the whole condensation heat transfer. The diameter of the droplet has been obtained during drop-wise condensation. The surface temperature after the droplets coalescence is different from that at the beginning without condensation and it is found that the surface is covered by precursor film after coalescence.