Browsing by Author "Olugasa, T. T."

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An artificial neural network model for forecasting daily global solar radiation in Ibadan, Nigeria
(2009) Fadare, D. A.; Olugasa, T. T.
Solar radiation, the primary driver for many physical, chemical and biological processes on the earth's surface is considered the most indispensable parameter in the performance prediction of solar power systems. In this study, an artificial neural network (ANN) model was developed for predicting missing solar radiation data for Ibadan (Lat. 7.43°N; Long. 3.9°E; Alt. 227.2m), Nigeria. This study utilized daily solar radiation data for the period of 1984 to 2007 (24 years) from a meteorological station in Ibadan. The ANN model was designed using the Matlab® Neural Network Toolbox and five different structures of the model were investigated. Structure 1 utilized solar radiation data for 5 days to predict the next 25 days expected data; structure 2 utilized data for 10 days to predict the next 20 days; structure 3 used data for 15 days to predict succeeding 15 days; structure 4 used data for 25 days to predict next 5 days data; structure 5 used data for 5 days to predict the next 1 day solar radiation. The different structures were trained by using solar radiation data for 22 years and one year and the prediction accuracies were evaluated using the solar radiation values for year 2007. Results showed that structure 5 with correlation coefficient of 0.73 and 0.79 when trained with 22 years and 1 year, respectively gave the best prediction performance. Thus, indicating the suitability of structure 5 for prediction of solar radiation missing data.
Crossflow flow and heat transfer characteristics across a cam-shaped tube bank: a numerical study
(2022) Petinrin, M. O.; Sikirullahi, B. A.; Olugasa, T. T.; Oyewola, O. M.
Tubes are commonly employed in heat exchangers for their ease of production and capacity to sustain high pressure. In this study, the heat and flow transfer behaviour of cam-shaped tube bank in staggered configuration at varying angles of attack 0° to 180° was numerically investigated. The study was carried out by solving the continuity, momentum, energy and realizable k-ε transport equations using the finite volume-based ANSYS Fluent solver. This was performed to acquire the friction factor and heat transfer characteristics in the air inlet velocity range of 9 to 15 m/s. The results showed that the cam-shaped tube bank at varying angles of attack provided enhanced heat transfer characteristics relative to the circular tube bank. Also, camshaped tube banks at angles of attack of 90° and 120° exhibited the maximum heat transfer with 33.9 and 32.1% increase in Nusselt number over the circular tubes. Their friction factor was higher by 183 and 140.7%, respectively. The cam-shaped tube banks generally exhibited higher performance than the circular tube bank. Tube banks at angles of attack of 150° and 180° demonstrated higher thermal-hydraulic performance by 167.6 and 284.3% than the circular tubes, respectively. However, the tube banks at angles 90° and 120° exhibited lesser performance by value of 52.6 and 45.1%.
Examination of flow and heat transfer phenomena in ducts with dimples and protrusions
(2020) Oyewola, O. M.; Petinrin, M. O.; Gbolasere, M. A.; Olugasa, T. T.
Dimples and protrusions create effective flow structure by improving fluid-surface interactions and fluid-mixing in ducts for thermal enhancement with minimal pressure losses. The experimental investigation of the effects of dimples and protrusions in the form of smooth surface duct, teardrop dimpled and teardrop protruded duct on flow and heat transfer characteristics were examined. Measurements of temperature, pressure drop and velocity were carried out in an experimental test rig and data collected were used to evaluate the heat transfer, flow friction, and the overall thermal performance of the three test ducts for the Reynolds number ranges from 30,000 to 57,000. The results show that with reference to the smooth duct, the Nusselt number of dimpled duct increases by 134.4% while those of protruded duct increases by 41.6%. Further, the heat transfer augmentation ranges from 1.53 to 4.76 and 1.07 to 2.32 for dimpled duct and protruded duct, respectively. In addition, the protruded duct demonstrated a higher friction factor in the range of 1.48 to 2.25 times that of the smooth duct, while dimpled duct friction factor increases in the range of 1.10 to 1.31. The overall result suggests that the dimpled duct have the best thermal-hydraulic performance as revealed by the performance evaluation criteria.