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2D numerical analysis of an H-Darrieus hydrokinetic turbine with passive improvement mechanisms

Guevara-Munoz Angie Judith, Hincapie-Zuluaga Diego Andres, Rodriguez-Cabal Miguel Angel, Sierra-Del-Rio Jorge Andres, Colmenares-Quintero Ramón Fernando, Torres-Lopez Edwar

Engineering Transactions

2023

Vol. 71, iss. 4

553--569

H-Darrieus hydrokinetic turbines are an alternative for small hydroelectric plants. These turbines are considered to have a low environmental impact as they do not require reservoirs. However, they have limited self-starting capacity, which limits their use. Nevertheless, the configuration of passive mechanisms in the H-Darrieus turbines affects their performance, as they tend to increase the flow velocity. This study is part of a project with the aim to design and build a turbine to generate energy in the Colombian river scenario in non-interconnected zones. The objective of this study is to analyze the performance through numerical simulations of four H-Darrieus rotors to be configured with passive improvement mechanisms. The study was conducted using ANSYSr Fluent software, employing transient, two-dimensional models under constant operating conditions. Overlapping meshes were used for the stationary and rotating domain configuration. The results show that increased solidity leads to decreased tip speed ranges and increased maximum rotor power. Improvement in the self-starting capability was found with passive mechanisms employing a diffuser geometry. Among the tested configurations, the rotor configured with a Venturi-shaped mechanism achieved a remarkable 660% improvement in the power coefficient compared to configurations without such mechanisms.

Preliminary analysis of catenoid chimney cooling towers

Wiśniowski Maciej, Walentyński Robert, Cornik Dawid

Bulletin of the Polish Academy of Sciences. Technical Sciences

2023

Vol. 71, nr 6

art. no. e147341

Optimization plays an important role in scientific and engineering research. This paper presents the effects of using the catenoidal shape to design the structure of a chimney cooling tower. The paper compares some geometrical variations of the catenoid with the reference existing hyperboloidal structure. It also compares internal forces, deformation and stability of the catenoidal structure. The comparison shows some predominance of the catenoid over the popular hyperboloid structure of the shell. The paper attempts to find an optimal shape of the cooling tower in order to reduce the amount of material and labor. The paper utilizes engineering tools and the designing process for chimney cooling towers.

Impact of elevated outdoor MRT station towards passenger thermal comfort: A case study in Jakarta MRT

Sugiono Sugiono, Nurlaela Siti, Kusuma Andyka, Wicaksono Achmad, Lukodono Rio P.

Przegląd Naukowy Inżynieria i Kształtowanie Środowiska

2020

Vol. 29, No. 1

93--107

Comfort of the train passengers is the main priority of modern mass rapid transit (MRT) management. Objective of this paper is to investigate the thermal comfort of the elevated MRT station in tropical climate. The first step of this study was to conduct literature review on human thermal comfort, environment ergonomics, computational fluid dynamic (CFD), computational aeroacoustics (CAA), and predicted mean vote (PMV). Air quality in elevated MRT station was measured based on several parameters: relative humidity, wind speed, temperature, and wind direction. A 3D model of MRT designed was used to describe existing condition prior to simulations with CFD and CAA softwares. Predicted mean vote is arranged based on the value of metabolism, wind speed, ambient temperature, mean radiant temperature, amount of insulation from clothing, and relative humidity. Whereas predicted percentage of dissatisfi ed (PPD) can be derived from PMV calculations. The analysis shows that the average PMV of existing condition for elevated outdoor MRT station is 3.6 (extremely hot) with PPD is 100% (all passengers felt discomfort). Some recommendations to reduce heat stress were addressed such as: adding plant, changing materials of the MRT station, and change the design of the elevated MRT station. Modifying open elevated MRT station into indoor elevated MRT station with installing six units of AC (2pk, ±23°C) can improve air quality and maintain the thermal comfort scale of PMV to be –0.04 (comfort) with PPD of < 8%. Based on the analysis, it can be concluded that the most suitable design for elevated MRT station in tropical climate (hot and humid) is indoor MRT station with pay attention to both direct and indirect heat exposure that hit the station.