Nawar Mohammed Ridha Hashim, Mohd. Zamri Yusoff and Hussein Ahmed Mohammed
The purpose of this paper is to numerically study the phenomenon of separation and subsequent reattachment that happens due to a sudden contraction or expansion in flow geometry…
Abstract
Purpose
The purpose of this paper is to numerically study the phenomenon of separation and subsequent reattachment that happens due to a sudden contraction or expansion in flow geometry, in addition, to investigating the effect of nanoparticles suspended in water on heat transfer enhancement and fluid flow characteristics.
Design/methodology/approach
Turbulent forced convection flow over triple forward facing step (FFS) in a duct is numerically studied by using different types of nanofluids. Finite volume method is employed to carry out the numerical investigations. with nanoparticles volume fraction in the range of 1-4 per cent and nanoparticles diameter in the range 30-75 nm, suspended in water. Several parameters were studied, such as the geometrical specification (different step heights), boundary conditions (different Reynolds [Re] numbers), types of fluids (base fluid with different types of nanoparticles), nanoparticle concentration (different volume fractions) and nanoparticle size.
Findings
The numerical results indicate that the Nusselt number increases as the volume fraction increases, but it decreases as the diameter of the nanoparticles of nanofluids increases. The turbulent kinetic energy and its dissipation rate increase as Re number increases. The velocity magnitude increases as the density of nanofluids decreases. No significant effect of increasing the three steps heights on Nusselt along the heated wall, except in front of first step where increasing the first step height leads to an increase in the recirculation zone size adjacent to it.
Research limitations/implications
The phenomenon of separation and subsequent reattachment happened due to a sudden contraction or expansion in flow geometry, such as forward facing and backward facing steps, respectively, can be recognized in many engineering applications where heat transfer enhancement is required. Some examples include cooling systems for electronic equipment, heat exchanger, diffusers and chemical process. Understanding the concept of these devices is very important from the engineering point of view.
Originality/value
Convective heat transfer can be enhanced passively by changing flow geometry, boundary conditions, the traditional fluids or by enhancing thermal conductivity of the fluid. Great attention has been paid to increase the thermal conductivity of base fluid by suspending nano-, micro- or larger-sized particles in fluid. The products from suspending these particles in the base fluid are called nanofluids. Many studies have been conducted to investigate the heat transfer and fluid flow characteristics over FFS. This study is the first where nanofluids are employed as working fluids for flow over triple FFS.
Details
Keywords
Husam Jasim Mohammed, Qasim Ali Mohammed and Mustafa Hatwan Rhima
The aim of the study is to investigate the effects of perceived healthcare service quality (human aspects, technical aspects and tangible aspects) on satisfaction and guest…
Abstract
Purpose
The aim of the study is to investigate the effects of perceived healthcare service quality (human aspects, technical aspects and tangible aspects) on satisfaction and guest loyalty in the hotel industry in the COVID-19 pandemic era.
Design/methodology/approach
A total of 130 guests in the hotel were selected purposively in Iraq. Data from self-administered questionnaires were analyzed through the VB-SEM statistical technique using Smart-PLS software towards testing the hypotheses.
Findings
The findings indicated that perceived service quality influences satisfaction and guest loyalty of guests in the hotel. This study reveals that human aspects, technical aspects and tangible aspects directly positively affect satisfaction and guest loyalty in the hotel industry.
Originality/value
This study highlights that perceived service quality (human aspects, technical aspects and tangible aspects) are vital and practical strategic tools that could be positioned to accelerate guest loyalty in the hotel industry. Furthermore, satisfaction mediates the relationship between human aspects, technical aspects, tangible aspects and guest loyalty.
Details
Keywords
H.A. Mohammed, G. Bhaskaran, N.H. Shuaib, H.I. Abu‐Mulaweh and R. Saidur
The purpose of this paper is to investigate numerically the thermal and hydrodynamics performance of circular microchannel heat exchanger (CMCHE) using various nanofluids.
Abstract
Purpose
The purpose of this paper is to investigate numerically the thermal and hydrodynamics performance of circular microchannel heat exchanger (CMCHE) using various nanofluids.
Design/methodology/approach
The three‐dimensional steady, laminar developing flow and conjugate heat transfer governing equations of a balanced MCHE are solved using finite volume method.
Findings
The results are shown in terms of temperature profile, heat transfer coefficient, pressure drop, wall shear stress, pumping power, effectiveness and performance index. The addition of nanoparticles increased the heat transfer rate of the base fluids. The temperature profiles of the fluids have revealed that higher average bulk temperatures were obtained by the nanofluids compared to water. The addition of nanoparticles also increased the pressure drop along the channels slightly. The increase in nanoparticle concentrations yielded better heat transfer rate while the increase in Reynolds number decreased the heat transfer rate.
Research limitations/implications
The tested nanofluids are Ag, Al2O3, CuO, SiO2, and TiO2. Reynolds number range varied from 100 to 800 and the nanoparticle concentration varied from 2 per cent to 10 per cent.
Practical implications
Parallel flow in CMCHEs is used in thermal engineering applications and the design and performance analysis of these CMCHE are of practical importance.
