• Issue 1 (2017)
• Issue 2 (2017)

Numerical Simulation of a Cylindrical Heat Pipe and Performance Study

IJTEE, volume-12 , Issue 2 (2017), PP 135 - 141

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.010

by Mohammed Noorul Hussain, Isam Janajreh from Masdar Institute of Science and Technology, Abu Dhabi, UAE

Abstract: Heat Pipes are passive devices used for transferring heat from a heat source to a heat sink with very small difference in temperature. They have three main sections namely the evaporator, adiabatic section and the condenser. In construction terms, they have three parts, the metal container, the porous wick region which lines the container from inside and the hollow flow chamber. Heat pipe performance is governed by several parameters such as the geometry, dimensions, working fluid, wick and container materials etc. In this study numerical simulation method was used to analyze the performance of the heat pipe. A numerical model based on Navier stokes equation, Energy equation and conjugate heat transfer was developed using COMSOL Multiphysics package. The top wall temperature profile obtained was validated with experimental results, and further the absolute thermal resistance was calculated. A sensitivity study was carried out to study the performance dependency of heat pipe on four parameters namely, porosity, condenser evaporator lengths, radius of heat pipe and the heat input, in terms of the absolute thermal resistance. The results showed that absolute thermal resistance varied directly with respect to porosity of the wick, and inversely in case of radius of the heat pipe. The absolute thermal resistance was maximum in case of equal condenser and evaporator lengths. Interestingly the absolute thermal resistance did not vary with the applied heat rate, demonstrating the practicality in using absolute thermal resistance as a performance characteristic parameter. read more... read less...

Keywords: Heat pipe performance, Absolute thermal resistance, Numerical simulation, Experimental validation.

Voltage Unbalance Reduction of a Local Transformer Area with Domestic Asymmetrical Inverter and Optimal Control Design

IJTEE, volume-12 , Issue 2 (2017), PP 129 - 134

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.009

by László Neukirchner, Attila Göllei, Péter Görbe, Attila Magyar from Department of Electrical Engineering and Information Systems, Faculty of Information Technology, University of Pannonia, Egyetem street 10. H-8200, Veszprém, Hungary

Abstract: The three-phase unbalance problem can introduce additional losses in distribution networks due to both negative and zero sequence components, which leads to inefficient power consumption and increased CO2 emission of low voltage transformer area, moreover it causes safety possible malfunction of energy transportation networks. The aim of this paper is to introduce a new voltage unbalance indicator and a control algorithm that compensates source voltage unbalances. To examine the available measures of voltage asymmetry and make a comparison from the transient behaviors point of view. Analytical and simulation, results are presented to illustrate the effectiveness of the new techniques. read more... read less...

Keywords: voltage, Transformer, inverter

Solar Powered Electrolysis System for Cooking Applications

IJTEE, volume-12 , Issue 2 (2017), PP 119 - 122

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.007

by Evangelia Topriska, Maria Kolokotroni, Zahir Dehouche, and Earle Wilson from Heriot Watt University Dubai Campus, Dubai, United Arab Emirates Brunel University, Uxbridge, United Kingdom University of Technology, Kingston, Jamaica

Abstract: This paper presents a numerical model for a solar-powered Proton Exchange Membrane Electrolyser (PEM) for the generation of hydrogen as a fuel for cooking applications. The model was developed in TRNSYS software and includes a novel FORTRAN numerical component to model the operation of the PEM electrolyzer, based on operational data from a small-scale experimental rig. The numerical model was calibrated using data from the experimental rig powered by operational data from a photovoltaic panel system in the UK and from Jamaica. The calibrated model was used to develop a case study for a small community in Jamaica with a daily cooking demand of 39.6 kWh or 1.68 kg of H2 gas. Simulation results indicate that the H2 production strategy is satisfactory for the cooking needs of the case study and appropriate according to the environmental considerations related to cooking read more... read less...

