Start Date
4-1969 8:00 AM
Description
Heat transfer in rarefied gases, a previously little investigated subject, has undergone advances in the past few years due to increased areas of application. Among new areas of application are the insulation of booster propellant storage vessels and heat transfer to exterior surfaces of space vehicles.
Low density heat transfer is subdivided into several regimes with the Knudsen number, Kn (The ration of mean free path to characteristic dimension of the system) serving as the criteria for designation.' At sufficiently low pressures Kn becomes large compared with unity. For Kn greater than about 3, intermolecular collisions in a gas become negligible compared with gas molecule - boundary collisions. This is referred to as the free molecule flow region of gas dynamics and heat conduction. Heat conducted between surfaces separated by a gas with Kn>3 occurs predominately by the mechanism of thermal exchange by direct molecule - wall collisions.
Methods of Determining Thermal Accommodation Coefficients from Free Molecular Flow Heat Transfer Data
Heat transfer in rarefied gases, a previously little investigated subject, has undergone advances in the past few years due to increased areas of application. Among new areas of application are the insulation of booster propellant storage vessels and heat transfer to exterior surfaces of space vehicles.
Low density heat transfer is subdivided into several regimes with the Knudsen number, Kn (The ration of mean free path to characteristic dimension of the system) serving as the criteria for designation.' At sufficiently low pressures Kn becomes large compared with unity. For Kn greater than about 3, intermolecular collisions in a gas become negligible compared with gas molecule - boundary collisions. This is referred to as the free molecule flow region of gas dynamics and heat conduction. Heat conducted between surfaces separated by a gas with Kn>3 occurs predominately by the mechanism of thermal exchange by direct molecule - wall collisions.
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