Originality/value
This paper provides the details of the thermal and hydrodynamics performance analysis of flow heat exchangers using nanofluids, which can be used for heat transfer augmentation in thermal design.
Details
Keywords
Abdullah A.A.A. Al-Rashed, Lioua Kolsi, Mohammed A. Tashkandi, Emad Hasani Malekshah, Ali J. Chamkha and Mohamad Naceur Borjini
The purpose of this paper is to investigate the coupled effect of magnetic field and radiation on convective heat transfer of low electrically conductive dielectric oxide melt.
Abstract
Purpose
The purpose of this paper is to investigate the coupled effect of magnetic field and radiation on convective heat transfer of low electrically conductive dielectric oxide melt.
Design/methodology/approach
The 3D Navier–Stokes equations are formulated using the vector potential-vorticity formulation and solved using the finite volume method (FVM). The radiative heat transfer equation is discretized using the FTnFVM method. A code was written using FORTRAN language.
Findings
The obtained numerical results are focused on the effect of the different parameters on the heat transfer and the flow structure with a special interest on the 3D transvers flow. It is found that the flow is developing in inner spirals and the magnetic field intensifies this 3D character. The radiation acts mainly at the core of the enclosure and causes the apparition of the merging phenomenon near the front and back walls.
Originality/value
The effect of magnetic field on convective heat transfer of highly electrically conductive fluids has been intensively studied. Reciprocally, the case of a fluid with low electrical conductivity is not so much investigated, especially when it is coupled with the effect of radiation. These two effects are studied in this paper for the case of a low-conductive LiNbO3 oxide melt.
Details
Keywords
Jamal K. Shakor, Atiya K. Mohammed and Yadgar H. Hama-karim
This study aims to find out the participation rate of women in the utilization of screening methods to determine the relationship of sociodemographic health characteristics and…
Abstract
Purpose
This study aims to find out the participation rate of women in the utilization of screening methods to determine the relationship of sociodemographic health characteristics and breast cancer (BC) awareness with the utilization of screening methods. The authors’ study aims to examine the relationship between women's belief and the utilization of screening methods.
Design/methodology/approach
A cross-sectional study was conducted in three health centers from December 13, 2016 to June 12, 2017. A questionnaire was constructed for data collection about sociodemographic characteristics, screening awareness and medical and health background variables. Additionally, BC awareness measure and champion health belief model scales were used to measure women's perceptiveness about BC.
Findings
Despite the awareness among 78.9% of women regarding clinical breast examination (CBE) as a screening method, only 9.5% women utilized it for screening. Due to prescription by physicians for diagnosis of BC, 23.6% women had done mammography at least once in their life. Having jobs and a good education significantly influenced the utilization of CBE as a screening method. The logistic regression analysis found that old age, family history of BC, good knowledge about BC, perceived susceptibility, low rate of perceived barriers to mammography and CBE predicted participation in screening.
Originality/value
Enhancing knowledge about BC and screening, emphasizing the susceptibility to BC and the benefits of screening will help in better participation. Importance should be given to illiterate and unemployed women.
Details
Keywords
Ehsan Nikbakht and Mohammed H.A. Tafti
An appropriate approach to determine and measure the characteristics of “good” borrowers has always been the subject of inquiry by various lenders both in domestic and…
Abstract
An appropriate approach to determine and measure the characteristics of “good” borrowers has always been the subject of inquiry by various lenders both in domestic and international financial markets. Cost of bad debts incurring from non‐payers and slow payers is a major source of loss which would affect profits and consequently the value of the lending firm. A carefully designed and economically feasible method to select the right borrowers is consistent with the goal of a modern lending institution which is to minimize the risk of bad debts and increase the wealth of its shareholders. The issue of selecting good borrowers is more serious in the case of potential credit card holders where the number of applicants is far greater than the number of commercial, real estate, and other institutional borrowers. Lending institutions cannot afford spending more than a certain limited amount of time to scrutinize the application of each applicant. Competition and increasing cost of information are other reasons that a lender should approve or reject submitted applications in a reasonably short period of time with minimum decision errors.
Ismail Arroub, Ahmed Bahlaoui, Abdelghani Raji, Mohammed Hasnaoui and Mohamed Naïmi
The purpose of this paper is to investigate numerically mixed convection of Al2O3-water nanofluids flowing through a horizontal ventilated cavity heated from below by a…
Abstract
Purpose
The purpose of this paper is to investigate numerically mixed convection of Al2O3-water nanofluids flowing through a horizontal ventilated cavity heated from below by a temperature varying sinusoidally along its lower wall. The simulations focus on the effects of different key parameters, such as Reynolds number (200 ≤ Re ≤ 5,000), nanoparticles’ concentration (0 ≤ ϕ ≤ 0.1) and phase shift of the heating temperature (0 ≤ γ ≤ π), on flow and thermal patterns and heat transfer performances.
Design/methodology/approach
The Navier–Stokes equations describing the nanofluid flow were discretized using a finite difference technique. The vorticity and energy equations were solved by the alternating direction implicit method. Values of the stream function were obtained by using the point successive over-relaxation method.
