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Article
Publication date: 20 August 2019

B. Saleh, Ayman A. Aly, M. Alsehli, M.M. Bassuoni and A. Elfasakhany

This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new…

Abstract

Purpose

This paper aims to investigate the performance and working fluids screening for an ejector refrigeration cycle (ERC) activated by solar energy. Several common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are proposed as refrigerants for the ERC to determine the most appropriate one.

Design/methodology/approach

The ejector performance is characterized by the ejector area ratio (EAR) and entrainment ratio (ω), while the cycle performance is described by the coefficient of performance (COP). The influences of many working parameters like the evaporator, condenser and generator temperatures on the ejector and cycle performances are investigated for all candidates as well.

Findings

The results indicate that the best ejector and cycle performances are attained with the highest critical temperature dry refrigerant, i.e. R601 under all studied working conditions. From the perspective of energy efficiency and environmental issues, R601 can be considered the most appropriate working fluid amongst all candidates. However, extra attention should be considered against its flammability. The maximum COP, the corresponding ω and the necessary EAR using R601 are 0.743, 1.02 and 15.5, respectively, with 25 ºC condenser temperature and the typical values for the rest operating conditions.

Originality/value

Many common and new hydrofluorocarbons, hydrocarbons, hydrofluoroolefins and hydrofluoroethers are suggested as working fluids for the ERC to determine the most appropriate one. The mixing process inside the ejector constant-area section is assumed constant-pressure process.

Details

World Journal of Engineering, vol. 16 no. 5
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 3 May 2016

Andrzej J Nowak, Michal Palacz, Jacek Smolka, Krzysztof Banasiak, Zbigniew Bulinski, Adam Fic and Armin Hafner

The purpose of this paper is to overview successful approaches to the computational simulation of real fluid (R744 – carbon dioxide (CO2)) flow within an ejector is presented…

Abstract

Purpose

The purpose of this paper is to overview successful approaches to the computational simulation of real fluid (R744 – carbon dioxide (CO2)) flow within an ejector is presented. Important issues such as the ejector geometry and its optimisation, the adapted equations of state and the proposed models of the process, fluid parameters, etc., are examined and critically discussed. Whenever possible, the discussed models are experimentally validated. In the conclusion, some trends in future research are pointed out.

Design/methodology/approach

Flow within CO2 ejector is generally transcritical and compressible. Models existing in the literature are shortly described and critically compared. Whenever possible, those models were validated against the experimental data. In a model validation process, the primary and secondary mass flow rates as well as the pressures at the selected points in the mixing section and diffuser were compared, showing a satisfactory agreement between experimental and computational results.

Findings

Developed CO2 ejector flow models are tested in few industrial applications. All these initiatives bring solutions which are interesting and very promising from technological point of view.

Originality/value

This is an extensive overview of successful approaches to computational simulation of the real fluid (R744 – CO2) flow within ejector. It brings many useful information.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 26 no. 3/4
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 14 July 2020

Mohammadreza Salehi, Nader Pourmahmoud, Amir Hassanzadeh, S. Hoseinzadeh and P.S. Heyns

Using the computational fluid dynamics (CFD) technique, this paper aims to investigate the influence of key parameters such as throat diameter; the suction ratio on the flow field…

Abstract

Purpose

Using the computational fluid dynamics (CFD) technique, this paper aims to investigate the influence of key parameters such as throat diameter; the suction ratio on the flow field behaviors such as Mach number; pressure; and temperature.

Design/methodology/approach

To investigate the effect of throat diameter, it is simulated for 4, 6, 8 and 10 mm as throat diameters. The governing equations have been solved by standard code of Fluent Software together with a compressible 2 D symmetric and turbulence model with the standard k–ε model. First, the influence of the throat diameter is investigated by keeping the inlet mass flow constant.

Findings

The results show that a place of shock wave creation is changed by changing the throat diameter. The obtained results illustrate that the maximum amount of Mach number is dependent on the throat diameter. It is obtained from the results that for smaller throats higher Mach numbers can be obtained. Therefore, for mixing purposes smaller throats and for exhausting bigger throats seems to be appropriate.

