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In this paper , analytical techniques are developed for evaluating the performance of passively heated buildings. As most buildings use conservatories to enhance their performance , the direct gain types having attached conservatories are considered in detail. The complexity of the problem is minimized by ensuring all equations are developed from first principles. Auxilliary energy predictions for space heating by the method is in close agreement with monitored data for three occupied houses in Milton Keynes in England.

A numerical analysis is performed for the three-dimensional, turbulent flow of air in a thyristor valve hall located at the Dorsey Converter Station, owned and operated by Manitoba Hydro. The goal of this analysis was to determine the configurations that result in increased air-side cooling effectiveness in the valve hall. The governing equations are solved using the Computational Fluid Dynamics (CFD) code CFX-5. This computer code uses a finite volume method of solution and is based on a finite element approach for representing the geometry. The effects of inlet and outlet opening geometry, inlet air mass flow rate, and inlet air angle on the thermal performance for the air-side cooling of the thyristor valve hall geometry are examined. / May 2006

A numerical analysis is performed for the three-dimensional, turbulent flow of air in a thyristor valve hall located at the Dorsey Converter Station, owned and operated by Manitoba Hydro. The goal of this analysis was to determine the configurations that result in increased air-side cooling effectiveness in the valve hall. The governing equations are solved using the Computational Fluid Dynamics (CFD) code CFX-5. This computer code uses a finite volume method of solution and is based on a finite element approach for representing the geometry. The effects of inlet and outlet opening geometry, inlet air mass flow rate, and inlet air angle on the thermal performance for the air-side cooling of the thyristor valve hall geometry are examined.

A numerical analysis is performed for the three-dimensional, turbulent flow of air in a thyristor valve hall located at the Dorsey Converter Station, owned and operated by Manitoba Hydro. The goal of this analysis was to determine the configurations that result in increased air-side cooling effectiveness in the valve hall. The governing equations are solved using the Computational Fluid Dynamics (CFD) code CFX-5. This computer code uses a finite volume method of solution and is based on a finite element approach for representing the geometry. The effects of inlet and outlet opening geometry, inlet air mass flow rate, and inlet air angle on the thermal performance for the air-side cooling of the thyristor valve hall geometry are examined.

No description available.

No description available.

Ce travail de thèse traite des modifications de l’écoulement et des transferts de chaleur en convection naturelle. La configuration retenue est celle de la cavité différentiellement chauffée de rapport de forme 4. Les modifications sont réalisées au moyen d’une perturbation locale de faible étendue spatiale positionnée sur la paroi chaude pour une valeur du nombre de Raleigh se situant autour de la valeur critique correspondant à la transition d’un état stationnaire à une état instationnaire. Deux études complémentaires ont été menées. Une étude numérique préliminaire a été réalisée, dans laquelle une perturbation d’origine thermique a été introduite sous la forme d’un changement local de la température imposé sur la paroi isotherme. Il a été montré que l’on peut changer le régime d’écoulement depuis un état stationnaire vers un état instationnaire. De plus, les transferts de chaleur peuvent être modifiés de façon significative par un choix approprié des paramètres de la perturbation (fréquence, amplitude et position). Une étude complémentaire sur un dispositif expérimental a été conduite avec le positionnement d’un obstacle cylindrique sur la paroi chaude. Deux types d’obstacles ont été choisis : isolant et conducteur. L’impact sur la thermique et la dynamique de la longueur de l’obstacle,de sa position verticale, du nombre de Rayleigh de l’écoulement ou encore du nombre d’obstacles introduits a été analysé dans le plan vertical à mi- profondeur. / This thesis deals with the modifications of heat transfer and fluid flow in natural convection. The configuration chosen is a differentially heated cavity of aspect ratio equal to 4. The modifications are achieved using a small spatial extent disturbance located at the hot wall at a Rayleigh number value close of the critical value corresponding to the transition from steady to unsteady state. Two complementary studies were conducted. A preliminary numerical study was carried out, in which a thermal disturbance was introduced by means of a local change of the imposed temperature at the isothermal wall. It was shown that the flow regime can be changed from a steady state to an unsteady one. In addition, the heat transfers can be significantly modified by an appropriate choice of disturbance parameters (frequency, magnitude and location). An additional study, using an experimental device, was conducted by positioning a cylindrical obstacle on the hotwall. Two types of obstacles were chosen : insulating and conductive. The influence on heat transfers of the length of the obstacle, its vertical location, the Rayleigh number ofthe flow as well as the number of obstacles was analyzed in the vertical mid-depth plane.

A computational fluid dynamics (CFD) validation experiment is conducted for convection flow from a heated plate in buoyancy aided and opposed orientations. The design of the experiment to meet CFD validation completeness standards is described. Previous experiments and simulations have been completed, but none measure or present to necessary boundary conditions to define the simulation boundary conditions. Experimental measurements of forced and mixed convection are presented, along with measured boundary conditions sufficient to compute simulations for validations purposes. Some simulation results are described, but a complete validation study is not included. Simulations are conducted to ensure all necessary boundary conditions are being measured. This document and the corresponding website will provide sufficient explanation and data to repeat the experiment and sped the setup of future validation experiments. The data and boundary conditions are available for download on a website dedicated to validation data dissemination. Along with the validation data, the response quantities provide some insight into the flow characteristics of the boundary layer for convective flow from a vertical flat plate.

This work treats the thermal and mechanical performances of gas-filled, flat plate solar collectors in order to achieve a better performance than that of air filled collectors. The gases examined are argon, krypton and xenon which all have lower thermal conductivity than air. The absorber is formed as a tray connected to the glass. The pressure of the gas inside is near to the ambient and since the gas volume will vary as the temperature changes, there are potential risks for fatigue in the material. One heat transfer model and one mechanical model were built. The mechanical model gave stresses and information on the movements. The factors of safety were calculated from the stresses, and the movements were used as input for the heat transfer model where the thermal performance was calculated. It is shown that gas-filled, flat plate solar collectors can be designed to achieve good thermal performance at a competitive cost. The best yield is achieved with a xenon gas filling together with a normal thick absorber, where normal thick means a 0.25 mm copper absorber. However, a great deal of energy is needed to produce the xenon gas, and if this aspect is taken into account, the krypton filling is better. Good thermal performance can also be achieved using less material; a collector with a 0.1 mm thick copper absorber and the third best gas, which is argon, still gives a better operating performance than a common, commercially produced, air filled collector with a 0.25 mm absorber. When manufacturing gas-filled flat plate solar collectors, one way of decreasing the total material costs significantly, is by changing absorber material from copper to aluminium. Best yield per monetary outlay is given by a thin (0.3 mm) alu-minium absorber with an argon filling. A high factor of safety is achieved with thin absorbers, large absorber areas, rectangular constructions with long tubes and short distances between glass and absorber. The latter will also give a thin layer of gas which gives good thermal performance. The only doubtii ful construction is an argon filled collector with a normal thick (> 0.50 mm) aluminium absorber. In general, an assessment of the stresses for the proposed construction together with appropriate tests are recommended before manufacturing, since it is hard to predict the factor of safety; if one part is reinforced, some other parts can experience more stress and the factor of safety actually drops.