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Article

R. Bennacer, K. Sefiane, M. El‐Ganaoui and C. Buffone

A computational model is developed to describe convection in volatile liquids evaporating in capillary tubes. Experimental work has demonstrated the existence of such…

Abstract

A computational model is developed to describe convection in volatile liquids evaporating in capillary tubes. Experimental work has demonstrated the existence of such convective structures. The correlation between this convection and the phase change process has been experimentally established. Temperature distribution on the liquid‐vapour interface is considered in order to characterise the minimum of radial temperature gradient required to initiate and orientate Marangoni convection. Direct numerical simulation using finite volume approximation is used to investigate the heat and mass transfer in the liquid phase. The case of a capillary tube filled with a volatile liquid is investigated for various Marangoni numbers, to characterise heat and mass transfers under conditions close to realistic operating parameters. The simulation shows that a minimum irregularity in evaporative flux along the liquid‐vapour interface is necessary to trigger thermocapillary convection. The enhancement of heat and mass transfer by Marangoni convection is also investigated.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 7
Type: Research Article
ISSN: 0961-5539

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Article

Guoxin Xie, Ziyi Cui, Lina Si and Dan Guo

This paper aims to introduce a series of experimental results which are the extension of our previous novel observations (Xie et al., Soft Matter, 2011), which could be…

Abstract

Purpose

This paper aims to introduce a series of experimental results which are the extension of our previous novel observations (Xie et al., Soft Matter, 2011), which could be helpful for revealing the lubrication failure mechanism in bearings when they are exposed to an electrical environment.

Design/methodology/approach

An experimental apparatus where a ball was in contact with a glass disk coated with a semi-reflective chromium layer. A small volume of oil droplet was put into the microgap of the ball-disk contact. Then, a potential was applied onto the oil micropool formed by the droplet surrounding the contact region.

Findings

It has been found that destabilization of the low-conducting oil micropool around the contact region could be induced after applying a potential. Thin oil films could be drained out of the oil pool and spread on the tribopair surfaces, resulting in the depletion of the oil pool. When the applied potential was increased, the occurrence of spreading would be easier and its development would be more obvious. In contrast, the electrospreading behavior would be suppressed when the oil viscosity, contact load and oil pool size were increased. Thermocapillary force due to thermal effect as a result of the current flow near the oil pool border has been proposed as the main driving force for the spreading behavior. The influences of the operating parameters have been ascribed to the change of the electric current near the oil pool border as well as the corresponding variations in the temperature rise and the surface tension of the oil pool.

Originality/value

This is the first study to directly observe that the lubricant oil micropool around the contact region could deplete after applying a potential, potentially resulting in oil starvation in the contact region.

Details

Industrial Lubrication and Tribology, vol. 69 no. 1
Type: Research Article
ISSN: 0036-8792

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Article

Elaine Lim and Yew Mun Hung

By solving a long-wave evolution model numerically for power-law fluids, the authors aim to investigate the hydrodynamic and thermal characteristics of thermocapillary…

Abstract

Purpose

By solving a long-wave evolution model numerically for power-law fluids, the authors aim to investigate the hydrodynamic and thermal characteristics of thermocapillary flow in an evaporating thin liquid film of pseudoplastic fluid.

Design/methodology/approach

The flow reversal attributed to the thermocapillary action is manifestly discernible through the streamline plots.

Findings

The thermocapillary strength is closely related to the viscosity of the fluid, besides its surface tension. The thermocapillary flow prevails in both Newtonian and pseudoplastic fluids at a large Marangoni number and the thermocapillary effect is more significant in the former. The overestimate in the Newtonian fluid is larger than that in the pseudoplastic fluid, owing to the shear-thinning characteristics of the latter.

Originality/value

This study provides insights into the essential attributes of the underlying flow characteristics in affecting the thermal behavior of thermocapillary convection in an evaporating thin liquid film of the shear-thinning fluids.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 29 no. 12
Type: Research Article
ISSN: 0961-5539

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Article

Vivekanand SVB and Raju VRK

The purpose of this paper is to investigate the effects of gravity on the heat transfer behavior of the two-phase flow of water undergoing phase change. Most of the…

Abstract

Purpose

The purpose of this paper is to investigate the effects of gravity on the heat transfer behavior of the two-phase flow of water undergoing phase change. Most of the earlier studies of convective boiling considered systems where the gravity is neglected. In contrast, the authors investigated systems where the gravity is considered. The heat transfer characteristics of water during its evaporation in microchannel heat sink are studied for different channel inclinations.

