Engineering and Informaticshttp://hdl.handle.net/10454/4132020-05-28T03:58:20Z2020-05-28T03:58:20ZSteam consumption minimization using genetic algorithm optimization method: an industrial case studyAlabdulkarem, A.Rahmanian, Nejathttp://hdl.handle.net/10454/178332020-05-28T01:27:18Z2020-01-01T00:00:00ZAlabdulkarem A and Rahmanian N (2020) Steam consumption minimization using genetic algorithm optimization method: an industrial case study. Energy Sources, Part A: Recovery, Utilization, and Environmental Effects. Accepted for publication.
Condensate stabilization is a process where hydrocarbon condensate recovered from natural gas reservoirs is processed to meet the required storage, transportation, and export specifications. The process involves stabilizing of hydrocarbon liquid by separation of light hydrocarbon such as methane from the heavier hydrocarbon constituents such as propane. An industrial scale back-up condensate stabilization unit was simulated using Aspen HYSYS software and validated with the plant data. The separation process consumes significant amount of energy in form of steam. The objectives of the paper are to find the minimum steam consumption of the process and conduct sensitivity and exergy analyses on the process. The minimum steam consumption was found using genetic algorithm optimization method for both winter and summer conditions. The optimization was carried out using MATLAB software coupled with Aspen HYSYS software. The optimization involves six design variables and four constraints, such that realistic results are achieved. The results of the optimization show that savings in steam consumption is 34% as compared to the baseline process while maintaining the desired specifications. The effect of natural gas feed temperature has been investigated. The results show that steam consumption is reduced by 46% when the natural gas feed temperature changes from 17.7 to 32.7°C. Exergy analysis shows that exergy destruction of the optimized process is 37% less than the baseline process.
2020-01-01T00:00:00ZEquivalence classes of coherent projectors in a Hilbert space with prime dimension: Q functions and their Gini indexVourdas, Apostoloshttp://hdl.handle.net/10454/178282020-05-21T01:10:55Z2020-05-01T00:00:00ZVourdas A (2020) Equivalence classes of coherent projectors in a Hilbert space with prime dimension: Q functions and their Gini index. Journal of Physics A: Mathematical and Theoretical. 53(21): 215201.
Coherent subspaces spanned by a finite number of coherent states are introduced, in a quantum system with Hilbert space that has odd prime dimension d. The set of all coherent subspaces is partitioned into equivalence classes, with d 2 subspaces in each class. The corresponding coherent projectors within an equivalence class, have the 'closure under displacements property' and also resolve the identity. Different equivalence classes provide different granularisation of the Hilbert space, and they form a partial order 'coarser' (and 'finer'). In the case of a two-dimensional coherent subspace spanned by two coherent states, the corresponding projector (of rank 2) is different than the sum of the two projectors to the subspaces related to each of the two coherent states. We quantify this with 'non-addditivity operators' which are a measure of quantum interference in phase space, and also of the non-commutativity of the projectors. Generalized Q and P functions of density matrices, which are based on coherent projectors in a given equivalence class, are introduced. Analogues of the Lorenz values and the Gini index (which are popular quantities in mathematical economics) are used here to quantify the inequality in the distribution of the Q function of a quantum state, within the granular structure of the Hilbert space. A comparison is made between Lorenz values and the Gini index for the cases of coarse and also fine granularisation of the Hilbert space. Lorenz values require an ordering of the d 2 values of the Q function of a density matrix, and this leads to the ranking permutation of a density matrix, and to comonotonic density matrices (which have the same ranking permutation). The Lorenz values are a superadditive function and the Gini index is a subadditive function (they are both additive quantities for comonotonic density matrices). Various examples demonstrate these ideas.
2020-05-01T00:00:00ZLotus-leaf inspired surfaces: hydrophobicity evolution of replicas due to mechanical cleaning and mold wearRomano, J-M.Garcia-Giron, A.Penchev, P.Gulcur, MertWhiteside, Benjamin R.Dimov, S.http://hdl.handle.net/10454/178222020-05-20T01:10:41Z2020-03-01T00:00:00ZRomano J-M, Garcia-Giron A, Penchev P et al (2020) Lotus-leaf inspired surfaces: hydrophobicity evolution of replicas due to mechanical cleaning and mold wear. Journal of Micro and Nano-Manufacturing. 8(1): 010913.
