Influence of the chamber inclination angle and heat-generating element location on thermal convection of power-law medium in a chamber

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Darya Loenko ◽  
Aroon Shenoy ◽  
Mikhail Sheremet
Keyword(s):  
Power Law ◽  
Thermal Convection ◽  
Correct Choice ◽  
Navier Stokes ◽  
Working Fluid ◽  
Thermal Conductivity Ratio ◽  
Pseudoplastic Fluid ◽  
Content Type ◽  
Area Of Interest ◽  
Passive Cooling Systems

Purpose This paper aims to study the mathematical modeling of passive cooling systems for electronic devices. Improving heat transfer is facilitated by the correct choice of the working fluid and the geometric configuration of the engineering cavity; therefore, this work is devoted to the analysis of the influence of the position of the heat-generating element and the tilted angle of the electronic cabinet on the thermal convection of a non-Newtonian fluid. Design/methodology/approach The area of interest is a square cavity with two cold vertical walls, while the horizontal boundaries are adiabatic. An element of constant volumetric heat generation is placed on the lower wall of the chamber. The problem is described by Navier–Stokes partial differential equations using dimensionless stream function and vorticity. The numerical solution is based on the developed computational code using the finite difference technique and a uniform rectangular grid. Findings The key conclusions of this work are the results of a detailed analysis of streamlines and isotherms, the average Nusselt number and profiles of the average heater temperature. It was found that more intensive cooling of the heat-generating element occurs when the cavity is filled with a pseudoplastic fluid (n < 1) and not inclined (α = 0). The Rayleigh number of Ra = 105 and the thermal conductivity ratio of k = 100 are characterized by the most positive effect. Originality/value The originality of the research lies in both the study of thermal convection in a square chamber filled with power-law fluid under the influence of a volumetric heat production element and the analysis of the influence of geometric and thermophysical parameters characterizing the considered process.

Effect of non-uniform heat source/sink on MHD boundary layer flow and melting heat transfer of Williamson nanofluid in porous medium

2019 ◽  
Vol 15 (2) ◽  
pp. 452-472 ◽  
Author(s):  
Jayarami Reddy Konda ◽  
Madhusudhana Reddy N.P. ◽  
Ramakrishna Konijeti ◽  
Abhishek Dasore
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Source ◽  
Radiation Effects ◽  
Navier Stokes ◽  
Working Fluid ◽  
Content Type ◽  
Linear Ordinary Differential Equations ◽  
Uniform Heat ◽  
Source Sink

PurposeThe purpose of this paper is to examine the influence of magnetic field on Williamson nanofluid embedded in a porous medium in the presence of non-uniform heat source/sink, chemical reaction and thermal radiation effects.Design/methodology/approachThe governing physical problem is presented using the traditional Navier–Stokes theory. Consequential system of equations is transformed into a set of non-linear ordinary differential equations by means of scaling group of transformation, which are solved using the Runge–Kutta–Fehlberg method.FindingsThe working fluid is examined for several sundry parameters graphically and in a tabular form. It is noticed that with an increase in Eckert number, there is an increase in velocity and temperature along with a decrease in shear stress and heat transfer rate.Originality/valueA good agreement of the present results has been observed by comparing with the existing literature results.

scholarly journals Natural Convection of Non-Newtonian Power-Law Fluid in a Square Cavity with a Heat-Generating Element

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2149 ◽  
Author(s):  
Darya S. Loenko ◽  
Aroon Shenoy ◽  
Mikhail A. Sheremet
Keyword(s):  
Heat Transfer ◽  
Stream Function ◽  
Power Law ◽  
Stokes Equations ◽  
Heat Removal ◽  
Modern Technology ◽  
Navier Stokes ◽  
Local Source ◽  
Thermal Conductivity Ratio ◽  
Square Cavity

Development of modern technology in microelectronics and power engineering necessitates the creation of effective cooling systems. This is made possible by the use of the special fins technology within the cavity or special heat transfer liquids in order to intensify the heat removal from the heat-generating elements. The present work is devoted to the mathematical modeling of thermogravitational convection of a non-Newtonian fluid in a closed square cavity with a local source of internal volumetric heat generation. The behavior of the fluid is described by the Ostwald-de Waele power law model. The defining Navier–Stokes equations written using the dimensionless stream function, vorticity and temperature are solved using the finite difference method. The effects of the Rayleigh number, power-law index, and thermal conductivity ratio on heat transfer and the flow structure are studied. The obtained results are presented in the form of isolines of the stream function and temperature, as well as the dependences of the average Nusselt number and average temperature on the governing parameters.