Design/methodology/approach

Computational fluid dynamics software ANSYS Fluent is used for the computational study. The volume of fluids multiphase method available in the package is used to capture the vapor–liquid interface. Heat transfer studies are carried out for a rectangular microchannel having a characteristic dimension of 825 µm at different inclinations, which varied from −90° (vertically downward) to 90° (vertically upward). During each simulation, the vapor quality is set at the inlet. Uniform heat flux of 250 kW/m2 is applied at the bottom wall of the channel in all orientations of the channel, keeping the upper wall insulated.

Findings

As compared to horizontal configuration, a significant increase in the values of heat transfer coefficient during the fluid flow in inclined microchannels is noticed. It is observed that the Nusselt number for the vertically upward (+90°) and horizontal (0°) configuration are similar and that for the 45° upward configuration exceeds other configurations. It is also observed that the heat transfer performance becomes lower in downward configurations; nearly 40-50 per cent drop in average Nusselt number is observed for a mass flux of 250 kg m-2 s-1 with respect to 45° inclined microchannel. This behavior can be attributed to the gravitational effect on the two-phase flow because of which the vapor phase being less dense moves away from the heated wall, whereas the primary phase being heavier moves towards the heated wall of the channel. Also, the conductivity of the liquid being higher than the vapor phase, as well as the aperture of the liquid being small during this process, its velocity increases resulting in the augmentation of heat transfer.

Originality/value

User-defined-functions for the mass and energy source terms have been written in C code and hooked in ANSYS Fluent to incorporate the phase change mechanism during the evaporation of water.

Details

World Journal of Engineering, vol. 16 no. 1
Type: Research Article
ISSN: 1708-5284

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Article

Alena Pietrikova, Peter Lukacs, Dagmar Jakubeczyova, Beata Ballokova, Jerzy Potencki, Grzegorz Tomaszewski, Jan Pekarek, Katerina Prikrylova and Martin Fides

This paper aims to find an optimal surface treatment of commonly used polymeric substrates for achieve the high adhesion of printed structures. For this reason, the…

Abstract

Purpose

This paper aims to find an optimal surface treatment of commonly used polymeric substrates for achieve the high adhesion of printed structures. For this reason, the investigation of substrates surfaces from different perspectives is presented in this paper.

Design/methodology/approach

The contact angle measurements as well as the roughness measurements were realised for the analysis of surface properties of investigated substrates. The impact of applied chemical agents for surface treatment onto the wettability is analysed for polyimide, polyethylene terephthalate and polyethylene naphthalene substrates.

Findings

The results prove the correlation among wettability, surface energy and work of adhesion with respect to the theoretical background. The surface treatment of polymeric substrates by chemical agents, such as acetone, toluene, ethanol, isopropyl and fluor silane polymer, has a significant impact onto the wettability of substrates which affects the final deposition process of nanoinks.

Originality/value

The main benefit of the surfaces’ investigation presented in this paper lays in surface modification by readily available chemical agents for optimising the deposition process nanoinks used in inkjet printing technology.

Details

Circuit World, vol. 42 no. 1
Type: Research Article
ISSN: 0305-6120

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Article

Shahzad Uddin and Mathew Tsamenyi

Aims to examine the changes to budgetary control and performance monitoring in the context of a series of World Bank sponsored public sector reforms.

Abstract

Purpose

Aims to examine the changes to budgetary control and performance monitoring in the context of a series of World Bank sponsored public sector reforms.

Design/methodology/approach

The paper uses a longitudinal study of a state enterprise (the Ghana Food Distribution Corporation (GFDC)) in which the World Bank‐sponsored reforms were imposed. This paper especially draws on the dialectic of control from structuration theory.

Findings

The paper shows that budgetary practices at the GFDC did not change substantially, with the exception of the reporting practices. Budgeting remained politicised, delayed, directionless and ineffective. Reporting to the monitoring agency did not make any positive changes to accountability and performance and was thereby unable to serve public interests.

Research limitations/implications

With hindsight, the authors wished they had undertaken more in‐depth investigations of workers' and farmers' roles in whole performance contracting scenarios and public sector reforms at the GFDC. The failure so to do was mainly because of a shortage of time and the difficulty of obtaining relevant data.

