Electric space heater employing a vaporizable heat exchange fluid

An electric space heater comprising a housing having:

• a substantially straight and uniform diameter main tube adapted to be disposed substantially horizontally,
• a substantially straight and uniform diameter secondary tube arranged to be above and in substantially parallel relationship with said main tube,
• conduit pipe means extending upwardly from the main tube to the secondary tube and interconnecting the tubes to define a closed space within the tubes and conduit pipe means;
• an elongated heat source extending axially through only the main tube, said heat source including an elongated protective pipe extending through the length of the main tube and having its end portions sealed respectively in end walls of the main tube and an electric resistance heating element extending the entire length of the protective pipe and having its ends projecting therefrom for connection to a power source, the secondary tube being empty;
• a vaporizable working fluid in the space within the main tube and being in liquid phase at the operating temperature of the apparatus so as to entirely immerse only the heat source in the fluid, but having the remainder of the closed space empty for expansion of vaporized working fluid thereunto;
• said main and secondary tubes being provided respectively with radiation fins evenly spaced along the length thereof, with the fins on the secondary tube being spaced at a wider clearance than those on the main tube;
• and
• said working fluid in the main tube absorbing the heat from the heat source to vaporize and expand in all regions of said closed space and condensing on the inner surface forming the closed space so as to give up its latent heat of vaporization to the surrounding air and then returning through the conduit pipe means to the main tube.