Ribachov S. Energy efficient air jet shielding of large industrial baths

Actuality of theme. The use of local exhaust ventilation systems continues to be the most reliable way to capture pollutants in the technological processes of various industries in Ukraine. The main purpose of the application of local exhaust ventilation systems is the effective capture of pollutants in the places of their formation. The efficiency of local exhausts and reducing the load of general ventilation can be achieved through the use of air screens. Most often, activated on-board suction pumps are used, which operate according to the "jet-suction" scheme, which are structurally located on one axis of the supply nozzle and slotted drain. According to this principle of operation, various activated extractors require air exchange in large volumes with significant energy consumption and at the same time with insufficiently high sanitary and hygienic indicators. In order to increase the efficiency of the local ventilation system, especially for tanks with large open surfaces, fundamentally new aerodynamic schemes are required, the feature of which is the formation of dynamic screens with inflow and rotation flows. Flows that form near the suction openings belong to the type of potential flows of an ideal fluid. Ideality is violated near hard surfaces, where a boundary layer is formed, in which the forces of density appear. In places with curvature of runoff lines, vortex circulation zones are formed, the elimination of which helps to get rid of the removal of pollutants into the environment. The defined boundaries of the detachment zones must be taken into account when designing on-board extractors. The most common designs of small baths for capturing gas and heat flows are local open-type extractors, mainly in the form of on-board, ring and single-board air-jet fences. Among the variants of activated suction pumps, the most common schemes are located on the same axis of the supply nozzle and the slotted drain above the liquid mirror. Industrial baths used for the treatment of large products larger than 3 m, traditional methods and design solutions to remove pests are not effective enough. The direction in which the means of increasing the speed of the tidal activating jet causes the formation of waves on its open surface, increasing heat and mass transfer and the transfer of harmful substances into the environment, so the topic is relevant. The purpose of the study is to scientifically substantiate the improvement and development of the theory of interaction of flat inflow-jet and rotating air flows in order to increase the efficiency of localization of harmful emissions from industrial baths using new solutions of dynamic air-jet barriers. Objectives of the study: - to analyze the existing systems of air-jet flows of onboard extractors, their design solutions and methods of research of turbulent transfer of momentum, energy and substances of activated extractors; - to develop the direction of increase of efficiency of work of system of local ventilation for industrial capacities with considerable surfaces of evaporation; - generalize and deepen the theory of aerodynamic and heat exchange processes on a physical-mathematical model with two-level air-jet shielding; - to perform experimental research on the model of an industrial bath with air-jet shielding to determine the patterns of the most effective capture of hazards by a two-level supply and exhaust system; - to develop a new energy-efficient design for the localization of harmful substances from industrial baths for various purposes; - to develop an engineering method for calculating the two-level air-jet flow for the open surface of industrial tanks. The object of research is a local ventilation system with a two-level air-jet screen of an industrial bath. The subject of research - the processes of movement of air jets for the localization of harmful substances from the open surfaces of industrial baths. Research methods. Physical and mathematical research methods are used in the work; methods of mathematical statistics and computational mathematics; methods of mathematical modeling and computer research; experimental researches in laboratory conditions of localization of harmful vapors from industrial baths. Scientific novelty of the obtained results: For the first time: - the efficiency of the dynamic relationship of the inflow-jet flow with the rotational flow is substantiated, the physical features of which determine the development of theoretical and experimental research in the direction that will ensure the maximum possible capture of harmful substances with minimal energy consumption; - the characteristics of the two-level air-jet screen are obtained, which confirms the adequacy of the developed physical and mathematical model; - the mathematical and geometrical characteristics of the two-level model of air-jet shielding with the ratios of the tidal county are specified