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Article
Publication date: 5 September 2023

Nikesh Chowrasia, Subramani S.N., Harish Pothukuchi and B.S.V. Patnaik

Subcooled flow boiling phenomenon is characterized by coolant phase change in the vicinity of the heated wall. Although coolant phase change from liquid to vapour phase…

Abstract

Purpose

Subcooled flow boiling phenomenon is characterized by coolant phase change in the vicinity of the heated wall. Although coolant phase change from liquid to vapour phase significantly enhances the heat transfer coefficient due to latent heat of vaporization, eventually the formed vapor bubbles may coalesce and deteriorate the heat transfer from the heated wall to the liquid phase. Due to the poor heat transfer characteristics of the vapour phase, the heat transfer rate drastically reduces when it reaches a specific value of wall heat flux. Such a threshold value is identified as critical heat flux (CHF), and the phenomenon is known as departure from nucleate boiling (DNB). An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Therefore, the present study aims at the prediction of DNB type CHF in a hexagonal sub-assembly.

Design/methodology/approach

Computational fluid dynamics (CFD) simulations are performed to predict DNB in a hexagonal sub-assembly. The methodology uses an Eulerian–Eulerian multiphase flow (EEMF) model in conjunction with multiple size group (MuSiG) model. The breakup and coalescence of vapour bubbles are accounted using a population balance approach.

Findings

Bubble departure diameter parameters in EEMF framework are recalibrated to simulate the near atmospheric pressure conditions. The predictions from the modified correlation for bubble departure diameter are found to be in good agreement against the experimental data. The simulations are further extended to investigate the influence of blockage (b) on DNB type CHF at low operating pressure conditions. Larger size vapour bubbles are observed to move away from the corner sub-channel region due to the presence of blockage. Corner sub-channels were found to be more prone to experience DNB type CHF compared to the interior and edge sub-channels.

Practical implications

An accurate prediction of CHF and its location is critical to the safe operation of nuclear reactors. Moreover, a wide spectrum of heat transfer equipment of engineering interest will be benefited by an accurate prediction of wall characteristics using breakup and coalescence-based models as described in the present study.

Originality/value

Simulations are performed to predict DNB type CHF. The EEMF and wall heat flux partition model framework coupled with the MuSiG model is novel, and a detailed variation of the coolant velocity, temperature and vapour volume fraction in a hexagonal sub-assembly was obtained. The present CFD model framework was observed to predict the onset of vapour volume fraction and DNB type CHF. Simulations are further extended to predict CHF in a hexagonal sub-assembly under the influence of blockage. For all the values of blockage, the vapour volume fraction is found to be higher in the corner region, and thus the corner sub-channel experiences CHF. Although DNB type CHF is observed in corner sub-channel, it is noticed that the presence of blockage in the interior sub-channel promotes the coolant mixing and results in higher values of CHF in the corner sub-channel.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 33 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 November 2011

Rajesh Sahu and B.S.V. Patnaik

The purpose of this paper is to achieve high‐performance aerofoils that enable delayed stall conditions and achieve high lift to drag ratios.

1042

Abstract

Purpose

The purpose of this paper is to achieve high‐performance aerofoils that enable delayed stall conditions and achieve high lift to drag ratios.

Design/methodology/approach

The unsteady Reynolds averaged Navier‐Stokes equations are employed in conjunction with a shear stress transport (κ‐ω) turbulence model. A control equation is designed and implemented to determine the temporal response of the actuator. A rotating element, in the form of an actuator disc, is embedded on the leading edge of NACA 0012 aerofoil, to inject momentum into the wake region. The actuator disc is rotated at different angular speeds, for angles of attack (α) between 00 and 240.

Findings

Phenomena such as flow separation, wake vortices, delayed stall, wake control, etc. are numerically investigated by means of streamlines, streaklines, isobars, etc. Streamwise and cross‐stream forces on the aerofoil are obtained. The influence of momentum injection parameter (ξ) on the fluid flow patterns, and hence on the forces acting on the streamlined body are determined. A synchronization‐based coupling scheme is designed and implemented to achieve annihilation of wake vortices. A delayed stall angle resulted with an attendant increase in maximum lift coefficient. Due to delay and/or prevention of separation, drag coefficient is also reduced considerably, resulting in a high‐performance lifting surface.

Research limitations/implications

The practicality of momentum injection principle requires both wide ranging and intensive further studies to move forward beyond the proof of concept stage.

Practical implications

Determination of forces and moments on an aerofoil is of vital interest in aero‐dynamic design. Perhaps, runways of the future can be shorter and/or more pay load can be carried by an aircraft, for the same stall speed.

