Remolding of Cross-Linked Polyethylene Cable Waste: Thermal and Mechanical Property Assessment
IJTEE, volume-05 , Issue 2 (2012), PP 191 - 198
Published: 17 Mar 2012
by Isam Janajreh, Mohammed Alshrah from Department of Mechanical Engineering, Masdar Institute of Science & Technology, Abu Dhabi, UAE
Abstract: Plastic has entered in all our manufacturing commodities, i.e. household, medical, automotive, and aerospace. It is offsetting metal, glass and cellulosic containers and is becoming the material choice Formos disposable items. On the average 12% ofour MSWareplastics(LDPE, Polypropylene, PET, Polystyrene).As itscharacterizedwithahigh value waste streamand slowlydegradable, effortsin reprocessing and reducing itsnegative environmental impactare increasing.Aspolymerization of methane, it draws aparamount amount of fossil fueland whenitburnsits reactin enthalpyisequivalent to dieselcombustion(43 MJ/kg).In attempt torecycle LDPE that mildly cross-linkedfor cable manufacturing, this work explores thechanges of material properties following remolding, re-extruding/calendaring and injection.This waste can mount over120 tons annually from onecable industryof single production line.Thermal analysis of the plastic using the Differential Scanning Calorimetry (DSC) to inferthemelting and molding conditionsis carried first.Second, tensileand dynamicsamplespreparationisconductedfollowingshredding, sieving, and infusion/mixinginmini extruder and theHAAKE MiniJet IIinjected mold.Third,uniaxial staticand dynamictestsare carriedutilizing Instron tensileandthe dynamicDMA 8000machine. It was observed as the amount of waste infusion is increased the sample ductility and strength ismildlyreduced. Dynamic testsshowed that the molded XLPEhas ahigher viscosity than LDPE at phase shift of10.75°for XLPE compared to9.88°for LDPE.Finally, in the view of these results a Visco-elastic material model is inferred for the reproduction of experimental result sin static and dynamic loading conditions. read more... read less...
Keywords: Cross-linked polyethylene, compounding waste plastic extrusion; molding, Material characterization, recycling
Efficiency Enhancements of Electric Power System and Economic Analysis- Practical Case Study
IJTEE, volume-05 , Issue 2 (2012), PP 183 - 190
Published: 17 Mar 2012
by A. Al-Hinai, A. Al-Badi, E. A. Feilat, M. Albadi from Sultan Qaboos University, Muscat, Oman, Yarmouk University, Irbid, Jordan
Abstract: Power system operators and planners are always faced with the problem of how to minimize the transmission and distribution losses. There are several ways to achieve this goal. Reducing losses improves the power system efficiency and yields a substantial energy savings. Other benefits also include released system capacity, possible deferral of capital expenditures for system improvements and expansion, and reduction of greenhouse gas emission. This paper, presents the results of a practical case study for assessing both technical and non-technical losses of a transmission and distribution network. Power system modeling, reconfiguration and generation relocation have been performed to reduce the power losses. Moreover, changing power system operational philosophy and adding capacitor banks to further optimizing the power system performance have also been investigated. Furthermore, economic analysis based on Net Present Value (NPV) is presented to quantify the losses. The economic analysis is conducted based on a rate of $75/MWH with a discount rate of 8% and a life cycle of 25 years. read more... read less...
