FACULTY OF TECHNOLOGY
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Item Numerical study of the effect of changing tube pitches on heat and flow characteristics from tube bundles in cross flow(2019) Petinrin, M. O.; Towoju, O. A.; Ajiboye, S. A.; Zebulun, O. E.Tube bundles are found in various heat transfer equipment for thermal energy transfer between fluids. However, the inter-spatial arrangement of the tubes of any tube bundle is a determining factor for its thermal and hydraulic performance. In this paper, the effect of varying the transverse and longitudinal pitches downstream staggered circular tube bundle on the heat transfer and flow characteristic was numerically analyzed. Seven variations of tube arrangements were studied by changing the tube pitches within a Reynolds number range of 7 381 to 22 214. The analyses were carried out using the k-ε equation model imposed with the realizability constraint and were solved with finite volume CFD code, COMSOL Multiphysics. The results obtained were found to be in good agreement with existing correlations. The tube bundles with decreasing pitches demonstrated better heat transfer performance while those with increasing pitches exhibited a lower friction factor. Thus, the best thermal-hydraulic performance was obtained from increasing pitch arrangements.Item Numerical investigation of the concave-cut baffles effect in shell-and-tube heat exchanger(2019) Petinrin, M. O.; Dare, A. A.In this paper, the performance of shell-and-tube heat exchangers with single-segmental baffle and varying configurations of concave-cut baffles (10, 15 and 20 %) was investigated. The study was carried out for a heat exchanger having either engine oil, water and air as shell-side fluid. For each configuration of the baffles, the results of both the k-ε and RNG k-ε turbulent models were in very close agreement. The heat exchangers with concavecut baffles had higher pressure drops and lower performance factors than that of single-segmental baffle at the same range of mass flow rates for all fluid cases. Also, the concave-cut baffle heat exchangers had lower shell-side heat transfer coefficients at the same pressure drop against that of single-segmental baffles. Thus, the use of concave-cut baffles did not exhibit desirable performance in heat exchanger as compared with the segmental baffles.Item Entropy generation minimisation of shell-and-tube heat exchanger in crude oil preheat train using firefly algorithm(2018) Petinrin, M. O.; Bello-Ochende, T.; Dare, A. A.; Oyewola, O. M.This paper presents the entropy generation analysis and optimisation of typical shell-and-tube heat exchanger in the preheat train of crude oil distillation unit. The implication of entropy minimisation on energy consumption associated with design of heat exchanger was studied. The developed optimisation model was solved by employing the firefly algorithm. A number of constraints were applied with thirteen decision variables. The ε-NTU method and Delaware method were used for the heat exchanger design. Four cases were considered for each of two selected samples and were categorised under two studies. Total entropy generation rates for all the four cases considered were almost the same, and the dominant irreversibility distribution is by heat transfer. However, the sharp decrease in entropy generation due to fluid friction caused a great reduction in pumping power in the range of 51.4–82.1% and 54.8–92.2% for the two studies, respectively. The results of sensitivity study on the decision variables showed sharp reduction in entropy generation rate and increased pumping power as the mass flow rate increases for all the variables. Also, the choices of the tube diameter and tube number had greater impact on the changes in entropy generation rate and pumping power.Item Numerical investigation of shell-and-tube heat exchanger with parabolic segmental baffle cut(2019-01) Ikpotokin, I.; Uguru-Okorie, D. C.; Osueke, C. O.; Dare, A. A.; Petinrin, M. O.An investigation was carried out on the effect of the use of a parabolic baffle at different baffle cuts on the performance of shell and tube heat exchangers. The numerical study was performed on a personal computer with 12 GB RAM and Intel® Core™ i7 2.50GHz CPU using a CFD software Comsol Multiphysics. The modeled heat exchanger had 37 tubes, shell internal diameter of 200 mm, 6 baffles with baffle spacing of 100 mm. The results from the effect of mass flow rate and baffle cut on heat transfer rate and pressure drop in the shell side of the heat exchanger were compared with the circular segmental baffle cut of 25% and that of the parabolic baffle cut of 25 and 30% of the inner shell diameter. At 25% of the shell diameter baffle cut, the parabolic cut had an improved heat transfer rate compared to that with the circular segmental baffle cut with a drawback of higher pressure drop. As the parabolic baffle cuts increased, there was a decrease in heat transfer rates and pressure drops at the various mass flow rates considered. At 30% of shell diameter cut, the performance of the parabolic segmental baffle cut gave results similar to the circular segmental baffle cut at 25% of the inner shell diameter. The investigation showed that for a parabolic baffle cut, 30% of the shell diameter is recommended for optimum performance.Item Effect of viscous dissipation term on a fluid between two moving parallel plates(2018-08) Petinrin, M. O.; Adegbola, A. A.The fully developed laminar heat transfer of a Newtonian fluid flowing between two parallel plates where the bottom plate is fixed and the top plate is moving in an axial direction at constant speed was analyzed taking into account the iscous dissipation of the flowing fluid. Applying the velocity profile obtained for the plane Coutte-Poiseuille laminar flow, the energy equation with the viscous