Keywords: Solar Hydrogen, Electrolysis, Photovoltaics, Integrated Renewable Energy, Cooking

A note on NDT Technology for Detection of Defects in Oil and Gas Pipes

IJTEE, volume-12 , Issue 2 (2017), PP 117 - 118

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.006

by Amjad Omar from School of Graduate Studies and Research, American University of Ras Al Khaimah, UAE

Abstract: This paper provides a general note on the state of the art in the application of nondestructive testing techniques (NDT) for the detection of defects or deteriorations in metallic and nonmetallic oil and gas pipes. The advantages and disadvantages of each technique will be pointed out. read more... read less...

Keywords: NDT, Nonmetallic, Microwave

Scopus-Based Analysis of Solar Energy Research in the United Arab Emirates

IJTEE, volume-12 , Issue 2 (2017), PP 111 - 115

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.005

by Omar Akash from RAK Research & Innovation Center, American University of Ras Al Khaimah, United Arab Emirates

Abstract: This paper examines and presents the solar energy research situation in the UAE using Scopus-database. Like other countries of GCC, the UAE realizes that it has to rely less on oil and gas and start to consider other sources of energy for power production. The country began to support scientific research to be conducted in alternative energy resources such as solar energy since the early Nineties. However, it was very limited. More research was conducted at a somewhat larger scale during the past 10 years. Many researchers worked on various applications of solar energy for electricity production, water desalination, space cooling, etc. This work can be used by researchers, politicians, industry, or decision-makers to see how much the UAE invested in the field of solar energy and how it compares to other countries in the GCC, Arab world, and worldwide. It presents and identifies those active institutions and researchers in the field of solar energy in the UAE using the data collected by Scopus. The progress of solar energy research in the UAE is also presented. read more... read less...

Keywords: Solar energy, Scopus, UAE

Flow Regimes and Heat Transfer Characteristics in Combustion Chambers

IJTEE, volume-12 , Issue 2 (2017), PP 105 - 110

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.004

by Saad A. Mohammed, Essam E. Khalil, Hatem Omar Haridy, and Esmail M. ElBialy from Ministry of Electricity, Baghdad, Iraq Mechanical, Engineering at Faculty of Engineering, Cairo University, Cairo, Egypt

Abstract: This paper presents numerical computations are performed to investigate the convective heat transfer characteristics of a gas turbine that can combustor under non-reacting flow conditions in a Reynolds number range 50,000 to 600,000 with a characteristic swirl number of 0.7. A sample of computational predictions of flow behaviors under reacting conditions is also shown for swirling furnace flow of 0.52. The RNG (K-ɛ Model) predictions are compared with the experimental data of local heat transfer distribution on the combustor liner wall. It was observed that the flow field in the combustor is characterized by an expanding swirling flow, which impinges on the liner wall close to the inlet of the combustor. The peak heat transfer augmentation ratio (compared with fully developed pipe flow) reduces from 10.5 to 2.7. Additionally, the peak location does not change with the Reynolds number since the flow structure in the combustor is also a function of the swirl number. The size of the corner recirculation zone near the combustor liner remains the same for all Reynolds numbers and hence the location of shear layer impingement and peak augmentation does not change. The heat transfer coefficient distribution on the liner wall predicted from the RNG (K-ɛ Model) is in good agreement with experimental values. The location and the magnitude of the peak heat transfer are predicted in very close agreement with the experiments. read more... read less...

Keywords: Furnaces, Modelling, Swirling Flows, Heat transfer

Smoke Spread in Underground Metro Station

IJTEE, volume-12 , Issue 2 (2017), PP 95 - 103

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.003

by Mahmoud A. Ahmed, Mahmoud A. Fouad, and Essam E. Khalil from Mechanical Power Engineering Department, Faculty of Engineering, Cairo University, Giza, Egypt

Abstract: In the event of a subway train, fire smoke is the most fatal factor because smoke spreads in a direction that coincides with a passenger’s evacuation path. It reduces visibility and can cause fatalities by asphyxiation. This research presents a numerical study to investigate the effect of exhausting smoke by single-point extraction and exhausting smoke by multi-point extraction on passengers’ life safety. Also, the effect of adding smoke barriers at the stairs entrance on passengers’ life safety is studied. Fire Dynamics Simulator (FDS) software version 5.5.3 is utilized to simulate 6 case studies in 150 m long, 20 m wide and 13 m height domain with a subway car fire source simulated as a fire with the unsteady heat release rate of 35 MW resulted from burning Heptane as a fuel. Results show that exhausting smoke by multipoint extraction system in underground subway station gives better performance than single point extraction system. By increasing the distance between vents in a multipoint extraction system, tenable conditions improve at a human level. Smoke barrier addition to ventilation system has a great effect on the efficiency of smoke extraction and improving tenable conditions at a human level. read more... read less...