Keywords: Losses Reduction, Technical Losses, Non-Technical Losses, Economic Analysise
Bioreactor Landfilling: Operations, Benefits and Prospects
IJTEE, volume-05 , Issue 2 (2012), PP 175 - 181
Published: 17 Mar 2012
by Isam Janajreh, Idowu Adeyemi, Sherien Elagroudy from Masdar Institute of Science and Technology, P. O. Box 54224, Abu Dhabi, UAE, Ein Shams University, Cairo, Egypt
Abstract: The amount of waste being discarded at the landfill and without tapped its associated landfill gas (LFG) is alarming. Almost five million tons of MSW is produced in Abu Dhabi annually and almost all waste produced is land filled. Nearly 30% of the 240 million tons generated waste in the US is recycled while the rest is primarily destined to land filling. Landfill gas (LFG), which is mainly composed of carbon dioxide and methane, is widely recognized as one of the largest sources of methane emission to the atmosphere and a central contributor to GHG. Methane, however, is 21 folds more potent than carbon dioxide by weight and is second most abundant GHG after carbon dioxide. The estimate of global methane emission from solid waste disposal sites ranges from 20- 70 Tg/yr., or about 5 to 20% of the total estimated methane emission of 375Tg/yr from anthropogenic sources. Therefore, LFG recovery presents an opportunity to reduce global warming and fossil fuel consumption. In this work the concept of Bioreactor landfill and its estimated gas production compared to dry tomb is presented. A review of their operation and their biodegradation steps and their intermediate that lead to stable compost is presented. The distribution of MSW of community in USA and Abu Dhabi are considered. The amount of biogas is calculated based on 1,000,000 residential metropolitan communities. The gas power production and the anthropogenic CO2 reduction are calculated through the use of conventional combined cycle. The bioreactor landfill yielded a carbon offset of 26,409.5 tons of CO2 as compared to a coal power plant with utilization of dry tomb. read more... read less...
Keywords: Dry tombs, Landfilling, LFG, GHG, MSW, Bioreactor, Combined Cycles
Development of Neural Networks for Enhancement of Thermal Energy Storage using Phase Change Material
IJTEE, volume-05 , Issue 2 (2012), PP 167 - 173
Published: 17 Mar 2012
by Y. Abdullat, M. Hamdan, E. Abdelhafez, A. Sakhrieh from Department of Industrial Engineering, The University of Jordan, Amman 11942, Jordan, Faculty of Engineering, Al-Zaytoonah University of Jordan, Amman11733, Jordan, Department of Mechanical Engineering, The University of Jordan, Amman 11942, Jordan
Abstract: Three Artificial Neural Network models (Feedforward, Elman, and Nonlinear Autoregressive Exogenous (NARX) networks) were used to find the performance of a thermal energy storage system with and without a phase change material. Previously obtained experimental data was used to train the neural network. Time, mass of water, mass flow rate, number of balls containing the PCM, hourly solar radiation, ambient temperature and inlet water temperature were used in the input layer of the network. The outlet water temperature was in the output layer. The obtained results were verified against previously obtained experimental data. It was found that Artificial Neural Network technique could be used to estimate the outlet temperature with excellent accuracy with the coefficient of determination of Elman, feedforward and NARX models were found to be 0.95006, 0.99411 and 0.88185, respectively. The obtained results showed that feedforward model had the best ability to estimate the required performance, while NARX and Elman network had the lowest ability to estimate it. read more... read less...
Keywords: Thermal energy storage, Phase change material, Artificial Neural Network, Elman, NARX, Feedforward.
Present and Future Trend in the Production and Energy Consumption of Desalinated Water in GCC Countries
IJTEE, volume-05 , Issue 2 (2012), PP 155 - 165
Published: 17 Mar 2012
by Hassan Fath, Ashraf Sadik, Toufic Mezher from Masdar Institute of Science and Technology, Abu Dhabi, United Arab Emirates,Qatar Environment and Energy Research Institute, Doha, Qatar
Abstract: Water is one of the pressing global challenges facing humanity. In the Gulf Cooperation Council (GCC) countries, it is considered as the most critical challenges and is expected to grow with time. GCC countries have chosen desalination as the strategic water resource option and is, therefore, the world largest desalinated water producing regions. The objective of this study is to explore the current desalination technologies and their respective energy demands in GCC countries with different alternatives to reduce energy consumption. The paper presents and analyses the present and the future prospective of water production rates and trends as well as the corresponding energy consumptions. The recent and historical desalination operational data have been studied and analysed and the results were presented using forecasted published data, up to the year 2025. Areas of possible efficiency improvements and reduction in the specific power consumption of the main commercially used desalination technologies thermal (Multi Stage Flash (MSF) and Multiple Effect Distillation (MED)) and membrane (Reverse Osmosis (RO)) including the rehabilitation of present operating plants are presented. In addition, alternative energy sources such as renewable and nuclear as well as new desalination technologies of potential commercialization are also highlighted. read more... read less...
