The article analyzes various theoretical approaches to describing the processes of formation of scale layers on the working surfaces of heat exchangers. The main tasks include analyzing existing models of contamination of heat exchange channels, determining the main mechanism of salt deposition on the heating surface of plate heat exchangers of heat supply systems, determining the main factors that determine the intensity of salt deposition on the working plate in accordance with the dynamics of heat and hydraulic processes in heat exchange channels formed by corrugated plates, as well as forming trends for further research. The article presents the main results of research devoted to the study of contamination processes on heating surfaces. Inaccuracies in the proposed approaches to describing the nature of the formation of salt deposition layers are identified. By generalizing existing approaches to the mathematical description of pollution processes, the main assumptions are revealed when describing the processes of salt deposition on working plates. A hypothesis is proposed about the influence of the location of channels relative to the inlet pipe on the uniformity of the flow distribution between parallel channels in the device. There is a fairly large gap between the existing computational methods for modeling pollution processes and the actual distribution of scale layers during the operation of heat exchange equipment of heat supply systems
The relevance of the work of information and diagnostic systems in the field of monitoring of plate heat exchange equipment is considered. The reliability of the monitoring devices requires an accurate mathematical description of the thermo hydrodynamic processes in the heat exchange channels. The classical description of these processes implies a uniform distribution of the flow rate of the working medium along the length of the plate package, which in turn implies equal conditions for the formation of salt deposition products on the heating surfaces of the plate heat exchanger. The use of dependencies that take into account the equality of costs for a package of plates reduces the reliability of diagnostics of the efficiency of hot water devices of the plate type. Since the geometric space formed by the plates is represented by parallel channels connected by sections of transit collectors, the method of resistance characteristics is proposed as a method of hydraulic calculation of the distribution features of liquid flows through heat exchange channels. The dependence of the design features of the location of the interplate channels relative to the input of the coolant into the distribution manifold is revealed. It is found that, the flow rate of the circulating coolant is less in the channels most remote from the inlet pipe than in the nearest channels. The hypothesis of the influence of the relative position of the channels in relation to the inlet pipe is confirmed by numerical studies of the hydrodynamic regime of the plate heat exchanger.
The heating system is one of the life support systems. The discrepancy between the thermal (temperature) conditions of the living quarters is one of the most urgent complaints of residents of apartment blocks in most regions of the Russian Federation. The object of the study is a single-pipe water heating system of a 14-storey apartment block with an overhead distribution, for which the heat output is determined to compensate for heat losses under various initial conditions (outdoor air temperature and infiltration airflow rate). As a result of the calculation of the thermal conditions, deviations in the indoor air temperature of living quarters from the permissible range are determined. To eliminate violations of the microclimate parameters, this paper considers ways to increase the heat transfer of heating appliances by increasing the area of the heating appliance, as well as increasing the flow rate of the heat-transfer agent passing through the appliance. The results of the calculation of the thermal conditions showed the impossibility of eliminating the violation of the thermal conditions by these methods: depending on the temperature of the outdoor air in the living quarters, there is an excess or lack of heat. To eliminate the thermal and hydraulic disarrangement, a mechanical method for adjusting the heat transfer is proposed by switching off the sections of the heating appliance with an increased number of them. Taking into account the recommendations on the need to ensure that the length of the radiator corresponds to 50-70% of the length of the window opening, this method is functional for use.
The problem of energy performance takes a leading position in world politics today. In the territory of RF a number of regulatory documents have been developed and put in force in construction industry, regulating the activity of design and construction organizations in the field of energy performance, including energy loss issues. The article analyses current methodology of calculating infiltration heat loss in a multi-storey residential building with account of the number of storeys. Calculation results in graphic form have been shown for the determination of infiltration heat loss for a 14-storey typical residential building, and imperfection of the methodology has been shown on the basis of these results. A conclusion has been drawn that infiltration loss calculation using current methodology gives overestimated values leading to unreasonable excess consumption of heat energy, and consequently, to economic losses. The article will be useful for engineers of designers of heating systems, employees of management companies.
Equipping heat points with plate-type heat exchangers is an integral structural element of the 3rd generation heat and power network and a component of the reliability of the heat supply system as a whole. It has been established that the optimization calculations of heat exchangers of this type are difficult due to the absence of dependences on heat transfer and hydraulic resistance between the channels in the structural space of the heat exchanger.Purpose of research. To clarify the method of calculating plate heat exchangers, excluding the equality of thermal and hydraulic conditions from the generally accepted assumptions.Methods. The research methodology is based on the use of the law of conservation of mass in order to determine the temperature parameters of working fluids in each channel. The solution of this problem is proposed in the form of a system of equations, each of the equations of which characterizes the thermal balance of the channel under consideration. A computer model of the heat exchanger is constructed in order to conduct a numerical study of the thermal regime of the heat exchanger.Results. It is indicated that as an assumption in the well-known mathematical model for calculating the thermal regime of a plate-type heat exchanger, the condition of equal distribution of fluid flows between channels is accepted. This restriction leads to equalization of liquid temperatures in each channel. Taking into account the geometric arrangement of the channels, the excess of the final temperature of the heating and heated coolant in the first and last channels with respect to known data is up to 10%. The results of the study confirm the hypothesis of uneven heating of the coolant along the length of the plate package due to the uneven flow distribution between the channels.Conclusion. The results of analytical calculation and modeling in the SolidWorks environment of the temperature regime in the channels of a plate-type heat exchanger indicate a significant influence of the geometric arrangement on the thermal regime in the channels. The formulated provisions of the mathematical description of the unevenness of the thermal regime of heat exchange channels, taking into account the location of the plates, are recommended to be used when improving the design parameters of plate-type heat exchangers.
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