Abstract
The temperature of the water returned to the heating network from consumers largely determines the energy efficiency of the heat supply system. It depends on a number of parameters: outside air temperature, hot water supply heaters connection scheme, daily water consumption in the hot water supply system. The calculation of this temperature is usually performed numerically, which makes it difficult to control the modes of the heat supply system. From a practical point of view, a simpler toolkit is needed. In this paper, equations are proposed that allow directly determining the change in the heat output of heat exchangers depending on the outside air temperature and the temperature of the network water returned to the heating network. These equations are obtained on the basis of systematic modeling of variable operating modes of the heat supply system, using the method previously proposed by the author. The operating characteristics of the heat station are taken into account by the coefficients of the equations, for the determination of which the calculation formulas were obtained. The equations used are valid for substations with a two-stage mixed scheme of hot water supply heaters in the mode of maximum water consumption.
Highlights
Regulation of heat flows and flow rates of network water in the heat supply system is carried out using temperature graphics [1, 2]
Equations are proposed that allow directly determining the change in the heat output of heat exchangers depending on the outside air temperature and the temperature of the network water returned to the heating network
In fig. 1 shows the results of calculating the thermal power of the I stage of hot water supply system (HWS) heat exchanger according to the formula (7) in comparison with the calculation according to the method [9] for some variants of the calculated characteristics of the heat point operation shown in Fig. 2, 3
Summary
Regulation of heat flows and flow rates of network water in the heat supply system is carried out using temperature graphics [1, 2]. In order to be able to identify ineffective modes of joint operation of heating and hot water supply systems at the design stage and to clarify the area and performance of heat exchangers, it is necessary to calculate the water temperatures after each stage of heat exchangers and returned to the heat supply network, which determined the relevance of this work. The problems of determining the dependence of the parameters of heat supply systems with a given heat load on the temperature graph for regulating the supply of heat energy were raised in [3−7]. In [10], dependences are proposed for determining the outside air temperature and the return water temperature only at the break point of the heating temperature graph. The purpose of this work is to obtain equations for constructing temperature graphs over the entire range of outdoor temperatures during the heating period
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