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Advanced nuclear power plants are equipped with passive systems for emergency decay heat removal from reactor equipment (PEHRSs) in case of development of accidents accompanied with primary cooling circuit leakage and for transferring heat to the final heat absorber (ambient air). Here, intensity of heat dissipation to air from the heat exchanger outer surface achieved by buoyance induced natural convection is extremely low, which necessitates the need to expand heat conductivity surfaces and to apply different types of heat transfer intensifiers (grooves, ribs and extended surfaces, positioning at higher altitudes, etc.). Intensity of heat removal is also strongly dependent on the ambient air temperature (disposable temperature head). Construction of nuclear power plants in countries with high ambient temperatures (Iran, Bangladesh, Egypt, Saudi Arabia and others) with characteristic high level of ambient air temperature imposes additional requirements on the expansion of heat exchange surfaces. Results of experimental investigation of intensification of heat exchange by low energy-intensity ultrasound supply of super-small liquid droplets (size ~3 mm) in the cooling air are provided in the present paper. In such case, transfer of heat between the cooled surface and cooling airflow involves the following three physical effects: convection, conductive heat exchange and evaporation of water droplets. The latter two effects weakly depend on the ambient air temperature and ensure active heat removal in any type of situation. Investigation was performed using high-precision calorimeter with controlled rate of heat supply (between 7800 and 12831 W/m2) imitating heated surface within the range of Reynolds numbers from 2500 to 55000 and liquid (water) flow rates from 23.39 to 111.68 kg/m2·h-1. The studies demonstrated that presence of finely dispersed water results in significant increase of heat transfer compared with the case of application of purely air-cooling. With fixed heat flow energy efficiency increases with increasing concentration of water reaching the values in excess of 600 W/m2·degree-1, which is 2.8 times higher than for the case of air-cooling. Application of the suggested technology for intensification of heat exchange in dry cooling towers of nuclear and thermal power plants used in the conditions of hot and extreme continental climate is possible subject to further investigation for the purpose of specification of optimal ranges of heat exchange intensification. © 2019 Obninsk Institute for Nuclear Power Engineering, National Research Nuclear University 'MEPhI'. All rights reserved.

В статье приведены результаты экспериментов по равномерности распыления водовоздушной смеси при орошении колец подшипников из стали ШХ15, проведенных в условиях опытного стенда ОАО «ВНИИМТ». Исследованы процессы истечения водо-воздушной смеси как из одиночных форсунок различного размера, так и из специальной конструкции водовоздушного коллектора с форсунками. Установлены углы раскрытия факелов, пределы изменения параметров водо-воздушной смеси, а именно соотношения расходов воды и воздуха, при которых достигается требуемая равномерность распыла. The article presents the results of experiments on the uniformity of spraying the air water mixture in the irrigation of bearing rings of steel SHKH15, carried out in the experimental stand of the OJSC "VNIIMT", the processes of expiration of the air water mixture from a single nozzle of varying size and of special design of air assisted manifold with nozzles. Set the angles of the disclosure of torches, the ranges of parameters of the air water mixture, namely the ratio of costs of water and air, which achieves the required uniformity of the spray.