dissipation term was exactly solved for the boundary conditions of constant wall heat flux at one wall with the other insulated. Special attention is given to the shear produced by the movable top plate over and above the viscous dissipation due to internal fluid friction. The reason behind the behaviour exhibits by the temperature profile obtained at different velocities can be attributed to the effect of viscous dissipation coming into play due to the shear stress within the fluid layer induced by the movement of the upper plateItem Numerical modelling of thermal distribution control in a furnace(2018) Petinrin, M. O.; Ajide, O. O.; Dare, A. A.; Oyewola, O. M.; Ismail, O. S.Application of control to heat treatment processes helps to achieve the desired mechanical properties of materials but improper controller design is a major problem causing short lifespan of components of locally made furnaces. In this study, the numerical control of the temperature distribution within a furnace cavity was carried out using COMSOL Multiphysics and Simulink. Six sensor points within the furnace cavity (with and without specimen) were selected and each point was consecutively used to observe the time response of the sensor to the desired temperature. The results from the time response analysis indicated uneven temperature distribution within the furnace with points located at the corners of the furnace recording the highest temperature rise while points at the centre of the furnace or within the specimen having the lowest temperature. Thus, the best position for a sensor is at any corner of the furnace to protect the components of the furnace from damage.Item Thermal lesion of renal tumour as a function of catheter material property(2018-09) Towoju, O. A.; Petinrin, M. O.The extent of lesion achieved during microwave ablation is dependent on some factors which include the time period of application, its intensity, antenna geometry, and relative permittivity of the tissue. Several studies have been conducted on microwave ablation for the treatment of tumours and have focused on different antenna geometries, its intensity, and time of application. This work seeks to find a correlation between the relative permittivity of the catheter and the temperature distribution which determines necrosis of the tissue by using Tefzel ETFE, Teflon FEP, PFA Teflon type A, PFA Teflon type B, Teflon AF, and PTFE Teflon type B while modelling using COMSOL Multiphysics. The extent of the thermal lesion was observed to be dependent on the relative permittivity of the catheter material, with Tefzel ETFE giving the best performance and Teflon AF providing the least.Item Voltage control in distribution feeders with high penetration of wind energy(2017-07) Petinrin, J. O.; Shaaban, M.; Petinrin, M. O.The recent drift towards balancing generation and consumption, along with increasing demands of high power quality and reliability, require the deployment of energy storage and application of demand response in the smart grid. The potential for using energy storage and demand response promise to have a major impact on schemes for voltage control in a smart grid. This paper presents a comprehensive optimisation architecture that do not only take into consideration the coordination of VAr control devices, but also manages storage facilities and demand response in an hourly operation fashion. An integrated framework on hybrid Particle Swarm Optimisation/Gravitational Search Algorithm (PSOGSA) is used for VAr control devices, energy storage and demand response optimisation scheduling. The effectiveness of the proposed method is validated through a quasi-time sequence analysis over a 24-hourly simulation period. Test results show that the smart coordinated operation among the control devices causes reduction in system losses and enhances system capability to maintain voltages within the prescribed bounds.Item Numerical modelling of effect of baffle orientation offset on shell-and-tube heat exchanger performance(2018-02) Petinrin, M. O.; Dare, A. A.The performance of a shell-and-tube heat exchanger (STHE) is largely dependent on the type, orientation and offset arrangement of the baffles employed. In this paper, the thermal-hydraulic characteristics of STHEs with 90°, 120° and 180° offset arrangements of baffles were studied numerically. The study was performed on 19-tube and 31-tube heat exchangers, and also for three shell-side working fluids: air, water and engine oil. The numerical analyses were carried out using the k-ε model with imposed realizability constraint, and were solved with COMSOL Multiphysics. The STHE with 180° had higher pressure drop than other STHEs for all the ranges of mass flow rate. STHE with 120° showed better performance for shell-side heat transfer coefficient at the same pressure drop while STHE with 90° had much higher performance factor at the same mass flow rate. It is concluded that baffle offset arrangements significantly affected the shell and tube heat exchanger performance.Item Bridging Nigeria energy gap by utilizing her coal(2017) Towoju, O. A.; Petinrin, M. O.Many nations who meet their energy generation requirements are one way or the other tapping from the vast resources which is inherent in coal. A wide gap exists between the energy requirement of the Nigerian populace and the generated amount. This can be bridged by the utilization of its vast amount of bituminous coal in her reserves, with favourable properties of low percentage moisture and ash which is an advantage in terms of handling costs, ease of transportation and better overall system efficiency. The percentage moisture value for the analyzed sample was 5.0 percent while the percentage ash value was 6.6 percent. Both determined values are relatively low when compared to results of the analysis reported for some other countries coal.