This paper reports on a numerical and experimental study of heat transfer phenomena through two different multilayer fibrous insulations for building applications. The investigated samples were composed of different layers of fibrous materials and aluminium foils, placed between one or two air gaps in the vertical dimension. An experimental apparatus (a guarded hot box) has been used to measure heat transfer through the samples, while a finite volume numerical model combined radiation/conduction heat transfer was developed to predict the temperature distribution and heat transfer in such insulation systems comprised of the materials separated by multiple reflective foils. The model takes into account the coupling between the solid conduction of the fibrous system and the gaseous conduction and radiation. The radiation heat transfer through the insulation system has been modelled via the two flux approximation. The numerical results were compared with the experimental data from the guarded hot box for model validation, as well as to assess the effectiveness of the reflective foils in changing the resistance of the insulations. The comparative verification of the model showed that the numerical results were consistent with the experimental data through the environmental conditions under examination.
Infrared (IR) thermography is a control method widely used for building diagnosis to investigate structural blemishes and thermal heat losses. Usually, collecting the thermal heat flux naturally emitted by a studied surface via an IR camera, we obtain critical information regarding its structure through passive infrared thermography. The thermogram can then reveal an abnormal variation of the heat flux and highlight a defection. However, on building applications in the case of Non Destructive Testing and Energy Consumption Investigation, spare control often only emits no significant heat due to the high thermal inertia materials that are often used. To overcome such problem, active impulse infrared thermography is an interesting alternative method, since we can access to information not provided spontaneously by analyzing the passive thermal emission of the surface. Hence, in this work, the front face flash method is proposed in order to analyse the subsurface thermal properties. Furthermore, it is proposed to couple impulse IR thermography with a stable Unmanned Aircraft Systems (UAV) to record and analyse the transient temperature response during convenient time duration. Preliminary results and several practical problems for the implementation of such experimental device are given and discussed here.
Building energy consumption is increasing rapidly demanding urgent improvement of insulation techniques in order to promote the buildings energy efficiency. Kingdom of Bahrain presents huge energy demands to the residential buildings due to the continuing air condition units operation. Due to this reason, in the present paper we present the design and development of a modified mini scale hot box experimental apparatus as well as an experimental and an analytical investigation of the used insulation blocks and techniques in Bahrain, with the aim to measure and evaluate the thermal resistance. The experimental process is developed on the basis of a standardized hot -box design and manufactured with appropriate dimensions, in order to measure the temperature distribution according various climate conditions. Important results and estimations are produced concerning the thermal resistance of insulation blocks, temperature distribution and heat transfer coefficients. The results are accurate enough and these are validated with the corresponded ones of the literature, of analytical calculations as well as of the manufacture side. It seems that the insulation blocks efficiency is adapted to the regional climate conditions and possible reliable solutions can be applied for further improvement.
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