Browsing by Author "Bello-Ochende, T."

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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.
Thermodynamic optimisation of solar thermal brayton cycle models and heat exchangers using particle swarm algorithm
(Elsevier BV on behalf of Faculty of Engineering, Ain Shams University, 2023) Oyewola, O. M.; Petinrin, M. O.; Labiran, M. J.; Bello-Ochende, T.
In this work, three variants of the Brayton cycle incorporating concentrated solar technologies and dual regenerative systems are modeled. The first variant employs reheat, intercooling, and regeneration, the second applies intercooling and regeneration while the third case involves regeneration only. With the application of the entropy generation method and particle swarm algorithm (PSA), processes with the largest irreversibilities are noted, minimized and the geometric parameters of participating components are optimized. Results show that irreversibilities occurring in the systems were largely due to finite temperature differences within components. In all cases, the solar receiver and intercooler are the dominant and modest sources of entropy generation respectively. The regenerative system entropy generation is highest in the first case while decreasing in the second and third cases respectively. An improvement in the exergy availability was observed in the first case, as the first and second law efficiency peaks at 44.9% and 59.68% respectively. Though, with a lower second law efficiency than the former, its percentage network output is equal to the first case at 43%. The aspect ratio, hydraulic diameter, and length of the receiver were observed to vary to enhance greater heat capture and increase the turbine inlet temperature (TIT). The high temperature (HT) regenerator had its geometric properties of a higher magnitude than the low temperature (LT) system as the waste heat recovery is aided by an enhanced heat transfer surface area. In comparison with the single regeneration system, the network output of the dual model was about 33.5% with a significant reduction in the entropy generated, creating a trade-off between operating the system for more power or less generation of irreversibilities.
Thermodynamic optimization of parallel and spiral plate heat exchangers for modified solar thermal brayton cycle models
(2022) Petinrin, M. O.; Labiran, M. J.; Bello-Ochende, T.; Oyewola, O. M.
The receiver and heat exchangers in a Solar Thermal Brayton Cycle (STBC) have been the main sources of exergy loss. Duct profiles used in the heat exchange process have been observed to possess varying degrees of heat transfer effectiveness. To this end, the effects of the elliptical, circular and rectangular absorber tubes are investigated on three variants of the dual serial-regenerative STBC models employing reheater, intercooler, or in a combined arrangement. Also, the impact of the parallel plate heat exchanger (PPHE) and spiral plate heat exchangers (SPHE) on irreversibility is investigated. The particle swarm algorithm (PSA), a stochastic optimization tool is used for the minimization of irreversibilities within the cycle and optimization of the geometric parameters of the STBC components. The largest irreversibility loss on a component-basis is observed on the receiver. The rectangular absorber system for the receiver has the least irreversibility loss compared to other profiles studied, though, a higher internal to external irreversibility ratio was noticed. Improved exergy use via the dual regenerative system was observed on all models with reductions of 22% and 15% in irreversibility obtained from the receiver and recuperator respectively. In addition, the SPHE produced less irreversibilities compared to the PPHE system and this could be attributed to its large surface area available for heat transfer. An optimal second law efficiency of 62% and 74% on the PPHE and SPHE STBC systems, respectively is achieved at around a pressure ratio of 2.2. The dual serial-regenerative sys- tem without reheats and intercooling has the advantage of optimal energy available and efficient exergy use followed by the combined system.