Keywords: Water desalination, energy, future trends, GCC counties
Modeling of the RHC System with Bond Graphs Approach
IJTEE, volume-05 , Issue 2 (2012), PP 145 - 153
Published: 17 Mar 2012
by Abdelatif Merabtine, Riad Benelmir from Ecole Normale Supérieure de Cachan - LMT, Cachan, France, 94235, Lorraine University - LERMAB, Vandoeuvre-lès-Nancy, France, 54506
Abstract: In this work, a simplified graphical modelling tool, which in some extent can be considered in halfway between detailed physical and Data driven dynamic models, has been developed. This model is based on Bond Graphs approach. This approach has the potential to display explicitly the nature of power in a building system, such as a phenomenon of storage, processing and dissipating energy such as Heating, Ventilation and Air-Conditioning (HVAC) systems. In this paper, thermal behaviour of an elementary referential building configured with two similar adjacent spaces has been modelled in order to assess the performance of the combined Radiant Heating and Cooling (RHC) systems. The thermal simulation of the building has been performed by using the Bond Graphs modelling approach, where both temperatures and heat flux annual profiles, according to the radiative heat exchange, have been calculated. Comparison with TRNSYS software results has also been made. It was found that the RHC system is able to meet energy demand of the building insuring a good thermal comfort level. read more... read less...
Keywords: Building Energy Efficiency, Bond Graphs modeling, HVAC.
New Power and Cooling Absorption Cycles
IJTEE, volume-05 , Issue 2 (2012), PP 135 - 143
Published: 15 Mar 2012
by Dereje S. Ayou, Joan Carles Bruno, Alberto Coronas from Universitat Rovira i Virgili, CREVER-Group of Applied Thermal Engineering, Tarragona, Spain, 43007
Abstract: In this study, new absorption cycles for the combined cooling and power production are presented. These cycles are designed by modifying basic (single-stage) and two-stage double-effect absorption cooling cycles, which use ammonia/water mixture as a working fluid. The performance and operating conditions of the cycles are analysed systematically through thermodynamic cycle simulation and sensitivity study. The proposed absorption cycles are capable of providing different ratio of power and cooling to cover varying demand profile for power and cooling. They can be activated by low and medium temperature heat sources such as solar thermal energy, biomass, geothermal energy or industrial waste heat. The performances of these cycles were evaluated by several performance indicators, based on energy and exergy concepts. It is found that the hybrid two-stage absorption cycle has an overall thermal efficiency of 55%, effective first law and exergy efficiencies of 13% and 40%, respectively, for the base-case conditions considered (at a split ratio of 50% and a heat source inlet temperature of 170°C). The effect of the non-conventional working fluid mixtures (NH3/LiNO3 and NH3/NaSCN) on the performance and operational working range of the single-stage hybrid cycles has been evaluated for different modes of operation, from pure refrigeration cycle mode to a combined cycle that give high priority to power production. read more... read less...
