Abstract: An improved heat exchanger for use in a gas compression/expansion apparatus. The heat exchanger comprises: a tube connected with a compression/expansion space of a compression/expansion cylinder of the apparatus; a central cylinder coaxially disposed in the tube such that a narrow gap for the working gas is formed only between the central cylinder and the tube. The heat exchanger may liberate heat from, or providing heat to, the compression/expansion cylinder through heat transfer between the working gas in the tube and an ambient medium surrounding said tube. The heat exchanger is capable to serve as a low/high temperature heat source for an external heat load.

Abstract: An apparatus is provided for compressing/expanding a refrigerant gas. The pistons 13 and 16 for use in the apparatus each have cavities formed in the pistons 13 and 16, and check valves 40 and 41 mounted on one end of the respective pistons for closing/opening the cavities so that the cavities are filled with the pressurized gas. The pistons also have a multiplicity of bores 42 and 43 communicating with the respective cavities for ejecting the high pressure gas into respective gaps between the pistons and cylinders accommodating the pistons. The ejected gas forms gas bearings for the pistons, keeping the pistons off the cylinders, thereby eliminating any mechanical friction between them and hence wear of the pistons and the cylinders. This helps significantly prolong life time of the apparatus.

Abstract: An apparatus for compressing/expanding a working gas (compression/expansion apparatus), including: a cylinder; a piston for compressing/expanding said working gas in a working space (front space) of said cylinder; a crank mechanism connected with a piston rod of said piston via an oil seal; a crank chamber for housing therein said crank mechanism and communicating with said cylinder via said oil seal, said apparatus comprising: a first tube allowing for a unidirectional flow of the working gas from said crank chamber to said front space in said cylinder, said first tube having therein an oil filter and a first check valve; and a second tube allowing for a unidirectional flow of the working gas from said front space to a second space (rear space) behind said piston in said cylinder, said second tube having therein a second check valve.