Simulation of water/FMWCNT nanofluid forced convection in a microchannel filled with porous material under slip velocity and temperature jump boundary conditions

2019 ◽  
Vol 30 (5) ◽  
pp. 2329-2349 ◽  
Author(s):  
Ehsan Gholamalizadeh ◽  
Farzad Pahlevanzadeh ◽  
Kamal Ghani ◽  
Arash Karimipour ◽  
Truong Khang Nguyen ◽  
...  
Keyword(s):  
Velocity Profile ◽  
Porous Material ◽  
Forced Convection ◽  
Slip Velocity ◽  
Stokes Equations ◽  
Computer Code ◽  
Darcy Number ◽  
Navier Stokes ◽  
Working Fluid ◽  
Content Type

Purpose This study aims to numerically study the forced convection effects on a two-dimensional microchannel filled with a porous material containing the water/FMWCNT nanofluid. The upper and lower microchannel walls were fully insulated thermally along 15 per cent of their lengths at each end of the microchannel, with the in-between length being exposed to a constant temperature. The slip velocity boundary condition was applied along the microchannel walls. Design/methodology/approach The Navier–Stokes equations were discretized before being solved numerically via a FORTRAN computer code. The following ranges were considered for the studied parameters: slip factor (B) equal to 0.001, 0.01 and 0.1; Reynolds number (Re) between 10 and 100; solid nanoparticle mass fraction (ϕ) between 0.0012 and 0.0025; Darcy number (Da) between 0.001 and 0.1; and porosity factor (ε) between 0.4 and 0.9. Findings Increasing the Da caused a greater increase in the velocity profile than increasing Re, whereas increasing porosity did not affect the velocity profile growth at all. Originality/value This paper is the continuation of the authors’ previous studies. Using the water/FMWCNT nanofluid as the working fluid in microchannels is among the achievements of this study.

The gamification of trust: the case of China’s “social credit”

2018 ◽  
Vol 36 (1) ◽  
pp. 93-107 ◽  
Author(s):  
Zahy Ramadan
Keyword(s):  
Conceptual Framework ◽  
Tax Evasion ◽  
Credit Rating ◽  
Rating System ◽  
Credit System ◽  
Content Type ◽  
Social Credit ◽  
Chinese Business ◽  
Area Of Interest ◽  
New Business

Purpose China is establishing a social credit rating system with the aim to score the trust level of citizens. The scores will be based on an integrated database that includes a vast range of information sources, rating aspects like professional conduct, corruption, type of products bought, peers’ own scores and tax evasion. While this form of gamification is expected to have dire consequences on brands and consumers alike, the literature in that particular area of interest remains non-existent. The paper aims to discuss these issues. Design/methodology/approach A conceptual framework is suggested that highlights early on the risks and implications on brands and companies operating in that particular upcoming landscape. Findings The gamification of trust that the social credit system focuses on presents potential risks on brand and consumer relationships. This in turn will affect brand sustainability vis-à-vis the expected drastic changes in the Chinese business landscape. This study suggests the strategies to follow which will be of high interest to companies, consumers, as well as to the Chinese authorities during and after implementation stage. Originality/value This paper is amongst the first to discuss the potential effects of the Chinese social credit rating system on brands. The conceptual framework fills a sizeable gap in the literature and pioneers the discussion on potential dilemmas brands will be faced with within this new business landscape.

Online ethnography: a study of software developers and software development

2015 ◽  
Vol 10 (2) ◽  
pp. 188-202 ◽  
Author(s):  
Jose Rodrigo Cordoba-Pachon ◽  
Cecilia Loureiro-Koechlin
Keyword(s):  
Qualitative Research ◽  
Lessons Learned ◽  
Human Interaction ◽  
Research Subjects ◽  
Software Developers ◽  
Online Data ◽  
Social Phenomena ◽  
Content Type ◽  
Online Ethnography ◽  
Area Of Interest

Purpose – Qualitative research has made important contributions to social science by enabling researchers to engage with people and get an in-depth understanding of their views, beliefs and perceptions about social phenomena. With new and electronically mediated forms of human interaction (e.g. the online world), there are new opportunities for researchers to gather data and participate with or observe people in online groups. The purpose of this paper is to present features, challenges and possibilities for online ethnography as an innovative form of qualitative research. Design/methodology/approach – Ethnography is about telling a story about what happens in a particular setting or settings. In order to do this online, it is important to revisit, adopt and adapt some ideas about traditional (offline) ethnography. The paper distinguishes online ethnography from other types of research. It draws some generic features of online ethnography and identifies challenges for it. With these ideas in mind the paper presents and provides a reflection of an online ethnography of software developers. Findings – Online ethnography can provide valuable insights about social phenomena. The paper identifies generic features of this approach and a number of challenges related to its practice. These challenges have to do with to the choice of settings, use of online data for research, representation of people and generation of valuable and useful knowledge. The paper also highlights issues for future consideration in research and practice. Practical implications – The ethnography helped the researcher to identify and address a number of methodological challenges in practice and position herself in relation to relevant audiences she wanted to speak to. The paper also suggests different orientations to online ethnography. Lessons learned highlight potential contributions as well as further possibilities for qualitative research in the online world. Originality/value – Online ethnography offers possibilities to engage with a global audience of research subjects. For academics and practitioners the paper opens up possibilities to use online tools for research and it shows that the use of these tools can help overcome difficulties in access and interaction with people and to study a diversity of research topics, not only those that exist online. The paper offers guidance for researchers about where to start and how to proceed if they want to conduct online ethnography and generate useful and valuable knowledge in their area of interest.