Keywords: Combined cooling and power, hybrid absorption cycles, working fluid mixtures, performance indicators
Predicting Bioreactor Landfill Air Space by Estimating Geotechnical Properties of Waste
IJTEE, volume-05 , Issue 2 (2012), PP 129 - 134
Published: 15 Mar 2012
by Sherien Elagroudy from Environmental Engineering Section, Ain Shams University, Cairo, Egypt, 11517
Abstract: Intensive research has focused on the settlement of the typical Municipal Solid Waste (MSW) in bioreactor landfills, but relatively little attention has been given to the settlement of individual refuse components. The objective of this paper is to estimate and compare the compressibility parameters of different waste fractions, such as: textile, paper, and mixed waste through measuring the change in the physical properties, and settlement characteristics of waste in six lab-scale bioreactor landfills operated under anaerobic conditions. Primary compression index (Cc), and coefficient of volume compressibility (mv) were estimated for all three waste materials using time-settlement data. The primary compression index (Cc) increased from 0.31 for textile waste to 0.45 for paper waste, and 0.63 for mixed waste. It can be noted that Cc increased with increasing the waste organic content. The value of the coefficient of volume compression (mv) suggests that the biodegradation increased the values of mv of all types of waste samples. Textile waste incorporated the lowest value of mv compared to all other solid waste fractions. This may be attributed to the fact that the textile is slowly biodegradable compared to paper and food wastes as stated earlier. Textile waste cells had the least value for all compressibility parameters. Proper estimation of the waste compressibility parameters would allow engineers and landfill designers formulate mathematical models to better estimate available air space saving and expected time dependent deformation patterns at field scale bioreactor landfill cells, which subsequently increases life time of bioreactor landfills. read more... read less...
Keywords: Compressibility of Solid Waste, Bioreactor Landfills, Compression Index, Coefficient of Consolidation, Waste Settlement
Advanced Modeling of High Density Polyethylene Pyrolysis
IJTEE, volume-05 , Issue 2 (2012), PP 123 - 128
Published: 15 Mar 2012
by Youssef Safadi,Joseph Zeaiter,Mohammad Ahmad from Department of Mechanical Engineering,Chemical Engineering Program, American University of Beirut, Lebanon
Abstract: This work presents a novel approach for predicting product composition during the pyrolysis of high-density polyethylene (HDPE) into fuel. A coupled two-model framework is suggested: A lumped-empirical model depicts the products from the first stage in terms of gas, oil and waxes and a population-balance model tracks the latter evolved products using mechanistic reactions to predict the carbon-chain length distribution in the end products. The lumped empirical model is developed specifically for this purpose and is based on literature data, whereby, reaction kinetics were estimated using a parameter estimation technique. The mechanistic model tracks 181 species according to their carbon-chain length distribution in a computationally efficient manner showing good fit with literature data. read more... read less...
Keywords: Pyrolysis model, plastic waste to fuel, chain length distribution.
Evaluation of Oxygen-Enriched Air Combustion Process Integrated with CO2 Post-Combustion Capture
IJTEE, volume-05 , Issue 2 (2012), PP 113 - 121
Published: 14 Mar 2012
by Adewale Adeosun, Aravind Muthiah, Mohammad R. M. Abu-Zahra from Separation Technology Laboratory, Masdar Institute of Science and Technology, P.O. Box 54224, Abu Dhabi, United Arab Emirates
Abstract: A novel concept combining membrane-based technology for air enrichment combustion process integrated with solvent based post-combustion capture is evaluated using Aspen Plus® process simulation tool. The aim of this integrated concept is to reduce the amount of Nitrogen used in the combustion process and as a result increase the CO2 concentration in the flue gas. The effects of the increased CO2 concentration on liquid-to-gas molar flow ratio, solvent flow rate, reboiler duty and washing water requirement are evaluated. Based on the cost analysis for the air separation unit and the CO2 capture solvent flow rate and washing water requirement, the optimum enrichment level of air was found to be 35% O2. However, in term of CO2 mole concentration in the flue gas and liquid-gas molar ratio in the absorption process, 40% enrichment shows highest value of 28.22% and 7.15, respectively. No significant benefit is observed in terms of reboiler duty as expected due to the fixed amount of CO2 captured and the limited increase in the solvent rich loading. On the other hand, the flue gas flow rate was reduced dramatically at higher CO2 concentration, which will result in a smaller absorption tower and consequently a lower capital investment. In addition, with improved membrane technology that can work at lower air inlet pressure and with higher oxygen permeability and selectivity, the target energy reduction is achievable. These results encourage a full-scale economic evaluation of the novel process of combining enriched air combustion and AMP-solvent based post-combustion capture to be conducted in order to weigh enrichment costs to absorber size reduction economic benefits. read more... read less...
