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Article
Publication date: 13 June 2008

J. Boran, L. Houdkova, V. Ucekaj and P. Stehlik

The purpose of this paper is to compare well‐known technologies of sludge utilization on the basis of energy and economical balances of real processes. The calculations…

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Abstract

Purpose

The purpose of this paper is to compare well‐known technologies of sludge utilization on the basis of energy and economical balances of real processes. The calculations are based on pilot tests in the Central Waste Water Treatment Plant (CWWTP) in Prague, the biggest waste water treatment plant in the Czech Republic.

Design/methodology/approach

A key issue for the comparison of mass and energy flow of sludge management is the attainable level of sludge dewaterability. Results of dewatering of anaerobic digested sludge are available from real applications since most sewage plants use digesters. The existing limited knowledge about mixed raw sludge (MRS) dewaterability have driven authors to make pilot tests targeted to establishment of an attainable level of MRS dewaterability. To get as close results as possible even anaerobic stabilized sludge was dewatered and various other data were collected to obtain a comprehensive data set for energy balance of the sludge management calculation. The pilot tests took place at CWWTP in 2005. Measured data were used to calculate energy balance of a number of different sludge managements.

Findings

To produce self‐reliant combusting sludge, a dry matter content of 35‐45 per cent for MRS and 45‐55 per cent for digested sludge has to be achieved by means of dewatering and potentially drying. In recent measurements at CWWTP a dry matter content of about 33 per cent was achieved by dewatering of MRS. This value is very close to the range of the dry matter content at which a self reliant combustion can be expected.

Practical implications

This comparison together with investment cost analysis should be one of the most important parameters in case of design a new or revamp an old waste water treatment plant.

Originality/value

The paper provides results from pilot tests at CWWTP together with three different energy balances comparison.

Details

Management of Environmental Quality: An International Journal, vol. 19 no. 4
Type: Research Article
ISSN: 1477-7835

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Article
Publication date: 27 February 2020

Xianzhi Mei, Yaping Chen, Jiafeng Wu and Xiaoyu Zhou

Conventional electric heaters mostly use U-shaped electric heating tubes and the hollow tube electric heaters are new type ones that rely on the heat transfer tubes as…

Abstract

Purpose

Conventional electric heaters mostly use U-shaped electric heating tubes and the hollow tube electric heaters are new type ones that rely on the heat transfer tubes as heating elements. However, in the original design, the fluid flows through the annular gaps between the shell wall and the supporting plates, the chambers between supporting plates are generally stagnant zones. The purpose of study is to overcome these deficiencies.

Design/methodology/approach

A modified approach is proposed in which the heating tubes are surrounded by holes on the supporting plates, thus the stagnant flow zone can be eliminated and the heating surfaces of both inside and outside the tube can be fully used. Numerical simulations were carried out on four schemes of hollow tube electric heaters, i.e. plate blocked, countercurrent, parallel and split. The results show that the two schemes of parallel and split can reduce the temperature difference between the two sides of the fixed tube plate, and thus reduce thermal stress and prolong the service life.

Findings

The split scheme of electric heater has the highest comprehensive index, moderate heat transfer coefficient and minimum pressure drop on the shell side. Its average heat transfer coefficient and comprehensive index are, respectively, 15.7% and 52.9% higher and its average pressure drop and tube wall temperature are, respectively, 57.6% and 19 K lower than those of the original plate blocked scheme, thus it can be recommended as the best scheme of the hollow tube electric heaters.

Originality/value

Based on the original design of hollow tube electric heater with plate blocked scheme, three plate perforated schemes were proposed and investigated. The thermal and flow features of the four schemes were compared in terms of heat transfer coefficient, pressure drop and comprehensive index ho·Δpo−1/3. The split scheme can reduce the temperature difference between two sides of the fixed tube plate with reduced thermal stress. It has moderate tube wall temperature and heat transfer coefficient, the smallest shell side pressure drop and the highest comprehensive index ho·Δpo−1/3, and it can be recommended as the optimal scheme.

