It is found that with selective coating, the absorber plate should be further from the cover glazing in order to prevent excessive convective heat loss, the distance is better of no less than 20 mm. Based on the first and second laws of thermodynamics, the optimal channel depths for type I and type III SAHs with black-painted absorber are suggested as 10 mm. Our study shows that the heat transfer corresponding to the temperature distribution across the channel in SAH varies greatly with the change of channel depth. Laminar model and k–ω turbulence model of Wilcox are used for the prediction of flow and temperature field in SAHs. In this paper, the effect of the channel depth on the energy gain of type I and type III SAHs has been investigated by computational fluid dynamics (CFD) simulations. In the design of solar air heaters (SAHs), channel depth is a principal variable to be fixed. The OSF fins with relatively large fin thickness-to-length ratio λ perform better in low Re region and the optimum decreases with the increasing Re number. The results show that there exists a specific fin thickness-to-height ratio α and fin density λ 3, which contribute to the highest fin performance for a given mass flux, and the optimal λ 3 (or α) increases (or decreases) as mass flux increases. With this method, the effects of the geometrical parameters of the OSF are discussed carefully. It physically represents the ratio of the heat flux over the fin surfaces and that over the primary surfaces in the fin channel. An actual fin effectiveness is then proposed to measure the fin performance. Further investigation indicates that the idealization of uniform heat transfer coefficient over all the surfaces in fin channel, which runs through the conventional concepts, is untenable, and strongly restricts the fin performance analysis. The comparative analysis shows that the conventional fin efficiency and fin effectiveness concepts provide an incomplete assessment of the fin performance of the fins, and lead to impractical suggestions of using OSF fin. The fin performance of offset strip fin (OSF) and plain fin is numerically investigated with well-validated 3D models in the present study. Complete unification of flow was not achieved by any of the models suggesting further design modification is needed.Īs an important consideration in the design of plate-fin heat exchangers, the selection of plate-fin surfaces is associated with the estimation of the fin performance in many cases. The two other models with curved outlets showed an increase in flow uniformity with the most uniform flow exhibited by model 1. It was found that a square duct with no curvature generated large maldistribution of flow to the heat exchanger, providing poor cooling rates for both scenarios. Each model was run using two different flow rate scenarios to simulate conditions of aircraft ground operations and in-flight (cruising) operations. A series of models were generated with three different duct designs to examine the effect of the duct shape on flow distribution. The aim of this research paper is to study the ECS system for an Airbus A320 aircraft and using computational fluid dynamics analyse the flow of RAM air through the inlet duct. If problems caused by a maldistribution of flow such as increased fouling or thermal stress fatigue or certain channels then they may be unnoticed and lead to further issues. With this high operation rate of the environmental control system (ECS) the heat exchanger packs undergo a large amount of work and are not maintained frequently (typically every 20 months). Commercial aircraft operate almost continuously throughout the year. Maldistribution of flow can cause efficiency drops and in extreme cases can lead to exchanger failure. Heat exchanger performance is directly related to flow distribution to the inlet.
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