Direct‐contact vaporization heat transfer is investigated by analyzing the heat transfer coefficient with the area of liquid‐liquid direct‐contact interface. The interface areas of liquid‐liquid heat transfer are determined by stroboscopic images. At higher temperature, the heat transfer area per unit volume decreases. The water temperature has no significant influence on the heat transfer coefficient. The effects on droplet size distributions of operating variables including inlet water temperature, n‐pentane flow rate, and test position with packing and without packing are compared.