In this work, an experimental model of a circuit diagram with pulsating circulation of a liquid coolant in a heated circuit of a plate heat exchanger was assembled and tested. As a result of hydraulic and energy calculations of the circuit, the optimal parameters for flow, pressure, and temperature of the coolant were selected at maximum efficiency of the impact unit. It has been established that with an increase in the operating frequency of the impact unit, the heat transfer coefficient of the heat exchanger first decreases and reaches a minimum of 452.47 W/(m2*0C) at a frequency of 0.5 Hz, and then begins to increase and reaches a maximum of 482.31 W/(m2* 0C) at a frequency of 2 Hz, after which it gradually decreases. It has also been experimentally established that the temperature at the outlet of the heat exchanger of the heated circuit increases with increasing frequency of the shock unit and reaches a maximum at a frequency of 2 Hz, after which it begins to gradually decrease. It has been established that the change in temperature at the outlet of the heat exchanger of the heated circuit exceeds the change in temperature at the outlet of the heat exchanger of the heating circuit at operating frequencies above 1 Hz, which is due to the stronger influence of cavitation at these frequencies.

Keywords: heat exchanger, heat transfer coefficient, impact unit, frequency, heat transfer

The paper proposes a model of a circuit with a pulsating circulation of a liquid coolant for cooling an oil transformer and investigates the dependence of the heat transfer coefficient on the frequency of the liquid pulsation in the heated circuit. As a result of the experiments, it was found that the pressure amplitude remains practically unchanged up to a frequency of 0.45 Hz, then sharply decreases and at a frequency of 0.9 Hz it is approximately 12.5 kPa. It was also found that in the heated circuit (circuit 1) the temperature difference exceeds the temperature difference in the heating circuit (circuit 2), which is due to the fact that the fluid flow rate in the heating circuit exceeds the flow rate in the heated circuit. The theoretical calculation carried out showed that in the proposed model the heat transfer coefficient reaches its maximum at a pulsation frequency of 0.6 Hz and is 133.675 W/m2K.

Keywords: energy efficiency, oil transformer, heat recovery, heat exchanger, transformer cooling

The paper proposes and calculates a scheme of a two-stage gas turbine plant using carbon dioxide as a working fluid in the second stage and using heating of the CO2 circuit, as well as heating water sent for heating. As a result, the following were calculated: for the first stage turbine: parameters of fuel combustion products; air compressor parameters; fuel compressor parameters; combustion chamber parameters for a real Brayton cycle; Efficiency of the first stage turbine; for the second stage of the gas turbine: a schematic diagram was drawn up using liquid CO2 as a working fluid; calculation of CO2 parameters at key points of the Brayton cycle; the efficiency of the turbine of the second stage is calculated.

Keywords: energy efficiency, gas turbine plant, carbon dioxide, pressure, pressure ratio, combustion chamber, recuperator

In this work, an experimental model of pulsed regeneration of a sodium-cationite filter was developed. This model can work both with a stationary water flow and with a pulsed one. It is established that at a high pulse frequency, the water flow tends to a stationary one. It is found that at any frequency in a pulsed water flow, hydraulic losses will always be less than at a stationary one. At the same time, the smallest hydraulic losses are observed at a low pulse frequency of 1 Hz, and there is also a decrease in hydraulic losses in the range from 4 to 6 Hz.. It is established that at the same concentration of salt solution, the hardness of the treated water is lower in the pulsed mode than in the stationary mode. At the same time, the lowest stiffness is achieved at a low pulse frequency of 1 Hz. It is established that the time spent on regeneration at an equal inlet pressure will be longer with a pulsed water flow than with a stationary one at any frequency of pulsed regeneration.

Keywords: cationite, water treatment, sodium-cationite filter, stationary water flow, pulse water flow, frequency, salt solution, parallel-flow regeneration, hydraulic losses, pressure