DSpace Collection:
http://hdl.handle.net/10174/29523
2024-03-28T21:34:55ZAN OPTIMIZED APPROACH FOR PHOTOVOLTAIC PARAMETERS EXTRACTION
http://hdl.handle.net/10174/36245
Title: AN OPTIMIZED APPROACH FOR PHOTOVOLTAIC PARAMETERS EXTRACTION
Authors: Mesbahi, Oumaima; Tlemçani, Mouhaydine; Janeiro, Fernando M.
Abstract: The state of deterioration of a photovoltaic technology's internal components, is the primary negative event that these technologies encounter [1]. The internal parameters of solar panels as well as the overall production might be affected by this degradation.
The optimization procedure for obtaining these parameters goes through three phases; measuring the solar cell's response (current and voltage); calculating the discrepancies between measured and estimated data; and applying an optimization method for minimization. IV tracers susceptibility to additive noise is examined, and in order to justify its use [2], a new optimization cost function is presented and contrasted with the traditional function [3]. Eleven metaheuristic approaches for extracting photovoltaic parameters were also used, and their effectiveness was compared [4]. The goal of this research was to determine the optimal electrical model, cost function, and optimization technique to utilize in order to acquire the best photovoltaic parameters and the appropriate instrument resolution.2023-03-29T23:00:00ZOn the enhancement of heat transfer in a backward-facing step using porous baffles
http://hdl.handle.net/10174/35862
Title: On the enhancement of heat transfer in a backward-facing step using porous baffles
Authors: Cavaleiro Costa, Sérgio; Janeiro, Fernando; Malico, Isabel
Abstract: The backward-facing step is a geometry often used not only to investigate the accuracy and performance of numerical models, but also to analyse fundamental flow and heat transfer characteristics, and the impact of different configurations for the most diverse problems primarily due to its similitude to tangible and more complex geometries. One of the fields of interest is its use for heat transfer problems, which is the focus of this work: using porous baffles to help increase heat transfer. The position and the dimensions of the baffle and operation conditions are varied and simulated using a 2-dimensional finite volume method. Flow is assumed to be steady, incompressible, and laminar. The optimal set of parameters is investigated using Genetic Algorithms. Due to the computational cost associated with the cost function, achieving results has been challenging, requiring the parallel computation of the cost function to shorten the computational time associated with each generation of the optimisation process. It is found that positioning the baffle in a way that deflects flow from the entry to the opposite and heated wall considerably increases heat transfer.2023-01-01T00:00:00ZSimulation of a recuperative heat exchanger integrated in a thermal incinerator with the Epsilon-NTU model
http://hdl.handle.net/10174/35861
Title: Simulation of a recuperative heat exchanger integrated in a thermal incinerator with the Epsilon-NTU model
Authors: Zdanowski, Francisco; Malico, Isabel; Pécurto, Flávio; Canhoto, Paulo; Lima, Rui Pedro
Abstract: Thermal recuperative incinerators are devices commonly used in the industry to control the emissions of organic compounds from the exhaust air of certain industrial process. This is achieved by using these compounds as a comburent in the incinerator and thus both controlling emissions and generating process heat. Thermal recuperative incinerators are designed to efficiently recuperate waste heat from the hot outbound combustion products and preheat the inbound process air. They are usually large and geometrically complex equipment, so modeling an entire thermal recuperative incinerator in detail is difficult. Along with the simulation of the combustion process, another of the challenging aspects is the detailed simulation of the combustion products-to-process gas heat exchanger that encloses the combustion chamber and that promotes heat recovery and thermal insulation of the chamber. One strategy to deal with this challenge is to decouple the simulation of the combustion products-to-process air heat exchanger from the simulation of the combustion chamber. By doing so, the amount of heat transfer from the combustion products to the inbound process air can be determined and imposed as a boundary condition for the simulation of the combustion chamber. This work presents a simple mathematical model for describing the combustion products-to-process air heat exchanger integrated in a TRI used in a paint shop of an automotive assembly plant. The model relies on the well-established effectiveness method for modeling heat exchangers, the ε-NTU method. The results obtained in this work are validated using experimental data obtained in an industrial environment2023-01-01T00:00:00ZOn lateral-longitudinal control coupling for short- and long-fuselage BWB aircraft configurations
http://hdl.handle.net/10174/34554
Title: On lateral-longitudinal control coupling for short- and long-fuselage BWB aircraft configurations
Authors: Campos, L.; Marques, J.M.G.
Abstract: The coupling of the longitudinal and lateral stability modes of an aeroplane is considered in two cases: (i) weak coupling, when the changes in the frequency and damping of the phugoid, short period, dutch roll, and helical modes are small, i.e., the square of the deviation is negligible compared to the square of the uncoupled value; (ii) strong coupling, when the coupled values may differ significantly from the uncoupled values. This allows a comparison of three values for the frequency and damping of each mode: (i) exact, i.e., fully coupled; (ii) with the approximation of weak coupling; (iii) with the assumption of decoupling. The comparison of these three values allows an assessment of the importance of coupling effects. The method is applied to two flying wing designs, concerning all modes in a total of eighteen flight conditions. It turns out that lateral-longitudinal coupling is small in all cases, and thus classical handling qualities criteria can be applied. The handling qualities are considered for all modes, namely the phugoid, short period, dutch roll, spiral, and roll modes. Additional focus is given to the pitch axis, considering the control anticipation parameter (CAP). The latter relates to the two kinds of manouever points, where damping vanishes, that are calculated for minimum speed, take-off, and initial and final cruise conditions. The conclusion compares two flying wings designs (the “long narrow” and “short wide” fuselage concepts) not only from the point of view of flight stability, but also from other viewpoints.2022-09-06T23:00:00Z