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Article

Abbas Naeimi, Mohammad Hossein Ahmadi, Milad Sadeghzadeh and Alibakhsh Kasaeian

This paper aims to determine the optimum arrangement of a reverse osmosis system in two methods of plug and concentrate recycling.

Abstract

Purpose

This paper aims to determine the optimum arrangement of a reverse osmosis system in two methods of plug and concentrate recycling.

Design/methodology/approach

To compare the optimum conditions of these two methods, a seawater reverse osmosis system was considered to produce fresh water at a rate of 4,000 m3/d for Mahyarkala city, located in north of Iran, for a period of 20 years. Using genetic algorithms and two-objective optimization method, the reverse osmosis system was designed.

Findings

The results showed that exergy efficiency in optimum condition for concentrate recycling and plug methods was 82.6 and 92.4 per cent, respectively. The optimizations results showed that concentrate recycling method, despite a 36 per cent reduction in the initial cost and a 2 per cent increase in maintenance expenses, provides 6 per cent higher recovery and 19.7 per cent less permeate concentration than two-stage plug method.

Originality/value

Optimization parameters include feed water pressure, the rate of water return from the brine for concentrate recycling system, type of SW membrane, feedwater flow rate and numbers of elements in each pressure vessel (PV). These parameters were also compared to each other in terms of recovery (R) and freshwater unit production cost. In addition, the exergy of all elements was analyzed by selecting the optimal mode of each system.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Zehba Raizah, Mitsuteru Asai and Abdelraheem M. Aly

The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin…

Abstract

Purpose

The purpose of this study is to apply the incompressible smoothed particle hydrodynamics (ISPH) method to simulate the natural convection flow from an inner heated Y-fin inside Y-shaped enclosure filled with nanofluid.

Design/methodology/approach

The dimensionless governing partial differential equations are described in the Lagrangian form and solved by an implicit scheme of the ISPH method. The embedded Y-fin is kept at a high temperature Th with variable heights during the simulations. The lower area of Y-shaped enclosure is squared with width L = 1 m and its side-walls are kept at a low temperature Tc. The upper area of the Y-shaped enclosure is V-shaped with width 0.5 L for each side and its walls are adiabatic.

Findings

The performed simulations revealed that the height of the inner heated Y-fin plays an important role in the heat transfer and fluid flow inside the Y-shaped enclosure, where it enhances the heat transfer. Rayleigh number augments the buoyancy force inside the Y-shaped enclosure and, consequently, it has a strong impact on temperature distributions and strength of the fluid flow inside Y-shaped enclosure. Adding more concentration of the nanofluid until 10% has a slight effect on the temperature distributions and it reduces the strength of the fluid flow inside Y-shaped enclosure. In addition, the average Nusselt number is measured along the inner heated Y-fin and it grows as the Rayleigh number increases. The average Nusselt number is decreasing by adding more concentrations of the nanofluid.

Originality/value

An improved ISPH method is used to simulate the natural convection flow of Y-fin embedded in the Y-shaped enclosure filled with a nanofluid.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 1
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Nurudeen Ayobami Ajadi, Osebekwin Asiribo and Ganiyu Dawodu

This study aims to focus on proposing a new memory-type chart called progressive mean exponentially weighted moving average (PMEWMA) control chart. This memory-type chart…

Abstract

Purpose

This study aims to focus on proposing a new memory-type chart called progressive mean exponentially weighted moving average (PMEWMA) control chart. This memory-type chart is an improvement on the existing progressive mean control chart, to detect small and moderate shifts in a process.

Design/methodology/approach

The PMEWMA control chart is developed by using a cumulative average of the exponentially weighted moving average scheme known as the progressive approach. This scheme is designed based on the assumption that data follow a normal distribution. In addition, the authors investigate the robustness of the proposed chart to the normality assumption.

