Experimental Research on a Heat Pump Applying a Ball-Circulating Type Automatic Fouling Cleaning System for Fish Farms

In this research, automatic fouling cleaning systems that clean and prevent the deposit of fouling by regularly circulating sponge or ceramic balls are proposed. Characteristics of the finned and twisted inner tubes of the double pipe heat exchanger for the heat pump unit are also compared. Lastly, the 50RT-scale field test of the automatic fouling cleaning system integrated with the heat pump system was conducted by targeting temperature control of fish farms. The finned inner tube types presented a higher heat transfer rate than that of the twisted inner tube types. For the finned tube types, the refrigerant supply from the tangential direction was more advantageous due to the uniform distribution of refrigerant into 16 channels. The twisted tubes showed a higher water pressure drop than the finned inner tubes. An obvious increase in the fouling factor according to the operating hours was observed; however, it could be successfully decreased by operating the fouling cleaning system for 24 h. The overall heat transfer coefficient could be recovered from 5.87 kW/K to 24.05 kW/K, which is about 92% of the initial value. In short, the automatic fouling cleaning system can successfully prevent performance degradation of heat pump system due to fouling.