Keywords: Carbon Capture,Post Combustion,Membrane,Coal power plant,Simulation
Microwave Pretreatment of Mixed Sludge for Anaerobic Digestion Enhancement
IJTEE, volume-05 , Issue 2 (2012), PP 105 - 111
Published: 14 Mar 2012
by Sherien Elagroudy, Fatma El-Gohary from Environmental Engineering Section, Ain Shams University, Cairo, Egypt, 11517,Water Pollution Research Dept., National Research Center, Giza, Egypt, 12622
Abstract: The impact of microwave (MW) irradiation of mixed sludge (MS) on biogas production has been investigated. For this purpose, mixed sludge from a nearby activated sludge treatment plant and domestic MW equipment were used in two separate runs. During the first run (TS=2.47% (w/w)), preliminary investigations were carried out to determine the effect of microwave intensity on mixed sludge samples. Second run experiments (TS=1.46% (w/w)) were conducted to further investigate the impact of temperature. Sludge samples microwaved at the same temperature and at different MW intensities, consequently different exposure times, achieved almost equal degree of solubility, as expressed in terms of CODS/CODT and VSS. At an ultimate pre-treatment temperature of 96±2oC, the level of particulate COD solubility resulted in 3.13±0.001, 2.69±0.33 and 3.48±0.25-fold increase of CODS/CODT ratios at MW intensities of 500, 800 and 1000 W, respectively compared to untreated. MS microwaved to 78oC and power intensity of 1000W produced the greatest improvement in cumulative biogas production with 84% increase as compared to the controls after digestion for 33 days at sludge concentration of 1.46% TSS (w/w). read more... read less...
Keywords: Anaerobic Digestion, Biochemical Methane Potential Test, Microwave Irradiation, Mixed sludge
Comparison of Resource Intensities and Operational Parameters of Renewable, Fossil Fuel, and Nuclear Power Systems
IJTEE, volume-05 , Issue 2 (2012), PP 95 - 104
Published: 14 Mar 2012
by Chaouki Ghenai, Isam Janajreh from Ocean and Mechanical Engineering Department, College of Engineering and Computer Science, Florida Atlantic University, Boca Raton, Florida, 33431 U.S.A , Masdar Institute of Science and Technology, United Arab Emirates
Abstract: Depletion of fossil, their associated thermal emission, and fear of global warming, have been exerting unparallel momentum to tap on natural energy resources. At the current state however some of these resources are associated with large capital, low capacity, large overall carbon footprint that we need to be aware off to make a judicial decision. A comparison study between renewable, fossil fuel and nuclear PowerSystems is presented in this work. The comparison includes the resource intensity, operational parameters and current status. The results show that the renewable power systems such as hydro power, tidal power (barrage), offshore wind power, and wave power utilize more materials during the construction than the conventional (coal, natural gas) and nuclear power systems the renewable energy systems require greater surface area reaches 50 to 150 times the conventional and nuclear power systems except geothermal power plant the renewable hydro-power system has the highest energy and CO2 intensities during the construction of the power plant solar power system has the highest capital intensity compared to all power systems as it requires more capital and energy to construct the same nominal generating capacity the system efficiency of solar power is only 10% to 18% compared to 30-50 % for conventional and nuclear power systems and the capacity factor for solar power is as low as 10% compared to 80% for conventional power system. Still, - most of the renewable power systems have low-capacity factor except the geothermal power that offers up to 95%. read more... read less...
