POSSIBILITIES OF STEAM-COMPRESSION HEAT AND COOLING SUPPLY BASED ON ENERGY FROM A BINARY LOW-TEMPERATURE -SOURCE IN CONDITIONS OF REGULATED HEAT STORAG

Abstract

The article is devoted to the development of opportunities and conceptual foundations for improving heat pump-based heating systems, including the development of new technical solutions for the rational combined use of binary low-temperature heat sources to provide energy-efficient heating and cooling for residential buildings during the relevant seasons.

The aim of this work is to improve the structural and functional design of the proposed heating and cooling supply system, providing a theoretical justification for the efficient utilisation of the energy potential of the binary heat exchange system utilising ground heat and ventilation air flows.

The paper establishes the relationship between the output parameters in the process of vapour-compression heat extraction from a low-temperature source in the evaporator, in accordance with the established relationship, as well as the conditions of its consumption by user subsystems downstream of the condenser under operational control conditions, forms the basis for a multi-factor assessment of the energy potential of a binary low-temperature source and the subsequent determination of the energy efficiency of the vapour compression heating and cooling system under consideration.

It has been established that in buildings with sufficient thermal energy resources in the ventilation air, the use of an improved heat pump system allows for a further extension of the period during which recovered heat is accumulated in the soil mass – at the beginning and end of the heating season. It has been demonstrated that the start of heat accumulation in the ground mass in buildings with a heat pump heating system can be achieved in regions of Ukraine where the outdoor air temperature equals its average value for the heating season.

The graphical relationships obtained show that an increase in the flow rate of the heat transfer medium through the ground heat exchanger, resulting from a reduction in the cross-sectional area of the heat exchanger used to cool the ventilation air, significantly reduces the system’s energy efficiency across the range of characteristic changes in circulating flow rates - through the evaporator 1 and condenser 3 GВ/GК over the entire considered range of outdoor air temperature variation (0...-18)°C. It has also been established that high energy efficiency in the conversion of energy flows in the analysed system can be achieved even under design conditions for the heating period (tзовн. = -18°C) with a ratio of circulating energy flow rates through the evaporator and the GВ/GК condenser > 1.8, provided that heat consumption is predominantly for heating and ventilation processes.

The performance characteristics of the improved system utilising integrated heat demonstrate enhanced efficiency in the conversion of energy flows for the heating and cooling of buildings, which indirectly justifies the feasibility of maximising the storage of excess heat from air flows in the ground, combined with the simultaneous cooling of buildings during the non-heating season. It follows that the use of integrated heat not only allows for the implementation of a combined or sequential process of general energy extraction, rationally coordinated with the optimal operational control regime of heat consumption systems, but also to ensure highly efficient accumulation of excess heat from a low-temperature source in the soil mass for its subsequent use during the heating season.

Conclusions. For the proposed vapour-compression heating and cooling system for buildings, a multifactorial relationship has been established for the actual conversion coefficient used to assess the efficiency of transforming low-grade heat from the ground and ventilation air. This allows for the analysis of the individual influence of parameters and operating modes of structural subsystems in the search for optimal conditions for utilising the energy of integrated flows for heating and cooling buildings during the relevant periods of the year. It has been established that high energy efficiency of the system is ensured under design and operating conditions during the heating season with a specific ratio of circulating energy carriers through the evaporator and condenser of the heat pump equipment.