Abstract: A heat exchanger comprises an array of tubes, a perforated end plate defining a plurality of holes, a support sleeve in each hole for holding an end of a respective tube in a respective hole, each support sleeve fitting the respective hole, the exterior and interior surface of the support sleeve each defining a groove, a toroidal gasket in each groove, and a clamping portion on each support sleeve. The clamping portion is affixed to the outer face of the perforated end plate and has an end projecting beyond the end of the respective tube held in the support sleeve, and has an inwardly extending abutment at the projecting end for limiting any movement of the tube beyond the abutment.