A heat exchanger comprises a glass body having a first flat face and a second flat face on opposing ends, and defining a longitudinal axis therebetween. A plurality of holes in the glass body are elongated along the longitudinal axis by extending from said first flat face to said second flat face. The plurality of holes are configured to receive and direct a gas therethrough, to exchange heat between the gas and the glass body.

Embodiments are directed to a heat pump element comprising: a thin-film polymer or ceramic material within a range of 0.1 microns-100 microns thickness, and electrodes coupled to both sides of the thin-film material to form an electroded active thin-film material, wherein the thin-film material is separated by, and in intimate contact with, a heat transfer fluid in channels within a range of 10 microns-10 millimeters thickness, in which the fluid is capable of being translated back and forth through the element by an imposed pressure field.

According to an embodiment, a cryogenic regenerator material contains a silver oxide. A molar ratio of silver atoms to oxygen atoms contained in the cryogenic regenerator material: Ag/O is 1.0 or more and 4.0 or less. The cryogenic regenerator material contains at least one selected from AgO, Ag.sub.2O and Ag.sub.3O as the silver oxide.

A thermoacoustic energy conversion system includes a closed circumferential encasing filled with a working fluid through which an acoustic wave can propagate in a propagation direction in use of the system, and at least one assembly of two heat exchangers with a regenerator sandwiched there-between arranged in said encasing. The at least one assembly is arranged substantially parallel to a local longitudinal axis of the encasing.

Provided is a group of rare-earth regenerator material particles having an average particle size of 0.01 to 3 mm, wherein the proportion of particles having a ratio of a long diameter to a short diameter of 2 or less is 90% or more by number, and the proportion of particles having a depressed portion having a length of 1/10 to of a circumferential length on a particle surface is 30% or more by number. By forming the depressed portion on the surface of the regenerator material particles, it is possible to increase permeability of an operating medium gas and a contact surface area with the operating medium gas.

A heat exchanger includes a glass body having a first flat face and a second flat face on opposing ends, and defining a longitudinal axis therebetween. A plurality of holes in the glass body are elongated along the longitudinal axis by extending from said first flat face to said second flat face. The plurality of holes are configured to receive and direct a gas therethrough, to exchange heat between the gas and the glass body.

Provided is a group of rare-earth regenerator material particles having an average particle size of 0.01 to 3 mm, wherein the proportion of particles having a ratio of a long diameter to a short diameter of 2 or less is 90% or more by number, and the proportion of particles having a depressed portion having a length of 1/10 to of a circumferential length on a particle surface is 30% or more by number. By forming the depressed portion on the surface of the regenerator material particles, it is possible to increase permeability of an operating medium gas and a contact surface area with the operating medium gas.

An apparatus includes a heat exchanger configured to transfer heat to a fluid and to absorb heat from the fluid as the fluid flows between a warm end and a cold end of a cryocooler. The heat exchanger includes at least one section having a substrate of at least one allotropic form of carbon and a layer of nanoparticles on or over the substrate. The heat exchanger could include multiple sections, and each section could include one of multiple substrates and one of multiple layers of nanoparticles. The heat exchanger can further include pores through the multiple sections of the heat exchanger, where the pores are configured to allow the fluid to flow through the heat exchanger and to contact the substrates and the layers of nanoparticles. The nanoparticles could include at least one lanthanide element or alloy, and the substrate could include carbon nanotubes or graphene.

A two-stage pulse tube cryocooler, having compact size, less vibration and lower manufacturing cost is disclosed, in which at least a first stage of the cryocooler is coaxial, but in which first and second stages may be coaxial by locating circular regenerators of each stage inside of corresponding annular pulse tubes. A second stage circular regenerator is installed below a first stage regenerator. This configuration allows preassembly of the regenerator assembly and a base tube assembly in one or more stages. The pulse tube, which is annular, is coaxially formed with an outside surface of the assembled regenerator assembly and an inner surface of the outer tube of the base tube assembly after installation of the regenerator assembly.

A regenerator material for a cryocooler includes bismuth as a main component, and at most, 10% by weight of silver as an additive.