The operation efficiency increase of the circulating water supply system with cooling tower of the 1000 MW power unit under its operating conditions at the Rivne NPP.
Students Name: Pryhanovych Artem Olehovych
Qualification Level: magister
Speciality: Heat and Power Engineering
Institute: Institute of Power Engineering and Control Systems
Mode of Study: part
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: Pryhanovych А. O., Matiko Н. F. (supervisor). The operation efficiency increase of the circulating water supply system with cooling tower of the 1000 MW power unit under its operating conditions at the Rivne NPP. Master’s thesis. – Lviv Polytechnic National University, Lviv, 2022. Extended abstract A cooling tower is a heat exchange device for removing heat from production processes into the environment due to the evaporation of part of the water. The share of evaporated water usually does not exceed 1.5%. Most of the used cooling towers were built 30-50 years ago. Practically all these installations are morally and physically obsolete. The cooling tower must meet a number of requirements - technical, operational and economic. This problem becomes particularly acute in winter and summer, since the efficiency of the production process directly depends on the temperature of the chilled water [1]. As it was shown in works [2, 3], the efficiency of cooling circulating water in cooling towers significantly affects the energy characteristics of all objects of the energy-generating and energy-consuming profile when there is a need to cool circulating water. One of the promising directions in solving this problem is the reconstruction of the existing, in most cases, outdated film and drip cooling towers. Losses of produced energy mainly occur due to inefficient heat and mass exchange caused by suboptimal dynamics of the interaction of hydraulic and aerodynamic flows in cooling tower heat exchangers. The consequence of this is the undercooling of the circulating water in the cooling tower and the insufficient vacuum level in the condenser, which generally affects the efficiency of the power unit and, as a result, there is an underproduction of electricity at the power plant. An increase in the temperature of the cooled water by 1 °C supplied to the condensers at the TPP reduces the vacuum in them by 0.5 %, which is equivalent to a decrease in the turbine power by 0.4%, and at the CHP leads to an increase of 1.2 - 2 g of conditional of fuel to produce 1 kWh of electricity. Study object – circulating water supply systems of power plants with tower cooling towers. Scope of research – methodical approaches to solving the problems of calculation substantiation of increasing the efficiency of the circulating water supply system with the tower cooling tower of the 1000 MW RAPP power unit under its operating conditions by means of hydrophobization of the inner surface of the cooling tower using mathematical modeling methods. Goal of research: development of a set of methods and approaches aimed at increasing the reliability and efficiency of operation of the circulating water supply system of power plants. Objectives of the study: – Analysis of features and problems of operation of each of the main elements of the circulating water supply system. Assessment of their impact on heat exchange processes in cooling towers and functioning of circulating systems in general. - Approbation of the method of intensification of heat exchange processes in the tower cooling tower. Carrying out computational and theoretical studies of the process of heat exchange between water droplets and air depending on the dispersion of the droplets. – Development of a method of protecting cooling towers from ice in the air inlet and outlet areas. - Analysis of the method of increasing the efficiency and reliability of the functioning of pumps of the recirculating water supply system. The task of the study is to determine the influence of the hydrophobicity of the inner surface of the cooling tower on the intensity of heat exchange. The presence of hydrophobicity on its inner surface makes it possible to increase the speed and flow of air as a result of reducing the coefficient of hydraulic friction (hydraulic losses) due to the reduction of the equivalent roughness of the surface and the modification of the wall boundary layer. In order to study the effect of hydrophobization of the inner surface of the cooling tower on its aerodynamic resistance, a study was carried out. At the first stage, it was established that the formation of hydrophobization is possible on samples of concrete grades typical for hydraulic structures. It is achieved by forming structured coatings on it. The results of the calculations showed that hydrophobization of the surface leads to an increase in the speed near this surface. This is caused by a change in the aerodynamic interaction of air with a solid surface. In general, a decrease in hydraulic losses was observed along the flow by 3.2% in the case of hydrophobization of the wall with a roughness of 25 mm and by 2.1% - with a roughness of 2.5 mm. In turn, the increase in air speed leads to the intensification of heat exchange processes in the cooling tower. An important factor affecting the intensity of heat exchange processes in the cooling tower is the degree of water dispersion. The large dispersion of water leads to a more significant and faster heating of the air, and, therefore, to a better cooling of the circulating water. The research results in general prove the intensification of heat exchange processes in cooling towers by increasing the dispersion of droplets, which is proposed to be achieved by changing the surface tension of the cooled water. A deeper cooling of the water is observed, which is very relevant even in the conditions of summer operation of cooling towers. Keywords: circulating water supply system, cooling tower, hydrophobization of the working surface.