Abstract: A heating system for supplying thermal energy to a heater of a machine such as a hot gas engine, this system using a heat-transporting medium which flows within a closed space between a heat-receiving portion to a heat-discharging portion. Thermal energy is supplied from a heat source through a wall in the heat-receiving portion with the transporting medium changing from the liquid phase to the-vapor phase, and the absorbed thermal energy is transferred to the heater in the heat-discharging portion by changing from the vapor phase into the liquid phase. The wall parts of the heat-receiving portion, through which thermal energy can be supplied from the heat source to the transporting medium, comprise on their surface contacting this medium of a layer of a porous material having a capillary structure whereby liquid-phase medium is distributed on said walls.

Abstract: A hot-gas engine including a heater and a source of heat in combination with a switching device for conveying heat from the heat source to heater, the device including a pair of spaced heat pipes with third intermediate heat pipe and means for introducing inert gas into said third heat pipe and removing said gas to vary the vaporization point therein and the rate of heat transfer therethrough.