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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

DEWAR CONFIGURATION AS AN APPROACH TO MAXIMIZING THE COOLING OF HEAT LOADS IN TWO-TEMPERATURE DEWAR'S

DOI: 10.1615/TFESC1.hte.012887
pages 1217-1231

Narcrisha Norman
Assistant Professor

Sonya T. Smith
Howard University, Washington, DC 20259, USA


KEY WORDS: 4K, 77K, Dewar, Dewar Configuration, Two Temperature Dewar, Helium Alternative, MLI, Powder Insulation

Abstract

This paper investigates a two temperature Dewar configuration as an approach to cooling 100W and 3000W of heat loads in a 4K/77K Dewar. Variants such as immersion versus conductive isolation, configuration, shape, closure size and insulation is discussed. Variation in configuration analyzed the location of 4K with respect to 77K and with respect to the systems closure. An analysis of thermal isolation in each system was considered. A comparison of the six systems with He as a cryogen for use at 4K and without He is discussed. A feasibility study based on: cost, input power and reliability, was conducted for each of six two-temperature Dewar design configurations. The optimal system will substitute for using 100W and 3000W heat loads will utilize a multistage Adiabatic Demagnetization Refrigerator. The spherical shaped system will operate by way of conduction and utilize graphene to insulate the walls on the inside of the system and multilayer insulation on the outside. The configuration will place the 3000W heat load below the 100W heat load and the throat of the system will have a gold plated copper radiation shield cemented to the inner nitrogen wall by means of conductive copper lacquer, and with a total open area of about 2.5cm2 in the shield to reduce the average rate of evaporation of liquid helium. A shutter shield of sliver plated coppered will be independently supported through a standing taper joint at the bottom of the Dewar to firm sliding contact with the outer shield.

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