Findings

The variance and the mean of the scheme are computed, and the mean is found to be an unbiased estimator of the population mean. The proposed chart's performance is compared with the existing charts in the literature by using the average run-length as the performance measure. Application examples from the petroleum and bottling industry are also presented for practical considerations. The comparison shows that the PMEWMA chart is quicker in detecting small shifts in the process than the other memory-type charts covered in this study. The authors also notice that the PMEWMA chart is affected by higher kurtosis and skewness.

Originality/value

A new memory-type scheme is developed in this research, which is efficient in detecting small and medium shifts of a process mean.

Details

International Journal of Quality & Reliability Management, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0265-671X

Keywords

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Article

Muhammad Ijaz Khan, Sohail Ahmad Khan, Tasawar Hayat, Muhammad Waqas and Ahmed Alsaedi

The purpose of this paper is to investigate the entropy optimization in magnetohydrodynamic hybrid nanomaterials flows toward a stretchable surface. The energy expression…

Abstract

Purpose

The purpose of this paper is to investigate the entropy optimization in magnetohydrodynamic hybrid nanomaterials flows toward a stretchable surface. The energy expression is modeled subject to dissipation, heat generation/absorption and Joule heating. Here silicon dioxide (SiO2) and molybdenum disulfide (MoS2) as nanoparticles and propylene glycol (C3H8O2) as base fluid, respectively. Furthermore, the authors discussed the comparative study of molybdenum disulfide and silicon dioxide diluted in propylene glycol. The total entropy optimization rate is computed through implementation of the second law of thermodynamics.

Design/methodology/approach

The nonlinear partial differential system is reduced to an ordinary one through implementation of transformation. Newton built-in shooting method is used for computational results for the given system. Influences of various flow variables on the temperature, Bejan number, velocity, concentration and entropy generation rate are examined graphically for both nanoparticles (SiO2 and MoS2). Gradients of velocity and temperature are computed numerically for various physical parameters. Also, take the comparison between the present and previously published results in tabulated form.

Findings

For higher estimation of ϕ both temperature and velocity are enhanced. Entropy optimization and Bejan number have the opposite outcome for viscosity parameter. Temperature and velocity have opposite behaviors for larger values of magnetic parameter. Molybdenum disulfide (MoS2) is more efficient than silicon dioxide (SiO2).

Originality/value

No such work is yet published in the literature.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 22 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

Anwar Hasan Abdullah Othman, Syed Musa Alhabshi, Salina Kassim and Ashurov Sharofiddin

With the continuing development of the financial technology revolution, a better understanding of bank deposits variability has become necessary for bank management and…

Abstract

Purpose

With the continuing development of the financial technology revolution, a better understanding of bank deposits variability has become necessary for bank management and policymakers, especially central banks. This is because the novel innovations of cryptocurrencies operate beyond the realm of the banking system, which may impact the performance of banks and their deposits variability. This study aims to investigate the long- and short-run effects of cryptocurrencies’ market capitalization development on the banks’ deposit variability in the Gulf Cooperation Council (GCC) region.

Design/methodology/approach

In this study, the Johansen–Juselius (1990) cointegration test with vector error correction model was applied to examine the long-run relationships, while the Engle and Granger (1987) and the Granger (1969) causality tests were used to detect causal relationships in the short term.

Findings

The findings of Johansen–Juselius cointegration test indicate that the banks’ deposits variability in all six states of the Gulf region share negative long-run equilibrium association with the development of global cryptocurrencies market capitalization, but with different statistically significant levels. For the short-run analysis, the study found that the development of cryptocurrencies market capitalization has significant unidirectional causal effects on bank deposits variabilities in only four states, namely, UAE, Qatar, Kuwait and Bahrain. The findings of the study therefore suggest that to eradicate the effects of cryptocurrencies industry and its threats to the banking industry, banks in GCC region are encouraged to either consider cryptocurrencies as an alternative investment asset for their portfolio investment diversification strategies or adopt the blockchain technology in their operation system to facilitate their customers with low transaction cost, high level of security and ease of use and real-time settlement.

