Journal Articles
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Item Technical aspects of biodiesel and its oxidation stability(2009) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.Biodiesel is a clean burning alternative renewable fuel made from natural renewable sources. It is defined as mono-alkyl esters of long chain fatty acids derived from vegetable oils or animal fats, which conform to ASTM specifications for use in diesel engines. Biodiesel present a very promising alternative fuel to diesel oil and properties of this oil offer the advantage of immediate substitution in existing diesel engines with little or no modifications at all. But one of the major technical problems associated with the biodiesel is its susceptibility to oxidation, which can cause the fuel to become acidic and to form insoluble gums and sediments that can plug fuel filters. This is due to the unsaturated fatty acid chains and the presence of the double bond in the molecule, which produce a high level of reactivity with the oxygen, especially when it placed in contact with air. The oxidation of fatty acid chains is a complex process that proceeds by a variety of mechanisms. The various other factors influence the oxidation process of biodiesel includes light, temperature, extraneous materials, peroxides, size of the surface area between biodiesel and air. One of the methods of improving biodiesel oxidative stability includes the deliberate addition of antioxidants or modification of the fatty ester profile. This article discusses the technical aspects of biodiesel and its oxidation stability.Item Thermodynamic simulation of ammonia-water absorption refrigeration system(Serbian Society of Heat Transfer Engineers, 2008) Sathyabhama, A.; Ashok Babu, T.P.The ammonia-water absorption refrigeration system is attracting increasing research interests, since the system can be powered by waste thermal energy, thus reducing demand on electricity supply. The development of this technology demands reliable and effective system simulations. In this work, a thermodynamic simulation of the cycle is carried out to investigate the effects of different operating variables on the performance of the cycle. A computer program in C language is written for the performance analysis of the cycle.Item Evaluation of properties and storage stability of Madhuca indica biodiesel(Japan Oil Chemists Society yukagaku@jocs-office.or.jp, 2009) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.Mahua Oil (MO) is an underutilized non-edible vegetable oil, which is available in large quantities in India. In the present work, biodiesel was derived from the MO by the transesterification process. The fuel properties of the MO biodiesel were found to be within the limits of biodiesel specifications of many countries. The chemical nature of biodiesel makes it more susceptible to oxidation during long-term storage which leads to degradation of fuel properties that can compromise fuel quality. The effect of long storage condition on the stability of the MO biodiesel was studied in the present work. The biodiesel samples were stored in plastic containers at room temperature. The study was conducted for a period of 12 months and the test sample was kept in the darkness. From the experimental results, it was observed that the acid value and viscosity increases with the storage time, but the iodine value decreased with increasing storage time. This is due to the presence of the double bond in the molecule of the biodiesel which produce a high level of reactivity. This high level reactivity produces formation of hydroperoxides, soluble polymers and other secondary products. From the experimental results, a slight difference in the acid value, iodine value and viscosity of the MO biodiesel stored for a period of 30 days was observed. But after this period, the differences were significant. © 2009 by Japan Oil Chemists' Society.Item Evaluation of heat transfer surfaces for compact recuperator using a CFD code(2009) Ashok Babu, T.P.; Talekala, M.S.Exhaust recovery recuperator is mandatory in order to realize a thermal efficiency of 30% or higher for micro turbines. In this work an attempt is made to select the cross corrugated heat transfer surface with minimum core volume of a recuperator matrix using a CFD code. Analysis is carried out for selected cross corrugated heat transfer surface configurations. The relation between the minimum core volume from design calculation and average skin friction coefficient from CFD analysis has been established. © 2008 Springer-Verlag.Item Assessment of mixture boiling heat transfer correlations for ammonia/water mixture(2009) Sathyabhama, A.; Ashok Babu, T.P.The aim of this work is to present a critical examination of both the available experimental data and the performance of the available mixture boiling heat transfer correlations for ammonia/water mixture. First, a selection and comparison of the experimental database found in the open literature at the mentioned working conditions is presented. Subsequently, after a short description of the most relevant heat transfer correlations, and in accordance with the selected data, a detailed analysis of the performance of each correlation is carried out. Results show a small divergence between the experimental data sets and conclude that the presently available correlations show considerable discrepancies in heat transfer coefficients within the selected conditions. © 2009 Wiley Periodicals, Inc.Item Characterization and effect of using Mahua oil biodiesel as fuel in compression ignition engine(2009) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.There is an increasing interest in India, to search for suitable alternative fuels that are environment friendly. This led to the choice of Mahua Oil (MO) as one of the main alternative fuels to diesel. In this investigation, Mahua Oil Biodiesel (MOB) and its blend with diesel were used as fuel in a single cylinder, direct injection and compression ignition engine. The MOB was prepared from MO by transesterification using methanol and potassium hydroxide. The fuel properties of MOB are close to the diesel and confirm to the ASTM standards. From the engine test analysis, it was observed that the MOB, B5 and B20 blend results in lower CO, HC and smoke emissions as compared to diesel. But the B5 and B20 blends results in