Journal Articles
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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 Modelling for organics and nutrients release during benthal sludge stabilisation part il - Nutrients(2009) Bhargava, D.S.; Shrihari, S.Settleable solids from untreated or partially treated domestic and industrial effluents undergoing stabilisation in stream beds contain significant amount or nutrients such as ammonia and phosphates apart from carbonaceous organic material. An experimental investigation was carried out to study the contribution of biochemical oxygen demand (BOD) and nutrients by this benthal-sludge undergoing stabillisation in steam beds. Sludge was collected from a sewage channel and placed at the bottom of an experimental reactor, and a continuous flow of clean tap water was maintained, in such a manner that the sludge was not disturbed. The first part of this work contained a discussion on degreadation of carbonaceous matter. The degradation of the nutrients, such as ammonia and phosphates being released from the sediments into the overlying waters at different flow rates of over laying waters is evaluated. It was noticed that the ammonia and phosphates released from the sediments into the overlying waters become more or less uniform after some days. The ammonia release and phosphate release were found to be affected by changes in the flowrates of overlying waters. The ammonia and phosphates remaining in the top and bottom layers of the sediments also showed similar trends. Predictive models have been presented for the variation of ammonia and phophate release into the overlying water, ammonia and phosphates remaining in the sediment layers at different times and different flow rates.Item Experimental investigation in pool boiling heat transfer of ammonia/water mixture and heat transfer correlations(2011) Sathyabhama, A.; Ashok Babu, T.P.A.The nucleate pool boiling heat transfer coefficient of ammonia/water mixture was investigated on a cylindrical heated surface at low pressure of 4-8bar and at low mass fraction of 0NH3<0.3 and at different heat flux. The effect of mass fraction, heat flux and pressure on boiling heat transfer coefficient was studied. The results indicate that the heat transfer coefficient in the mixture decreases with increase in ammonia mass fraction, increases with increase in heat flux and pressure in the investigated range. The measured heat transfer coefficient was compared with existing correlations. The experimental data were predicted with an accuracy of ±20% by the correlation of Calus&Rice, correlation of Stephan-Koorner and Inoue-Monde correlation for ammonia/water mixture in the investigated range of low ammonia mass fraction. The empirical constant of the first two correlations is modified by fitting the correlation to the present experimental data. The modified Calus&Rice correlation predicts the present experimental data with an accuracy of ±18% and the modified Stephan-Koorner correlation with an accuracy of ±16%. © 2011 Elsevier Inc.Item Vapor-liquid equilibrium of ammonia-water-lithium nitrate solutions(2011) Sathyabhama, A.; Ashok Babu, T.P.Experimental results on the pressure-temperature data for the NH3-H2O binary and NH3-H2O-LiNO3 ternary solutions are reported. The pressure was varied between 100 and 800 kPa, while the mass fraction of ammonia was varied in the range 0-0.30. The lithium nitrate concentration of the solution was chosen in the range of 10-50% of mass ratio of lithium nitrate in pure water. An analytical equation for the equilibrium pressure as a function of temperature and concentration was obtained with a good fit to experimental data. © 2011 Wiley Periodicals, Inc.Item Experimental study of nucleate pool boiling heat transfer to ammonia-water-lithium bromide solution(2011) Sathyabhama, A.; Ashok Babu, T.P.Visualization of bubble nucleation during nucleate pool boiling outside a vertical cylindrical heated surface was done for ammonia-water binary and ammonia-water-lithium bromide ternary mixture in order to obtain a descriptive behavior of the boiling which was directly compared with the measured heat transfer coefficient at low pressure of 4-8. bar and at low ammonia mass fraction of 0Item Nucleate pool boiling heat transfer measurement and flow visualization for ammonia-water mixture(2011) Sathyabhama, A.; Ashok Babu, T.P.Visualization of bubble nucleation during nucleate pool boiling outside a vertical cylindrical heated surface was done for ammonia-water binary mixture in order to obtain a descriptive behavior of the boiling, which was directly compared with the measured heat transfer coefficient data at low pressure of 4-8 bar and at low mass fraction of 0 < x < 0.3 and at different heat flux. Still images taken with high speed camera are used to demonstrate the decrease in boiling heat transfer coefficient with increase in ammonia mass fraction. Jensen and