Research limitations/implications

The empirical findings of the study will provide valuable input for policymakers, especially central banks and bank managements, to evaluate the current situation and the threats of the cryptocurrencies market growth and its effect on the banking industry’s performance, future survival and their deposits variability for better regulation and policy planning and investment strategies.

Originality/value

This is a pioneering study that empirically explores the phenomenon of bank deposits variability as a consequence of expansion in cryptocurrencies market capitalization, where the findings proved evidence of a drastic decline in banks’ deposits size due to the substantial growth in cryptocurrencies market capitalization.

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Article

Najiyah Safwa Khashi'ie, Norihan M. Arifin, John H. Merkin, Rusya Iryanti Yahaya and Ioan Pop

The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder.

Abstract

Purpose

The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder.

Design/methodology/approach

The similarity equations that reduced from the boundary layer and energy equations are solved using the bvp4c solver. The duality of solutions is observed within the specific range of the control parameters, namely, mixed convection parameter λ, curvature parameter γ and nanoparticles volumetric concentration ϕ1 for alumina, while for copper ϕ2. The stability analysis is also designed to justify the particular solutions’ stability. Additionally, the idea to obtain the solution for large value of λ and γ is also presented in this paper.

Findings

Two solutions exist in opposing and assisting flows up to a critical value λc where λc lies in the opposing region. An upsurge of the curvature parameter tends to extend the critical value (delay the separation process), whilst increase the heat transfer performance of the working fluid. Meanwhile, the application of hybrid Cu-Al2O3/water nanofluid also can decelerate the separation of laminar boundary layer flow and produce higher heat transfer rate than the Cu–water nanofluid and pure water.

Originality/value

The results are new and original. This study benefits to the other researchers, specifically in the observation of the fluid flow characteristics and heat transfer rate of the hybrid nanofluid. Also, this paper features with the mathematical formulation for the solution with large values of λ and γ.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

Keywords

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Article

H.M. Tawancy, A. Ul‐Hamid, A.I. Mohammed and N.M. Abbas

To determine if the interim use of liquid waste as a fuel in a catalytic steam reformer unit had any deleterious effect on the long‐term life of the reformer tubes.

Abstract

Purpose

To determine if the interim use of liquid waste as a fuel in a catalytic steam reformer unit had any deleterious effect on the long‐term life of the reformer tubes.

Design/methodology/approach

Standard metallographic techniques were used to prepare representative samples obtained from various sections of the reformer tubes for metallurgical evaluation. Microstructural characterization was carried out in a scanning electron microscope equipped with an energy dispersive X‐ray spectrometer. Imaging and elemental analysis was used for the identification of the alloy material, corrosion products and other microstructural features.

Findings

Hydrogen was produced in a catalytic steam reformer by cracking methane using natural gas as a fuel. Corrosion of reformer tubes occurred when natural gas fuel was replaced with a liquid waste. Use of liquid fuel waste accelerated the rate of oxidation at the outer tube surface. However, foreign species from the fuel were not transported into the tube material. The heat‐resistant steel casting used for this application was susceptible to precipitation of Si‐stabilized Ni‐Nb Laves phase, thus reducing rupture life of the component. Voids at grain boundaries indicative of creep damage were observed.

Practical implications

Although, the interim use of liquid waste fuel appeared not to have damaged the tubes, it was concluded that the expected service life of the tubes may not be realized because of the susceptibility of the material to precipitation of Laves phase. An Fe‐base superalloy UNS N08810 or UNS N08811 was recommended as a replacement material for this application.

Originality/value

This paper provides an account of a failure analysis study. It identifies incorrect materials selection for a particular application and suggests better alternative along with its justification. The information is deemed useful for plant designers and engineers working in the related industry.

