Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
Experimental Evaluation of the Thermal Conductivity of Frost built-up on Parallel Plate Channels
Submission Author:
Silvia Negrelli , PR
Co-Authors:
Valter Salles do Nascimento Junior, Christian Hermes
Presenter: Silvia Negrelli
doi://10.26678/ABCM.ENCIT2016.CIT2016-0136
Abstract
Computational models used to predict the growth of a frost layer are usually based on the fundamental principles of Thermodynamics and Transport Phenomena. However, those models rely on empirical correlations to compute the thermophysical properties of the frosted medium, particularly the density and the effective thermal conductivity. A literature review shows that the open literature lacks of a physically-based model for the thermal conductivity of frost formed in different operating conditions. Therefore, the present study is aimed at investigating, by means of an experimental approach, the frost growth process on parallel plate channels and the influence of the key parameters on the effective thermal conductivity of frost. A theoretical analysis was conducted based on the limiting cases of serial and parallel association of the thermal resistances of moist air and ice crystals, thus setting the theoretical background for a dimensionless model for the thermal conductivity as a function of the porosity of the frosted medium. The experimental work was carried out by means of a closed-loop wind-tunnel facility, which provides a strict control of the psychrometric conditions at the entrance of the test section as well as the plate surface temperatures. A dataset comprising of 45 experimental points was gathered in order to come up with a semi-empirical correlation for the thermal conductivity of frost as a function of the frost porosity and the surface temperature. The correlation is able to predict ~90% of the experimental data points within the ±15% thresholds.
Keywords
frost, thermal conductivity, density, semi-empirical correlation, experimental work, plate channels
