The article notes the disadvantages of application of dry cooling towers and air-cooled condensers for heat elimination. The cooling air humidifying is considered as a prevalent method of these heat removers efficiency increasing. The way of heat-transfer coefficient rise is proposed using the water mist which enables the latent heat of water evaporation. The physical process of cooling with water mist is analyzed. The effect of water mist rate on the heat transfer enhancement is investigated experimentally in conditions of natural convection. The experimental facility with a heated tube bundle and transversal flow is described. The results of the experiments are given in the form of Nusselt number depending on Rayleigh number and water mist rate. © The Authors, published by EDP Sciences.