volume-10-Issue 2 (2016)
Performance Investigation of Direct Evaporative Cooling in Major Cities of Iraq
IJTEE, volume-10, Issue 2 (2016) , PP 177 - 183
Published: 12 Aug 2016
by Abdulrahman Th. Mohammad from Baqubah Technical Institute, Middle Technical University, Baghdad, Iraq
Abstract: The cities of Baghdad, Basrah, and Mousl are the major cities in the middle, southern and northern parts of Iraq, respectively. In this paper, TRNSYS model is investigated to study the performance of direct evaporative cooler (DEC) in these cities. Based on the hourly climate data of each month in Typical Meteorological Year (TMY), the period of 1st of June to 31th of August is used to estimate the performance of DEC in terms of evaporative supply temperature and cooling capacity. The simulation results show that the performance of DEC is capable of providing comfort conditions in Baghdad and Mosul by lowering supply air dry bulb temperature below the design condition (24ºC) up to 2ºC in June and July and 1.5ºC in August. In addition, the maximum cooling capacity of DEC is obtained in July about (3617, 3417 and 3160) kW for Baghdad, Mosul and Basrah, respectively. read more... read less...
Keywords: Evaporative cooling, cooling capacity, TRNSYS
Parametric Quantification of Low GWP Refrigerant for Thermosyphon Driven Solar Water Heating System
IJTEE, volume-10, Issue 2 (2016) , PP 167 - 176
Published: 12 Aug 2016
by N.Abasa,b, N.Khana from Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan, Department of Electrical Engineering, University of Gujrat, Hafiz Hayat Campus, Gujrat, Pakistan
Abstract: Modern lifestyle, industrialization and economy thrive on energy which is getting expensive overtime. Thermosyphon based systems are getting attraction for their promising heat transfer efficiency and zero energy utilization. Refrigerants having ozone depletion potential (ODP) and high Global Warming Potential (GWP) have been banned or under time bared permission under Montreal (1987) and Kyoto (1997) protocols. We have devolved a Refrigerant Parametric Quantification (RPQ) method for the choice of optimal refrigerant for density driven solar water heaters. A set of 29 refrigerants are simulated Using REFPROP under various temperature and pressure conditions. The optimal parameters of thermosyphon system are identified from governing equations, international environment safety protocols and open literature. The proposed RPQ method shows most appropriate refrigerant for given temperature range. In second part, the proposed system is simulated in TRNSYS using forced circulation method. In the end, a glass evacuated tube collector is developed and tested on the principal of thermosyphon, employing the best refrigerant emerged from simulation study. read more... read less...
Keywords: Thermosyphon, natural refrigerants, thermodynamics, supercritical fluid.
Effect of Thermal Pretreatment on the Solubilization of Organic Matters in a Mixture of Primary and Waste Activated Sludge
IJTEE, volume-10, Issue 2 (2016) , PP 161 - 166
Published: 10 Aug 2016
by A. M. Aboulfotoh, E. H. El Gohary, O. D. El Monayeri from Environmental engineering department, Faculty of engineering, Zagazig university, Egypt, Arab Academy for Science, Technology and Marine Transportation, Egypt
Abstract: The increased demand for advanced techniques in anaerobic digestion over the last few years has led to the employment of various pre-treatment methods prior to anaerobic digestion to increase gas production. These pre-treatment methods alter the physical and chemical properties of sludge in order to make it more readily degradable by anaerobic digestion. Although the thermal pre-treatment presents high energy consumption, the main part of this energy to heat can be recovered from the biogas produced in the anaerobic process. In this research a mixture of primary and waste activated sludge was thermally pretreated at 100, 125, 150, 175 and 200 oC in order to determine the reaction kinetics for the increase of soluble organic fraction (expressed as CODs and VFAs). Experimental results proved that the solubilization of sludge is a 1st order reaction with respect to both CODs and VFAs, KCODs (reaction rate constant of CODs solubilization) increased from 4.59*10-3 (min-1) to 7.55*10-3 (min-1) as the temperature increased from 100 to 200 oC, with a reaction activation energy of 7447.21 (J/mole) and frequency factor of 0.051 (min-1), While KVFAs (reaction rate constant of VFAs solubilization) increased from 5.33*10-3 (min-1) to 7.97*10-3 (min-1) for the same increase in temperature, with a reaction activation energy of 5947.22 (J/mole) and frequency factor of 0.0364 (min-1). read more... read less...
