Abstract: A precooled vapor-liquid refrigeration cycle includes a basic vapor-liquid cycle and an auxiliary regenerative vapor-liquid cycle having a heat exchange relationship between them. The basic cycle includes a compressor connected in series with a condenser, throttle device, and evaporator. The auxiliary cycle includes a compressor, condenser, throttle device, and a counterflow heat exchanger, successively connected. The cycles each have condensers that are cooled by ambient air; the basic cycle is able to operate independently of the auxiliary cycle. To maximize the coefficient of performance, the basic cycle operates with a small pressure differential between compressor discharge and return. In the heat exchanger, refrigerant flow from the basic cycle condenser is further cooled in a counterflow arrangement by the low temperature refrigerant from the auxiliary cycle until the refrigerant in the basic cycle has been precooled from near ambient temperature to near the intended refrigeration temperature.

Abstract: Mixed refrigerants provide refrigeration at cryogenic temperatures with throttling cycles operating with a one-stage compressor. The refrigerants include noncondensable gases such as helium, neon, or hydrogen to increase the overall cooling capacity of a refrigeration system at the same refrigeration temperature which is attainable without such noncondensable gases. More refrigeration can be produced with existing systems at temperatures above the normal boiling point of nitrogen or argon by adding, for example, helium, than for refrigerant blends without helium. By increasing the return pressure value of the refrigeration cycle in relation to the molar percent of helium present in the refrigerant, a constant refrigeration temperature may be maintained which exhibits greater stability than prior systems operating at the same temperature without helium enrichment.

Abstract: A Group I gas cryopumping system includes a compressor throttle cycle refrigerator using mixed refrigerants. Cold refrigerant flows through a cryopumping surface located in a vacuum chamber, whereon vapor freezes. The refrigerant then passes through a heat exchanger in cross flow with refrigerant from the compressor. Refrigerant flow entering and leaving the heat exchanger is in uninsulated lines at substantially room temperature. All exposed cold lines are eliminated. The throttle device and cold cryopumping surface are an integral unit that connects directly to the flow paths of the heat exchanger without intermediate lines. The compressor/aftercooler unit may be located at any convenient distance from the heat exchanger and cryopumping surface, and the heat exchanger is located immediately adjacent to the pumping surface in a separate housing outside the vacuum chamber. The heat exchanger housing may share or be isolated from the vacuum of the vacuum chamber.

Abstract: A cryogenic cold head in a canister is partially surrounded by an isolation mass. An open portion of the mass permits access for connection of a vapor compression refrigeration unit to the cold head, which is highly conductive. Straps of braided copper suspend the isolation mass from the cold head. The isolation mass and straps have a fundamental frequency that is below the first harmonic frequency at the cold head as caused by the refrigeration unit. A temperature differential between the cold head and a device-mounting interface on the isolation mass is preferably less than 2.5K per watt of heat transferred. The device to be cooled is mounted directly to the isolation mass when the mass of the device is insignificant relative to the isolation mass. For further vibration isolation, the device is separated from the isolation mass by another braided strap.

Abstract: An integral combination of expansion valve and evaporator in a cryostat using a single support member. The valve includes two flow orifices, one orifice being used primarily for steady-state operation and the other orifice being used only during cool-down. An actuator having a high coefficient of thermal expansion moves a needle positioned in the cool-down orifice such that a large orifice flow area at the start of cool-down is automatically and continuously reduced as the actuator temperature decreases as refrigerant is throttled through the orifice. Within a range of approximately 30 K from the desired steady-state evaporator temperature, the needle completely blocks the cool-down orifice. Then, refrigerant flows through the steady-state orifice which has a remotely adjustable needle. In the final stage of cool-down, the refrigerant system is entirely controlled by the steady-state orifice and its associated needle.

Abstract: A closed cycle cryogenic refrigerating system with a fixed restrictor operates with a compressor inlet pressure in a range of 0.1 Mpa to 0.4 Mpa and compressor discharge pressure in a range of 1.5 Mpa and 2.5 Mpa. A basic cryogenic refrigerant mixture is used to which is added approximately 3% to 25% of helium, hydrogen and/or neon. A ratio of refrigerant density at the inlet of the fixed restrictor between steady-state operation and operation at the beginning of cool-down is in an approximate range of 7 to 17. Relatively rapid cool-down is achieved and evaporator temperature is maintained in an approximate range of 70K to 120K.

Abstract: Apparatus and methods for cooling a superconducting magnet by circulating a pressurized helium gas through a convective cooling loop by natural convection, and apparatus and methods have been provided for quickly and effectively cooling a warm superconducting magnet down to operating temperature.

Abstract: In a cryostat, an isothermal boundary is proximate a large plurality of devices that are being cooled. The barrier is slightly colder than the devices so that heat flux therebetween is very small. The devices are in good thermal contact with a cold plate, which is made of a high thermal conductivity material. A single heater and a temperature sensor control the temperature of the cold plate as heat flows from the cold plate to the isothermal boundary. By limiting heat flow from the cold plate, temperature gradients throughout the temperature controlled region are very small. All of the devices to be cooled are very close to the same temperature. The isothermal boundary is maintained at the desired temperature by a flow of cryogenic refrigerant and a temperature sensor on the isothermal boundary provides inputs to a controller of refrigerant flow. The cryostat is constructed to minimize the amount of energy required from the heater to maintain the temperatures, and to minimize refrigerant flow.

