A refrigeration circuit of an air-conditioning system for a motor vehicle

A refrigeration circuit (1) of an air-conditioning system for a motor vehicle (2) comprises: a first pipe (10); a second pipe (19); an expansion valve (12), which is provided with a pair of connection inlets (23, 26); and connection means (20) for connecting the first pipe (10) and the second pipe (19) to the respective inlets of the expansion valve (12), said connection means (20) comprising a flange (21) that is designed to be rigidly fixed to the component (12). The first pipe (10) is rigidly fixed to the flange and has an end portion (22) .mounted so that it passes through the flange so as to engage a respective inlet (23). The flange carries a pipe fitting (24), which comprises an end portion (25) designed to engage a respective inlet of the expansion valve (12) and, at an opposite end, a fast-coupling element (27) for engagement with a corresponding fast-coupling element (28) carried by the second pipe (19).