Heat Supply System Using Transformer Waste Heat

Abstract

The task is to use the waste heat of powerful electric transformers for hot water supply in residential and industrial buildings. The high heat of transformers is of low-temperature and therefore requires heaters. The thermal scheme of the hot water supply system with electric transformer and heater - heat pump and electric heater is considered. In the scheme, the heat from the transformer is transmitted to oil, from oil to the heat in the oil-heat exchanger is transferred to water, from water to the evaporator of the heat pump installation (HPI) is transferred to the freon and from the freon to the water of the hot water system is transmitted in the condenser of the HPI. After the HPI condenser, water is heated in the electric heater and is supplied to the consumer. The thermal capacity of the transformer and the temperature of hot water supplied to the consumer are known. The temperature of the water supplied to the heater after the HPI condenser is unknown. According to the criterion of quality of variants with different water temperatures, the total cost of equipment of the scheme of hot water supply system is accepted. The method of determination of the total reduced costs of the hot water supply system with regeneration of waste heat of the transformer is offered. Costs for the hot water supply system are defined as the sum of the costs of heat exchangers, pumps and their consumed electricity, the costs of HPI and consumed electricity of its compressor, the cost of the heater and the consumption of electricity. A computer program for determining the total reduced costs of a hot water supply system with regeneration of the transformer discharge heat has been developed. The results of calculations of the total reduced costs for hot water system options are presented. The variants without HPI with heating of water in the electric heater, with heating of water in HPI and heating it in the electric heater are investigated. The HPI thermal capacities and the compressor drive electrical capacities at different water temperatures from the condensers were determined using the well-known FKW Cycle program. The comparative analysis of the obtained results is performed and it is shown that the cumulative cited costs for the variant of HPI are lower than the cumulative cited costs of the variant without HPI, that the nature of change of the cumulative reduced costs when the temperature of the heated in HPI of water is the same for a wide range of specific costs of HPI and electricity. The lowest total costs shown correspond to the lowest water heating in the HPI and, accordingly, the highest heating in the electric heater.