Keywords: Anaerobic digestion, CODs, solubilization reaction kinetics, thermal pretreatment and VFAs.
Heat Disposal through Horizontal Submerged Jets
IJTEE, volume-10, Issue 2 (2016) , PP 155 - 160
Published: 09 Aug 2016
by Mohammed A. Azim from Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh
Abstract: The governing equations for submerged buoyant jet are solved numerically using the standard k model for turbulence closure. Comparison shows that results from simulation of this jet in quiescent ambient are in good agreement with the existing data. Simulation is also performed for this submerged jet in moving ambient for the seasonal conditions of a typical steam power plant situated nearby a river. Study of trajectories and excess temperatures of the jets in moving ambient show small vertical rises for the regulated excess temperatures over the year. read more... read less...
Keywords: Heat Disposal, Submerged Jet, Turbulent, Seasonal Condition
Exergy Analysis of Modified Solar Still
IJTEE, volume-10, Issue 2 (2016) , PP 149 - 154
Published: 09 Aug 2016
by Abdul Hadi N. Khalifa from Engineering Technical College, Middle Technical University, Baghdad, Iraq
Abstract: A new design of solar still consist of flat plate solar collector, heat exchanger and cooling tower, was built and tested under Iraq weather at March. The still was tested under different mass flow rate of brackish water entering the flate plate solar collector, ranging from 0.01 to 0.015 kg/s. The volume flow rate of air through cooling tower was 0.0195 m3 /s. A full details of overall system as well as for system components exergy analysis were achieved. It was found that the maximum daily exergy efficiency of the still is less than 1%. While the maximum hourly exergy efficiency and maximum productivity for such combination were 3.46 kg/day and 1.6% , respectively, when the mass flow rate of brackish water was 0.013 kg/s. read more... read less...
Keywords: Solar still, exergy analysis, solar collector, cooling tower
Control of DFIG on Variable Wind Speed
IJTEE, volume-10, Issue 2 (2016) , PP 143 - 148
Published: 08 Aug 2016
by N. Khan, N. Abas, T. Bukhari from Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan, Department of Electrical Engineering, University of Gujrat, Hafiz Hayat Campus, Gujrat, Pakistan
Abstract: Doubly Fed Induction Generator (DFIG) is one of the most reliable wind generator. Major problem in wind power generation is to generate constant frequency output on variable speed. This paper summarizes & reviews major techniques used in DFIG, and investigate various technologies developed by and solution proposed by different researchers to maintain constant frequency. In addition authors proposed method on these issues is discussed and experimental results are also included. DFIG experiment is demonstrated by driving it with a motor instead of real wind turbine. A variable frequency drive will be used to cause drive motor speed variations. Control circuit is attached with rotor windings, which will try to maintain the rotor excitation constant during speed variations. Proposed DFIG model controls the rotating magnetic field of the rotor in such a way that stator frequency becomes independent of RPM. Experiment is successfully performed on +/- 12 % speed variations. read more... read less...
Keywords: DFIG, VFD, constant frequency, wind power generation, pitch control.
Performance Study of a Biogas Pilot Plant Using Domestic Wastes from Benin Metropolis
IJTEE, volume-10, Issue 2 (2016) , PP 135 - 141
Published: 08 Aug 2016
by P.O. Ebunilo, S.A. Aliu and E. K. Orhorhoro from Mechanical Engineering Department, University of Benin, P.M.B 1154, Benin City 300001, Nigeria
Abstract: Increasing demand for energy and high waste generation in Nigeria necessitates the adoption of technologies that promote renewable energy and wastes conversion into viable commodity. The biogas technology is one of such systems that have been found to be cost effective and environmentally friendly. In this paper the performance study of a biogas pilot plant using domestic wastes from Benin metropolis was done. Two different samples of substrates composition were made to undergo anaerobic digestion at two different mesophillic temperatures and pH ranges. The gas produced was analyzed for percentage composition. It was observed that good mesophilic temperature range leads to faster digestion and that pH of slurry depend on substrates composition, period of production and temperature. read more... read less...
