District heating is one way to reduce the carbon footprint and improve the energy image. For the proper operation of district heating, it is necessary to cool the primary medium as much as possible with consumers, which is largely due to the preparation of hot sanitary water without accumulation. However, such a domestic hot water system is critically linked to the stability of temperature regulation. The physical variables in the primary part of district heating are, in addition to temperatures and flow, also pressures. And because the flow depends on the pressure difference, it affects the quality of regulation. That is why the doctoral dissertation initially examined the design of thermal substations and selected the basic control loop, which consists of a temperature sensor, electronic controller, electric motor drive, control valve, heat exchanger and with or without pressure differential regulator. All of these elements are dynamically characterized by both a mathematical model and that one is numerically solved, and an experimental model, that is compensated for the dynamic error of pressure difference, flow, and temperature sensor. A test rig with an associated measuring system for capturing and displaying measured values was also made, which enables experimental validation of numerical models of elements and, of course, the entire control system, where one can change the inlet temperature on the primary side. Thus, we can show the influence of the flow parameters on the secondary side, the pressure difference on the primary side and the supply temperature, and with the possibility of installing an additional differential pressure controller, one can also get the influence of pressure-temperature control coupling. Digital twin made on the basis of mathematical models and performed numerical experiments, allows numerical experimentation.
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