An annular heat exchanger for a turbomachine, is intended, for example, to be supported by an annular ferrule of a housing of the turbomachine, and includes an annular one-piece part having a first fluid circuit having at least one first conduit and at least one second conduit extending in an annular manner. The first conduit and the second conduit lead into a first cavity formed on a first circumferential end of said annular part, and the heat exchanger includes detachable sealing means which are applied to said first end and designed to allow a flow of fluid from the second conduit into the first cavity then into the first conduit.