A cold storage material having a large thermal capacity in a ultra-low temperature range of 10 K or less and being highly durable against thermal shock and mechanical vibration. The cold storage material contains a rare earth oxysulfide ceramic represented by the general formula R.sub.2O.sub.2S in which R is one or more kinds of rare earth elements selected from La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Y, and Al.sub.2O.sub.3 having a specific surface area of 0.3 m.sup.2/g to 11 m.sup.2/g is added to the cold storage material.

The subject of this invention is a method of heat transfer in the embedded structure of a heat regenerator and the design thereof. It regards the related heat regenerators, which operate on the principle of the described method and enable a reduction of the pressure drop due to the fluid flow through the heat regenerator and consequently an increase of the power density. The concept of the operation of the heat regenerator by this invention, in which for the oscillation of the flow of the primary (first) fluid (P), electromechanical elements are applied. In the housing (1) between the elements (2) for the oscillation of the primary (first) fluid (P), there are positioned a primary hot heat exchanger (PT) and a primary cold heat exchanger (PH). In the direction of the arrow (A) the unidirectional flow of the secondary (second) fluid (S) flows from the heat sink into the primary cold heat exchanger (PH). In the direction of the arrow (B) the unidirectional flow of the secondary (second) fluid (S) exits from the primary cold heat exchanger (PH) and flows towards the heat source. Meanwhile, in the direction of the arrow (C), the unidirectional flow of the secondary (second) fluid S enters the primary hot heat exchanger (PT) and exits in the direction of the arrow (D) as the unidirectional flow of the secondary (second) fluid S of the primary hot heat exchanger (PT) towards the heat sink. Between both primary heat exchangers, (PT) and (PH), the porous regenerative material is positioned, which is part of the regenerator 4, with the hydraulically separated segments.

A gas refrigerating machine comprising: an input (2) for gas; a recuperator (10); a compressor (40) having a compressor input (41), the compressor input (41) being coupled to a first recuperator output (12); a heat exchanger (60); a turbine (70); and a gas output (5), wherein the gas refrigerating machine is configured as open system, and wherein the gas refrigerating machine is configured such that a working medium in at least one element of the group of elements comprising the recuperator (10), the compressor (40), the heat exchanger (60) and the turbine (70), is the gas, and wherein the input (2) is arranged at a first portion of a housing (100) of the gas refrigerating machine where the input (2) and the gas output (5) are configured, wherein the gas output (5) is arranged at a second portion of the housing (100) of the gas refrigerating machine, and wherein the first portion is arranged above the second portion in an operating direction in which the gas refrigerating machine is set up for an operation of the gas refrigerating machine.

A two-stage heat regenerating cryogenic refrigerator may include: a vacuum vessel; a first and second cylinder in the vessel; the second cylinder coaxially connected to the first cylinder; a 1.sup.st regenerator in the first cylinder and accommodating heat regenerating material (HRM) 1; and a second regenerator in the 2.sup.nd cylinder accommodating HRM 2, HRM 2 including HRM particles, each HRM particle including a metal element and a heat regenerating substance including an oxide or oxysulfide and having a maximum specific heat at ≤20 K of ≥0.3 J/cm.sup.3.Math.K; each HRM particle including a 1.sup.st and 2.sup.nd region, the 2.sup.nd region being closer to each HRM particle's outer edge than the 1.sup.st, and the 2.sup.nd region having a higher metal element concentration than the 1.sup.st, the 1.sup.st and 2.sup.nd region containing the heat regenerating substance.

A thermoacoustic stack includes an outer wall which is cylindrical and has a length extending between a first end and a second end. An internal wall structure is disposed inside the outer wall. The internal wall structure includes a plurality of spaced adjacent wall surfaces extending along the length of the outer wall to provide open flow passages between the spaced adjacent wall surfaces. A first cross member extends across the outer wall at the first end and is connected to the outer wall and the internal wall structure at the first end.

A cryocooler is disclosed. The cryocooler may include a magnetic spring, a regenerator/displacer, a working fluid, and a cold finger configured to contain the working fluid in a closed system, and to contain the regenerator/displacer that is configured to travel linearly within the cold finger. The magnetic spring may provide a force to cause the regenerator/displacer to return to a center position during thermal cycle operation of the cryocooler. Additional systems and related methods are also provided.

A cold storage material particle of an embodiment includes at least one first element selected from the group consisting of a rare earth element, silver (Ag), and copper (Cu) and a second element that is different from the first element and forms a multivalent metal ion in an aqueous solution, in which an atomic concentration of the second element is 0.001 atomic % or more and 60 atomic % or less, and a maximum value of volume specific heat at a temperature of 20K or less is 0.3 J/cm.sup.3.Math.K or more.

A chuck includes a chuck surface, a plurality of vacuum ports being distributed over the chuck surface. Each of the vacuum ports is open to a conduit that is connectable to a suction source that is operable to apply suction to that vacuum port. A flow restrictor is located within each conduit and is characterized by a flow resistance. The flow resistance of the flow restrictor in at least one conduit is less than the flow resistance of the flow restrictor in at least one other conduit.

A regenerator for a cryocooler includes a cell, a flow passage, a capillary and supporting elements. A cell wall encloses a cavity with sub-cavities. A connecting passage connects a first sub-cavity to a second sub-cavity. A first cell partition is disposed between the first and second sub-cavities. The flow passage is also disposed between the first and second sub-cavities. During operation of the regenerator, helium in the cavity functions as a heat-storing material, while helium that flows through the flow passage functions as a working gas. The capillary forms a pressure-equalizing opening in the cell wall and connects the helium that functions as the heat-storing material inside the cavity to the helium that functions as the working gas outside the cavity. The supporting elements are inside the first sub-cavity and separate the first cell partition from a second cell partition. The first and second cell partitions enclose the first sub-cavity.

A two-stage heat regenerating cryogenic refrigerator may include: a vacuum vessel; a first and second cylinder in the vessel; the second cylinder coaxially connected to the first cylinder; a first regenerator in the first cylinder, the first regenerator accommodating heat regenerating material (HRM) 1; and a second regenerator in the second cylinder accommodating HRM 2, HRM 2 including plural HRM particles, each HRM particle including a heat regenerating substance having a maximum value of specific heat at a temperature of 20 K or less of 0.3 J/cm3.Math.K or more and a metal element; each HRM particle including a first and second region, the second region being closer to each HRM particle's outer edge than the first, and the second region having a metal element higher concentration than the first, the first and second region containing the heat regenerating substance, and the heat regenerating substance contains an oxide or oxysulfide component.