Memmel model has better agreement with experimental bubble diameter. Further work is required to obtain quantitative information about bubble nucleation parameters. It is found that both Calus and Rice and Stephan-Koorner correlation can predict the experimental heat transfer coefficient values with a maximum deviation of ±20%. © 2011 American Society of Mechanical Engineers.Item Experimental investigation of pool boiling heat transfer in ammonia-water-lithium nitrate solution(2012) Sathyabhama, A.; Ashok Babu, T.P.The nucleate pool boiling heat transfer coefficient of an NH 3-H 2O-LiNO 3 mixture was investigated on a cylindrical heated surface at low pressure of 4 to 8 bar, low ammonia mass fraction of 0 < xNH 3 < 0.3, and different heat fluxes. The lithium nitrate concentration of the solution was chosen in the range of 10-50% of mass ratio of lithium nitrate in pure water. The effects of concentrations, heat flux, and pressure on boiling heat transfer coefficient was studied. The results indicate that the heat transfer coefficient in the mixture decreases with increase in ammonia mass fraction, increases with the addition of lithium nitrate, and increases with an increase in heat flux and pressure in the investigated range. © 2012 Copyright Taylor and Francis Group, LLC.Item Removal of ammonia and particulate matter using a modified turbulent wet scrubbing system(2012) Byeon, S.-H.; Lee, B.-K.; Raj Mohan, B.Conventional scrubbers are typically modified to serve the needs of modern industries that discharge effluents that cause synergetic, adverse effects on the environment. We designed and developed a modified turbulent wet scrubber (MTWS) to remove air pollutants as they emerge from a coal furnace. Experiments were conducted to estimate the pressure drop and the efficiencies of ammonia gas and particulate removal via the MTWS. The optimum water levels and gas flow rates for effective scrubbing of ammonia gas at different concentrations and particulate matter at different feed rates were estimated. For ammonia gas at a concentration of 45 ppm, a gas flow rate of 3.5 m 3/s and a water level of 58 cm in MTWS and position B (central position of the nozzle) in the water level of the nozzle yielded efficient ammonia gas removal for the given time. Similarly, for a fly ash feeding rate of 140 mg/min, the same gas flow rate and water level in the MTWS yielded high efficiencies even for particles at the submicron level. © 2012 Elsevier B.V. All rights reserved.Item The experimental and simulation study of selective catalytic reduction system in a single cylinder diesel engine using NH3 as a reducing agent(Hindawi Publishing Corporation 410 Park Avenue, 15th Floor, 287 pmb New York NY 10022, 2014) Athrashalil Phaily, M.K.; Sreekumar, S.J.; Mohanan, P.Selective catalytic reduction (SCR) technology has been widely used in automotive applications in order to meet the stringent limits on emission standards. The maximum NOx conversion efficiency of an SCR depends on temperature and mass flow rate of an exhaust gas. In order to assess the suitability of Cordierite/Pt catalyst for low temperature application, an experimental work is carried out using single cylinder diesel engine for different load conditions by varying ammonia induction rate from 0.2 kg/hr to 0.8 kg/hr. The simulation is carried out using AVL FIRE for the validation of experimental results. From the study, it has been found that for 0.6 kg/hr ammonia induction rate the maximum conversion is achieved, whereas, for 0.8 kg/hr, conversion is reduced due to desorption of ammonia. Also it has been found that, at 75% of load, for all mass flow rates of ammonia the conversion was drastically reduced due to higher exhaust gas temperature and higher emission of unburnt hydrocarbons. More than 55% of NOx conversion was achieved using Cordierite/Pt catalyst at a temperature of 320°C. © 2014 Manoj Kumar Athrashalil Phaily et al.Item Polyaniline/poly(styrene-co-acrylonitrile) blend nanofibers exhibit enhanced ammonia and nitrogen dioxide sensing characteristics(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Reddy, N.R.; Anandhan, S.Polyaniline (PANI) nanofibers were synthesized by interfacial polymerization method and p-toluene sulfonic acid was used as a dopant to enhance the conductivity of the resultant emeraldine base of PANI. A blend of PANI and poly(styrene-co-acrylonitrile) (SAN) in the form of nanofibers was electrospun on interdigitated copper electrode and was used for sensing of ammonia and nitrogen dioxide. The sensor exhibited excellent sensitivity and responded quickly to those gases at ppm levels as low as 10. Transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy results revealed that there is a good molecular level interaction between PANI and SAN, which is believed to be the major reason for the excellent gas sensitivity of these blend nanofibers. © 2016, Springer Science+Business Media New York.