Étude numérique et expérimentale du transfert de chaleur dans un capteur solaire à perforations doté d'un collecteur transparent et opaque

Abstract

Solar Air Heating systems are becoming more and more popular as they provide many possibilities for energy savings and for preheating air in various applications. They use solar energy to heat and ventilate indoor air spaces. Interest in solar air heating systems development has grown in recent years, motivating the development of new environmental energy devices; among these devices we can found the Unglazed Transpired Collector (UTCs) and the Transparent Transpired Collector (TTCs). The objective of the work presented in this thesis is to study the thermal performance of these two solar air heating systems UTC and TTC. This work is structured in three main parts: First, the methodology of design of experiments was used in the case of a UTC. The plan adopted uses at least three levels experimental factors. The approach is well suited to model and optimize the thermal performance of the UTC. A UTC prototype has been built in the Centre of thermal technology (CTT) at École de technologie supérieure. Experimental measurements of temperature, radiation and flow rates are achieved, according to the strategy defined by the experimental design. The experimental design methodology has allowed to determine the influence of four parameters (the absorber coating, the mass flow of air through the perforations, hole diameter and the irradiation intensity) on the efficiency of the UTC. A quadratic polynomial model for the efficiency was established, and it is shown to explain 95.47% of the output result’s variability. Various diagnostic tests (residuals analysis and analysis of variance (ANOVA)) were used to assess the validity of the best-fit model. Finally, the developed model was optimized using response surface representations. An optimum combination of the four parameters under consideration was obtained for collector efficiency of between 70-80 %. Second, we studied in depth the thermal efficiency of an unglazed transpired collector both experimentally and numerically. Experimental investigations were carried out in a laboratory with a controlled environment. Measurements of temperatures, air velocity and irradiance were performed for three air mass flow rates, three distinct irradiances and two plenum thicknesses. Perforations in the form of slot were selected to enable a comparison with 2D numerical simulations. Meanwhile, a commercial finite volume software was used to model the heat transfer and air flow through the collector. The CFD simulation shows good agreement with experimental results. Numerical modeling has provided a detailed analysis of heat transfer through the UTC. It was found that a weak heat exchange process took place in the plenum: the maximum efficiency difference between the two plenum thicknesses (5 and 15 cm) was only 3.25%. Third, the goal of this last section is to provide measurements from a reduced-scale prototype that can be used to estimate the thermal performance of a transpired transparent collector (TTC) and to study, the influence of five parameters (the plenum thickness, the pitch spacing, the slots width, the air mass flow rate, and the incident solar radiation) including interactions in terms of collector efficiency. To determine these parameters effects, this experimental work uses a multi level full factorial plan of replicated 48 tests. It is found that the air mass flow rate has the strongest effect on the efficiency of the transparent transpired collector. The irradiation, slots width, pitch spacing, plenum thicknesses seems to have a moderate effect. The thesis is presented in the form of three articles. The first article is published in the journal Solar Energy, the second is accepted in the same journal and the third was submitted to Energy and Buildings. Five other articles have been published in conferences with reviewing committee. Pdf versions of these papers are available on the site web of the technologies of energy and energy efficiency industrial research chair (t3e) (www.t3e.info). This work is based on five distinct parts which are detailed in the various sections of the thesis.

Date	30 Aug 2013
Original language	French
Awarding Institution	École de technologie supérieure
Supervisor	Daniel Rousse (Supervisor) & Stéphane Hallé (Co-supervisor)