Details

Engineering Computations, vol. 37 no. 7
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 23 August 2019

Michal Plaček, Martin Schmidt, František Ochrana, Gabriela Vaceková and Jana Soukopová

The paper aims to deal with the analysis of the factor leading to the repeated selection of the specific supplier and the effect of this recurrent selection on overpricing…

Abstract

Purpose

The paper aims to deal with the analysis of the factor leading to the repeated selection of the specific supplier and the effect of this recurrent selection on overpricing of public contracts.

Design/methodology/approach

A mix of quantitative and qualitative methods is used to achieve this goal. To analyze the chances of obtaining repeated contracts, the logistic regression method is used. To analyze the factor of overpriced contracts, the classic ordinary least squares regression model is used. The focus group method is then used to explain the factors acting on the part of the contracting authorities.

Findings

The results show that the prior procurement of a given contracting authority, or work for the public sector in general, has a statistically significant effect on the conclusion of contracts. The use of less-transparent forms of input has a strong impact. The non-transparent selection of suppliers rather than repetition of contracts generally results in the over-pricing of contracts. The IT sector is an exception.

Social implications

This research is also essential for real public policy. Given the amount of GDP allocated to the public procurement market, it makes sense to continually seek room for improvement. Here is an attempt to find this by examining the contracting authorities’ behavior when awarding repeated contracts.

Originality/value

This research is original because it looks at the problem of the contracting authority in the wider context and optics of the path dependency theory, which has not yet been applied to the public procurement environment. The focus is also on IT procurement, which according to this study has not been empirically investigated in this way, is also innovative.

Details

Journal of Public Procurement, vol. 19 no. 4
Type: Research Article
ISSN: 1535-0118

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Book part
Publication date: 29 August 2017

Karsten E. Zegwaard, Matthew Campbell and T. Judene Pretti

Much rhetoric around the construct of a work-ready graduate has focused on the technical abilities of students to fulfill the expectations of the future workplace. Efforts…

Abstract

Much rhetoric around the construct of a work-ready graduate has focused on the technical abilities of students to fulfill the expectations of the future workplace. Efforts have been made to extend from the technical skills (e.g., skills in calculation for engineers) to include soft or behavioral skills (e.g., communication). However, within previous models of understanding of the work-ready graduate there has been little done to explore them as critical moral agents within the workplace. That is, whilst the focus has been on being work-ready, it is argued here that in current and future workplaces it is more important for university graduates to be profession-ready. Our understanding of the profession-ready graduate is characterized by the ability to demonstrate capacities in critical thinking and reflection, and to have an ability to navigate the ethical challenges and shape the organizational culture of the future workplace.

This chapter aims to explore a movement of thinking away from simply aspiring to develop work-ready graduates, expanding this understanding to argue for the development of profession-ready graduates. The chapter begins with an exploration of the debates around the characteristics of being work-ready, and through a consideration of two professional elements: professional identity and critical moral agency, argues for a reframing of work-readiness towards professional-readiness. The chapter then considers the role of work-integrated learning (WIL) in being able to support the development of the profession-ready graduate.

Details

Work-Integrated Learning in the 21st Century
Type: Book
ISBN: 978-1-78714-859-8

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Article
Publication date: 13 April 2010

Clara Inés Pardo Martínez

The purpose of this paper is twofold. The first is to examine in detail energy efficiency performance of German and Colombian food industries. The second is to explain the…

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Abstract

Purpose

The purpose of this paper is twofold. The first is to examine in detail energy efficiency performance of German and Colombian food industries. The second is to explain the factors that have influenced energy efficiency.

Design/methodology/approach

Using data at the three‐digit level of aggregation, the paper compares energy efficiency across sectors of the food industry for the period 1998‐2005. Energy efficiency is analysed using the energy intensity (EI) indicator as well as a decomposition analysis. To determine the factors that have influenced energy efficiency performance, the concept of the production function is used.

Findings

The results show that both countries' food industries improved energy efficiency. During the period of study, energy consumption in the German food industry increased by an average of 1.3 per cent per year and the EI decreased 7 per cent, whereas the Colombian food industry decreased its energy consumption by an average of 1.9 per cent per the year and the EI decreased 11 per cent. However, the Colombian food industry needs 2.2 times more energy than the German food industry to produce a unit of gross production. A decomposition analysis indicated that economic and technical factors have played an important role in the energy efficiency performance because increases in economic growth and technology improvements increase the industrial sector's ability to improve energy efficiency. A second‐stage empirical analysis reveals that capital, material, investments and value‐added variables had a positive influence on energy efficiency performance in both countries. Energy prices are shown to have a positive influence on energy efficiency in the German food industry, whereas the sizes of enterprises and concentration processes played an important role on energy efficiency performance in the Colombian food industry.

