Abstract: A thermally insulating lining for the housing of the heater system ensures that on the outside of the heater system only low temperatures are reached which are not dangerous to operators in the vicinity of the engine. Combustion air duct means between an air preheater and a burner is formed by a large number of tubes arranged alongside each other in at least one row and along an inside wall of the combustion chamber. These tubes ensure that the flow state remains satisfactory and constant and they are substantially more durable than sheet metal duct means as used hitherto.

Abstract: A thermally insulating lining for the housing of a heater system for a Stirling, or hot air engine ensures that only safe temperature will be reached on the outside of the heater system. The insulating lining is arranged in two parts. An insulating wall is made up of individually adjacentely placed, replaceable insulating elements in the form of ceramic tiles, and/or ceramic tubes, and an intermediate space between the tiles and the outer wall. The intermediate space is separated, if desired, from the insulating elements by a ceramic paper. The intermediate space is packed with ceramic fiber batts, or loose, lump ceramic insulating material.