Data envelopment analysis (DEA) and analytical hierarchy process (AHP) are two widely applied methods to evaluate and rank suppliers in terms of sustainability. In this study, to…
Abstract
Purpose
Data envelopment analysis (DEA) and analytical hierarchy process (AHP) are two widely applied methods to evaluate and rank suppliers in terms of sustainability. In this study, to investigate the extent to which potential differences in the outcomes of these two methods influence the benchmarking strategies, a comparative analysis based on a common set of data gathered from 19 logistics service providers is implemented.
Design/methodology/approach
As suppliers' sustainability cannot be improved in a single-step process due to several limitations, improvement needs to proceed gradually. Therefore, using the self-organising map method, the suppliers were classified into clusters within a novel framework for gradually improving their sustainability. Then, the two processes of gradual improvement based on the outcomes of DEA and AHP were compared.
Findings
The findings show that although the rankings of suppliers guided by the methods correlated to a high degree, the benchmarking strategies provided by the methods for gradually improving the sustainability of suppliers differed considerably. In particular, whereas AHP suggests a benchmarking policy better suited for unsustainable or less sustainable suppliers with limited access to resources, DEA proposes one for suppliers able to dramatically boost their sustainability with few quick, significant leaps in performance.
Originality/value
First, this study revealed a novel gradual improvement framework using the self-organising map method. Second, it clarified the extent to which the benchmarking policies are influenced by the type of evaluation method.
Details
Keywords
Syed Tauseef Mohyud-Din, Muhammad Usman, Kamran Afaq, Muhammad Hamid and Wei Wang
The purpose of this study is to analyze the effects of carbon nanotubes (CNTs) in the Marangoni convection boundary layer viscous fluid flow. The analysis and formulation for both…
Abstract
Purpose
The purpose of this study is to analyze the effects of carbon nanotubes (CNTs) in the Marangoni convection boundary layer viscous fluid flow. The analysis and formulation for both types of CNTs, namely, single-walled (SWCNTs) and multi-walled (MWCNTs), are described. The influence of thermal radiation effect assumed in the form of energy expression.
Design/methodology/approach
Appropriate transformations reduced the partial differential systems to a set of nonlinear ordinary differential equations (ODEs). The obtained nonlinear ODE set is solved via the least squares method. A detailed comparison between outcomes obtained by the least squares method, RK-4 and already published work is available.
Findings
Nusselt number was analyzed and found to be more effective for nanoparticle volume fraction and larger radiation parameters. Additionally, the error and convergence analysis for the least squares method was presented to show the efficiency of the said algorithm.
Originality/value
The results reveal that velocity is a decreasing function of suction for both CNTs. While enhancing the nanoparticle volume fraction, an increase for both thermal boundary layer thickness and temperature was attained. The radiation parameter has an increasing function as temperature. Velocity behavior is the same for nanoparticle volume fraction and suction. It was observed that velocity is less in SWCNTs as compared to MWCNTs.
Details
Keywords
In this article, we consider the magnetohydrodynamic (MHD) nanofluid flow over a rotating stretchable disk through porous medium. For porous medium, Darcy’s relation is used. It…
Abstract
Purpose
In this article, we consider the magnetohydrodynamic (MHD) nanofluid flow over a rotating stretchable disk through porous medium. For porous medium, Darcy’s relation is used. It also encompassed the impact of nanoparticles shape on MHD nanofluid flow and heat transfer. The effect of thermal radiation and Joule heating is also being considered.
Design/methodology/approach
Three categories of nanoparticles are taken into deliberation, i.e. copper, silver and titanium oxide. The nanofluid is made of pure water and various types of sphere- and lamina-shaped nanoparticles. By using appropriate similarity transformation, the governing partial differential equations are transformed to ordinary one. The coupled ordinary differential equations system is tackled numerically by bvp4c method.
