volume-05-Issue 1 (2012)
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