Development of industrial hot water heat pump for mechanical parts cleaning process
In general, in the cleaning process for mechanical parts, metal fragments and lubricating oil are adhered to the parts in the previous process, so they are showered with a cleaning solution at 60°C. A boiler or electric heater is used as a heat source to warm the cleaning solution. If a hot water heat pump with a plate heat exchanger is introduced into this process, indirect heat exchange between the cleaning solution and hot water is required, which reduces system efficiency. In addition, periodic cleaning and maintenance of the heat exchanger is mandatory, which has been an obstacle to its introduction. In this study, a hot water heat pump with a rated heating capacity of 13 kW and a rated COP of 3.1 was developed using a new coil-type heat exchanger that enables direct heat exchange between the refrigerant and the cleaning liquid, significantly improving system efficiency and ease of maintenance. Assuming a standard cleaning process, the annual primary energy consumption of the developed heat pump can be reduced by 67% compared to an electric heater, 60% compared to a gas boiler, and 11% compared to a conventional indirect heating heat pump system. Furthermore, the system has the lowest CO2 emissions and running costs, is highly energy efficient, environmentally friendly, and economical. This paper describes the features and performance of this heat pump, introduces the developed heat pump into the cleaning process of mechanical parts, and reports on the system performance and the effect of dirt and cleaning of the heat exchanger on the performance.