Keywords: Renewable Energy, Fossil Fuel Energy, Nuclear Energy, Carbon Foot Print, Capital Intensity, Energy Intensity, Area Intensity, Material Intensity, Capacity Factor, System Efficiency, Life Time, Current Installed Capacity
Special Issue Devoted to Selected Papers from the 10th Arab Academy of Sciences International Conference on "Energy and Water Sustainability"
IJTEE, volume-05 , Issue 2 (2012), PP 91 - 94
Published: 14 Mar 2012
by Isam Janajreh from Masdar Institute of Science and Technology, United Arab Emirates
Abstract: This was the 10th international conference organized by the Arab Academy of Sciences (AAS) that was held in Beirut, Lebanon, December 7–9, 2012. More than 40 papers were presented during this event dealing with various issues relating to energy and water sustainability. It was a stimulating gathering of over 70 scientists, researchers and experts from the international scientific community to exchange ideas and research findings, to pass their experiences on to others, network and establish collaborative research. Formal presentations in the today Conference comprised the Opening Ceremony, the Presidential Address, three Keynote Addresses, and 21 shorter papers. Panel discussions were held at the end of each of the first four Sessions. The final Session VI was a general discussion that aimed at the development of a set of recommendations. Additionally, informal discussions took place in break periods and social gatherings. In this special issue of Int. J. of Thermal & Environmental Engineering, twelve papers were selected, extended beyond the versions presented at the conference, and published. In these papers, a great variety of theory, applications, and methodologies in various areas of water, waste management, and energy utilization and sustainability were presented. The editor of this special issue would like to thank the authors for their efforts in providing an extended version of their papers. Also, he would like to express his deep appreciation for the hard work and diligence of the other reviewers that helped in the reviews for Int. J. of Thermal & Environmental Engineering. The published papers, the established networks, and collaborative work were amongst the fruitful goals of the conference. The AAS would like to personally thank the Coordinating Editor and Editor-in Chief of the journal, Dr. Bilal Akash, for his willingness in giving us the opportunity to read more... read less...
Keywords: Sciences (AAS),
Effect of Using Packing Material on the Performances of the Double Pass Photovoltaic-Thermal (PVT) Air Heater
IJTEE, volume-05 , Issue 1 (2012), PP 61 - 70
Published: 20 Feb 2012
by M. Amin Mezoued, A. Kaabi from Laboratory of Génie Climatique, Faculty of Engineering, Department of Génie Climatique, University of Constantine, 25000 Constantine, Algeria
Abstract: The current work aims to demonstrate the effect of the packing material on the performance of the double pass (PVT) solar air heater in terms of energy and exergy. In addition, the influence of porosity and air mass flow rate is also evaluated. A theoretical analysis for the system with and without packed bed has been presented. A numerical simulation program developed in Matlab 2012 has been performed for the solution of the thermal model. The latter is applied for a sunny day (15 June) on the basis of the climatic conditions of Jijel (east of Algeria, Latitude 36.52 ° N, Longitude 6.57 ° E). The results show that the presence of packing material in the lower channel of double pass photovoltaic-thermal (PVT) air collector increases the convective heat transfer. This improves the energy and exergy performance. Under the same conditions, the PVT system with packed bed provides higher overall thermal efficiency, which is better of about 11-13% compared to the system without packed bed. read more... read less...
Keywords: Packing material, Performance, Double pass, Hybrid solar collector
Thermochemical Liquefaction of Coal
IJTEE, volume-05 , Issue 1 (2012), PP 51 - 60
Published: 20 Feb 2012
by Bilal A. Akash from Department of Mechanical Engineering, College of Engineering, Dhofar University, Salalah, Oman
Abstract: This paper presents a review of various methods coal liquefaction processes they can be a result of pyrolysis, solvent extraction, direct or indirect coal liquefaction. Bituminous coals are considered to be the most Favorite feed-stock for liquefaction, because of their high yield of liquid hydrocarbon products. The direct coal liquefaction process is more energy efficient than the indirect liquefaction process but is much harder to control. Thermal hydro-cracking of lignin bounds to produce intermediates which then react further with coal producing lower molecular weight material, which more desirable. Enhancement of coal conversion due to the addition of lignin is found to be a function of time. It is dependent upon temperature of reaction and the type of lignin used. By increasing the ratio of lignin to coal will result in depolymerizing larger portions of coal. This finding is proposed in reaction pathway. read more... read less...
