Abo Bibliothek: Guest

ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

FROST DENSITY PROFILE MEASURED BY USING X-RAY RADIOGRAPHY

Get access (open in a dialog) DOI: 10.1615/IHTC16.mpf.023967
pages 6369-6374

Abstrakt

Frost formation on the heat exchanger which are operated at 0 deg.C below causes serious problem to the heat transfer performance. Structure of frost is porous consisting ice crystal and air, which causes the thermal conductivity of frost remarkably low. The frost layer becomes a thermal resistance between cooling surface and ambient air. Frost density profile is important property to estimate the heat transfer performance of the heat exchanger under the frosting conditions. However, the frost density profile in the frost layer has been reported only three papers due to the experimental difficulties. In this study, the frost density profiles on the vertical cylindrical cooling-surface were quantitatively estimated by X-ray radiography. X-ray radiography is one of non-destructive inspection methods. X-ray beam was attenuated with the penetration thickness and the mass attenuation coefficient of ice crystal of the frost. By applying the X-ray beam to the cooling cylinder perpendicularly, the projection image was obtained for the chordal attenuation of X-ray beam by the frost layer. Abel inversion was applied to the X-ray image to re-construct the frost density profiles under the circularly symmetric condition of frost formation around the cylindrical surface. The frost density profiles were continuously changed in the frost layer and it decreases toward the thickness direction. A relative maximum of the frost density appeared near the frost layer surface.