Originality/value

The obtained numerical results are compared to the existing experimental ones which show good agreement.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 31 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 October 2019

Soroush Sadripour, Mohammad Estajloo, Seyed Abdolmehdi Hashemi, Ali J. Chamkha and Mahmoud Abbaszadeh

The purpose of this study is to reduce energy consumption in bakeries. Due to fulfill this demand, quite a few parameters such as energy and exergy efficiency, energy waste and…

Abstract

Purpose

The purpose of this study is to reduce energy consumption in bakeries. Due to fulfill this demand, quite a few parameters such as energy and exergy efficiency, energy waste and fuel consumption by different traditional flatbreads bakeries (Sangak, Barbari, Taftun and Lavash should be monitored and their roles should not be neglected.

Design/methodology/approach

In the present study, experimental measurements and mathematical modeling are used to scrutinize and investigate the effects of the aforementioned parameters on energy consumption by bakeries.

Findings

The results show that by doing reported methods in this paper, the wasted energy of the walls can be decreased by about 65 per cent; and also, by controlling the combustion reaction to perform with 5 per cent excess air, the wasted energy of excess air declines by about 90 per cent. And finally, the energy and exergy efficiency of bakeries is increased, and as a result, the annual energy consumption of Sangak, Barbari, Taftun and Lavash bakeries diminish about 71, 59, 57 and 40 per cent, respectively.

Originality/value

As evidenced by the literature review, it can be observed that neither numerical studies nor experimental investigations have been conducted about energy and exergy analyses of Iranian machinery traditional flatbread bakeries. It is clear that due to a high preference of Iranians to use the traditional bread and also the popularity of baking this kind of bread in Iran, if it is possible to enhance the traditional oven conditions to decrease the loss of natural gas instead of industrializing the bread baking, the energy consumption in the country can be optimized.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 30 no. 6
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 February 1959

In introducing the subject some of the advantages of pneumatics for high speed aircraft are pointed out. Owing to its suitability for airborne conditioning systems, it is pointed…

Abstract

In introducing the subject some of the advantages of pneumatics for high speed aircraft are pointed out. Owing to its suitability for airborne conditioning systems, it is pointed out that it is logical to combine this characteristic in producing a combined air turbine and electric generator without the need of a separate cooling system. This was the thought behind the design of the Turbonator AC generating machine It includes a turbine wheel integral with the generator which is arranged to allow the turbine exhaust gas to pass over the generator for cooling purposes. The generator rotor windings are supported solidly by titanium retainers. Rotor bearings may either be of the sealed oil type or air bearings. Both have been tested, but, while the former is the simplest and suitable for present‐day standards, the air bearing has distinct possibilities for future uses. Thrust loads are taken up by an air bearing using the turbine wheel face as the bearing journal. No liquid is therefore used as a lubricant, thereby eliminating this high temperature problem. Materials for the generator are considered, one of which is ceramic insulation. Consideration was given to the inductor generator, but although this type of machine may be more suitable for high speeds, the rotating winding generator displays more advantages. A test rotor of the latter type has withstood speeds of 62,000 r.p.m. which is 25 per cent above normal speeds. The recent availability of a 24,000 r.p.m. generator makes it possible to eliminate a reduction gear.

Details

Aircraft Engineering and Aerospace Technology, vol. 31 no. 2
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 13 February 2017

Muhammad Usman, Qazi Shehzad Ali and Muhammed Bilal

Decreasing sources of fossil fuels has caused an increase in importance of the renewable energy resources and systems that directly utilize renewable energy are even more…

Abstract

Purpose

Decreasing sources of fossil fuels has caused an increase in importance of the renewable energy resources and systems that directly utilize renewable energy are even more important. The purpose of the paper is to compare the most common solar cooling technologies against the most important requirements.

Design/methodology/approach

A multi-criteria decision methodology, analytical hierarchical process, has been used to prioritize these technologies with respect to each other.

Findings

The findings of this study are the priorities of selected solar cooling concepts against performance affecting criteria. The solar vapour adsorption cooling system has been found to be the optimum solar cooling concept with practically the highest performance number compared with the other cooling systems.

