Faculty Publications

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    Behavioral study of alumina nanoparticles in pool boiling heat transfer on a vertical surface
    (2011) Hegde, R.N.; Reddy, R.P.; Rao, S.S.
    Experiments were carried out to investigate the pool boiling of alumina-water nanofluid at 0.1 g/l to 0.5 g/l of distilled water, and the nucleate pool boiling heat transfer of pure water and nanofluid at different mass concentrations were compared at and above the atmospheric pressure. At atmospheric pressure, different concentrations of nanofluids display different degrees of deterioration in boiling heat transfer. The effect of pressure and concentration of nanoparticles revealed significant enhancement in heat flux and deterioration in pool boiling. The heat transfer coefficient of 0.5 g/l alumina-water nanofluid was compared with pure water and clearly indicates deterioration. At all pressures the heat transfer coefficients of the nanofluid were lower than those of pure water. Experimental observation revealed particles coating over the heater surface and subsequent SEM inspection of the heater surface showed nanoparticles coating on the surface forming a porous layer. To substantiate the nanoparticle deposition and its effect on heat flux, investigation was done by measuring the surface roughness of the heater surface before and after the experiment. While SEM images of the heater surface revealed nanoparticle deposition, surface roughness of the heater surface confirmed it. Based on the experimental investigations it can be concluded that an optimum thickness of nanoparticles coating favors an increase in heat flux. Higher surface temperature due to the presence of nanoparticles coating results in the deterioration of boiling heat transfer. © 2011 Wiley Periodicals, Inc.
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    Experimental study on CuO nanoparticles in distilled water and its effect on heat transfer on a vertical surface
    (2011) Hegde, R.N.; Rao, S.S.; Reddy, R.P.
    The pool boiling characteristics of dilute dispersions of CuO nanoparticles in water were studied at atmospheric pressure on a vertical heating surface. Experimental investigation of different weight concentrations of nanoparticles revealed significant enhancement in heat flux and deterioration in pool boiling. Out of many reasons, nanoparticles coating the heater surface was believed to be the reason behind this. Subsequent inspection of the heater surface showed nanoparticles coating the surface, forming a porous layer. To substantiate the nanoparticle deposition and its effect on heat flux, an investigation was performed by measuring the surface roughness of the heater surface before and after the experiment. While SEM images of the heater surface revealed nanoparticle deposition, measurement of surface roughness of the heater surface confirmed it. Formation of the porous layer on the heater surface as revealed by SEM images provided an excellent location for nucleation sites enhancing heat transfer. However, deterioration in nucleate boiling at different weight concentrations indicated some phenomenon is working behind this. © 2011 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg.
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    Effect of addition of aluminum nanoparticles on cooling performance and quench severity of water during immersion quenching
    (ASTM International, 2012) Ramesh, G.; Prabhu, K.N.
    In the present work, the effect of the addition of aluminum nanoparticles in concentrations varying from 0.001 to 0.5 vol. % on the cooling performance and quench severity of water during immersion quenching is investigated. The results of cooling curve analyses show that an increase in nanoparticle concentration increased the cooling rates at critical temperatures up to 0.05 vol. % and decreased them thereafter. The transition from the vapor blanket stage to the nucleate boiling stage was also altered by quenching in nanofluids. A finite difference heat transfer program was employed to generate cooling curves at different values of heat transfer coefficient from thermo-physical properties of the quench probe material. A Grossmann H quench severity versus cooling rate curve was established, and from this curve, the H factors of prepared nanofluids were estimated. An increase in nanoparticle concentration up to 0.05 vol. % resulted in an increase of the H value of water from 63 m -1 to 93 m-1, and any further increase in the concentration of nanoparticles resulted in a decrease in H. The results suggest both the enhancement and the deterioration of the cooling performance of water by the addition of aluminum nanoparticles. Copyright © 2012 by ASTM International.
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    Nonlocal linear minimum mean square error methods for denoising MRI
    (Elsevier Ltd, 2015) Sudeep, P.V.; Ponnusamy, P.; Kesavadas, C.; Rajan, J.
