Abstract
An integrated system of maintaining functioning of heat pump power supply based on prediction of a change of local water temperature was developed. A change in refrigerant vapor flow rate, the number of rotations of the electric motor of the compressor occurs at measuring of the refrigerant temperature at the outlet of the condenser, evaporation pressure, condensation pressure and voltage frequency. Comprehensive mathematic modeling of the heat pump system, based on the integrated system of maintaining soil heat discharge at the level of 8–10 °C was performed. Refrigerant flow rate, compressor motor power, voltage, voltage frequency, the number of rotations of electric motor of the compressor, coefficients of efficiency of a heat pump system for the established levels of functioning were determined. Parameters of convective heat exchange in the condenser, time constants and coefficients of the mathematical models of dynamics of a change in local water temperature, refrigerant flow rate, the number of rotations of the electric motor of the compressor were established. The functional estimation of a change in local water temperature in the range of 35–55 °C within the heating season, refrigerant vapor flow rate, the number of rotations of the electric motor of the compressor was obtained. Determining of the resulting functional information allows makes it possible to obtain the following advancing decisions: to maintain a change in evaporation pressure to change the refrigerant vapor flow rate for digital control; to maintain a change in evaporation pressure to change the refrigerant vapor flow rate and to change voltage frequency on a change of the number of rotations of the electric motor of the compressor for frequency control. That is why prediction of a change in local water temperature based on measurement of the refrigerant temperature at the outlet of the condenser was proposed. This estimation in the ratio with the measured evaporation pressure is included in analytical determining of refrigerant flow rate and the number of rotations of the electric motor of the compressor. Obtaining such estimation and measurement of frequency voltage makes it possible to make an advancing influence on coordination of functioning of the internal and external circuits of a heat pump system both at digital and frequency control.
Highlights
Under conditions for saving natural fuel and decreasing harmful emissions into the atmosphere, heat pump power supply with the use of renewable power sources is gaining further development [1,2,3]
For example, the heat pump, using fermented must as a low-potential energy source, is recommended in order to maintain the operation of the biogas plant as a part of a cogeneration power system
The outside air as a low-potential power source is available in heat pump power supply, but the change of air temperature in a wide range makes it difficult to maintain functioning of heat pump systems [1]
Summary
Under conditions for saving natural fuel and decreasing harmful emissions into the atmosphere, heat pump power supply with the use of renewable power sources is gaining further development [1,2,3]. Under condition of the change of parameters of renewable power sources, a relevant task regarding further development of technologies of heat pump power supply is to maintain efficiency of heat pump systems based on coordination of production and power flow rate in terms of energy saving. Maintaining the productivity of the heat pump system requires ensuring that changes in pressure evaporation in the evaporator should correspond to a change in pressure of refrigerant condensation in the condenser, which is difficult to execute based on measuring a change in refrigerant pressure in the evaporator For this purpose, it is necessary to predict a change in the temperature of local water when measuring the refrigerant temperature at the outlet of the condenser. Making advancing decisions on a change in refrigerant flow rate and the number of rotations of the motor of a compressor when measuring evaporation pressure, condensation pressure and voltage frequency will ensure a compliance of a change in evaporation pressure in the evaporator with a change in refrigerant condensation pressure in the condenser
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