Abstract: A heat source includes a cartridge which contains a first chemical having properties for maintaining a liquid state below its particular melting point. A second chemical, which can be introduced through a valve into the cartridge, triggers the crystallization of the first chemical; this crystallization occurs at the substantially constant temperatures of the particular melting point. The first chemical can be recycled by heating the cartridge above its melting point and subsequently cooling the first chemical below its melting point while maintaining its liquid state. A particularly desirable melting point for the first chemical is provided by a eutectic compound which may include sodium thiosulfate pentahydrate and sodium acetate trihydrate. The heat source is particularly adapted to be disposed in a transportable apparatus for heating a baby even during transport.

Abstract: In a system for converting heat energy to mechanical energy, a working fluid is vaporized and then permitted to expand in an expander. The vaporized working fluid is introduced to a condenser including a container and a conduit for guiding the working fluid through the container. A condensing medium in a generally solid state is disposed in the container in contact with the conduit to absorb heat from and thereby condense the working fluid. In response to the absorbed heat, the condensing medium liquifies, in which state it can be supercooled at ambient temperatures and stored for an extended period of time. The supercooled condensing medium can be triggered at a predetermined time to release the absorbed heat to the system. The provision of a super-coolable condensing medium in the condenser minimizes the heat loss thus providing a significant increase in the overall efficiency of the system.