Abstract: A heat exchanger, such as a condenser for a motor vehicle air conditioning installation, has a fluid manifold comprising a tubular wall having a number of through apertures in which the ends of fluid flow tubes of the heat exchanger are fitted. These apertures are aligned in the axial direction. In the region of the tubular wall lying between two consecutive ones of the said apertures, the tubular wall is formed with a concavity or a flat extending in the circumferential direction. The tubular wall can thus be immobilized against rotation by applying it against a flat surface so that the flow tubes can be correctly introduced into the apertures.