Effects of moving lid direction on mixed convection and entropy generation in a cubical cavity with longitudinal triangular fin insertion

2017 ◽  
Vol 27 (4) ◽  
pp. 839-860 ◽  
Author(s):  
Lioua Kolsi ◽  
Hakan F. Öztop ◽  
Nidal Abu-Hamdeh ◽  
Borjini Mohamad Naceur ◽  
Habib Ben Assia
Keyword(s):  
Mixed Convection ◽  
Entropy Generation ◽  
Three Dimensional ◽  
Thermal Conductivity Ratio ◽  
Governing Equations ◽  
Content Type ◽  
Driven Cavity ◽  
Triangular Fin ◽  
Cubical Cavity ◽  
3D Problem

Purpose The main purpose of this work is to arrive at a three-dimensional (3D) numerical solution on mixed convection in a cubic cavity with a longitudinally located triangular fin in different sides. Design/methodology/approach The 3D governing equations are solved via finite volume technique by writing a code in FORTRAN platform. The governing parameters are chosen as Richardson number, 0.01 ≤ Ri ≤ 10 and thermal conductivity ratio 0.01 ≤ Rc ≤ 100 for fixed parameters of Pr = 0.7 and Re = 100. Two cases are considered for a lid-driven wall from left to right (V+) and right to left (V−). Findings It is observed that entropy generation due to heat transfer becomes dominant onto entropy generation because of fluid friction. The most important parameter is the direction of the moving lid, and lower values are obtained when the lid moves from right to left. Originality The main originality of this work is to arrive at a solution of a 3D problem of mixed convection and entropy generation for lid-driven cavity with conductive triangular fin attachments.

VIKOR power law-based customer-oriented FMEA with complete unique risk priority numbers

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Randula L. Hettiarachchi ◽  
Pisut Koomsap ◽  
Panarpa Ardneam
Keyword(s):  
Case Studies ◽  
Power Law ◽  
Design Methodology ◽  
Service Sector ◽  
Failure Modes ◽  
Risk Priority Number ◽  
Effect Analysis ◽  
Content Type ◽  
Industrial Sectors ◽  
Inherent Problem

PurposeAn inherent problem on risk priority number (RPN) value duplication of traditional failure modes and effect analysis (FMEA) also exists in two customer-oriented FMEAs. One has no unique value, and another has 1% unique values out of 4,000 possible values. The RPN value duplication has motivated the development of a new customer-oriented FMEA presented in this paper to achieve practically all 4,000 unique values and delivering reliable prioritization.Design/methodology/approachThe drastic improvement is the result of power-law and VlseKriterijumska Optimizacija I Kompromisno Resenje (VIKOR). By having all three risk factors in a power-law form, all unique values can be obtained, and by applying VIKOR to these power-law terms, the prioritization is more practical and reliable.FindingsThe proposed VIKOR power law-based customer-oriented FMEA can achieve practically all 4,000 unique values and is tested with two case studies. The results are more logical than the results from the other two customer-oriented FMEAs.Research limitations/implicationsThe evaluation has been done on two case studies for the service sector. Therefore, additional case studies in other industrial sectors will be required to confirm the effectiveness of this new customer-oriented RPN calculation.Originality/valueAchieving all 1,000 unique values could only be done by having experts tabulate all possible combinations for the traditional FMEA. Therefore, achieving all 4,000 unique values will be much more challenging. A customer-oriented FMEA has been developed to achieve practically all 4,000 unique risk priority numbers, and that the prioritization is more practical and reliable. Furthermore, it has a connection to the traditional FMEA, which helps explain the traditional one from a broader perspective.