Inspired from the low wetting properties of Lotus leaves, the fabrication of dual micro/nano-scale topographies is of interest to many applications. In this research, superhydrophobic surfaces are fabricated by a process chain combining ultrashort pulsed laser texturing of steel inserts and injection moulding to produce textured polypropylene parts. This manufacturing route is very promising and could be economically viable for mass production of polymeric parts with superhydrophobic properties. However, surface damages, such as wear and abrasion phenomena, can be detrimental to the attractive wetting properties of replicated textured surfaces. Therefore, the final product lifespan is investigated by employing mechanical cleaning of textured polypropylene surfaces with multipurpose cloths following the ASTM D3450 standard. Secondly, the surface damage of replication masters after 350 injection moulding cycles with glass-fiber reinforced polypropylene, especially to intensify mould wear, was investigated. In both cases, the degradation of the dual-scale surface textures had a clear impact on surface topography of the replicas and thus on their wetting properties, too.
2020-03-01T00:00:00ZMathematical modelling of performance and wear prediction of PDC drill bits: impact of bit profile, bit hydraulic, and rock strengthMazen, Ahmed Z.Mujtaba, Iqbal M.Hassanpour, A.Rahmanian, Nejathttp://hdl.handle.net/10454/178322020-05-26T13:33:12Z2020-05-01T00:00:00ZMazen AZ, Mujtaba IM, Hassanpour A et al (2020) Mathematical modelling of performance and wear prediction of PDC drill bits: impact of bit profile, bit hydraulic, and rock strength. Journal of Petroleum Science and Engineering. 188: 106849.
The estimation of Polycrystalline Diamond Compact (PDC) cutters wear has been an area of concern for the drilling industry for years now. The cutter's wear has been measured practically by pulling the bit out for evaluation at the surface. It is important to find the right time for tripping out as this helps to avoid the fishing job and reduces the operational cost significantly. The prediction of the drilling performance is based on the interaction of cutter and rock. Several authors focused on the cutter-rock interface but only a few researchers tried to model the wear of the PDC bit cutters. The aim of this research is to understand the relationships between the rate of penetration (ROP) and the drilling variables per each foot, and then determine the overall bit efficiency for the whole drilling operation. A new mathematical model is derived to predict the PDC bit performance by considering the factors that were already not taken into account. These factors include rock strength, bit design, and bit hydraulic. The model investigates the effect of these parameters to estimate the abrasive cutters wear on the inner and the outer bit cones by deriving modified equations to calculate the mechanical specific energy (MSE), torque, and depth of cut (DOC) as a function of effective blades (EB). The model is used to forecast the bit cutters wear conditions in four wells in the oil fields located in Libya, which were drilled with three different PDC's sizes. The model enables the results to be compared to the actual bit cutters wear measured for inner and outer cones. The results are found that are well in agreement with the actual field data obtained in bit records.
2020-05-01T00:00:00ZFlow structures in wake of a pile-supported horizontal axis tidal stream turbineZhang, J.Lin, X.Wang, R.Guo, YakunZhang, C.Zhang, Y.http://hdl.handle.net/10454/177962020-05-13T01:10:50Z2020-03-01T00:00:00ZZhang J, Lin X, Wang R et al (2020) Flow structures in wake of a pile-supported horizontal axis tidal stream turbine. Renewable Energy. 147(1): 2321-2334.
This study presents results from laboratory experiments to investigate the wake structure in the lee side of a scaled three-bladed horizontal axis tidal stream turbine with a mono-pile support structure. Experiments are conducted for a range of approaching flow velocity and installation height of rotor. Analysis of the results shows that bed shear stress increases with the increase of approaching velocity and decrease of installation height within 2D (D is the diameter of the rotor) downstream of the rotor. The flow field within 2D downstream of the rotor is greatly influenced by the presence of nacelle and mono-pile. Low stream-wise flow velocity and large turbulence intensity level is detected along the flume center right behind the nacelle and mono-pile from 1D to 2D downstream of the rotor. Stream-wise velocity at the blade tip height lower than the nacelle increases sharply from 1D to 2D and gradually grows afterwards. Correspondingly, the turbulence intensity decreases quickly from 1D to 2D and slowly afterwards. Large bed shear stress is measured from 1D to 2D, which is closely related to turbulence induced by the mono-pile. It is also found that the presence of the mono-pile might make the flow field more ‘disc-shaped’.
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