Abstract: A central space heating apparatus comprises a furnace having a chamber adapted to receive and contain a gas and a source a heat for heating the gas in the chamber, conduits connected in closed circuit to the furnace chamber for conducting the gas from the chamber and returning it to the chamber, helium gas filling the chamber and the conduit circuit under a pressure of from about 25 psig to about 100 psig at the operating temperature of the apparatus, a fan for circulating the helium gas through the conduit circuit and the furnace chamber, and a multiplicity of convector means connected in the conduit circuit for flow of the helium gas therethrough and installed at selected locations in the space to be heated for transferring heat from the flowing helium gas to the space.

Abstract: A very simple and inexpensive heat exchanger comprises a closed vessel having thermally conducting walls and helium gas within the vessel. The helium gas is a heat transfer medium between a source of heat or cold and the vessel walls and the vessel walls are a heat transfer medium between the helium gas and a fluid in contact with the walls to be heated or cooled.