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    ABSTRACT: This paper presents stress intensity factors (SIFs) and fatigue growth analyses of a corner crack emanating from a pinhole of a cylinder under cyclic tension. No such work has been reported in the literature. Stress intensity factors for different crack aspect ratios and pinhole sizes in different diameters of solid cylinder are presented. A larger SIF was found at the smaller crack size of a or c in a larger diameter of a pinhole of the smaller-diameter cylinder. Crack growths at the pinhole edge were found to be faster than those at the cylinder edge.
    Engineering Fracture Mechanics 09/2014;
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    ABSTRACT: Zero-emission fuel cell driven systems are regarded as promising technological advances in the future of the transportation industry that have the potential to replace internal combustion engines. The design, performance, and efficiency properties of a vehicle are often stated to be some of the key challenges in its commercialization. This paper highlights a polymer electrolyte membrane fuel cell (PEMFC)-powered system of an electric bicycle. The system consists of a 250-W fuel cell, ECU, battery pack, DC/DC converter, electric motor, and other supporting equipment. After introducing the different parts of the bicycle, its overall efficiency will be discussed in great detail. The efficiency of fuel cells is not specific; it is a subordinate to the power density where the system operates. Experimental work has been conducted to measure the values of the efficiency and energy flow. The results indicated a maximum fuel cell efficiency of 63% and an overall system efficiency of 35.4%. The latter value is expressed with regards to the Lower Heating Value (LHV) of hydrogen. All measurements were taken for the cruising conditions of the vehicle and its corresponding to power consumption. The results are superior to those of a standard internal ignition engine. The fuel cell performance is least efficient when functioning under maximum output power conditions.
    International Journal of Hydrogen Energy 08/2014; 39(25):13276–13284.
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    ABSTRACT: In recent years, palm and jatropha biodiesels have been considered as potential renewable energy sources in Malaysia. Therefore, this experimental investigation was conducted to improve the blend of these two biodiesels (20% biodiesel blend, named P20 and J20, respectively) with the help of oxygenated additives. The comparative improvement of P20 and J20 blends with ethanol, n-butanol, or diethyl ether as additives was evaluated in terms of performance and emissions characteristics of a four-stroke single cylinder diesel engine. The final blend consisted of 80% diesel, 15% biodiesel, and 5% additive. Tests were conducted at different speeds (1200–2400 rpm) at constant full load conditions. Use of additives significantly improved brake power and brake thermal efficiency (BTE). Compared with P20 blend, the use of diethyl ether as additive increased brake power and BTE by about 4.10% and 4.4%, respectively, at 2200 rpm. A similar improvement was observed for J20. The other two additives also improved performance. Although HC emission increased slightly, all blends with additives reduced more NOx and CO emissions than P20 and J20 almost throughout the entire engine test. The use of ethanol as additive reduced CO emission by up to 40%, while the use of diethyl ether as additive reduced NOx emissions by up to 13%. The additives’ oxygen content, volatility, and latent evaporation heat controlled the emissions characteristics of the blends. An analysis of the combustion chamber pressure, temperature and heat release rate of the modified blends revealed interesting features of combustion mechanism, which are indicative of the performance and emissions characteristics. This experiment reveals the potential improvement of palm and jatropha biodiesel blends with the addition of three promising additives.
    Energy Conversion and Management 07/2014; 83:149–158.
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    ABSTRACT: Nanofluid is one of the novel inventions of science. Nanofluid can be used for energy savings by increasing the heat transfer performance of the heat recovery systems, which are generally struggling to overcome the present challenging issues such as global warming, greenhouse effect, climate change, and fuel crisis. Specific heat capacity is necessary to analyze energy and exergy performances. This paper extant different characteristic of specific heat capacity of nanofluids containing preparation and measuring methods, effects of volume fraction, temperature, types and sizes of nanoparticles and base fluids. Additionally a compilation has been done on available theoretical correlation related to specific heat of nanofluid. Based on existing experimental and theoretical results, nanofluid specific heat falls with the enhancement of volume concentration of nanoparticle though there are some inconsistencies among outcomes. Moreover, specific heat of the nanofluids are generally increased after adding dispersant in the mixtures. However, many contradictory results about the effects of temperatures on specific heat of nanofluids found in the literatures. Therefore, this review will help the researchers and related peoples to get enough information to select a nanofluid based on specific heat for their practical applications.
