Development of Economical Viable Vapour Compression Refrigeration Cycle based Domestic Water Heater

Abstract

India's present electricity production is above 164000 MW while the per capita power consumption stood at 612 kWh. Total demand for electricity in India is expected to cross 950,000 MW by 2030 [1]. With fast depleting fuel resources, it is necessary to explore other sources of energy. At the same time, it is also necessary to use the available energy judiciously. It is correctly said that saving electricity mean electricity produced. This paper deals with the development of an economically viable Domestic Water Heater based on Vapour Compression Refrigeration (VCR) cycle and to demonstrate the energy saving potential compared to resistance heating. It is well known fact that mechanical heat pump has thermodynamic advantage over electric heating since useful heat available for heating is always greater than work consumed for pumping the heat. While for the electric heaters, the heat available is always less than or equal to work consumed. Therefore it is economically beneficial to use heat rejected in the condenser of VCR system. A domestic water heater (DWH) of 1 kW heating capacity has been designed, fabricated and tested. For the 1 kW heating capacity, evaporator duty and hence compressor capacity has been evaluated from VCR cycle calculations. Various designs of evaporator and condenser have been reviewed. Helical coil shaped evaporator directly exchanging heat with atmospheric air has been designed. Since it was intended to develop storage type water heater, helical coil shaped condenser brazed outside the water storage tank has been designed. Since the capacity of the VCR system is less, capillary tube has been used as an expansion device which has been sized for the 50 ̊C condensing temperature and 5 ̊C evaporating temperature. The VCR cycle based DWH has been tested extensively and heating capacity of about 950 W has been obtained. When compared with conventional storage water heater using electric resistance heater the simple payback period of 2.5 years has been calculated. Reduction in CO2 emission due to lesser power consumption of the DWH is calculated to be 1219 kg per year. Thus VCR cycle based DWH is economically viable and environment friendly compare to conventional electric resistance heater based DWH.