Transfer function coefficients for time varying coupled heat transfers in vertically heated hollow concrete bricks

Abstract

This paper describes a two step numerical procedure to determinate empirical transfer function coefficients (TFCs) for vertically heated hollow concrete bricks. For such systems TFCs cannot be generated using the analytical techniques available in the literature such as the z-transfer function method or the space state representation method because of the nonlinear local character of the heat transfer by natural convection and radiation in the air cells of the hollow concrete bricks. The first step of the procedure consists in predicting coupled heat transfer by conduction, convection, and radiation in realistic time varying conditions using a detailed numerical simulation. In the second step, the results of the simulation (the time-varying heat fluxes at the hollow brick surfaces) are used to obtain empirical transfer function coefficients using an identification technique. Transfer function coefficients are generated for three different types of hollow concrete bricks mostly used in practice. It is shown that the empirical transfer function coefficients permit fast and accurate prediction of heat transfer for thermal excitations that differ markedly from those used to generate these coefficients without solving the complex system of equations governing the coupled heat transfer mechanisms.

Coupled heat transfers in a three cavity hollow block subjected to an incident solar flux: Effect of heat conductivity

“…Whereas the other part studied the effect of radiation exchange between cavity surfaces on natural convection [9][10]. Recently, Ait-Taleb et al [11][12][13] presented a series of numerical studies that take into account the three modes of heat transfer in alveolar blocks heated from below or above, but submitted to the imposed temperatures excitation. These studies play an important role in simulating the thermal performance and optimizing the configurations of the hollow block.…”

Coupled Conductive-Convective-Radiative Heat Transfer in Hollow Blocks with Two Air Cells in the Vertical Direction Subjected to an Incident Solar Flux

“…Certain exceptions are nevertheless to be found. numerically investigated coupled heat transfers by conduction, natural convection and radiation in hollow structures heated from below or above are discussed for example, in studies by Ait-Taleb et al [7,8]. Antar et al [9] examined conjugate heat transfer across a hollow block.…”

Numerical study of coupled heat transfers through hollow structures exposed to a solar flux

“…However, for the upper floors of buildings, in general, the heat transfer is mainly done in vertical direction. For this kind of configurations, Ait-Taleb et al [15,16] investigate numerically the coupling between the heat transfers by conduction, natural convection and radiation in alveolar structures subjected to a vertical gradient temperature imposed. After, these studies have been extended by the same authors [17,18] to the hollow tiles with one or two air cells in the vertical direction and they are uniformly heated from below or from above.…”