Findings
The impact of various pertinent parameters, i.e. solid volume fraction, Hartman number, thermal radiations parameter, Reynolds number, Eckert number, porosity parameter and ratio parameter, on flow and Nusselt number with a fixed value of Prandtl number at 6.2 is discussed in details. The obtained results are presented in the concluding section. The lamina shape of nanoparticles in silver-water performed an excellent role on temperature distribution. The heat transfer rate of lamina shape in copper-water was found to be greater in the system of flow regime.
Originality/value
The authors have discussed the shape effect of nanoparticles on MHD nanofluid flow over a rotating stretchable disk through porous medium using three categories of nanoparticles, such as copper, silver and titanium oxide. To the best of the authors’ knowledge, this is the first study on mass and heat transfer nanofluid flow and no such study is yet published in literature. A detailed mathematical analysis has also to be carried out to prove the regularity of model. The authors believe that the numerical results are original and have not been copied from any other sources.
Details
Keywords
Ankita Bisht and Rajesh Sharma
The purpose of this study is to provide a numerical investigation of Casson nanofluid along a vertical nonlinear stretching sheet with variable thermal conductivity and viscosity.
Abstract
Purpose
The purpose of this study is to provide a numerical investigation of Casson nanofluid along a vertical nonlinear stretching sheet with variable thermal conductivity and viscosity.
Design/methodology/approach
The boundary-layer equations are presented in the dimensionless form using proper non-similar transformations. The subsequent non-dimensional nonlinear partial differential equations are solved using the implicit finite difference technique. To linearize the nonlinear terms present in these equations, the quasilinearization technique is used.
Findings
The investigation showed graphically the temperature, velocity and nanoparticle volume fraction for particular included physical parameters. It is observed that the velocity profile decreases with an increase in the values of Casson fluid parameter while increases with an increase in the viscosity variation parameter. The temperature profile enhances for large values of velocity variation parameter and thermal conductivity parameter while it reduces for large values of thermal buoyancy parameter. Further, the Nusselt number and skin-friction coefficient are introduced which are helpful in determining the physical aspects of Casson nanofluid flow.
Practical implications
The immediate control of heat transfer in the industrial system is crucial because of increasing energy prices. Recently, nanotechnology is proposed to control the heat transfer phenomenon. Ongoing research in complex nanofluid has been fruitful in various applications such as solar thermal collectors, nuclear reactors, electronic equipment and diesel–electric conductor. A reasonable amount of nanoparticle when added to the base fluid in solar thermal collectors serves to deeper absorption of incident radiation, and hence it upgrades the efficiency of the solar thermal collectors.
Originality/value
The non-similar solution of Casson nanofluid due to a vertical nonlinear stretching sheet with variable viscosity and thermal conductivity is discussed in this work.
Details
Keywords
Fully developed Casson fluid flow through vertical microchannel is deliberated in the presence of thermal radiation. The two predominant features of micro scale phenomenon such as…
Abstract
Purpose
Fully developed Casson fluid flow through vertical microchannel is deliberated in the presence of thermal radiation. The two predominant features of micro scale phenomenon such as velocity slip and temperature jump are considered. The paper aims to discuss this issue.
Design/methodology/approach
The governing equations of the physical phenomenon are solved using Runge–Kutta–Fehlberg fourth fifth order method.
Findings
The outcome of the present work is discussed through graphs. This computation shows that entropy generation rate decreases with enhancing wall ambient temperature difference ratio and fluid wall interaction parameter. Also, it is found that Bejan number is fully retarded with rise in fluid wall interaction parameter. Enhancement in heat transfer or Nusselt number is achieved by increasing the wall ambient temperature ratio and fluid wall interaction parameter.
Originality/value
Casson liquid flow through microchannel is analyzed by considering temperature jump and velocity slip. This computation shows that entropy generation rate decreases with enhancing wall ambient temperature difference ratio.
