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The cogeneration power plant (CPP) has two technological circuits: the circuit of electric energy generation and the circuit of thermal energy generation. Depending on the external consumer, the CPP may switch to partial load modes. The transition of the cogeneration unit to the modes of partial electrical loads leads to a change in technological parameters and dynamic characteristics. The purpose of the work is to perform modeling and analysis of the dynamic properties of the CPP thermal circuit during the electrical load change in the range of 100…50 %. A mathematical model consists of nine first order differential equations, which describe the dynamic properties of a gas-water surface heat utilizer, a water-water heater and hot water heater. The dynamics of heat exchangers are described by differential equations for the heating medium, for the heated medium, and for the metal of the wall of the heat exchanger tubes. The analysis of the dynamic characteristics of the thermal circuit elements showed their significant change while reducing the electrical load of the cogeneration power plant by up to 50 %. With the decrease of electrical load on all channels, there is an increase in the values of the constant time and delay time and the decrease in the values of the transmission coefficients. This indicates an increase in inertia in the circuit and a decrease in the influence on the parameters of disturbing influences. The lower the electrical load, the less effective the regulating effect on the adjustable parameter. [ABSTRACT FROM AUTHOR]

The paper deals with the basic scheme of the combined heat pump system of low-temperature water heating -- "floor panel heating system" and ventilation. We present the results of energy efficiency analysis of this system both taking into account and disregarding the energy expenses for air transportation through the heat pump evaporator. We show that the energy efficiency of the combined heat pump heating system and ventilation is higher than the efficiency of the corresponding heating system (without ventilation) with the ratio of heat flows for heating and ventilation m > 1, and it grows with the increasing m value. [ABSTRACT FROM AUTHOR]