Originality/value

The paper describes how a synchronization‐based coupling scheme is designed and implemented along with the RANS solver. Furthermore, it is tested to verify the dynamic adaptability of the wake vortex annihilation for NACA 0012 aerofoils.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 21 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 24 October 2018

Sai Nikhil Subraveti, V. Vinod Kumar, Harish Pothukuchi, P.S.T. Sai and B.S.V. Patnaik

Better membrane oxygenators need to be developed to enable efficient gas exchange between venous blood and air.

Abstract

Purpose

Better membrane oxygenators need to be developed to enable efficient gas exchange between venous blood and air.

Design/methodology/approach

Optimal design and analysis of such devices are achieved through mathematical modeling tools such as computational fluid dynamics (CFD). In this study, a control volume-based one-dimensional (1D) sub-channel analysis code is developed to analyze the gas exchange between the hollow fiber bundle and the venous blood. DIANA computer code, which is popular with the thermal hydraulic analysis of sub-channels in nuclear reactors, was suitably modified to solve the conservation equations for the blood oxygenators. The gas exchange between the tube-side fluid and the shell-side venous blood is modeled by solving mass, momentum and species conservation equations.

Findings

Simulations using sub-channel analysis are performed for the first time. As the DIANA-based approach is well known in rod bundle heat transfer, it is applied to membrane oxygenators. After detailed validations, the artificial membrane oxygenator is analyzed for different bundle sizes (L/W) and bundle porosity (epsilon) values, and oxygen saturation levels are predicted along the bundle. The present sub-channel analysis is found to be reasonably accurate and computationally efficient when compared to conventional CFD calculations.

Research limitations/implications

This approach is promising and has far-reaching ramifications to connect and extend a well-known rod bundle heat transfer algorithm to a membrane oxygenator community. As a variety of devices need to be analyzed, simplified approaches will be attractive. Although the 1D nature of the simulations facilitates handling complexity, it cannot easily compete with expensive and detailed CFD calculations.

Practical implications

This work has high practical value and impacts the design community directly. Detailed numerical simulations can be validated and benchmarked for future membrane oxygenator designs.

Social implications

Future membrane oxygenators can be designed and analyzed easily and efficiently.

Originality/value

The DIANA algorithm is popularly used in sub-channel analysis codes in rod bundle heat transfer. This efficient approach is being implemented into membrane oxygenator community for the first time.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 28 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 September 2000

B.S.V. Patnaik, P.A.A. Narayana and K.N. Seetharamu

Flow past an isolated circular cylinder and two cylinders in tandem is numerically simulated, under the influence of buoyancy aiding and opposing the flow. A modified velocity…

1436

Abstract

Flow past an isolated circular cylinder and two cylinders in tandem is numerically simulated, under the influence of buoyancy aiding and opposing the flow. A modified velocity correction method is employed, which has second order accuracy in both space and time. The influence of buoyancy on the temporal fluid flow patterns is investigated, with respect to streamlines, isotherms and streaklines. Comparisons are made with respect to mean center line velocities, drag coefficients, Strouhal number and streakline patterns. Degeneration of naturally occurring Kármán vortex street into a twin eddy pattern is noticed in the Reynolds number (Re) range of 41‐200, under buoyancy aided convection. On the contrary, buoyancy opposed convection could trigger vortex shedding even at a low Re range of 20‐40, where only twin eddies are found in the natural wake. Temporal evolution of unsteady eddy patterns is visualized by means of numerical particle release (NPR). Zones of vortex shedding and twin vortices are demarcated on a plot of Richardson number against Strouhal number. Root mean square (RMS) lift coefficients (CL,RMS) and average drag coefficient (\overline Cd) are obtained as a function of Richardson number (Ri).

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 10 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 28 October 2014

Amit K. Chauhan, B.V.S.S.S. Prasad and B.S.V. Patnaik

The purpose of this paper is to investigate the effect of narrow gap on the fluid flow and heat transfer through an eccentric annular region is numerically. Flow through an…

393

Abstract

Purpose

The purpose of this paper is to investigate the effect of narrow gap on the fluid flow and heat transfer through an eccentric annular region is numerically. Flow through an eccentric annular geometry is a model problem of practical interest.

Design/methodology/approach

The approach involves standard finite volume-based SIMPLE scheme. The numerical simulations cover the practically relevant Reynolds number range of 104-106.