Findings
The simulations were performed for two modes of imposed external flow (injection and suction). The main findings are that the dynamical and thermal fields are affected by the parameters Re, ϕ, γ and the applied ventilation mode; the addition of nanoparticles leads to an improvement of heat transfer rate and an increase of mean temperature inside the enclosure; the heat exchange performance and the better cooling are more pronounced in suction mode; the phase shift of the heating temperature may lead to periodic solutions for weaker values of Re and contributes to an increase or a decrease of heat transfer depending on the value of ϕ and the convection regime.
Originality/value
To the best of the authors’ knowledge, the problem of mixed convection of a nanofluid inside a vented cavity using the injection or suction technics and submitted to non-uniform heating conditions has not been treated so far.
Details
Keywords
Mohammed H. A. Tafti and Ehsan Nikbakht
Neural networks and expert systems are two major branches ofartificial intelligence (AI). Their emergence has created the potentialfor a new generation of computer‐based…
Abstract
Neural networks and expert systems are two major branches of artificial intelligence (AI). Their emergence has created the potential for a new generation of computer‐based applications in the area of financial decision making. Both systems are used by financial institutions and corporations for a variety of new applications from credit scoring to bond rating to detection of credit card fraud. While both systems belong to the applied field of artificial intelligence, there are many differences between them which differentiate their potential capabilities in the field of business. Presents an analysis of both neural networks and expert systems applications in terms of their capabilities and weaknesses. Uses examples of financial applications of expert systems and neural networks to provide a unified context for the comparison.
Details
Keywords
Ali Akbar Abbasian Arani and Reza Moradi
Using turbulators, obstacles, ribs, corrugations, baffles and different tube geometry, and also various arrangements of these components have a noticeable effect on the shell and…
Abstract
Purpose
Using turbulators, obstacles, ribs, corrugations, baffles and different tube geometry, and also various arrangements of these components have a noticeable effect on the shell and tube heat exchangers (STHEs) thermal-hydraulic performance. This study aims to investigate non-Newtonian fluid flow characteristics and heat transfer features of water and carboxyl methyl cellulose (H2O 99.5%:0.5% CMC)-based Al2O3 nanofluid inside the STHE equipped with corrugated tubes and baffles using two-phase mixture model.
Design/methodology/approach
Five different corrugated tubes and two baffle shapes are studied numerically using finite volume method based on SIMPLEC algorithm using ANSYS-Fluent software.
Findings
Based on the obtained results, it is shown that for low-mass flow rates, the disk baffle (DB) has more heat transfer coefficient than that of segmental baffle (SB) configuration, while for mass flow rate more than 1 kg/s, using the SB leads to more heat transfer coefficient than that of DB configuration. Using the DB leads to higher thermal-hydraulic performance evaluation criteria (THPEC) than that of SB configuration in heat exchanger. The THPEC values are between 1.32 and 1.45.
Originality/value
Using inner, outer or inner/outer corrugations (outer circular rib and inner circular rib [OCR+ICR]) tubes for all mass flow rates can increase the THPEC significantly. Based on the present study, STHE with DB and OCR+ICR tubes configuration filled with water/CMC/Al2O3 with f = 1.5% and dnp = 100 nm is the optimum configuration. The value of THPEC in referred case was 1.73, while for outer corrugations and inner smooth, this value is between 1.34 and 1.57, and for outer smooth and inner corrugations, this value is between 1.33 and 1.52.
Details
Keywords
Mohammed Ali Al-Awlaqi and Ammar Mohamed Aamer
The purpose of this paper is to discover the most important productivity determinants of Yemeni microfinance institutions. In addition, this study tests the most appropriate tool…
Abstract
Purpose
The purpose of this paper is to discover the most important productivity determinants of Yemeni microfinance institutions. In addition, this study tests the most appropriate tool to measure productivity in such unique industry.
Design/methodology/approach
The authors applied data envelopment analysis (DEA) with the variable return to scale after testing the technology return to scale assumption. Then, they used DEA with bootstrapping technique to overcome the borne biasness in the conventional DEA analysis. Finally, the authors presented the Hicks–Moorsteen (total factor productivity [TFP]) as the most suitable tool for the technology presented in this study.
Findings
In this paper, the authors found a prolonged deterioration in the productivity scores of microfinance institutions in Yemen. This study highlights the importance of operating in rural areas to improve micro finance institutions’ (MFIs’) productivity. In contrast, they found no significant differences in productivity, neither between microfinance banks and non-governmental organizations nor between Islamic and non-Islamic MFIs.
Research limitations/implications
This study extends previous research in the area of productivity and its determinants. It also adds to the body of productivity knowledge and methodology within the context of the microfinance industry in Yemen.
Originality/value
The study discovered new productivity determinants and re-assessed the importance of some already known ones. These determinants have been studied for the first time in Yemen’s microfinance industry and have contributed to answer the question of what is the most suitable productivity method that should be used. This study proved that the Hicks–Moorsteen TFP and the variable return to scale assumption are the only suitable methods to study productivity in the microfinance industry.