FGaz, leackage detection, data based models, condensing units, subcooling
The European regulation has set a series of limitation to reach the objective of reducing the high Global Warming Potential (GWP) gases emissions. Among these limits, the ban of Hydrofluorocarbons (HFC) refrigerants having a GWP higher than 2500 starting 2020 and a stringent leakage control on refrigeration equipments. Many continuous leakage detection technologies exist but they are not applicable in many cases such as open space or outside equipments. A software based leak detection technique may be interesting in these cases. This technique is based on machine data monitoring and data derived models. In order to be more precise and avoid outlier alarms, the sensitivity of usually measured variables such as temperatures and pressures should be correlated to refrigerant charge level. In this paper, an experimental campaign is performed on a condensing unit under a controlled leakage. The tested condensing unit having a piston compressor of 16 m3/h is cooling a secondary glycol loop. It has a thermostatic expansion device and a liquid receiver. The condensing unit is first charged in a way to overfill the liquid receiver. A leakage is simulated by connecting the receiver’s outlet to a micro valve that delivers the refrigerant to an external empty cylinder continuously weighted. Different usually measured variables are recorded. These are pressures and inlet and outlet temperatures of condenser and suction temperature. Compressor electricity consumption and the produced cooling capacity are also monitored. Results show the sensitivity of the high pressure and the subcooling to the charge level until the liquid receiver starts to be partially filled. The cooling capacity is also impacted.