Originality/value

The literature indicates the relative lack of attention paid to the analysis of energy use across sectors of food industry as well as the lack of studies determining the factors that have affected energy consumption and energy efficiency performance using cross‐country and cross‐sectoral comparisons.

Details

International Journal of Energy Sector Management, vol. 4 no. 1
Type: Research Article
ISSN: 1750-6220

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Article
Publication date: 9 March 2015

Carlos Alberto Schuch Bork, Janaina Fracaro Souza Gonçalves and Jefferson Oliveira Gomes

This article aims to collect data on the aluminum alloy 7050-T7451 machinability used in the manufacturing of aeronautical structures, using the combination of the…

Abstract

Purpose

This article aims to collect data on the aluminum alloy 7050-T7451 machinability used in the manufacturing of aeronautical structures, using the combination of the jatropha vegetable-base soluble cutting oil in relation to the canola vegetal and semisynthetic mineral oils and the technique to apply cutting fluid by flood in relation to the Minimum Quantity Lubrication (MQL) in the milling process (HSM – high-speed machining).

Design/methodology/approach

It was observed that the jatropha vegetal cutting oil presented the best results in relation to requirements for lubrication, superficial mean roughness (index Ra) and shape errors in relation to the other oils in both the techniques to apply fluid which were tested. Comparing the application techniques, the jatropha vegetal oil offered an increase in the life span of the cutting tool, using the flood technique, exceeding in almost six times the machined length of the cutting tool in relation to the MQL technique in the same process conditions.

Findings

The Jatropha vegetable-base cutting oil, besides being produced from a renewable source, has inherent characteristics that can help attain a sustainable manufacturing, mainly with the use of the flood technique to apply cutting fluid in the aluminum alloy 7050-T7451 machining.

Originality/value

The Jatropha (vegetable) oil, in relation to its physicochemical properties, appeared to be the best one fit for being used in the machining of aluminum alloys 7050-T7451 because it did not interfere with any of the elements involved in the formation of intergranular corrosion and/or pitting, which are not allowed in the aeronautical production of parts. Jatropha (vegetable) cutting oil, besides being produced from a clean and renewable source, has the inherent characteristics that can help attain a sustainable manufacturing.

Details

Industrial Lubrication and Tribology, vol. 67 no. 2
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 21 January 2019

Habib Karimi, Hossein Ahmadi Danesh Ashtiani and Cyrus Aghanajafi

This paper aims to examine total annual cost from economic view mixed materials heat exchangers based on three optimization algorithms. This study compares the use of…

Abstract

Purpose

This paper aims to examine total annual cost from economic view mixed materials heat exchangers based on three optimization algorithms. This study compares the use of three optimization algorithms in the design of economic optimization shell and tube mixed material heat exchangers.

Design/methodology/approach

A shell and tube mixed materials heat exchanger optimization design approach is expanded based on the total annual cost measured by dividing the costs of the heat exchanger to area of surface and power consumption. In this study, optimization and minimization of the total annual cost is considered as the objective function. There are three types of exchangers: cheap, expensive and mixed. Mixed materials are used in corrosive flows in the heat exchanger network. The present study explores the use of three optimization techniques, namely, hybrid genetic-particle swarm optimization, shuffled frog leaping algorithm techniques and ant colony optimization.

Findings

There are three parameters as decision variables such as tube outer diameter, shell diameter and central baffle spacing considered for optimization. Results have been compared with the findings of previous studies to demonstrate the accuracy of algorithms.

Originality/value

The present study explores the use of three optimization techniques, namely, hybrid genetic-particle swarm optimization, shuffled frog leaping algorithm techniques and ant colony optimization. This study has demonstrated successful application of each technique for the optimal design of a mixed material shell and tube heat exchanger from the economic view point.

