Non-invasive refrigerant leakage detection in receiver-equipped heat pumps: Leveraging vibration sensors

Conventional refrigerant leakage detection is limited by liquid-buffering effects, which delay detection until significant refrigerant loss has occurred. With annual leakage rates of 3.5 % to 3.8 % reported for domestic and non-domestic applications, substantial amounts of refrigerant are released into the environment, posing several risks: high-GWP refrigerants accelerate climate change, while low-GWP alternatives are flammable and hazardous if undetected. Undetected leakage also degrades system performance and causes avoidable energy consumption. This study investigates vibration-based refrigerant leakage detection as a cheap, non-invasive alternative. Experiments were conducted on a propane (R290) heat pump across a diverse range of operating points. Strong correlations between refrigerant charge and vibration characteristics were identified. The vibration-based approach detected leakage 600 g earlier than conventional methods, corresponding to 40 % of the design charge. This earlier detection mitigates ignition risks for flammable refrigerants and prevents efficiency losses before system performance degrades. The non-invasive nature and low-cost sensor make this approach promising for field implementation.