Heat exchanger and turbine engine comprising such an exchanger

1. A heat exchanger for heat exchange between a first fluid and a second fluid, comprising a membrane separating the two fluids and a heat-conductive element in thermal contact with both the membrane and the first fluid, said heat-conductive element being movable between an active position and an inactive position such that the capacity of heat exchange with the first fluid is less in the inactive position than in the active position, wherein the heat-conductive element is in the form of a blade, the blade being rigidly connected to the membrane by a connecting edge, wherein said element is prestressed in the active position and the transition from the active position to the inactive position is achieved by deforming the membrane along the connecting edge connecting the blade to the membrane, the deformation of the membrane being achieved by applying a force that is parallel to the plane of the membrane, and comprising a piston by means of which the force is applied to the membrane.

2. The heat exchanger according to claim 1 , wherein in the active position, the blade is moved away from the membrane so as to be in contact with the first fluid by the two faces thereof.

3. The heat exchanger according to claim 2 , wherein in the inactive position the blade is arranged by one face close to the membrane.

4. The heat exchanger according to claim 2 , wherein in the active position the blade has a curved shape which moves away from the membrane at the connecting edge.

5. The heat exchanger according to claim 4 , wherein the connecting edge is rectilinear and the blade is curved around the connecting edge in the active position.

6. The heat exchanger according to claim 1 , wherein the deformation of the membrane is achieved by applying a compressive force.

7. A turboshaft engine comprising a heat exchanger according to claim 1 .