THE ENERGY EFFICIENCY OF THE HEAT PUMP RECUPERATIVE SYSTEM OF WATER HEATING AND VENTILATION USING THE HEAT OF THE SOIL AND VENTILATION EMISSIONS

Abstract

The combined heat pump-recuperative scheme of water heating and ventilation using ground heat and ventilation emissions is considered. A thermodynamic analysis of the heat supply scheme was completed. Based on this analysis, the temperature parameters at the nodal points of the system, the unit cost of external energy per unit of heat produced at the entrance to the object of heating and ventilation and the proportion of heat load covered by the soil heat exchanger are determined. The graphical dependences of the efficiency criteria on the quantities that determine the conditions of operation of the circuit are constructed and analysed. A comparison of the obtained energy efficiency criteria with the corresponding values for a traditional heat pump system with the ground heat exchanger was completed. The introduction of the proposed combined scheme increases the air temperature supplied to the heater of the ventilation system. This, in turn, reduces the capacity of the heat exchangers of the ventilation system and improves the conditions of their operation, reducing the risk of icing over ducts. The proposed heat pump scheme leads to a decrease in specific energy consumption per unit of heat to meet the needs of water heating and ventilation of the premises. The energy efficiency of the heat supply system increases with the increase of both the recuperation coefficient of the recuperator and the relative heat consumption for ventilation compared with the heat consumption for heating. Reducing the total energy consumption for the heating and ventilation system results not only in increasing the energy efficiency of the heat supply system, but also leads to a decrease in capital costs for the construction of a heat pump unit (in particular, for the construction of a pre-heavily ground heat exchanger) in proportion to the reduction of its required capacity.