Development of a Falling Film Evaporator for Refrigerant Charge Reduction in Industrial 160°C High-Temperature Heat Pumps
Recently, driven by the need to achieve carbon neutrality, research on the electrification of industrial heat using high-temperature heat pumps has intensified. The Korea Institute of Energy Research has developed a hightemperature heat pump using the low-GWP refrigerant R1336mzz(Z). The system is capable of producing 350 kW of steam at 160 °C from an 80 °C heat source. The cycle is a two-stage compression system equipped with an economizer, and it employs a falling-film evaporator. While conventional flooded evaporators are filled entirely with refrigerant, the falling film configuration requires only a minimal amount of refrigerant to wet the tube surfaces. This design significantly reduces the refrigerant charge, making it advantageous when using expensive, low-GWP refrigerants. Although falling film evaporators present challenges in design and control, they offer benefits in reducing both system cost and environmental impact from refrigerant leakage or disposal. In this study, the falling film heat transfer coefficient was experimentally measured for enhanced heat transfer tubes such as E-tubes. Based on the results, a 200 kW-scale falling film evaporator was designed, fabricated, and evaluated through preliminary performance testing.