<p>The influence of the working liquid (distilled water) temperature of a spray system on heat transfer on a vertical smooth surface without boiling was experimentally studied. During the experiments, a droplet flow was formed using a hydraulic nozzle; the coolant temperature and the specific mass flow of water were varied in the ranges of 13 ÷ 70°C and 3.4 ÷ 4.5 kg/(s·m²), respectively. The heat-loaded surface was a stainless-steel foil 20 µm thick with a square working surface of 0.07 × 0.07 m². Heating was carried out using a DC source. The surface heat flux did not exceed 479.6 kW/m². The surface temperature was maintained below 80°C. The study results showed that in a single-phase cooling regime and with an increase in the working fluid temperature to 60°C, the heat transfer coefficient increases in accordance with a dependence close to a linear law. A further increase in water temperature leads to an increase in the temperature of the heat-loaded surface and, consequently, a decrease in heat transfer.</p>