higher efficiency as compared to MOB. Hence MOB or blends of MOB and diesel (B5 or B20) can be used as a substitute for diesel in diesel engines used in transportation as well as in the agriculture sector. © 2009 Science Press, Institute of Engineering Thermophysics, CAS and Springer Berlin Heidelberg.Item Improvement of performance of dual fuel engine operated at part load(Universiti Malaysia Pahang editor.ijame@gmail.com, 2010) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.Rising petroleum prices, an increasing threat to the environment from exhaust emissions, global warming and the threat of supply instabilities has led to the choice of inedible Mahua oil (MO) as one of the main alternative fuels to diesel oil in India. In the present work, MO was converted into biodiesel by transesterification using methanol and sodium hydroxide. The cost of Mahua oil biodiesel (MOB) is higher than diesel. Hence liquefied petroleum gas (LPG), which is one of the cheapest gaseous fuels available in India, was fumigated along with the air to reduce the operating cost and to reduce emissions. The dual fuel engine resulted in lower efficiency and higher emissions at part load. Hence in the present work, the injection time was varied and the performance of the dual fuel engine was studied. From the engine tests, it is observed that an advanced injection time results in higher efficiency and lower emissions. Hence, advancing the injection timing is one of the ways of increasing the efficiency of LPG+MOB dual fuel engine operated at part load. © Universiti Malaysia Pahang.Item Experimental analysis of SI engine performance and emission characteristics with gasoline-denatured spirit blends as alternative fuels(2010) Hubballi, P.A.; Ashok Babu, T.P.The experimental study focused on investigating benefits of unleaded gasoline (P100) - denatured spirit [DNS (ethanol 93.3% v/v + water 6.7% v/v)] blends as fuel in a four cylinder four stroke SI engine. Performance tests were conducted to study volumetric efficiency (VolE), brake thermal efficiency (BThE), brake power (BP), engine torque (torque), brake specific fuel consumption (BSFC). Engine exhaust emissions were investigated for carbon monoxide (CO), hydrocarbons (HC), oxides of nitrogen (NOx) and carbon dioxide (CO2). Experiments were conducted at different engine speeds between 2500 - 4500 rpm maintaining throttle position of 50% throughout the experiments. The fuel blends used include DNS30P70 (ethanol 28 % + water 2% + gasoline 70 %), DNS50P50 (ethanol 46.65 % + water 3.35 % + gasoline 50 %) and DNS85P15 (ethanol 79.3 % + water 5.7 % + gasoline 15 %) which were compared with base fuel P100. The investigations revealed that blending DNS with P100 increases BThE, VolE, BP, torque and BSFC. The CO, HC, NOx and CO2 emissions in the exhaust decrease when compared to P100 operation. The DNS85P15 blend produced encouraging results in improved engine performance and decreased engine exhaust emission.Item Performance characteristics of a dual fuel engine operated with Mahua biodiesel and liquefied petroleum gas(ASTM International, 2011) Kapilan, N.; Ashok Babu, T.P.; Reddy, R.P.Fuel crisis because of dramatic increase in vehicular population and environmental concerns have renewed the interest of the scientific community to look for alternative fuels of bio-origin such as vegetable oils and ethanol. India is looking at biodiesel derived from Mahua oil (MO), as one of the renewable alternative fuels for compression ignition (CI) engine. Although MO biodiesel (MOB) has several advantages over fossil diesel, in the present scenario, the use of biodiesel is restricted due to its high cost. In India, liquefied petroleum gas (LPG) is easily available and is one of the cheapest gaseous fuels. Hence, use of LPG to fuel a CI engine along with MOB seems to be an option for substitution of fossil diesel. In the present work, LPG, which was fumigated along with the air and biodiesel was admitted into the engine cylinder through conventional fueling device as an igniter. A single cylinder CI engine was modified to work in dual fuel mode and engine tests were carried out at rated speed under variable load conditions. The performance of the engine in dual fuel mode was compared with the diesel. The dual fuel operation results in thermal efficiency close to the diesel and also reduces the NOx and smoke emissions significantly. From the experimental results, we concluded that biodiesel in dual fuel mode with cheaper gaseous fuel induction is an option for reducing the operating cost of the biodiesel fuelled CI engine. Copyright ©2011 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.Item Semi-analytical method for heat and moisture transfer in packed bed of silica gel(2011) Ramzy K, A.; Ashok Babu, T.P.; Kadoli, R.A semi-analytical model for the heat and mass transfer of adsorption and desorption processes of the vertical solid desiccant packed bed dehumidifier is presented on the basis of quasi-steady state assumption, and is solved using close form integration with the limits equivalent to bed and time increments, and numerically by Runge-Kutta Fehlberg and forward scheme finite difference techniques. The most important parameters during the dehumidifier operation, namely, (i) exit air temperature and humidity, (ii) axial temperature distribution in the bed and (iii) water content are evaluated. Stability of the semi-analytical method is investigated and found that the main parameters affecting the model stability are the bed and time increments size. A dimensionless parameter combining time and bed increments size and air velocity named velocity ratio is defined and investigated. It is found that when the velocity ratio equals the ratio of particle diameter to bed length, the method is stable, and as the velocity ratio is made smaller beyond the stable velocity ratio, the results remain unchanged. The results of semi-analytical and numerical models agree well with the experimental results for both desorption and adsorption processes. Using the proposed semi-analytical model, the minimum and maximum relative errors for exit air temperature are 2.24% and 11.78%, respectively and for exit air humidity the minimum and maximum errors are 3.79% and 27.17% respectively. © 2010 Published by Elsevier Ltd. All rights reserved.
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