Abstract: In the cryo-probe, refrigerant is furnished from a high pressure, room temperature supply. Insulation of the refrigerant lines is unnecessary. Refrigerant flows through a pre-cooling heat exchanger in the probe and through a restrictor wherein the pressure drops. In accordance with the Joule-Thompson effect, the refrigerant expands and becomes cold and liquid is applied in the region of the cryo-tip to provide rapid cooling thereof. Expanded refrigerant gas at low pressure reverses direction and flows back from the cold tip in counterflow arrangement through the aforementioned heat exchanger to give a pre-cooling effect to the refrigerant incoming from the external supply. A second tube for conveying warm-up gas is located in the probe and extends to the cold tip. After cryosurgery is complete, the high pressure flow is stopped and warm gas is delivered to the tip in the probe at reduced pressure through the second tube from the same refrigerant supply as is used for cooling.

Abstract: A mixed gas refrigerant for use in the cryogenic range of temperatures between 80.degree. K. and 100.degree. K., with single stage compressor providing high pressures up to 30 Arms. The refrigerant consists of nitrogen between 30 and 50 molar percent, methane less than 20 molar percent, propane, more than 30 molar percent, and ethane the balance.

Abstract: A mixed gas refrigerant for use as a replacement for CFC refrigerants, and specifically, for R-12, which includes at least three components including R-134a, R-124, and n-butane.

Abstract: Apparatus and methods for low pressure cooling of superconducting magnets, for example, on a magnetic levitated train, through a separate circulation loop from a sealed, unvented thermal reservoir to provide a lightweight cooling system. In a second embodiment, forced flow cooling is directed to the superconducting magnets and shields through a separate circulation loop from a sealed thermal reservoir to further reduce the weight of the cooling system.

Abstract: A device for cryogenic refrigerating of an object below the triple point temperature of the cryogen. The device includes a housing in which is placed a porous plug. A liquid cryogen is supplied to one side of the plug at a pressure greater than the triple point of the cryogen. A pressure below the triple point is maintained on the other side of the porous plug. The cryogen flows through the plug and forms a solid on the supply side of the plug. The solid cryogen provides cooling by sublimation on a continuous basis to a cold station thermally coupled to the plug.

Abstract: A closed cycle refrigerating system for cryogenic temperatures using a single stage compressor with a refrigerant comprising a gas mixture. The refrigerating system includes a heat exchanger having a throttling orifice which is arranged to provide refrigeration, and a single stage oil lubricated compressor for compressing the refrigerant. The compressor is typically of the rolling piston type. The refrigerant is a mixture of at least one cryogenic gas having a normal boiling point below 120 degrees K and at least two other gases having normal boiling point temperatures below 300 degrees different from each other and from said one gas. There is also included means for cooling the compressed refrigerant and for circulating the cooled refrigerant to the heat exchanger and its throttling orifice and then back to the compressor. The system does not require any cascaded heat exchangers or intermediate phase separators.

Abstract: The throttling sensitivity of a demand flow cryostat may be controlled and stabilized by selectively exposing refrigerant to the surface of a sensor which actuates a refrigerant throttle valve. The sensor is formed of a plastic material such as high density polyethylene which has a high coefficient of thermal contraction.

Abstract: A cryostat in which a venting conduit is connected to a reservoir of the cryostat but no venting of cryogen within the reservoir can occur while fluid is flowing under pressure within the heat exchanger of the cryostat.

Abstract: A method and apparatus for cooling and filling a cryogen reservoir with liquid cryogen from the gas/liquid discharge of a heat exchanger. The cryogen reservoir has a cryogen liquid retaining material and a temperature sensing means remote from the heat exchanger. The gas/liquid discharge is located in a region within the reservoir proximate to the temperature sensing means. At least a portion of the discharge is passed through the liquid retaining material to be absorbed, thereby.

Abstract: Thermal storage matrices, particularly useful in conjunction with the cooling of the infra-red detectors employed in space related or missile guidance systems are taught. Also taught are cryostat assemblies, including such thermal storage assemblies.

Abstract: A counter flow heat exchanger comprising a plurality of tubes disposed in a bundle array or tube within tube configuration to enhance heat transfer between high and low pressure tubes in the array or tube in tube configuration. Also disclosed are a method of increasing the heat transfer capacity of a tube bundle heat exchanger and a liquid helium temperature refrigerator or a reliquefier utilizing the heat exchanger.

Abstract: A heat exchanger for a fast cooldown cryostat having high pressure and low pressure flow paths wherein a low pressure flow path is defined by a finely divided matrix which in turn defines a plurality of flow paths and said high pressure flow path is disposed in heat exchange relationshp to said matrix.