Practical implications

This paper has raised a number of important but neglected issues concerning the public sector reforms in less developed countries (LDCs) for aid agencies and policy makers.

Originality/value

This paper demonstrates the usefulness of Giddens' idea of the dialectic of control in the contextual study of management controls, including budgeting and performance in the public sector in LDCs. Also, the paper makes an important contribution highlighting the public interest role of management controls especially in the context of public sector reforms.

Details

Accounting, Auditing & Accountability Journal, vol. 18 no. 5
Type: Research Article
ISSN: 0951-3574

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Article

Hamid Nayebpur and Mohsen Nazem Bokaei

The purpose of this paper is to present a new technique to portfolio selection using a genetic algorithm (GA) and fuzzy synthetic evaluation (FSE). Portfolio selection is…

Abstract

Purpose

The purpose of this paper is to present a new technique to portfolio selection using a genetic algorithm (GA) and fuzzy synthetic evaluation (FSE). Portfolio selection is a multi-objective/criteria decision-making problem in financial management.

Design/methodology/approach

The proposed approach solves the problem in two stages. In the first stage, by using a GA and FSE, the weight of criteria will be calculated. Euclidean distance between the computed overall performance evaluation and the surveyed overall performance evaluation is used to determine the weight of criteria. In the second stage, by using a GA and FSE, portfolios will be prioritized. A multi-objective GA is used to determine return and risk in the efficient frontier. A decision making approach is based on FSE to select the best portfolio from among the solutions obtained by a multi objective GA.

Findings

The main advantage of the proposed approach is to help an investor to find a portfolio which has best performance, and portfolio selection does not rely on expert knowledge.

Originality/value

The value of the paper is in it using a new approach to determine the weight of criteria and portfolio selection. It surveys firms’ performance in the stock market, based on which the weight of criteria will be determined and portfolios will be prioritized.

Details

Engineering Computations, vol. 34 no. 7
Type: Research Article
ISSN: 0264-4401

Keywords

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Article

Claudia Barrios Álvarez, Pawan Adhikari and Alina Gómez Mejía

The purpose of this paper is to examine how a state-owned Colombian multi-utility conglomerate (CMC) has used management accounting practices (MAPs) to shape efficiency…

Abstract

Purpose

The purpose of this paper is to examine how a state-owned Colombian multi-utility conglomerate (CMC) has used management accounting practices (MAPs) to shape efficiency. The authors bring out the interplay between structures and agency in the process of shaping efficiency, which has enabled the company to operate as a private enterprise, taking advantage of NPM-led reforms and management accounting technologies.

Design/methodology/approach

This is an interpretative case study of a CMC. Data for the study are derived from interviews, non-participative observations and document analysis. Giddens' structuration theory (ST) provides the theoretical approach for the study.

Findings

Results show that MAPs have shaped efficiency in a CMC, promoting the profitability criteria prevailing in private enterprises. Theoretically, the paper shows how structure and agency are embedded in shaping efficiency in an emerging economy context through MAPs. It does this by analysing both the broader influence of the School of Mines and multilateral development banks and the micro-situated practices of employees at the CMC. The employees who have worked in the company for long periods of time have transformed the profitability criteria into a corporate value that influences their day-to-day practices.

Originality/value

The paper adds to the literature that draws on the ST by illustrating a paradigmatic case, in which agents have brought in knowledge and values to a state-owned company, and changed its ethos and practices whilst remaining under state control.

Details

Journal of Accounting in Emerging Economies, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 2042-1168

Keywords

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Article

Trevor Hopper, Mathew Tsamenyi, Shahzad Uddin and Danture Wickramasinghe

The purpose of this paper is to evaluate management accounting research in developing countries and formulate suggestions for its progression.

Abstract

Purpose

The purpose of this paper is to evaluate management accounting research in developing countries and formulate suggestions for its progression.

Design/methodology/approach

This is a desk based study of existing literature analysed through a framework of management control transformation in developing countries derived from the authors' research.

Findings

Research is growing, especially on accounting in state‐owned and privatised enterprises but more is needed on small and micro enterprises, agriculture, non‐governmental organisations, and transnational institutions.

Originality/value

This is the first review of this area and thus should help intending and existing scholars.

Details

Accounting, Auditing & Accountability Journal, vol. 22 no. 3
Type: Research Article
ISSN: 0951-3574

Keywords

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