Findings

In the narrow gap region, temperature shoot up was observed due to flow maldistribution with an attendant reduction in the heat removal from the wall surfaces. CFD analysis is presented with the aid of, streamlines, isotherms, axial velocity contours, etc. The engineering parameters of interest such as, Nusselt number, wall shear stress, etc., is presented to study the effect of eccentricity and radius ratio.

Research limitations/implications

The present investigation is a simplified model for the rod bundle heat transfer studies. However, the detailed study of sectorial mass flux distribution is a useful precursor to the thermal hydraulics of rod bundles.

Practical implications

For nuclear reactor fuel rods, the effect of eccentricity is going to be detrimental and might lead to the condition of critical heat flux. A thorough sub-channel analysis is very useful.

Social implications

Nuclear safety standards require answers to a wide a range of what-if type hypothetical scenarios to enable preparedness. This study is a highly simplified model and a first step in that direction.

Originality/value

The narrow gap region has been systematically investigated for the first time. A detailed sectorial analysis reveals that, flow maldistribution and the attendant temperature shoot up in the narrow gap region is detrimental to the safe operation.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 24 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 27 May 2014

Yijiang Peng, Nana Zong, Lijuan Zhang and Jiwei Pu

The purpose of this paper is to present a two-dimensional (2D) model of the base force element method (BFEM) based on the complementary energy principle. The study proposes a…

Abstract

Purpose

The purpose of this paper is to present a two-dimensional (2D) model of the base force element method (BFEM) based on the complementary energy principle. The study proposes a model of the BFEM for arbitrary mesh problems.

Design/methodology/approach

The BFEM uses the base forces given by Gao (2003) as fundamental variables to describe the stress state of an elastic system. An explicit expression of element compliance matrix is derived using the concept of base forces. The detailed formulations of governing equations for the BFEM are given using the Lagrange multiplier method. The explicit displacement expression of nodes is given. To verify the 2D model, a program on the BFEM using MATLAB language is made and a number of examples on arbitrary polygonal meshes and aberrant meshes are provided to illustrate the BFEM.

Findings

A good agreement is obtained between the numerical and theoretical results. Based on the studies, it is found that the 2D formulation of BFEM with complementary energy principle provides reliable predictions for arbitrary mesh problems.

Research limitations/implications

Due to the use of Lagrange multiplier method, there are more basic unknowns in the control equation. The proposed method will be improved in the future.

Practical implications

This paper presents a new idea and a new numerical method, and to explore new ways to solve the problem of arbitrary meshes.

Originality/value

The paper presents a 2D model of the BFEM using the complementary energy principle for arbitrary mesh problems.

Details

Engineering Computations, vol. 31 no. 4
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 21 October 2013

Bikash Ranjan Debata, Kumar Sree, Bhaswati Patnaik and Siba Sankar Mahapatra

The purpose of this paper is to develop a comprehensive framework to identify and classify key medical tourism enablers (MTEs) and to study the direct and indirect effects of each…

2288

Abstract

Purpose

The purpose of this paper is to develop a comprehensive framework to identify and classify key medical tourism enablers (MTEs) and to study the direct and indirect effects of each enabler on the growth of medical tourism in India.

Design/methodology/approach

In this paper, an integrated approach using interpretive structural modeling (ISM) and Fuzzy Matrice d'Impacts Croisés Multiplication Appliquée á un Classement (FMICMAC) analysis has been developed to identify and classify the key MTEs, typically identified by a comprehensive review of literature and expert opinion. The key enablers are also modeled to find their role and mutual influence.

Findings

The key finding of this modeling helps to identify and classify the enablers which may be useful for medical tourism decision makers to employ this model for formulating strategies in order to overcome challenges and to become a preferred medical tourism destination. Integrated model reveals enablers such as medicine insurance coverage, international healthcare collaboration, and efficient information system as dependent enablers. No enabler is found to be autonomous enablers. The important enablers like healthcare infrastructure facilities and global competition are found as the linkage enablers. Research in medicine and pharmaceutical science, medical tourism market, transplantation law, top management commitment, national healthcare policy, competent medical and para-medical staffs are found as the independent enablers. Integrated model also establishes the direct and indirect relationship among various enablers.

Originality/value

The research provides an integrated model using ISM and FMICMAC to identify and classify various key enablers of medical tourism in India. In conventional cross-impact matrix multiplication applied to classification analysis, binary relationship of various enablers is considered. FMICMAC analysis helps to establish possibility of relationship among various enablers so that low-key hidden factors can be identified. The low-key hidden factors may initially exhibit marginal influence but they may show significant influence later on during analysis. The uncertainty and fuzziness of relationship among various enablers can be conveniently handled by FMICMAC and expert opinions can easily be captured. This research will help medical tourism decision makers to select right enablers for the growth of medical tourism in India.