Aerodynamic ground effects on DLRF6 vehicle

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Mojtaba Tahani ◽  
Mehran Masdari ◽  
Ali Bargestan
Keyword(s):  
Stokes Equations ◽  
Ground Effect ◽  
Longitudinal Direction ◽  
Propulsion System ◽  
Navier Stokes ◽  
Noticeable Effect ◽  
Navier Stokes Equations ◽  
Vehicle Performance ◽  
Content Type ◽  
Logical Connection

Purpose The overall performance of an aerial vehicle strongly depends on the specifics of the propulsion system and its position relative to the other components. The purpose of paper is this factor can be characterized by changing several contributing parameters, such as distance from the ground, fuselage and wing as well as the nacelle outlet velocity and analyzing the aerodynamic performance. Design/methodology/approach Navier–Stokes equations are discretized in space using finite volume method. A KW-SST model is implemented to model the turbulence. The flow is assumed steady, single-phase, viscous, Newtonian and compressible. Accordingly, after validation and verification against experimental and numerical results of DLRF6 configuration, the location of the propulsion system relative to configuration body is examined. Findings At the nacelle outlet velocity of V/Vinf = 4, the optimal location identified in this study delivers 16% larger lift to drag ratio compared to the baseline configuration. Practical implications Altering the position of the propulsion system along the longitudinal direction does not have a noticeable effect on the vehicle performance. Originality/value Aerial vehicles including wing-in-ground effect vehicles require thrust to fly. Generating this necessary thrust for motion and acceleration is thoroughly affected by the vehicle aerodynamics. There is a lack of rigorous understanding of such topics owing to the immaturity of science in this area. Complexity and diversity of performance variables for a numerical solution and finding a logical connection between these parameters are among the related challenges.

Risk transfer in project finance loans for toll road using credit default swaps

2022 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Wei Yang ◽  
Afshin Firouzi ◽  
Chun-Qing Li
Keyword(s):  
Power Law ◽  
Credit Default Swaps ◽  
Free Cash Flow ◽  
Project Finance ◽  
Cost Of Debt ◽  
Power Law Model ◽  
Data Set ◽  
Content Type ◽  
Toll Road ◽  
Credit Default

Purpose The purpose of this paper is to demonstrate the applicability of the Credit Default Swaps (CDS), as a financial instrument, for transferring of risk in project finance loans. Also, an equation has been derived for pricing of CDS spreads. Design/methodology/approach The debt service cover ratio (DSCR) is modeled as a Brownian Motion (BM) with a power-law model fitted to the mean and half-variance of the existing data set of DSCRs. The survival probability of DSCR is calculated during the operational phase of the project finance deal, using a closed-form analytical method, and the results are verified by Monte Carlo simulation (MCS). Findings It is found that using the power-law model yields higher CDS premiums. This in turn confirms the necessity of conducting rigorous statistical analysis in fitting the best performing model as uninformed reliance on constant time-invariant drift and diffusion model can erroneously result in smaller CDS spreads. A sensitivity analysis also shows that the results are very sensitive to the recovery rate and cost of debt values. Originality/value Insufficiency of free cash flow is a major risk in the toll road project finance and hence there is a need to develop innovative financial instruments for risk management. In this paper, a novel valuation method of CDS is proposed assuming that DSCR follows the BM stochastic process.

Numerical investigation of an anti-icing method on airfoil based on the NSDBD plasma actuator

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Junjie Niu ◽  
Weimin Sang ◽  
Feng Zhou ◽  
Dong Li
Keyword(s):  
Phenomenological Model ◽  
Stokes Equations ◽  
Pulse Repetition Frequency ◽  
Leading Edge ◽  
Pulse Frequency ◽  
Plasma Actuator ◽  
Navier Stokes ◽  
Peak Voltage ◽  
Content Type ◽  
Naca0012 Airfoil

Purpose This paper aims to investigate the anti-icing performance of the nanosecond dielectric barrier discharge (NSDBD) plasma actuator. Design/methodology/approach With the Lagrangian approach and the Messinger model, two different ice shapes known as rime and glaze icing are predicted. The air heating in the boundary layer over a flat plate has been simulated using a phenomenological model of the NSDBD plasma. The NSDBD plasma actuators are planted in the leading edge anti-icing area of NACA0012 airfoil. Combining the unsteady Reynolds-averaged Navier–Stokes equations and the phenomenological model, the flow field around the airfoil is simulated and the effects of the peak voltage, the pulse repetition frequency and the direction arrangement of the NSDBD on anti-icing performance are numerically investigated, respectively. Findings The agreement between the numerical results and the experimental data indicates that the present method is accurate. The results show that there is hot air covering the anti-icing area. The increase of the peak voltage and pulse frequency improves the anti-icing performance, and the direction arrangement of NSDBD also influences the anti-icing performance. Originality/value A numerical strategy is developed combining the icing algorithm with the phenomenological model. The effects of three parameters of NSDBD on anti-icing performance are discussed. The predicted results show that the anti-icing method is effective and may be helpful for the design of the anti-icing system of the unmanned aerial vehicle.

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