Details

Journal of Engineering, Design and Technology, vol. 17 no. 2
Type: Research Article
ISSN: 1726-0531

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Article
Publication date: 19 June 2019

Ali Akbar Abbasian Arani, Ali Arefmanesh and Hamidreza Ehteram

The purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the…

Abstract

Purpose

The purpose of this paper is to recommend a validated numerical model for simulation the flue gases heat recovery recuperators. Due to fulfill of this demand, the influences of ash fouling characteristics during the transient/steady-state simulation and optimization of a 3D complex heat exchanger equipped with inner plain fins and side plate fins are studied.

Design/methodology/approach

For the particle dispersion modeling, the discrete phase model is applied and the flow field has been solved using SIMPLE algorithm.

Findings

According to obtained results, for the recuperator equipped with combine inner plain and side plate fins, determination of ash fouling characteristics is really important, effective and determinative. It is clear that by underestimating the ash fouling characteristics, the achieved results are wrong and different with reality.

Originality/value

Finally, the configuration with inner plain fins with characteristics of: di =5 mm, do = 6 mm, dg = 2 mm, dk = 3 mm and NIPFT = 9 and side plate fins with characteristics of: TF = 3 mm, PF = 19 mm, NSPF = 17·2 = 34, WF = 10 mm, HF = 25 mm, LF = 24 mm and ß = 0° is introduced as the optimum model with the best performance among all studied configurations.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 5
Type: Research Article
ISSN: 0961-5539

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Book part
Publication date: 17 July 2006

David H. Kamens

A number of commentators have noted significant changes in the American polity over the last half century. More interest groups with more issues are active in the polity…

Abstract

A number of commentators have noted significant changes in the American polity over the last half century. More interest groups with more issues are active in the polity now (Dahl, 1994). There is more ideological polarization among political elites (DiMaggio, Evans, & Bryson, 1996, 2004). Participation in voluntary associations has declined among the post 1945 generations, weakening civil society (Putnam, 2000). The new organizations in the polity are more hierarchical in structure, unlike the older voluntary associations that were built on lateral ties (Skocpol, 1996, 1999). Rising education levels have produced lower voter participation rates (Brody, 1978; Nie, Junn, & Stehlik-Berry, 1996). Finally, a number of observers have noted that public opinion, constructed in part by extensive polling, has become a significant force in the polity and this has helped fuel the rise of a media centered politics (Herbst, 1993; Schudson, 1991). This is not an exhaustive list of changes that observers have noted, but it is enough to suggest that the older Tocquevillian polity and the civic culture of the U.S., portrayed so effectively by Almond and Verba (1963), have been transformed in significant ways.

Details

The Impact of Comparative Education Research on Institutional Theory
Type: Book
ISBN: 978-0-76231-308-2

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Article
Publication date: 8 March 2021

Jiri Dvorak, Lenka Komarkova and Lukas Stehlik

The market for goods and services is a continually changing environment influenced by many internal and external factors. The majority of economies in the World were…

Abstract

Purpose

The market for goods and services is a continually changing environment influenced by many internal and external factors. The majority of economies in the World were deeply hit by the coronavirus epidemic (COVID-19) in the first half of 2020. This paper aims to contribute to the understanding of the role of a crisis, COVID-19 in this case, in moderating the market environment and its ability to accelerate or slow down ongoing processes.

Design/methodology/approach

A questionnaire survey was used to obtain the opinions of 100 customers and 100 local retailers on the digitisation of the shopping process in a medium-sized Czech town. After the first wave of crisis faded away, the respondents reflected on their opinions before, during and after the crisis. The data were processed using linear mixed models respecting repeated measures.

Findings

The crisis seems to have shifted the interest of both groups towards e-commerce but it did not change the disproportion in opinions between them. The interest of customers was significantly higher, even after the crisis.

Research limitations/implications

The credibility of the results is limited mainly by the one-time gathering of the data after the crisis. However, the results indicate a persistent challenge to which small retailers are exposed.

Originality/value

The originality of the results comes from the specific situation brought about by the COVID-19 crisis and the structure of respondents, enabling us to catch an immediate shift of opinions caused by the crisis and to compare the changes in both groups of respondents.

Details

Journal of Entrepreneurship in Emerging Economies, vol. 13 no. 4
Type: Research Article
ISSN: 2053-4604

Keywords

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