Keywords: Pilot plant, anaerobic digestion, Domestic wastes, Benin metropolis
A Test Device for Optimize PMU-Based Islanding Detection Technology
IJTEE, volume-10, Issue 2 (2016) , PP 129 - 134
Published: 08 Aug 2016
by Yuchen Zeng, Furong Liu, Xianbing Chen, Wei Liu from College of Automation, Wuhan University of Technology, Wuhan, P.R. China, 430070
Abstract: Islanding detection is a necessary function for grid connected distributed generators. Usually, islanding detection methods can be classified as two catalogues: remote detecting methods and local detecting methods. Most of them have limitation and defects when they are applied in photovoltaic power stations. Recently synchronous phasor measuring units (PMU) is proposed to be applied for islanding detecting. Although the islanding detection method is supposed to be applied for traditional bulk power systems, it is also suitable for renewable generation power plants. To do this islanding detection will be implemented on central management unit of photovoltaic power station instead of on grid-tied inverters as traditionally. In implementing, the criteria of this method and the threshold of algorithm are needed to be optimized. This paper develops a test device which can optimize PMU-based islanding detection technology to validate the proposed islanding detection method applying in PV station. Then using simulation to discuss how to set a reasonable threshold for the researched islanding detection method applied in PV stations. Finally the paper provides a platform for the algorithm optimization. read more... read less...
Keywords: Synchronous measurement, islanding detection, photovoltaic power station
A Standard Process for Sustainable Design
IJTEE, volume-10, Issue 2 (2016) , PP 121 - 128
Published: 08 Aug 2016
by Francisco J. Farias Stipo from Kay Elliott Architects, Torquay, Devon, TQ1 2JP, United Kingdom
Abstract: This exploratory research examined the degree of adoption and impact of the concepts of Building Information Model (BIM), Integrated Project Delivery (IPD), Integrated Design Process (IDP) and Building Energy Simulation (BES) on the design processes of advanced architectural firms when executing sustainable design. Six offices identified by the press and peers’ recognition for a strong commitment to sustainable design and influence in the design of high performance buildings were selected. In semi-standardized interviews, these firms presented their perceptions of the influence of BIM, BES, and IPD/IDP. The results show that a generalization of sustainable design processes is possible. A design process for sustainability (DEPROSU) model was created by collecting best practices from data gathered from the interviews and the critical literature review. This research provides evidence of commonalities found in the design processes of the selected firms. These commonalities represented in the DEPROSU model can potentially be validated as protocols or standards for sustainable design, providing architectural design practices with concrete patterns for improvement and or validation of their design methods. read more... read less...
Keywords: sustainability, Building Information Modelling, building energy simulation, design processes, integrated design.
Financial Risk and market Effects for the Congestion Costs of the electricity System in Italy
IJTEE, volume-10, Issue 2 (2016) , PP 113 - 120
Published: 08 Aug 2016
by Enrico Maria Mosconi, Stefano Poponi, Cecilia Silvestri from Department of Economics and Management, University La Tuscia, Via del Paradiso, 47, 01100, Viterbo – Italy
Abstract: The physical and structural constraints of the electricity grid economically and financially affect the operators imposing on them a set of measures designed to contain the problem of electric congestions. The Congestion costs occur in the electricity market when the power flows, equivalent to a projection mapping of energy injection and withdrawal, established by the “electricity stock exchange” and by “bi-lateral contracts”, are incompatible with the transfer capacity guaranteed by the power grid, in required security conditions. Transfer restrictions in the national and transboundary transmission grid can potentially determine the market segmentation in different geographical areas, preventing the producers to compete freely to satisfy the overall demand in those areas. As a result of power congestions, those producers that have reduced limitations in the power transfer are obviously favored, also if in the presence of high marginal production costs and prices, leading to the constitution of pools of producers that de facto control the local market. Through a critical survey of the situation of the Italian electricity market the paper aims to describe and discuss the problem of power congestions costs, the electricity price formation and the congestion risk management. read more... read less...
Keywords: Power congestions, Electricity market, Congestion Risk
Modeling Domestic Lighting Energy Consumption in Romania and Integrating Consumers’ Behavior
IJTEE, volume-10, Issue 2 (2016) , PP 105 - 111
Published: 08 Aug 2016
by Ion Smeureanu, Roman Kanala, Adriana Reveiua, Marian Dardala from Bucharest University of Economic Studies, 6 Piata Romana, 1st district, Bucharest, Romania,010374, University of Geneva, Institute of Environmental Sciences, Site de Batelle, Bat. D / 7 route de Drize, Carouge, Geneva, Switzerland, CH-1227
Abstract: Sustainable energy consumption is a research area of a large interest in the last years. New energy-efficient lighting technologies exist, and can significantly reduce household electricity consumption, but their adoption has been slow. A considerable number of international studies show that sustainable development scenarios will be realistic if they involve the human behavior. The paper provides a solution to integrate consumer behavior with techno-economic energy issues, inside a complex energy model. This approach aims to reduce the systematic error on the demand side of the energy model that stems from the hypotheses of perfect information and of perfect economic rationality. These hypotheses are common to all optimization models based on the concept of economic equilibria. The TIMES energy modeling software tool has been used to integrate the techno-economic energy specific data and consumer behavior. Consumer behavior in energy consumption is described using specific attributes of energy technologies as virtual technologies. Technical coefficients of virtual technologies come from a sociological survey about Romanians’ behavior in energy consumption. This approach, known as “Social MARKAL”, allows the analyst to evaluate the possible contribution of information campaigns in changing lighting consumers’ behavior and effect of technology switch. The model is developed for the period 2010-2026, and is implemented by using TIMES/VEDA software platform. The implementation presented this paper focuses on the household lighting technologies but the approach can be extended to other demand sectors as well. read more... read less...
