In situ measurement methods of air to air heat pump performance

• Heating power measurement methods for the air-to-air heat pump are validated.
• The methods are fully applicable in situ.
• The refrigerant flow rate is non-intrusively measured (maximum error of 4%).
• The refrigerant pressure is non-intrusively measured (maximum error of 2.7%).
• The air flow rate is determined via air velocity measurements (error of 4%).

There is no in situ reliable measurement method of air-to-air heat pump heating performances. This paper tests and validates two methods in laboratory and in steady-state conditions. The first method based on refrigerant fluid measurements determines the refrigerant flow rate by using the compressor thermal balance. In particular, the evaporation pressure is measured by a saturation temperature measurement and the compressor ambient heat losses are evaluated from the heat exchanges. The method uses only non-intrusive sensors, except for the condensation pressure sensor installed at the refrigerant charging plug. The second method based on air measurements determines the air flow rate via a multi-point velocity measurement. According to the experimental results, these methods are fully applicable on field with deviations of 4% and 10%, for the refrigerant method and the air method respectively, when compared to the “etalon” measurement.