Heat transfer in microwave transistors at cryogenic temperatures

Scilight ◽  
2021 ◽  
Vol 2021 (43) ◽  
pp. 431107
Author(s):  
Aili McConnon
Keyword(s):  
Heat Transfer ◽  
Cryogenic Temperatures ◽  
Microwave Transistors

Design, Fabrication and Heat Transfer Analysis of a Mesoscopic Pulse Tube as an Integrated Micro-Refrigeration System

2000 ◽  
Author(s):  
Ninad Shinde ◽  
Rashid Bashir ◽  
Eckhard Groll ◽  
George Chiu
Keyword(s):  
Heat Transfer ◽  
Surface Heat ◽  
Heat Transfer Analysis ◽  
Pulse Tube ◽  
Cryogenic Temperatures ◽  
Refrigeration System ◽  
Macro Scale ◽  
Pulse Tube Refrigerators ◽  
Effect Of Surface ◽  
Heat Pumping

Abstract The phenomenon of surface heat pumping has been widely used to accomplish refrigeration in macro-scale devices such as pulse-tubes and thermo-acoustic devices. Pulse tube refrigerators are typically used to lift heat at cryogenic temperatures. The advantage of a pulse tube as a no moving part device makes it amenable to miniaturization at dimensional scales where areal effects, such as friction and viscosity, dominate. In this paper, the design and preliminary fabrication results of such a device to investigate the effect of surface heat pumping in mesoscopic glass channels are presented.

Heat Transfer by Natural Convection of Helium Between Horizontal Isothermal Concentric Cylinders at Cryogenic Temperature

1988 ◽  
Vol 110 (1) ◽  
pp. 109-115 ◽  
Author(s):  
E. H. Bishop
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Rayleigh Number ◽  
Transfer Rate ◽  
Correlation Equation ◽  
Diameter Ratio ◽  
Temperature Profiles ◽  
Cryogenic Temperatures ◽  
Transfer Rates ◽  
Concentric Cylinders

An experimental study was performed of the heat transfer by natural convection of helium between horizontal isothermal concentric cylinders at cryogenic temperatures. Time-averaged temperature profiles at various locations in the annulus and overall heat transfer rates were measured as the Rayleigh number was varied from 6 × 106 to 2 × 109 and the expansion number from 0.20 to 1.0 for a constant Prandtl number of 0.688 and diameter ratio of 3.36. It was found that the heat transfer rate depends on the magnitude of the expansion number as well as on the magnitude of the Rayleigh number. With gas properties evaluated at a volume-weighted reference temperature, a correlation equation is presented that correlates the heat transfer data with maximum deviations of −8.2 and +8.5 percent. The results of this study are compared with previously published studies of other investigators.

Near field radiative heat transfer between macro-scale metallic surfaces at cryogenic temperatures

Cryogenics ◽  
2020 ◽  
pp. 103156
Author(s):  
Tomáš Králík ◽  
Pavel Hanzelka ◽  
Věra Musilová ◽  
Aleš Srnka ◽  
Pavel Urban
Keyword(s):  
Heat Transfer ◽  
Radiative Heat Transfer ◽  
Radiative Heat ◽  
Near Field ◽  
Cryogenic Temperatures ◽  
Metallic Surfaces ◽  
Macro Scale

Measurement of Heat Transfer Coefficients for Non-Azeotropic Hydrocarbon Mixtures at Cryogenic Temperatures

2004 ◽  
Author(s):  
Cory B. Hughes ◽  
Gregory F. Nellis ◽  
John M. Pfotenhauer
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Circular Cross Section ◽  
Small Scale ◽  
Hydrocarbon Mixture ◽  
Cryogenic Temperatures ◽  
Hydrocarbon Mixtures ◽  
Experimental Apparatus

The use of non-azeotropic hydrocarbon mixtures in throttle-cycle refrigeration systems has resulted in large increases in the performance of Joule-Thomson type cryocoolers. However, there is very little data or theory currently available in the literature regarding the thermal-fluid behavior of multi-component, multi-phase mixtures at cryogenic temperatures. The design of these systems is therefore semi-empirical, relying heavily on experimental iteration. In this paper, an experimental apparatus is described that is capable of making precise and controlled measurements of the heat transfer coefficient over a range of cryogenic temperatures, compositions, geometries, and flow rates that are relevant to small-scale, throttle-cycle refrigeration systems. The experimental apparatus is used to carry out a study of the horizontal flow boiling heat transfer coefficient for a non-azeotropic hydrocarbon mixture in a circular cross-section with a constant wall temperature. The measurements are carried out over a range of cryogenic temperatures and the data is presented in the form of heat transfer coefficient as a function of temperature and thermodynamic quality. The experimental uncertainty of the measurements is theoretically estimated to be 10%. Measurements of the single-phase heat transfer coefficient for pure nitrogen fall within 10% of the Dittus-Boelter correlation.

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