Keywords: Subway train fire, Smoke spread, FDS, Smoke barrier, Life safety.

Investigation of the Current Energy Sector in Jordan: Energy Strategy, Resources and Regulatory Framework

IJTEE, volume-12 , Issue 2 (2017), PP 89 - 93

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.002

by Ahmed Al-Salaymeh, Heba AlZaben, and Nadeen Habash from Mechanical Engineering Department, Faculty of Engineering & Technology, University of Jordan, Amman 11924, Jordan

Abstract: Due to the increase in demand for energy resources and the effect of the ongoing events in the region of Jordan. The energy resources are decreasing over time and that also has a negative effect on the Jordanian economy. Providing energy is always a vital and significant problem in Jordan. Jordan on the other hand is rich in some of the renewable energy resources, which are not fully used until this moment. Therefore, it is essential to find alternative and renewable energy resources. Moreover, there is also a lack in creating clear and long-term future plans in the energy field. In this paper, energy sources and the efficiency of the energy sector in Jordan will be specified, in addition to the determination of the cofounders and sponsors for enhancing and developing the energy sector. The shift in policy that is needed to increase this efficiency will be also investigated. read more... read less...

Keywords: Energy resources. Renewable energy. Energy sector. Energy policy

Performance Study of a Domestic Boiler Fueled By Biodiesel Produced From Rapeseed

IJTEE, volume-12 , Issue 2 (2017), PP 85 - 88

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.02.001

by Mohammad A. Hamdan and Derar A. Almomani from Faculty of Engineering and Technology, The University of Jordan, Jordan

Abstract: A domestic boiler was used in this work to compare its performance when it is powered by diesel fuel and biodiesel fuel that is produced from rapeseed oil, then blends of both fuels were prepared with different concentrations of biofuel (B5, B10 and B20). The performance measurements included the efficiency of the boiler, the specific fuel consumption in addition to the environmental impact represented by exhaust gases analysis; this included the concentration measurements of main species such as NOX, NO2, NO, SO2, CO2, and hydrocarbon. It was found that there is a small decrease in boiler efficiency resulting from using biodiesel fuel. Moreover, an increase in specific fuel consumption has been noticed. The performance of a domestic boiler when operating using B20, B5, and B10 blends has similar fuel consumption and efficiency when it is powered by petroleum diesel fuel. The regulated emissions from biodiesel fuel found to be more ecological than petroleum diesel, with the concentrations of all pollutants decrease with the percentages of biodiesel in the blends. read more... read less...

Keywords: Boiler, Biodiesel, Rapeseed

A Stable DC Power Supply for Photovoltaic Systems

IJTEE, volume-12 , Issue 1 (2017), PP 67 - 71

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.009

by Hussain A. Attia, Beza Negash Getu, and Nasser A. Hamad from Department of Electrical, Electronics and Communications Engineering, American University of Ras Al Khaimah, Ras Al Khaimah, UAE

Abstract: The use of solar energy as a source of power is becoming not a choice but a necessity due to the unprecedented growth in the demand and consumption of electrical power for various applications. The solar power from the Photovoltaic (PV) systems are currently used as a standalone PV system or integrated with the electric grid. However, the generated DC power from PV systems is not stable due to weather, atmospheric and environmental conditions, which requires the design of a DC power supply to produce a stable and regulated DC voltage output. In this paper, a new design of power supply is presented that provides a stable output voltage (Vout = +12 V, 0 V, -12V) over a significant range of input voltage variations (Vin = +15 V to +50 V) emulating the variation of the output voltage of PV systems. The stabilization of the output voltage reflects the effectiveness of the proposed design for photovoltaic systems applications. The system is simulated using NI-MULTI SIM software. A satisfactory simulation result is obtained showing a strong promise to practically implement using discrete components. read more... read less...

