Faculty Publications
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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 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 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 Effect of surface vibration on boiling heat transfer froma copper flat circular disc(Begell House Inc. orders@begellhouse.com, 2016) Sathyabhama, A.; Pandiyan, P.S.This paper presents the experimental investigation of the effect of surface vibration on pool boiling heat transfer from a copper flat circular surface immersed in saturated water at atmospheric pressure. The forced vertical vibrations were induced on this copper test surface with the help of a mechanical vibrator. The frequency was varied in the range 0-25 Hz and the amplitude of vibration was varied in the range 0-5 mm. The results indicate that the heat transfer coefficient increases at low frequency and amplitudes; at higher amplitude and frequency, heat transfer deteriorates in the investigated range. Rohsenow-type correlation was developed, which predicts the present experimental data with an average absolute error of 30%. © 2018 by Begell House, Inc.Item Experimental and numerical investigation of pool boiling heat transfer from finned surfaces(Elsevier Ltd, 2023) Jaswal, R.; Sathyabhama, A.; Singh, K.; Yandapalli, A.V.V.R.P.An experimental study of the pool boiling process on three test surfaces, namely, Plain surface, Rectangular finned surface, and Trapezoidal finned surface, was carried out using distilled water as the working fluid at atmospheric pressure. A parametric study of finned surfaces was performed to understand the effect of fin spacing and fin height on the pool boiling performance. A high-speed camera was employed to capture the pool boiling process. A numerical investigation was also performed using the Eulerian multiphase model associated with the RPI wall boiling model. A 2-D rectangular boiling chamber filled with distilled water was considered for the numerical study. The numerical results with default models were validated with the experimental results. A correction was proposed for the Bubble Waiting Time coefficient (Cw) of the quenching heat flux to improve the numerical results. Experimental results showed that using rectangular and trapezoidal finned surfaces improved the heat flux values by 52.3% and 101.5%, respectively, compared to the plain surface. The heat transfer coefficient (HTC) depends upon the area availability and type of boiling surface used. Increasing the height of the fins was beneficial, whereas increasing the fin spacing adversely affected the fin performance. © 2023 Elsevier Ltd