Because of technological, economic and environmental constraints, many refrigeration and air conditioning units are equipped with a simple air cooled condenser. Spraying the condenser seems to be an original solution to improve the energetic performances of such systems. To characterise this energetic benefit, a semi-local mathematical model was developed and applied to a refrigerating machine with and without spraying its air cooled condenser. It is found that, compared to a dry air cooled condenser, both the calorific capacity and machine COP increase by 13% and 55%, respectively. Furthermore, the model shows that a spray flow rate threshold occurs. It should not be exceeded to assure an effective and rational spray use. (c) 2007 Elsevier Ltd. All rights reserved.