Originality/value

This study can be used in the future development of solar cooling technologies to benefit from the best collective features of the specific technologies.

Details

World Journal of Engineering, vol. 14 no. 1
Type: Research Article
ISSN: 1708-5284

Keywords

Article
Publication date: 27 October 2023

Chiara Kuenzle, Julia Wein and Sven Bienert

This paper investigates the impact of CO2 vs CO2 “equivalents” (CO2e) by analyzing fugitive emissions, with a particular focus on Fluorinated gases (F-gases), arising from…

Abstract

Purpose

This paper investigates the impact of CO2 vs CO2 “equivalents” (CO2e) by analyzing fugitive emissions, with a particular focus on Fluorinated gases (F-gases), arising from refrigerant leakages in buildings. F-gases are an especially powerful set of GHGs with a global warming potential hundreds to thousands of times greater than that of CO2.

Design/methodology/approach

The significant impact of CO2e is tested by means of an empirical study with current consumption data from German food retail warehouses. This evaluation involves the analysis of the Carbon Risk Real Estate Monitor's country- and property-type specific pathway, coupled with a paired samples t-test to examine the hypotheses. The assessment is undertaken by evaluating the type of gas and the amount of leakage reported in the baseline year, subsequently converting these values to CO2e units.

Findings

On average, F-gases account for 40% of total building emissions and nearly 45% of cumulative emissions until 2050. In light of ongoing climate change and the rising number of Cooling Degree Days (CDDs), it becomes imperative to assess both the environmental and economic impact of F-gases and to transition toward environmentally friendly refrigerants.

Originality/value

The analysis sheds light on the seldom-addressed threats posed by CO2e emissions stemming from refrigerant losses. By identifying these threats, investors can devise strategies to mitigate potential future costs and carbon risks.

Details

Journal of European Real Estate Research, vol. 16 no. 3
Type: Research Article
ISSN: 1753-9269

Keywords

Article
Publication date: 1 June 1962

THIS has already been dealt with in some detail in the first article describing the aerodynamic features of the VC10, but it is relevant here to discuss the controls from the…

Abstract

THIS has already been dealt with in some detail in the first article describing the aerodynamic features of the VC10, but it is relevant here to discuss the controls from the systems viewpoint. Eleven powered flying control units are incorporated in the system; four aileron units, four elevator units and three rudder units. The units are fully‐powered and arranged such that each operates, independently, a portion of a split control surface. A high degree of interchangeability has been achieved by manufac‐turing a basic unit which can be readily adapted for the operation of any one of the three control surfaces, so that the spares and maintenance problem is eased. Each unit consists basically of the standard Boulton Paul hydraulic pump which supplies fluid to a hydraulic ram connected directly to a control surface. The power control consists of two pumping elements one of which operates on the ‘live‐line’ principle and generates a servo pressure of approximately 280 lb./sq. in., together with a main pressure pump, controlled by a servo valve, which supplies fluid direct to the hydraulic ram.

Details

Aircraft Engineering and Aerospace Technology, vol. 34 no. 6
Type: Research Article
ISSN: 0002-2667

Article
Publication date: 1 July 1963

W.N.C. Moore

In the first section of the symposium, published last month, Mr Moore contributed some thoughts on the layout of a laboratory for Applied Thermodynamics.

Abstract

In the first section of the symposium, published last month, Mr Moore contributed some thoughts on the layout of a laboratory for Applied Thermodynamics.

Details

Education + Training, vol. 5 no. 7
Type: Research Article
ISSN: 0040-0912

Article
Publication date: 1 May 1971

ELEVEN years ago a small group, of whom the writer was one, met in Oud Poelgeest Castle in Holland to consider forming a European body concerned with Work Study. They share a…

Abstract

ELEVEN years ago a small group, of whom the writer was one, met in Oud Poelgeest Castle in Holland to consider forming a European body concerned with Work Study. They share a sense of pride that the Federation which emerged will celebrate its decennary next month. Sadly, of the four British members of that group only two survive to greet the event.

Details

Work Study, vol. 20 no. 5
Type: Research Article
ISSN: 0043-8022

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