    Renewable and Sustainable Energy Reviews 06/2014; 38:88-98.
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    ABSTRACT: Energy demand is increasing dramatically because of the fast industrial development, rising population, expanding urbanization, and economic growth in the world. To fulfill this energy demand, a large amount of fuel is widely used from different fossil resources. Burning of fossil fuels has caused serious detrimental environmental consequences. The application of biodiesel has shown a positive impact in resolving these issues. Edible vegetable oils are one of the potential feedstocks for biodiesel production. However, as the use of edible oils will jeopardize food supplies and biodiversity, non-edible vegetable oils, also known as second-generation feedstocks, are considered potential substitutes of edible food crops for biodiesel production. This paper introduces some species of non-edible vegetables whose oils are potential sources of biodiesel. These species are Pongamia pinnata (karanja), Calophyllum inophyllum (Polanga), Maduca indica (mahua), Hevea brasiliensis (rubber seed), Cotton seed, Simmondsia chinesnsis (Jojoba), Nicotianna tabacum (tobacco), Azadirachta indica (Neem), Linum usitatissimum (Linseed) and Jatropha curcas (Jatropha). Various aspects of non-edible feedstocks, such as biology, distribution, and chemistry, the biodiesel’s physicochemical properties, and its effect on engine performance and emission, are reviewed based on published articles. From the review, fuel properties are found to considerably vary depending on feedstocks. Analysis of the performance results revealed that most of the biodiesel generally give higher brake thermal efficiency and lower brake-specific fuel consumption. Emission results showed that in most cases, NOx emission is increased, and HC, CO, and PM emissions are decreases. It was reported that a diesel engine could be successfully run and could give excellent performance and the study revealed the most effective regulated emissions on the application of karanja, mahua, rubber seed, and tobacco biodiesel and their blends as fuel in a CI engine.
    Energy Conversion and Management 04/2014; 80:202–228.
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    ABSTRACT: The study of the effect of weather variation on a split air cooled ducted blower (ADB) air conditioner in an office building located in Malaysia is conducted. In the present study, the influence of weather variation on the performance of the ADB air-conditioning (AC) systems in terms of total cooling capacity and sensible heat factor (SHF) are studied. In addition, the impact of a suction line heat exchanger (SLHX) system when subjected to the climate change is analyzed. Based on the result, it is found that every 1 °C increment in outdoor temperature will cause the COP and the total cooling capacity of the existing ADB system reduce by 2% while the SHF drops less than 2% from 2020 to 2080. Thus, the weather variation effect is a key factor in the AC systems’ initial design stage, which must be analyzed to preserve substantial of energy. Conversely, the SLHX system can improve the COP of the existing AC systems by about 2%, and the improvement is more significant when the outdoor ambient temperature is high. Besides, the SLHX system is strongly recommended for a machine cooling application since the SHF is higher by 4% compared to the normal AC system.
    Energy and Buildings 04/2014; 72:1–7.