Details

Benchmarking: An International Journal, vol. 20 no. 6
Type: Research Article
ISSN: 1463-5771

Keywords

Article
Publication date: 5 September 2023

Karen Ramos and Onesimo Cuamea

The purpose of this study is to find out the factors that influence dental travelers’ revisit intention (RI) to Tijuana, Mexico.

Abstract

Purpose

The purpose of this study is to find out the factors that influence dental travelers’ revisit intention (RI) to Tijuana, Mexico.

Design/methodology/approach

Based on the push and pull model, five constructs were included: quality service, price, supporting services, cultural proximity and quality information. The information was obtained by applying an online survey to a sample of 384 dental tourists in Tijuana, Mexico, who were repeat patients of a dental clinic in Tijuana after the COVID-19 pandemic. Exploratory factor analysis, average variance explained and composite reliability were conducted to ensure the validity of each construct. Multiple regression analysis was done to identify predictors of travelers’ RI.

Findings

The results obtained show that cultural proximity, quality service, price and supporting services influenced the travelers’ revisit behavior after the COVID-19 pandemic lockdowns.

Originality/value

This study contributes to the body of knowledge on travel behavior in dental tourism after the COVID-19 pandemic lockdowns, which has been scarcely studied. Also, RI was analyzed, focusing on repeated travelers to propose a model mainly for borders or frontiers where developed and developing countries co-exist and interact.

Details

International Journal of Tourism Cities, vol. 9 no. 3
Type: Research Article
ISSN: 2056-5607

Keywords

Article
Publication date: 1 April 1996

B.S.V.P. Patnaik, K.N. Seetharamu and P.A. Aswatha Narayana

A finite element method is used to study the effect of flow past acircular cylinder with an integral wake splitter. A fractional step algorithmis employed to solve the…

Abstract

A finite element method is used to study the effect of flow past a circular cylinder with an integral wake splitter. A fractional step algorithm is employed to solve the Navier‐Stokes and Energy equations with a Galerkin weighted residual formulation. The vortex shedding process is simulated and the effect of splitter addition on the time period of shedding is studied at a Reynolds number of 200 and a blockage ratio of 0.25. The effect of splitter and the Strouhal number and heat transfer augmentation per unit pressure drop has been investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 6 no. 4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 17 May 2022

Samir Ramdas Kale, Srinivas Kota, Naga Vamsi Krishna Jasti, Gunjan Soni and Surya Prakash

The manufacturing sector has been observing various benefits by the implementation of lean manufacturing practices. However, the manufacturing sector has neglected the…

Abstract

Purpose

The manufacturing sector has been observing various benefits by the implementation of lean manufacturing practices. However, the manufacturing sector has neglected the significance of health and safety management system implementation. The purpose of this research is to propose and validate an occupational health and safety management systems (OHSMS) framework based on critical success factors and their relationships in the lean manufacturing organizations.

Design/methodology/approach

A critical literature review was conducted to identify the success factors of OHSMS. Subsequently, a questionnaire survey and semi-structured interviews were conducted with experts from process industries to consolidate the critical success factors. After consolidating the critical success factors, relationships among critical success factors were established with the help of interpretive structural modelling using a team of 12 experts from industry and academia. These established relationships helped in proposing the hierarchical implementation framework. Finally, the validation of the proposed implementation framework was carried out using structural equation modelling (SEM).

Findings

This study has identified nine broader critical success factors for implementation of OHSMS in lean manufacturing organizations, especially the process industry. Subsequently, this study has proposed an OHSMS framework with nine broader critical success factors to implement in lean manufacturing organizations. Finally, the proposed framework has been validated using SEM with an appropriate sample size.

Practical implications

This study is helpful to the organizations to implement OHSMS without losing the essence of lean manufacturing strategy. This study has proposed a framework for implementation of OHSMS in the lean manufacturing organizations, especially process industry sector. This study also provided confidence to the organization through the validation of proposed framework in the process industry.

Originality/value

To the best of the authors’ knowledge, this study is first of its kind in this field of OHSMS in lean manufacturing organizations, especially the process industry. This study has involved both academicians and industry experts to bring more robust outcomes. This study proposed a unique framework to implement OHSMS in lean manufacturing organizations. This study has considered a comprehensive literature to develop a framework for OHSMS in lean manufacturing organizations. An implementation framework was proposed by considering both the academicians’ and industry professionals’ opinions. The proposed framework was statistically validated. This will be helpful in effective implementation of OHSMS strategy in lean manufacturing organizations, especially process industry sector.

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