Keywords: PV System, Voltage Variation, Sensing & Protection Circuit, Op-Amp, Zener Diode, DC Supply

Utilizing Reclaimed Asphalt Pavement (RAP) Materials in New Pavements - A Review

IJTEE, volume-12 , Issue 1 (2017), PP 61 - 66

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.008

by Ahmad M. Abu Abdo from Department of Civil & Infrastructure Engineering, American University of Ras Al Khaimah, Ras Al Khaimah, UAE

Abstract: Recently, prices of asphalt pavement materials have been increasing tremendously, which led to attempts to find alternative cheap materials. In addition, more concerns are directed to preserving natural resources and reducing environmental impacts of using virgin asphalt binders, thus more attention is focused on the use of recycled materials in pavement designs. Transportation agencies worldwide are incorporating reclaimed asphalt pavement (RAP) materials in new pavement designs. RAP was used for the first time in 1973, however, with low percentages due to the lack of understanding of its effect on the performance of asphalt mixes. Currently, higher percentages (e.g. >50%) are being utilized to reduce costs and natural resources and make use of demolished old asphalt pavements. The main concern of combining RAP in new asphalt mixes is how it will affect the resistance of these mixes to permanent deformation (rutting), fatigue cracks, and thermal cracks, which are the main distresses that affect the performance of asphalt mixes. Many studies were conducted to evaluate the effects of RAP on asphalt mixes, and all results showed that RAP increased the stiffness of asphalt mixes, thus improving rutting resistance at high temperatures. On the other hand, results were in conflict with regard to fatigue and thermal cracking. Recently, the Department of Public Works and Services at Ras Al Khaimah, UAE started adopting RAP mixes in ongoing projects (e.g. Kadra-Shawka Road) with no clear guidelines, in hope of reducing costs and that these roads would have better performance. To address the concerns of the effects of RAP and to determine the correct RAP percentage for projects in Ras Al Khaimah, this study was initiated and as a first stage, a literature review was conducted and presented in this article. read more... read less...

Keywords: Asphalt Pavements, Reclaimed Asphalt Pavement, Recycling, Rutting, Fatigue Cracking, Thermal Cracking

Waste Heat Recovery from Gas Turbine Flue Gases for Power Generation Enhancement in a Process Plant

IJTEE, volume-12 , Issue 1 (2017), PP 53 - 60

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.007

by Valerie Eveloy, Peter Rodgers, Adesola Olufade, Yuyao Wang, and Ali Al Alili from Department of Mechanical Engineering, the Petroleum Institute, Abu Dhabi, United Arab Emirates

Abstract: To improve on-site power generation capacity and efficiency in process facilities, the thermal coupling of an industrial gas turbine cycle with a bottoming organic Rankine cycle for power plant flue gas waste heat recovery in a processing facility is investigated. Using 1,1,1,3,3-pentafluoropropane (R245fa) as a heat carrier in the Rankine cycle, 5.2 MW of additional electric power is generated, enhancing on-site power generation capacity and energy/exergy efficiency by approximately 23% and 6%, respectively. The overall energy and exergy efficiencies of the waste heat recovery system are estimated at 9% and 24%, respectively. Primary energy savings of approximately 1.3 million standard cubic feet per day (MMSCFD) of natural gas, or net annual operating expenditure savings of 1.6 million USD could be realized with the proposed flue gas waste heat recovery system based on subsidized industrial electricity tariffs in the UAE, with 457 tons of avoided CO2 emissions per year. read more... read less...

