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Second Thermal and Fluids Engineering  Conference

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

PREDICTING THE FROST DENSITY ON HYDROPHILIC AND HYDROPHOBIC SURFACES: A NEW SEMI-EMPIRICAL CORRELATION

Andrew C. Napora
Department of Mechanical and Manufacturing Engineering, Miami University, 56 Garland Hall, 650 East High Street, Oxford, OH 45056 USA

Nicholas L. Truster
Department of Mechanical and Manufacturing Engineering, Miami University, 56 Garland Hall, 650 East High Street, Oxford, OH 45056 USA

Edgar J. Caraballo
Department of Mechanical and Manufacturing Engineering, Miami University, 56 Garland Hall, 650 East High Street, Oxford, OH 45056 USA

Christian J.L. Hermes
Federal University of Paraná, 81531990 Curitiba-PR, Brazil

Andrew D. Sommers
Department of Mechanical and Manufacturing Engineering, Miami University, 56 Garland Hall, 650 East High Street, Oxford, OH 45056 USA

Abstract

A new semi-empirical correlation for the prediction of the frost density on hydrophilic and hydrophobic surfaces is proposed. The proposed correlation is a function of the modified Jakob number and contains two correction terms, one for the surface contact angle and another for relative humidity. Whereas most frost correlations found in the open literature generally do not include surface wettability as a parameter, our research has shown that surface wettability can be important when trying to accurately predict the properties of a growing frost layer.

The correlation was developed using frost density data obtained from three different surfaces—namely, an uncoated, untreated aluminum plate (Surface 1), an identical plate coated with a hydrophobic coating (Surface 2), and a plate containing a hydrophilic coating (Surface 3). On each surface, the frost was grown for a period of three hours and then defrosted. Various operating conditions were examined including different relative humidity levels, surface temperatures and air temperatures. The proposed correlation was able to predict more than 92% of the experimental frost density data to within a ±20% error band. The new correlation is proposed for use on vertical surfaces with contact angles 45° < θ < 160°, relative humidity 0.40 < ∅ < 0.80, plate temperatures −13°C < Tw < −5°C, and air temperatures 18°C < Ta < 24°C under natural convection conditions.

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