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The refrigerant R22 has great damage to the ozone layer. R404A is currently the mainstream environmentally friendly refrigerant approved and recommended by most countries in the world, and has zero damage to the ozone layer. Based on this, the performance of heat exchangers of R22 and R404A with different inlet qualities with the circuit number were simulated and compared by EVAP-COND software. The results show that the capacity of the evaporator with R404A was greater than that with R22. Moreover, the difference in the capacity of the evaporator with R410A and R22 drops first, and then it rises. The flow path with the number of circuits 2 had the largest heat exchange rate. The heat exchange rates of R22 and R404A are 4.40kW and 4.50kW, respectively. The heat exchange amount of R404A was larger than that of R22, and the difference in heat exchange amount decreases first and then increases with the increase of branches, and the maximum difference was 4.41%. R404A can be used as a substitute for R22 and had a higher heat exchange rate. It is more environmentally friendly and saves energy.

With the continuous development of industrial technology, the safety and efficiency of thermal equipment work in related industries and industrial fields are facing many problems. First, with the improvement of integrated level, the size of electronic components is getting smaller and smaller, and the heat load per unit area is increasing, which makes the traditional heat dissipation method difficult to meet the requirements; second, with the increase of energy-saving pressure, the temperature difference of low-temperature waste heat recovery is reduced, and the traditional heat exchange equipment is difficult to meet the working requirements. The pulsating heat pipe has the characteristics of small volume and excellent heat transfer performance. In view of the heat transfer performance of the pulsating heat pipe, we designed the gas-liquid pulsating heat pipe heat exchanger and studied its heat transfer performance, which has been verified to be effective.

One of the important issues is the assessment of the strength of the elements of hydraulic structures, spillway structures, reservoirs, and hydraulic complexes, the determination of the connection mode of the basins, and the reduction of kinetic energy in the reinforced fields of the downstream pool. In this regard, it is especially important to determine the hydrodynamic characteristics of the flow of water moving in the apron and risberme area, which provides the stability of the downstream pool - the areas that indicate the distribution and direction of velocity and pressure.

The aim of this study was to determine favorable operation conditions for ceiling panels containing phase change materials (PCM) for cooling applications in office rooms. A recently renovated room in the Technical University of Denmark was used to have realistic boundary conditions. Using TRNSYS 17, the performance of the PCM panels during the cooling season in passive operation, discharge by air, and discharge by water circulation were investigated. A set of simulations were performed during a representative week in the cooling period. The room was simulated with no climatic systems, PCM without active discharge, ventilation during occupied hours only, and PCM with ventilation during occupied hours. Afterwards, two discharge methods were investigated, night ventilation at different flow rates and water circulation in pipes embedded in the panels. A parametric analysis was performed to identify the influence of operation factors in the thermal environment of the room. The parameters studied were the water flow rate, supply water temperature and circulation schedule as well as the conductivity of the PCM. After selecting different operating conditions of the water discharge, simulations were performed from May to October to observe the performance of the selected operation conditions. The results show that the PCM is more effective to provide adequate indoor thermal conditions if it is discharged actively by means of water. The parameters that affect the thermal indoor environment the most are the water circulation schedule, the water supply temperature, and the PCM thermal conductivity. The water flow rate did not have a significant influence. The study shows the importance of selecting an appropriate operation and control strategy for the PCM system. The process used in the study can be potentially used as a procedure for the design of similar climatic systems to determine if active discharge of the PCM is needed and if yes, which discharge method is needed.

At metallurgical enterprises, slab transfer devices are widely used, the principle of operation of which is to lift slabs in the steel casting area and transport them to the storage area. The article considers the existing control system of the slab transfer device. At the moment, the mechanism has a DC motor controlled by a thyristor Converter. This system is difficult to maintain and has a large size. As an upgrade, the installation of an asynchronous motor with a frequency Converter is proposed. In the Matlab environment, mathematical models of single-circuit and double-circuit DC motor control systems and a model of asynchronous motor with a short-circuited rotor have been developed. A vector control system is used as an AC motor control system. As a result of simulation performed analysis of the characteristics. As an optimization of the system with vector control, in order to reduce dynamic loads on the turntable, it is proposed to introduce an intensity setter into the system, the use of which provides the necessary restriction of accelerations and jerks, reduces shock loads on the mechanical components of the electric drive, including a reduction in the load on the turntable when lowering the slab.

In recent years, the concept of sponge city has been applied in different places. There are also many experts on sponge cities who believe that to build a sponge city in the city, we need to improve and optimize the rainwater system. In this way, we can better explore the way to plan and design the stormwater system when conducting the construction of the sponge city. This paper will also analyze and study the characteristics and functions of rainwater system planning in the construction of sponge city, and also point out the difficulties of the city in the construction of sponge city. Nowadays, the city must make clear its optimization direction, methods and principles in the transformation of rainwater system, and the optimization and transformation of rainwater system can also improve the construction progress of sponge city faster. The optimization and application of rainwater system can lay a solid foundation for the construction of sponge city.

The object of the study is the water supply and sanitation system of an industrial enterprise. Currently, many enterprises do not use the treated industrial waste water in the water supply cycle. Therefore, the use of treated wastewater is of practical importance. The scheme of thermal treatment of waste water for obtaining pure condensate by evaporation is proposed. The main results of the study are the technical solution for the development of the enterprise's wastewater treatment complex. Pure condensate is obtained in an instant boiling evaporator. The research method is based on the calculation of energy costs in wastewater treatment for different types of waste water. The results of the study allow us to determine the optimal set of energy equipment for obtaining pure condensate and its further use. The specific practical significance lies in the development of a technical solution that helps the treatment of wastewater and the reduction of emissions into the water basin.

The paper the one of current problem of transition of district heating systems (DHS) to the new type of intelligent and integrated systems. This problem is related to the implementation the technology of prosumer, which allows regulating its own heat loading ensuring the most efficiency heating modes by using its own heat sources (HS) and/or heat storages. The statement of considered problem is formulated as the search of the optimal loading relation between the own distributed HS of prosumer and the district HS of DHS, based on the criterion of minimal cost on heating to prosumer for each calculated time interval during the heating period. The practical researches based on calculating experiment using the test scheme of DHS is provided. The results of calculations are presented as diagram of prosumer’s and district HS loading for the considered DHS scheme, as well as the economic benefit when using distributed generation of prosumers.