Details
Keywords
N. Nithyadevi, P. Gayathri and A. Chamkha
The paper aims to examine the boundary layers of a three-dimensional stagnation point flow of Al-Cu nanoparticle-suspended water-based nanofluid in an electrically conducting…
Abstract
Purpose
The paper aims to examine the boundary layers of a three-dimensional stagnation point flow of Al-Cu nanoparticle-suspended water-based nanofluid in an electrically conducting medium. The effect of magnetic field on second-order slip effect and convective heating is also taken into account.
Design/methodology/approach
The thermophysical properties of alloy nanoparticles such as density, specific heat capacity and thermal conductivity are computed using appropriate formula. The non-linear parabolic partial differential equations are transformed to ordinary differential equations and solved by shooting technique.
Findings
The influence of compositional variation of alloy nanoparticle, nanoparticle concentration, magnetic effect, slip parameters and Biot number are presented for various flow characteristics. Interesting results on skin friction and Nusselt number are obtained for different composition of aluminium and copper.
Originality/value
A novel result of the analysis reveals that impact of magnetic field near the boundary is suppressed by the slip effect.
Details
Keywords
Tahir Naseem and Azeem Shahzad
The purpose of this study is to examine the flow and heat transfer performance of titanium oxide/water and copper/water nanofluids with varying nanoparticle morphologies by…
Abstract
Purpose
The purpose of this study is to examine the flow and heat transfer performance of titanium oxide/water and copper/water nanofluids with varying nanoparticle morphologies by considering magnetic, Joule heating and viscous dissipation effects. Furthermore, it studies the irreversibility caused by the flow of a hydromagnetic nanofluid past a radiated stretching sheet by considering different shapes of TiO2 and Cu nanoparticles with water as the base fluid.
Design/methodology/approach
In this study, the authors investigated entropy production in an unsteady two-dimensional magneto-hydrodynamic nanofluid regime using water as the base fluid and five unique TiO2 and Cu nanoparticle morphologies. Using appropriate similarity transformations, the controlling nonlinear system of partial differential equations is transformed into a system of ordinary differential equations. The shooting technique with Runge–Kutta method was then used to solve these equations quantitatively. The findings of this study are depicted graphically, and the skin friction corresponding to various nanoparticle geometries and physical parameter variations is tabulated.
Findings
To assess the reliability of the current findings, a tabular representation of the data was compared to that of previously published studies. It is noted that a reduction in thermal energy was detected as a result of the higher levels of Prandtl number (Pr). It is further analysed that the highest heat energy generation of TiO2 nanoparticles was larger than that of Cu nanoparticles. The most important finding was that the sphere-shaped Cu/H2O nanofluid had the lowest velocity and greatest temperature. Also, Cu nanoparticles in the shape of platelets generate the most entropy, while TiO2 nanoparticles in the shape of spheres generate the least.
Originality/value
To the best of the knowledge of the authors, the attempt to investigate the previously unexplored shape effects of TiO2 and Cu nanoparticles on the heat transfer enhancement and inherent irreversibility caused by hydromagnetic nanofluid flow past a radiated stretching sheet with magnetic, Joule heating and viscous dissipation effects. This study fills this gap in the existing literature and encourages scientists, engineers and businesses to do more research in this area. This model can be used to improve heat transfer in systems that use renewable energy, thermal management in industry and the processing of materials.
Details
Keywords
Abdulaziz Alsenafi, Fares Alazemi and M. Nawaz
To improve the thermal performance of base fluid, nanoparticles of three types are dispersed in the base fluid. A novel theory of non-Fourier heat transfer is used for design and…
Abstract
Purpose
To improve the thermal performance of base fluid, nanoparticles of three types are dispersed in the base fluid. A novel theory of non-Fourier heat transfer is used for design and development of models. The thermal performance of sample fluids is compared to determine which types of combination of nanoparticles are the best for an optimized enhancement in thermal performance of fluids. This article aims to: (i) investigate the impact of nanoparticles on thermal performance; and (ii) implement the Galerkin finite element method (GFEM) to thermal problems.
