Abstract: An apparatus having a wall configured to serve as at least part of a chamber for containing a charge fluid is provided. The wall includes a heat exchanger portion integrally formed with the wall. The heat exchanger portion includes an array of conduits passing therethrough and providing fluid communication with outside of the heat exchange portion. The heat exchange portion is configured to contribute strength to the wall to provide containment of the charge fluid.

Abstract: A Stirling cycle machine has a piston (11) which reciprocates in a cylinder (12) and defines a hot chamber (23) between the piston (11) and end of cylinder (12). Heat exchange for the working fluid in the hot chamber (23) is effected while the working fluid is outside the hot chamber (23) in a flow path (24) communicating with that chamber (23). The piston (11) has a concave crown forming a surface (31) of the hot chamber (23). A seal is provided by a land (33) of larger diameter than the general diameter of the piston (11) formed around the upper periphery of the piston (11) and at least one annular groove (36) formed in the land (33) to disrupt free flow of working fluid along the gap between the land (33) and the cylinder wall.