Use of Heat Discharge of Refrigeration Installation and Electric Transformers of Hypermarket

Abstract

A refrigeration unit is installed in the hypermarket, and power transformers operate at the electrical substation of the hypermarket. In the refrigeration unit, the heat from the products is fed to the refrigerant - ammonia or freon, and from it to the water. This water goes to the cooling tower ― a device for cooling water, which is installed on the roof of the hypermarket. Water in the cooling tower housing is distributed through pipes with holes through which jets flow down. Atmospheric air moves towards the jets, which is removed from the body of the cooling tower by a fan. Electrical processes in transformers are accompanied by their heating. Transformers are cooled by oil radiators, the heat of which is also dissipated to the ambient air. It is advisable to use waste heat from the refrigeration unit and transformers in the heat supply system of the hypermarket. However, this heat is low temperature, 20…30 °C. It can be heated to 50…60 °C in a heat pump, gas and electric heaters. According to the principle of operation, the heat pump is the same refrigeration unit. The difference is that the heat of condensation of freon from the outer wall of the home refrigerator or from the water cooler of the hypermarket refrigerator is discharged into the atmosphere, and in the heat pump this heat in the heat exchanger is transferred to the heating circuit water. The condensing temperature of the refrigerant in the heat pump unit (HPU) increases with increasing compressor pressure. If necessary, the heating water is still heated in the heater. Heat pumps are quite expensive. The aim of the work is to determine the payback period of heat pump installations for variants of heat supply schemes with the lowest total discounted costs. The electric power of the HPU compressor drives was determined using the well-known FKW Cycle program. Calculations of HPU on ammonia and CFCs showed the feasibility of HPU operation on the same refrigerant as in the refrigeration unit of the hypermarket ― ammonia. The capacities of the HPU compressor at different ammonia condensing temperatures at the specified thermal capacities of the HPU and the specified maximum total thermal capacity of the HPU and the heater were determined. Low-capacity gas boilers existing at the enterprise are accepted as heaters. Calculated total discounted costs for options with and without heater. According to this indicator, the option without a heater is preferred. Payback periods and other technical and economic indicators of the scheme of regeneration of waste heat of the refrigeration unit with the help of HPU are determined. In the part of research of use of heat of radiators of power transformers for district heating of substation premises the existing variant with heating of water in an electric heater and variants with heating of water in HPU and its heating in an electric heater is calculated. A comparative analysis of the obtained results is performed and it is shown that the total discounted costs for the option with HPU are less than the total discounted costs for the option without HPU, that the nature of changes in total discounted costs with changes in temperature of water heated in HPU is the same. The lowest total discounted costs correspond to the lowest water heating in the HPU and, accordingly, the highest heating in the electric heater. The main results of the work are as follows. At specific prices of electricity 3 UAH/kWh, gas ― 11.8 UAH/m³, heat pump installation ― 6000 UAH/kW static and dynamic payback periods of HPU for regeneration of waste heat of the refrigeration unit are 2.83 and 3.5 years, respectively. In the scheme of use of waste heat of transformers with HPU and electric heater the minimum heating of water in HPU and the maximum heating in the electric heater are expedient. The payback period of the circuit with HPU for regeneration of waste heat of the transformer is less than one year.