Design/methodology/approach
The mathematical models are developed using novel non-Fourier heat flux theory, conservation laws of computational fluid dynamics (CFD) and no-slip thermal boundary conditions. The models are approximated using thermal boundary layer approximations, and transformed models are solved numerically using GFEM. A grid-sensitivity test is performed. The accuracy, correction and stability of solutions is ensured. The numerical method adopted for the calculations is validated with published data. Quantities of engineering interest, i.e. wall shear stress, wall mass flow rate and wall heat flux, are calculated and examined versus emerging rheological parameters and thermal relaxation time.
Findings
The thermal relaxation time measures the ability of a fluid to restore its original thermal state, called thermal equilibrium and therefore, simulations have shown that the thermal relaxation time associated with a mono nanofluid has the most substantial effect on the temperature of fluid, whereas a ternary nanofluid has the smallest thermal relaxation time. A ternary nanofluid has a wider thermal boundary thickness in comparison with base and di- and mono nanofluids. The wall heat flux (in the case of the ternary nanofluids) has the most significant value compared with the wall shear stresses for the mono and hybrid nanofluids. The wall heat and mass fluxes have the highest values for the case of non-Fourier heat and mass diffusion compared to the case of Fourier heat and mass transfer.
Originality/value
An extensive literature review reveals that no study has considered thermal and concentration memory effects on transport mechanisms in fluids of cross-rheological liquid using novel theory of heat and mass [presented by Cattaneo (Cattaneo, 1958) and Christov (Christov, 2009)] so far. Moreover, the finite element method for coupled and nonlinear CFD problems has not been implemented so far. To the best of the authors’ knowledge for the first time, the dynamics of wall heat flow rate and mass flow rate under simultaneous effects of thermal and solute relaxation times, Ohmic dissipation and first-order chemical reactions are studied.
Details
Keywords
Saeed Dinarvand, Hamza Berrehal, Ioan Pop and Ali. J. Chamkha
The purpose of this paper is to study and analyze the converging/diverging channel flow and heat transfer with the multiple slips effect, which is a development of the…
Abstract
Purpose
The purpose of this paper is to study and analyze the converging/diverging channel flow and heat transfer with the multiple slips effect, which is a development of the Jeffery–Hamel problem using the mass-based hybrid nanofluid algorithm. Whereas transferring biological liquid by arteries is a vital issue, mathematical modeling of hybrid nanofluid flow containing titanium dioxide and silver as nanoparticles and blood as base liquid through a converging/diverging duct, which can be a useful analysis for the fields of drug delivery, has been investigated.
Design/methodology/approach
The present approach is based on the Tiwari–Das nanofluid method. In this modeling, the volume fraction of nanoparticles is replaced with nanoparticles masses. The partial differential equations of the mass, momentum and energy conservations are changed to the system of ordinary differential equations through the similarity solution method. The final governing equations are solved by Runge–Kutta–Fehlberg procedure and shooting method.
Findings
The effect of emerging parameters on the temperature, the velocity, the Nusselt number and the skin friction have been analyzed by graphical and tabular reports. It is observed that the opposition to hybrid nanofluid flow in the attendance of particles of nonspherical shapes is more enhanced than those in the attendance of particles of spherical shapes. This issue demonstrates that the rheology of a hybrid nanofluid is dependent on the shape of particles. Besides, backflow regimes form in the divergent channel for high values of Reynolds number, m2 and a. Indeed, this modeling for the hybrid nanofluid can be useful in different technologies and industries such as biological ones. It is worth mentioning that the excellent achievement of the mass-based algorithm for heat transfer and hybrid nanofluid flow is the most important success of this study.
Originality/value
The main originality is related to the development of the Jeffery–Hamel problem using the mass-based hybrid nanofluid algorithm. This new mass-based method is a single-phase hybrid nanofluid approach that the inputs are masses of nanoparticles and base liquid. Besides, considering the multiple slips effect and also pure blood as base fluid in this problem are also new.