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    ABSTRACT: Currently, the application of diamond-like carbon (DLC) coatings for automotive components is becoming a favorable strategy to cope with the new challenges faced by the automotive industry. DLC coatings can effectively lower the coefficient of friction (CoF) and wear rate of engine components, consequently improving the fuel efficiency and durability of these components. Commercially available fully formulated lubricating oils enhance the lubrication of ferrous materials. Therefore, the interaction between nonferrous coatings (e.g., DLC) and commercial lubricating oil must be investigated. A ball-on-plate tribotester was used to run the experiments using stainless steel plates coated with amorphous hydrogenated DLC (a-C:H) and tetrahedral DLC (ta-C) sliding against a 440C stainless steel ball. Wear track was investigated by scanning electron microscopy and atomic force microscopy. Energy dispersive spectroscopy and X-ray photoelectron spectroscopy were used to analyze the tribofilms inside the wear track. Raman analysis was performed to investigate the structural change of the coatings. At high temperatures, the CoF decreases but the wear rate increases in the a-C:H and ta-C DLC–coated plates. CoF and wear rate (coated layer and counter surface) are mostly influenced by coating graphitization. Tribochemical films, such as polyphosphate glass, are formed in ta-C and act as protective layers. Therefore, the wear rate of ta-C DLC is lower than that of a-C:H DLC.
    Surface and Coatings Technology 04/2014;
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    ABSTRACT: Research on alternative fuels is increasing due to environmental concerns and diminishing fossil fuel reserves. Biodiesel is one of the best renewable replacements for petroleum-based fuels. This paper examines the potential of biodiesel obtained from Jatropha curcas and Moringa oleifera oils. The physico-chemical properties of J. curcas and M. oleifera methyl esters were presented, and their 10% by volume blends (JB10 and MB10) were compared with diesel fuel (B0). The performance of these fuels and their emissions were assessed in a fully loaded multi-cylinder diesel engine at various engine speeds. The properties of J. curcas and M. oleifera biodiesels and their blends agreed with ASTM D6751 and EN 14214 standards. Engine performance test results indicated that the JB10 and the MB10 fuels produced slightly lower brake powers and higher brake specific fuel consumption values compared to diesel fuel over the entire range of speeds. Engine emission results indicated that the JB10 and MB10 fuels reduced the average emissions of carbon monoxide by 14 and 11%, respectively; and hydrocarbons by 16 and 12%, respectively. However, the JB10 and MB10 fuels slightly increased nitrous oxides emissions by 7 and 9%, respectively, and carbon dioxide by 7 and 5%, respectively compared to B0. In conclusion, J. curcas and M. oleifera are potential feedstock for biodiesel production, and the JB10 and MB10 blends can replace diesel fuel without modifying engines to produce cleaner exhaust emissions.
    Journal of Cleaner Production 01/2014; 65(2):304-310.
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    ABSTRACT: Nanofluid is a new type of heat transfer fluid with superior thermal performance characteristics, which is very promising for thermal engineering applications. This paper presents new findings on the thermal conductivity, viscosity, density, and specific heat of Al2O3 nanoparticles dispersed into water and ethylene glycol based coolant used in car radiator. The nanofluids were prepared by the two-step method by using an ultrasonic homogenizer with no surfactants. Thermal conductivity, viscosity, density, and specific heat have been measured at different volume concentrations (i.e. 0 to 1 vol.%) of nanoparticles and various temperature ranges (i.e. from 10 °C to 50 °C). It was found that thermal conductivity, viscosity, and density of the nanofluid increased with the increase of volume concentrations. However, specific heat of nanofluid was found to be decreased with the increase of nanoparticle volume concentrations. Moreover, by increasing the temperature, thermal conductivity and specific heat were observed to be intensified, while the viscosity and density were decreased.
    International Communications in Heat and Mass Transfer 01/2014;
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    ABSTRACT: Laser Beam machining (LBM) is a widely used thermal advance machining process capable of high accuracy machining of almost any material with complex geometries. CO2 and Nd:YAG lasers are mostly used for industrial purposes. Drilling, cutting, grooving, turning and milling are the application of LBM with different material removal mechanism. Modelling and simulation of LBM process is indispensable for optimization purposes. Modelling can be done by implementing analytical, numerical, experimental and Artificial Intelligence based methods. This paper provide a review on the various methods used for modelling and simulation of laser beam machining process as well as key researches done in this field so far.
    International Journal of Machine Tools and Manufacture 01/2014;
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