INTERNATIONAL JOURNAL OF ENERGY AND ENVIRONMENTAL ENGINEERING
Year:2012 | Volume:3 | Issue:3|Papers Count:5

The mechanical aspect of entropy-exergy relationship, together with the thermal aspect usually considered, leads to a formulation of physical exergy based on both useful work and useful heat that are the outcomes of available energy of a thermodynamic system with respect to a reservoir. This approach suggests that a mechanical entropy contribution can be defined, in addition to the already used thermal entropy contribution, with respect to work interaction due to pressure and volume variations. The mechanical entropy is related to energy transfer by means of work interaction and it is complementary to the thermal entropy that accounts energy transfer by means of heat interaction. Furthermore, the study proposes a definition of exergy based on Carnot cycle that is reconsidered in the case the inverse cycle is adopted and, as a consequence, the concept that work depends on pressure similarly as heat depends on temperature, is pointed out. Then, the logical sequence to get mechanical exergy expression to evaluate useful work withdrawn from available energy is demonstrated. Based on mechanical exergy expression, the mechanical entropy set forth is deduced in a general form valid for any process. Finally, the formulation of physical exergy is proposed that summarizes the contribution of either heat or work interactions and related thermal exergy as well as mechanical exergy that both result as the outcome from the available energy of the composite of the system interacting with a reservoir. This formulation contains an additional term that takes into account the volume and, consequently, the pressure that allow to evaluate exergy with respect to the reservoir characterized by constant pressure other than constant temperature. The basis and related conclusions of this paper are not in contrast with principles and theoretical framework of thermodynamics and highlight a more extended approach to exergy definitions already reported in literature that remain the reference ground of present analysis.

Potable water is always a need of every human being in the world. Only one third of water is potable water, and two thirds of water is saline water, which is not used for drinking purposes. Solar still is a device, which converts the saline or brackish water into drinkable water. Here, in place of saline water, industrial wastewater is used to convert potable water. In this research work, three solar stills have developed by locally available materials and tested in climate conditions of Mehsana (latitude of 23o59’ and the longitude of 72o38’). Among three solar stills, two solar stills are consist of floating plates like aluminum and galvanized iron. Third solar still that is used as a reference solar still is called a conventional solar still. Three-month research showed that solar still, consists of aluminum floating plate, gave considerable daily distillate as well as cumulative output compared with galvanized iron floating plate solar still as well as conventional solar still. Hence, the performance of solar still could increase by the use of aluminum floating plate, which can be used as an energy absorbing plate.

The new architecture produced recently in the south of Algeria known as ‘modern construction’ following the trend of the northern cities, which have different climate, is completely non-adapted to the harsh climate of the south of Algeria and, therefore, has high-energy consumption. The Ksar of Kenadsa is considered among the most important old cities of the south-west region of Algeria by its cultural and religious dimensions. In this area, the traditional architecture has been built to achieve the comfort in hot season. The new constructed houses have been built following the north architectural design neglecting the very harsh climate of the south region of Algeria characterized by very hot and dry climate. To evaluate the thermal comfort of this modern housing, a comparative analysis for the existing traditional housing is carried out using TRNSYS software. The simulation results show that the modern typical house seems to be inappropriate for the desert climate. Indeed, except the use of airconditioning in summer, there is no other solution which can ensure thermal comfort.

In this study, the wind speed characteristics and energy potential in three selected locations in the southeastern part of Nigeria were investigated using wind speed data that span between 24 and 37 years and measured at a height of 10 m. It was shown that the annual mean wind speed at a height of 10 m for Enugu, Owerri and Onitsha are 5.42, 3.36 and 3.59 m/s, respectively, while the annual mean power densities are 96.98, 23.23 and 28.34 W/m2, respectively. It was further shown that the mean annual value of the most probable wind speed are 5.47, 3.72 and 3.50 m/s for Enugu, Owerri and Onitsha, respectively, while the respective annual value of the wind speed carrying maximum energy are 6.48, 4.33 and 3.90 m/s. The performance of selected commercial wind turbine models (with rated power between 50 and 1, 000 kW) designed for electricity generation and a windmill (rated power, 0.36 kW) for water pumping located in these sites was examined. The annual energy output and capacity factor for these turbines, as well as the water produced by the windmill, were determined. The minimum required design parameters for a wind turbine to be a viable option for electricity generation in each location are also suggested.

Fuel blend of alcohol and conventional hydrocarbon fuels for a spark-ignition engine can increase the fuel octane rating and the power for a given engine displacement and compression ratio. In this work, the influence of butanol addition to gasoline in a port fuel injection, spark-ignition engine was investigated. The experiments were realized in a single-cylinder ported fuel injection spark-ignition (SI) engine with an external boosting device. The optically accessible engine was equipped with the head of a commercial SI turbocharged engine with the same geometrical specifications (bore, stroke and compression ratio) as the research engine. The effect on the spark ignition combustion process of 20% and 40% of n-butanol blended in volume with pure gasoline was investigated through cycle-resolved visualization. The engine worked at low speed, medium boosting and wide-open throttle. Fuel injections both in closed-valve and open-valve conditions were considered. Comparisons between the parameters related to the flame luminosity and the pressure signals were performed. Butanol blends allowed working in more advanced spark timing without knocking occurrence. The duration of injection for butanol blends was increased to obtain a stoichiometric mixture. In open-valve injection condition, the fuel deposits on intake manifold and piston surfaces decreased, allowing a reduction in fuel consumption. BU40 granted the performance levels of gasoline and, in open-valve injection, allowed to minimize the abnormal combustion effects including the emission of ultrafine carbonaceous particles at the exhaust. In-cylinder investigations were correlated to engine out emissions.