In this paper, the predicted performance of a shell-and-tube (1-2) evaporator installed in a vapour compression liquid chiller is analysed. The classical thermal design methods are applied to the evaporator performance with two HFC refrigerants, a pure fluid (R134a) and a zeotropic blend with an appreciable glide (R407C). From the experimental results obtained it is possible to discuss the validation of the simplificatory assumptions usually taken, evaluating the resulting error introduced due to the no consideration of pressure drops and temperature glide (in the case of zeotropic blends) at the evaporator. Concluding that is not possible to consider the behaviour of a zeotropic refrigerant as a pure refrigerant, rejecting the glide. Whereas the assumption of no pressure drops in evaporator, leads to an error of about 5% in cooling capacity calculation. Copyright (C) 2004 John Wiley Sons, Ltd.