Cryogenic Thermal Switch Research Articles

Механический тепловой ключ криогенного магнитного рефрижератора

This work study the operating parameters of a cryogenic mechanical thermal switch, a detachable contact pair made of a alloy GdNi2 disk and a copper cylinder. The mechanical thermal switch operates in a vacuum in the temperature range of 8-325 K with a pressure of 250-350 kPa. The time of thermal equilibrium is studied at different contact areas with and without an indium thermal interface at an initial temperature difference of 0.8-10 K in the contact pair in the temperature range from 8 to 122 K. The temperature relaxation value is 33.7...39.9 seconds at a temperature difference of 3±0.14 K in the range of 50...122 K. Reducing the nominal contact area from 177 mm2 to 2.5 mm2 increases the temperature relaxation time at a temperature of 73.3 K from 36.6 to 63.5 seconds. This temperature range corresponds to the maximum magnetocaloric effect near the Curie temperature of the GdNi2 alloy. The values of the heat that must be removed to maintain the required temperature of the cooling object in a cryogenic magnetic refrigerator have been obtained.

A lightweight thermal heat switch for redundant cryocooling on satellites

A previously designed cryogenic thermal heat switch for space applications has been optimized for low mass, high structural stability, and reliability. The heat switch makes use of the large linear thermal expansion coefficient (CTE) of the thermoplastic UHMW-PE for actuation. A structure model, which includes the temperature dependent properties of the actuator, is derived to be able to predict the contact pressure between the switch parts. This pressure was used in a thermal model in order to predict the switch performance under different heat loads and operating temperatures. The two models were used to optimize the mass and stability of the switch. Its reliability was proven by cyclic actuation of the switch and by shaker tests.

A 63 K phase change unit integrating with pulse tube cryocoolers

This article presents the design and computer model results of an integrated cooler system which consists of a single stage pulse tube cryocooler integrated with a small amount of a phase change material. A cryogenic thermal switch was used to thermally connect the phase change unit to the cold end of the cryocooler. During heat load operation, the cryogenic thermal switch is turned off to avoid vibrations. The phase change unit absorbs heat loads by melting a substance in a constant pressure-temperature-volume process. Once the substance has been melted, the cryogenic thermal turned on, the cryocooler can then refreeze the material. Advantages of this type of cooler are no vibrations during sensor operations; the ability to absorb increased heat loads; potentially longer system lifetime; and a lower mass, volume and cost. A numerical model was constructed from derived thermodynamic relationships for the cooling/heating and freezing/melting processes.

Development and testing of an advanced cryogenic thermal switch and cryogenic thermal switch test bed

This paper describes development details and performance results of a high performance, highly reliable cryogenic thermal switch (CTSW), US Patent Number 6,276,144 B1, and cryogenic thermal switch test bed. The principle application for this device is to couple redundant cryocoolers to a cryogenic component with minimal parasitic heat leak from the non-operating cryocooler. Additional applications for the CTSW are also considered. Constructed of only three parts and weighing less than 80 g, the device operates based on differential thermal expansion. The design is readily scalable and operates with a variety of material selections. The device has demonstrated an “On” conductance greater than 3.5 W/K, an “Off” resistance of greater than 2300 K/W and a switching ratio of more than 5000, with no performance degradation due to thermal cycling. A cryogenic thermal switch test bed has been designed to demonstrate the system benefits of the device for systems utilizing redundant cryocoolers. This test bed utilizes two CTSWs in conjunction with two tactical cryocoolers to quantitatively measure the power savings and/or the operating temperature benefits of the CTSW. Additionally, the test bed may be used to life test and thermally cycle the CTSW.