Details

Anti-Corrosion Methods and Materials, vol. 52 no. 6
Type: Research Article
ISSN: 0003-5599

Keywords

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Article

A. Ul‐Hamid, H.M. Tawancy, A.I. Mohammed, S.S. Al‐Jaroudi and N.M. Abbas

The oxidation behaviour of a wrought Ni‐Mo‐Cr alloy was studied under thermal cyclic conditions in air at 800°C for exposure periods of up to 1,000 h. The morphologies…

Abstract

The oxidation behaviour of a wrought Ni‐Mo‐Cr alloy was studied under thermal cyclic conditions in air at 800°C for exposure periods of up to 1,000 h. The morphologies, microstructures and compositions of the oxide scales were characterized by scanning electron microscopy, energy dispersive X‐ray spectroscopy and X‐ray diffraction. Oxidation kinetics were determined by weight gain measurements. Results show that steady‐state oxidation was achieved within 1 h of exposure while partial scale spalling was observed after 400 h. The alloy grain boundaries intersecting the alloy surface showed preferential oxidation. They became depleted in Ni and enriched in Mo and Cr during transient oxidation. The scale initially formed at the surface was NiO which grew outwardly and laterally to cover the entire alloy. Upon continued oxidation, the scale developed into an outer NiO layer and an inner Cr2O3 layer while the presence of NiMoO4 was also observed within the scale.

Details

Anti-Corrosion Methods and Materials, vol. 51 no. 5
Type: Research Article
ISSN: 0003-5599

Keywords

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Article

Dirk De Clercq, Inam Ul Haq and Muhammad Umer Azeem

With a basis in the conservation of resources theory, the purpose of this paper is to investigate the relationship between employees’ experience of time-related work…

Abstract

Purpose

With a basis in the conservation of resources theory, the purpose of this paper is to investigate the relationship between employees’ experience of time-related work stress and their engagement in counterproductive work behavior (CWB), as well as the invigorating roles that different deviant personality traits might play in this process.

Design/methodology/approach

Two-wave survey data with a time lag of three weeks were collected from 127 employees in Pakistani organizations.

Findings

Employees’ sense that they have insufficient time to do their job tasks spurs their CWB, and this effect is particularly strong if they have strong Machiavellian, narcissistic or psychopathic tendencies.

Originality/value

This study adds to extant research by identifying employees’ time-related work stress as an understudied driver of their CWB and the three personality traits that constitute the dark triad as triggers of the translation of time-related work stress into CWB.

Details

Personnel Review, vol. 48 no. 7
Type: Research Article
ISSN: 0048-3486

Keywords

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Article

Mohd Ezad Hafidz Hafidzuddin, Roslinda Nazar, Norihan M. Arifin and Ioan Pop

This study aims to investigate the unsteady two-dimensional viscous flow and heat transfer over an unsteady permeable stretching/shrinking sheet (surface) with generalized…

Abstract

Purpose

This study aims to investigate the unsteady two-dimensional viscous flow and heat transfer over an unsteady permeable stretching/shrinking sheet (surface) with generalized slip velocity condition.

Design/methodology/approach

Similarity transformation is used to reduce the system of partial differential equations into a system of nonlinear ordinary differential equations. The resulting equations are then solved numerically using “bvp4c” function in MATLAB software.

Findings

Dual solutions are found for a certain range of the unsteady, suction and stretching/shrinking parameters. Stability analysis is performed, and it is revealed that the first (upper branch) solution is stable and physically realizable, whereas the second (lower branch) solution is unstable.

Practical implications

The results obtained can be used to explain the characteristics and applications of the generalized slip in boundary layer flow. Such condition is applied for particulate fluids such as foams, emulsions, polymer solutions and suspensions. Furthermore, the phenomenon of stretching/shrinking sheet can be found on the manufacturing of polymer sheets, rising and shrinking balloon or moving and shrinking polymer film.

Originality/value

The present numerical results are original and new for the study of unsteady flow and heat transfer over a permeable stretching/shrinking sheet with generalized slip velocity.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

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