Keywords: TIMES/VEDA model for Romania, behavior change, energy savings, consumer behavior modeling
Mixed Convection in Superposed Nanofluid and Porous Layers Inside Lid-Driven Square Cavity
IJTEE, volume-10, Issue 2 (2016) , PP 93 - 104
Published: 08 Aug 2016
by Ahlam A. Hassan, Muneer A. Ismael from Mechanical Engineering Department, Engineering College, University of Basrah, Basrah61004, Iraq.
Abstract: Mixed convection in a lid-driven composite square cavity is studied numerically. The cavity is composed of two layers; a Cu–water nanofluid layer superposed a porous layer. The porous layer is saturated with the same nanofluid. The left and right walls of the cavity are thermally insulated. The bottom wall which is in contact with the porous layer is isothermally heated and being lid to the left, while the top wall is isothermally cooled and being lid to the right. Cavity walls are impermeable except the interface between the porous layer and the nanofluid. Maxwell-Brinkman model is invoked for the momentum exchange within the porous layer. Equations govern the conservation of mass, momentum, and energy within the two layers were modeled and solved numerically using under successive relaxation (USR) up- wind finite difference scheme. Four pertinent parameters are studied; nanoparticles volume fraction φ (0.0 - 0.05), porous layer thickness Wp (0.1 - 0.9), Darcy number Da (10-7 – 10-1), and Richardson number Ri (0.01 - 10). The results have showed that the existence of the porous layer in a specified value can enhance the convective heat transfer when Ri ≥ 1, while an adverse action of nanoparticles is recorded when Da ≥ 10-4 . read more... read less...
Keywords: Composite cavity, lid-driven, porous medium, nanofluid.
Theory and Design of Counter Flow Shell-and-Coil Heat Exchanger for CO2Based Solar Water Heater
IJTEE, volume-10, Issue 2 (2016) , PP 87 - 93
Published: 08 Aug 2016
by N. Abasa, N. Khan from Department of Electrical Engineering, COMSATS Institute of Information Technology, Islamabad, Pakistan, Department of Electrical Engineering, University of Gujrat, Hafiz Hayat Campus, Gujrat, Pakistan
Abstract: A shell type helical tube countercurrent flow heat exchanger was designed, fabricated and tested using CO2 refrigerant material. Helical copper tube was immersed in bulk water tank. Hot CO2 was piped to upper coil baffle and cold CO2 was circulated into collector loop through lower baffle. Cold water was made to enter through lower tap and hot water was taken out from upper tap. Both in/out pipes were inserted from the top and coil tubes from upper and lower sides of water tank. Supercritical thermosyphon operation was achieved by evacuated glass tube solar heat collector using CO2 refrigerant. U shaped copper pipes enveloped in aluminum foil were inserted in evacuated glass tubes to transfer heat under thermosiphon principle to upper header connected to inlet baffle of shell type helical coil heat exchanger. Lower header was connected to heat exchanger helical coil outlet baffle. Solar collector heat raised CO2 refrigerant temperature from 35 to 78C giving temperature difference of 43C. Temperature of CO2 refrigerant at exit from heat exchanger was found to be 40C at surrounding ambient temperature of 36C. Heat exchanger raised the inlet water temperature from 26 to 55C under off water tap condition in about 3 hours. Inlet and outlet temperature difference of heat exchanger was measured to be 27C. We believe system efficiency can further increase if we use the system in mild sunshine cold weather regions duplicating geothermal loop. read more... read less...
Keywords: Heat exchanger, Shell & Helical Tube, Counter flow, Countercurrent.