Time Dependent Surface Heat Transfer in Light Weight Aggregate Cement Based Materials

Abstract

Surface temperature changes of building materials affect the calculation of heat flow and thus the energy use in heating and cooling. The surface heat transfer coefficient , limiting the heat flow between material surface and ambient air is normally taken as a constant. In this study we propose a time-dependent function . We estimate from unidirectional heat flow experiments with transient and steady-state conditions. Using temperature measurements and the conservation of energy at the surface including convective and irradiative boundary conditions, the value of was obtained both using Finite Difference and Taylor Polynomials methods. Numerical solutions of temperature distribution as function of time were improved with the obtained -functions compared to with constant . There were no clear difference between on different materials, and the final values observed were in the order of magnitude expected from the literature.

Surface temperature changes of building materials affect the calculation of heat flow and thus the energy use in heating and cooling. The surface heat transfer coefficient , limiting the heat flow between material surface and ambient air is normally taken as a constant. In this study we propose a time-dependent function . We estimate from unidirectional heat flow experiments with transient and steady-state conditions. Using temperature measurements and the conservation of energy at the surface including convective and irradiative boundary conditions, the value of was obtained both using Finite Difference and Taylor Polynomials methods. Numerical solutions of temperature distribution as function of time were improved with the obtained -functions compared to with constant . There were no clear difference between on different materials, and the final values observed were in the order of magnitude expected from the literature.

Keywords

Heat Flow, Surface Heat Transfer Coefficient, Numerical Methods, Light Weight Aggregate, Cements Based Materials

Heat Flow, Surface Heat Transfer Coefficient, Numerical Methods, Light Weight Aggregate, Cements Based Materials

Cite this paper

nullH. Nguyen, F. Melandso and S. Jacobsen, "Time Dependent Surface Heat Transfer in Light Weight Aggregate Cement Based Materials,"*Engineering*, Vol. 2 No. 5, 2010, pp. 307-317. doi: 10.4236/eng.2010.25040.

nullH. Nguyen, F. Melandso and S. Jacobsen, "Time Dependent Surface Heat Transfer in Light Weight Aggregate Cement Based Materials,"

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