Keywords: Organic Rankine Cycle, ORC, Waste Heat, Industrial, Gas Turbine, Exergy

Performance Analysis of a New Waste Heat Recovery System

IJTEE, volume-12 , Issue 1 (2017), PP 47 - 52

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.006

by Saed A. Musmar, Nasim Razavinia, Frank Mucciard, Iskander Tlili from Department of Industrial Engineering, Faculty of Engineering and Technology, University of Jordan, Amman, Jordan Materials and Metallurgical Department, McGill University, Montreal, Canada Mechanical Engineering Department, Engineering College, Majmaah University. Kingdom of Saudi Arabia

Abstract: The overall theme of this research is to capture, concentrate and convert some of the waste heat generated at industrial plants to a valuable form of energy. A new system for heat recovery from low-grade energy has been built and tested based on a modified heat pipe technology. A single heat pipe used in this research was able to extract 2 kW of energy from waste heat of 250 oC. However, a heat pipe can extract 11.5 kW/m2 heat fluxes. The maximum energy extraction by such a system from low grad energy can be up to 3 kW. While a heat pipe regardless of its size can have heat flux up to 16.5 kW/m2 from waste heat flow at 250 oC and 12.3 m/s velocities. Also, the system can extract about 1 kW heat or 6.5 kW/m2 heat flux at temperatures as low as 150 oC. However, the system doesn’t function properly at temperatures lower than 150 oC read more... read less...

Keywords: Waste heat recovery, Latent heat, Heat pipe, Vortex promoters, thermal conveying

Finite Element Analysis with COMSOL Code for Air Flow and Thermal Convection in Sealed Attic Spaces with Experimental Validation

IJTEE, volume-12 , Issue 1 (2017), PP 39 - 46

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.005

by Antonio Campo, and Jaime Sieres from Department of Environmental Engineering, Faculty of Engineering, University of Vermont, Burlington, VT 05405, USA Área de Máquinas y Motores Térmicos, Escuela de Ingeniería Industrial, Universidad de Vigo, Campus Universitario Lagoas-Marcosende, 36310 Vigo, Spain

Abstract: The scope of the present paper is concerned with the numerical prediction of the confined airflow characteristics and thermal convection patterns in sealed attic spaces in roofs with upper inverted V-shapes and horizontally suspended ceilings of conventional houses and buildings. For these isosceles triangular cavities, two relevant cases involve prescribed wall temperatures wherein the bottom base wall is cooled/heated and the upper two inclined walls are symmetrically heated/cooled during the summer and winter seasons. Based on finite element analysis, the COMSOL code is implemented to perform numerical solutions of the two-dimensional system of coupled NavierStokesBoussinesq and energy equations. The computational domain is made coincident with the physical domain to handle potential non-symmetric velocities and non-symmetric temperatures that may occur when exposed to vigorous air flows. The numerical solution via finite elements provides the two velocity fields u (x, y), v (x, y), and the temperature field T (x, y) for the confined air flows. Overall, the target design quantity is the mean wall heat fluxes w q varying with the attic aspect ratio and the temperature difference at two opposing walls. The predicted w q values match the experimental measurements for the two distinct cases related to summer and winter seasons. In the end, comprehensive correlation equations are constructed for the quantification of the mean Nusselt number in terms of the Grashof number and the attic aspect ratio, which could be used in building science research. read more... read less...

Keywords: Sealed Attics of Houses And Buildings, Circulatory Air Flow, Thermal Convection, Finite Element Analysis, COMSOL Code, Experimental Measurements)

Cooling a Solid Disc with Uniform Heat Generation Using Inserts of High Thermal Conductivity within the Constructal Design Platform

IJTEE, volume-12 , Issue 1 (2017), PP 15 - 26

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.003

by F. Sharfi, R. M. Salimpuor, and A. Campo from Department of Mechanical Engineering, Ishafan University of Technology, Ishafan, Iran Department of Mechanical Engineering, The University of Vermont, Burlington, VT 05405, USA

Abstract: In the present study, the problem of cooling a solid disc by way of placing inserts with high thermal conductivity was examined analytically and numerically within the platform of the Constructal Theory. The work was accomplished using a fixed amount of highly conductive material distributed in the form of incomplete inserts from the center (sink). Using Constructal Theory, the magnitudes of the heat resistance in the radial and the branching configurations were calculated analytically. Additionally, to validate the analytical solution, a numerical solution with the Finite Element Method was employed. The one-to-one comparison between the two distinct results reveals a good agreement. In the present case, the length of the inserts was different from the disc radius viz. a new degree of freedom was considered and the solution was remarkably different from the case involving a complete insert. The heat resistance was minimized with respect to the aspect ratio in order to determine the optimal number of inserts as well as the disc radius. It was demonstrated that within a certain range of parameters, the heat conduction performance of incomplete inserts in the solid disc surpasses the heat conduction performance of standard complete inserts. read more... read less...

