Abstract: There is described a heat exchanger with tubes mounted in tubular bearing plates, each plate being provided with passage openings for said tubes, the cross-section area of said openings being larger than the outer cross-section of the tubes proper and a seal being provided between each tube and the tubular bearing plate, which comprises on either side of the medial plane of each plate, lips which bear resiliently and substantially tightly against the outer wall of the tube passing through the opening while retaining said tube some distance away from the edges bounding the opening.