Improved energy performance of a refrigerating machine using water spray upstream of the condenser

• Spray application upstream from a condenser is studied.
• An instrumented heat pump is used for the performance evaluation.
• A complete model for the multi-pass condenser is validated.
• Experimental and numerical results confirm a COP increase.
• Water droplet evaporation increases the heat exchange at the condenser.

An experimental and numerical study has been carried out on the improvement of the energy performance of a refrigerating machine using a water spray upstream of the condenser. The experimental setup is based on a reversible heat pump used in cooling mode. The spray has been simply added upstream from the heat pump in order to investigate the possible performance improvements on a real machine, leaving its own control system free to adapt itself. Condensation temperature and pressure data have been measured on the refrigerating fluid side, while temperature and humidity have been measured on the air upstream and downstream the condenser. A complete model has been developed, combining a thermodynamic model for the system and heat transfer models on the air and refrigerating fluid sides. Comparisons have been carried out. Results show that water spraying upstream of the condenser may increase the global COP of the system (refrigerating machine plus spraying system) up to 28.9% for relatively hot and dry air conditions (relative humidity 19,7% and temperature 308 K).