Keywords: Cooling, Solid Disc, Uniform Heat Generation, Incomplete Inserts, High Thermal Conductivity, Constructal Theory.

Experimental Determination of the Global Mass Transfer Coefficients of the Tropical Woods in order to Deduce the Drying Curves at the Lower Temperature

IJTEE, volume-12 , Issue 1 (2017), PP 9 - 14

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.002

by Merlin Simo-Tagne, Louis Monkam, Romain Rémond, André Zoulalian, Yann Rogaume, Beguidé Bonoma from University of Yaoundé I, Higher Teacher Training College, Applied Physic Laboratory, PO Box 47, Yaoundé, Cameroon Douala Institute of Technology (DIT), PO Box 1623, Douala, Cameroon University of Douala , Energy Laboratory of the Doctorate School of Physics and Engineering Sciences, PO Box 8698, Douala, Cameroon University of Lorraine, LERMAB, ENSTIB, 27 rue Philippe Séguin, PO Box 1041, F-88051 Epinal, France University of Lorraine, LERMAB, Faculty of Sciences and Technologies - Aiguillettes Campus- PO Box 70239 - 54506 Vandoeuvre les Nancy Cedex, Nancy, France

Abstract: We determine the global mass transfer coefficients of five tropical woods (obeche, iroko, loofa, Sapele, and freak) coming from Cameroon. In this effect, drying kinetics using a solar dryer and a conventional dryer is utilized. In addition, the comparison is doing between the values obtained and these coming from Chileans tropical woods and temperate. Thus, when the drying kinetics are between 0.25 to 1.5m/s, dry temperature equal to 33.5°C and wet temperature equal to 25°C, global mass transfer coefficients are between 2x10-5 and 4x10-5 kg/(m2 .s), for the conventional dryer. These values conform to those obtained on the Chilean tropical woods and less than those obtained on the temperate woods. In the case of an indirect solar dryer functioning between October and November 2004 at Yaoundé, this coefficient is lower because the wood thickness is almost 24mm in the case of conventional drying and 50mm in the case of solar drying. read more... read less...

Keywords: Global mass transfer coefficients, Drying kinetics, Tropical woods, Conventional dryer, Solar dryer, Experiment, Modeling, Cameroon.

Building Eco-Cities of the Future: The Example of Masdar City

IJTEE, volume-12 , Issue 1 (2017), PP 1 - 8

Published: 19 Dec 2017

DOI: 10.5383/ijtee.12.01.001

by T. Mezher, G. Dawelbait, I, Tsai, N. Al-Hosany from Masdar Institute of Science and Technology, iSmart Center, Abu Dhabi, UAE Masdar Company, Abu Dhabi, UAE

Abstract: Global warming and increased population growth are putting more pressure on policy decision-makers to adopt more sustainable approaches to planning and designing future cities. This has led to the rise of Eco-Cities that have smart and sustainable infrastructures such as green buildings; intelligent transportation systems; and efficient electricity, water, wastewater, and solid waste networks. In addition, these cities should be less dependent on fossil fuels and ensure healthier life and comfort. This paper gives a brief overview of the sustainable design concept of six Eco-cities from around the world such as Vauban in Germany, BedZed in the UK, Sonoma Mountain in California, Dongtan, and Tianjin in China, and Songdo in Korea. Masdar City is discussed in more detail including the green buildings, intelligent transportation systems, and other important infrastructure systems. This endeavor requires the managing of complex systems which necessitates the coordination and collaboration of all the stakeholders that are involved in designing, constructing, and operating the city. The paper concludes with lessons learned so far from Masdar City read more... read less...

Keywords: Eco-City, Masdar, sustainable Abu Dhabi