Keywords: Coal, Liquefaction, Depolymerization, Pyrolysis, Gasification
A Statistical Analysis of a Liquid Desiccant Dehumidifier/Regenerator in an Air Conditioning System
IJTEE, volume-05 , Issue 1 (2012), PP 41 - 50
Published: 20 Feb 2012
by Abdulrahman T. Mohammad, Sohif Bin Mat, M.Y. Sulaiman, K. Sopian, Abduljalil A. Al-Abidi from Solar Energy Research Institute, University Kebangsaan Malaysia, 43600 Bangi, Selangor, Malaysia
Abstract: A packed bed is the most common technology employed today as a dehumidifier or a regenerator in a liquid desiccant air conditioning system. During the experiments, the inlet and outlet parameters in the dehumidifier and regenerator can be easily measured, however, in the theoretical analysis it is difficult to predict the relationship between these parameters because of the complexity of the combined heat and mass transfer process in the dehumidifier or regenerator. In this paper statistical analysis using (SPSS) software was used to predict the functional relationships between the input and output parameters in the dehumidifier/regenerator. The analysis of variance (ANOVA) was investigated to analyse the effect of inlet operating variables (independent) on the water condensation rate in the dehumidifier and the water evaporation rate in the regenerator. Statistical analysis shows that the inlet air humidity ratio, inlet air mass flow rate, and inlet solution temperature cause good significant variation (P<0.01) in the water condensation rate. The inlet air mass flow rate, and inlet solution temperature cause also good significant variation (P<0.01) in the water evaporation rate in the regenerator. Experimental results for a counter dehumidifier and regenerator were taken from previous study. read more... read less...
Keywords: Statistical, Dehumidifier, Regenerator, SPSS, ANOV
Energy and Exergy Analysis of a combined Diesel-Engine Gas-Turbine System for Distributed Power Generation
IJTEE, volume-05 , Issue 1 (2012), PP 31 - 39
Published: 20 Feb 2012
by Mohamed M. El-Awad from Sohar College of Applied Sciences, P.O. Box 135, Sohar, Sultanate of Oman
Abstract: This paper presents a combined diesel-engine gas-turbine system that enables distributed power generation plants to attain high thermal efficiencies while enjoying the operational advantages of both diesel engines and gas turbines. The configuration of the system presented here improves upon previously proposed configurations through the appropriate use of regeneration and inter-cooling. Energy and exergy analyses of the system's performance were performed using an Excel-based thermodynamic model. The energy analysis studied the effect of the diesel-engine's compression ratio, the gas-turbine's inlet temperature, and the compressors' pressure ratios on the system's performance. This analysis determined the pressure ratios that permit the system to be designed with fewer compressors and turbines. The second law analysis determined the main exergy losses and destructions of the system. Finally, the paper compares the thermal efficiency and network of the proposed system at different modes of operation read more... read less...
Keywords: Combined Diesel-Brayton cycle, Small-scale power generation, Energy and exergy analysis
Energy Saving in Building with Latent Heat Storage
IJTEE, volume-05 , Issue 1 (2012), PP 21 - 30
Published: 20 Feb 2012
by E.S. Mettawee A.I. Ead from Solar Energy Department, National Research Center of Egypt, Cairo, 11241, Egypt, Faculty of Technical Study, National Research Center of Egypt, Cairo, 11241, Egypt
Abstract: This article presents an experimental analysis of peak load shifting for air conditioning system using PCM (phase change material) in a room. The melting range of the used PCM is from 20 to 25°C. The amount of the PCM is determined according to the cooling load of the room during the peak time. The hourly cooling load is calculated. A low-power fan is used to drive air over the PCM capsules, which are arranged in a chamber above the room. Auxiliary cooling unit is used to freeze the PCM when the night temperature is higher than 18°C. The temperatures of the PCM are measured by 9 thermocouples inserted inside a capsule. The variant degrees of temperature of the air at the inlet, at the middle, and at the outlet of the air-passing chamber as well as at the room are measured during day and night. In addition to that, the climate conditions are measured. As a result, during the peak load shifting time, which is within 2 hours, the decrease of the room temperature is between 7-10 °C by using PCM ceiling system. Consequently, it can be concluded that the PCM system is effective for the peak load shifting. read more... read less...
Keywords: peak load shifting - PCM thermal storage- air-conditioning
A standardized Empirical Method of Testing Solar Simulator Coupled with Solar Tube and Concentrator Collectors
IJTEE, volume-05 , Issue 1 (2012), PP 13 - 20
Published: 20 Feb 2012
by Mahmoud Shatat, Abdulkarym Mayere, Saffa Riffat from Institute of Sustainable Energy Technology, University of Nottingham, Nottingham, NG7 2RD, UK
Abstract: This paper describes a novel an empirical method for testing a solar simulator testing facility based on an experimental performance. A uniform geometrical configuration design for solar simulator was preliminary evaluated by illuminance distribution to optimize the maximum source-to-target transfer efficiency of irradiative power. A number of experimental tests were carried out for various distances from the simulator surface. It was determined that the optimal distance between the light surface simulator and solar collector is about 23 cm at different solar irradiance. The unevenness difference of solar radiation values was investigated at different points under the simulator facility where the maximum unevenness error percentages was about 9.1% which is in a good agreement within the allowable limits of 15% provided by the British Standards for testing the solar simulator. The performance of solar concentrator and an evacuated solar collector with an aperture area of 1.73 m2 for real solar insolation during spring in the Middle East region have been investigated and it was proved that the calculated efficiency of solar collector was closely correlated within the efficiency provided by the manufacture. Similarly, the thermal efficiency of the combined system (both solar concentrator and water tank) was found to be 38%. The design of such solar simulator associated with the development of standardized test procedure can be utilized as a reliable and efficient experimental platform to investigate various solar collectors and materials read more... read less...
Keywords: Solar intensity fluctuations, light, Solar simulator, solar concentrator.
Energetic and Ecological Benefits of Heat Pump Application in Energy Transformation Systems
IJTEE, volume-05 , Issue 1 (2012), PP 1 - 11
Published: 12 Mar 2012
by Jovan Mitrovica, Petar Avdalovic from Faculty for Production and Management, University East Sarajevo, Trebinje, B&H, 89101, Bosnia and Herzegovina, Power Utility of Republic of Srpska, Parent Joint-Stock Co, Trebinje, B&H, 89101, Bosnia and Herzegovina
Abstract: In 1900, Nikola Tesla published a paper: The problem of increasing human energy, stressing that generating electricity from burning of coal we would be destroying material, which would be a barbarous process. This message is still vitally important, and one method to mitigate the barbarous effects is e.g., application of heat pump. Its benefits are twofold: economic and ecological. Heat pump reduces fuel consumption and lessens the burden on the environment through combustion products. As example, we have quantified its application in the area of heating, but the results obtained are extendable to any energy system. The most significant parameters are the efficiency of the energy conversion process and the COP of the heat pump. When the product of these two parameters is equal to one, part of energy losses, occurring in the energy conversion process which is associated with the heat pump application, can be completely utilised by the heat pump as useful heat. This is of paramount importance for reduction of energy conversion losses and protection of the environment. In general, both the fuel consumption and amount of combustion products decrease with increasing COP, that is, with increasing evaporation temperature and/or decreasing condensation temperature of the working fluid used in the heat pump. read more... read less...
Keywords: Heat pump, Heating, Environment, Energy losses, Energy balance