    The presence of noise results in quality deterioration of magnetic resonance (MR) images and thus limits the visual inspection and influence the quantitative measurements from the data. In this work, an efficient two stage linear minimum mean square error (LMMSE) method is proposed for the enhancement of magnitude MR images in which data in the presence of noise follows a Rician distribution. The conventional Rician LMMSE estimator determines a closed-form analytical solution to the aforementioned inverse problem. Even-though computationally efficient, this approach fails to take advantage of data redundancy in the 3D MR data and hence leads to a suboptimal filtering performance. Motivated by this observation, we put forward the concept of nonlocal implementation with LMMSE estimation method. To select appropriate samples for the nonlocal version of the LMMSE estimation, the similarity weights are computed using Euclidean distance between either the gray level values in the spatial domain or the coefficients in the transformed domain. Assuming that the signal dependent component of the noise is optimally suppressed by this filtering and the rest is a white and uncorrelated noise with the image, we adopt a second stage LMMSE filtering in the principal component analysis (PCA) domain to further enhance the image and the noise variance is adaptively adjusted. Experiments on both simulated and real data show that the proposed filters have excellent filtering performance over other state-of-the-art methods. © 2015 Elsevier Ltd. All rights reserved.
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    Groundwater quality assessment of urban Bengaluru using multivariate statistical techniques
    (Springer Verlag, 2018) Gulgundi, M.S.; Shetty, A.
    Groundwater quality deterioration due to anthropogenic activities has become a subject of prime concern. The objective of the study was to assess the spatial and temporal variations in groundwater quality and to identify the sources in the western half of the Bengaluru city using multivariate statistical techniques. Water quality index rating was calculated for pre and post monsoon seasons to quantify overall water quality for human consumption. The post-monsoon samples show signs of poor quality in drinking purpose compared to pre-monsoon. Cluster analysis (CA), principal component analysis (PCA) and discriminant analysis (DA) were applied to the groundwater quality data measured on 14 parameters from 67 sites distributed across the city. Hierarchical cluster analysis (CA) grouped the 67 sampling stations into two groups, cluster 1 having high pollution and cluster 2 having lesser pollution. Discriminant analysis (DA) was applied to delineate the most meaningful parameters accounting for temporal and spatial variations in groundwater quality of the study area. Temporal DA identified pH as the most important parameter, which discriminates between water quality in the pre-monsoon and post-monsoon seasons and accounts for 72% seasonal assignation of cases. Spatial DA identified Mg, Cl and NO3 as the three most important parameters discriminating between two clusters and accounting for 89% spatial assignation of cases. Principal component analysis was applied to the dataset obtained from the two clusters, which evolved three factors in each cluster, explaining 85.4 and 84% of the total variance, respectively. Varifactors obtained from principal component analysis showed that groundwater quality variation is mainly explained by dissolution of minerals from rock water interactions in the aquifer, effect of anthropogenic activities and ion exchange processes in water. © 2018, The Author(s).
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    Characterization and performance of processed lateritic fine aggregates in cement mortars and concretes
    (Elsevier Ltd, 2019) Yaragal, S.C.; Basavana Gowda, S.N.; C, C.
    Availability of river sand is becoming scarce, due to rapid increase in infrastructure projects in India. Acute shortage of river sand, has led to indiscriminate sand mining. Adverse effect of sand mining includes river bank erosion, river bed degradation, loss of biodiversity and deterioration of river water quality and ground water availability. To address the above issues, research efforts are on, to find substitutes for river sand to be used as fine aggregate in mortars and concretes. One among the locally available resources is laterite. Laterite is a product of tropical or sub-tropical weathering, which is an abundant soil material in many parts of India. An attempt has been made to characterize the processing technique to obtain good quality lateritic fine aggregates (lateritic FA). Experiments were designed and conducted to study the performance of lateritic FA as replacement to river sand, in cement mortars and concretes. Processed lateritic FA in replacement levels of 0, 25, 50, 75 and 100 wt% to river sand at all fineness levels (Zone I to Zone IV as per Indian standards) is considered. Microstructure studies were conducted to understand the arrangement of river sand and lateritic FA with cement matrix and their Interfacial Transition Zones (ITZ) using Scanning Electron Microscope (SEM). The workability and compressive strength characteristics of cement mortars and concretes are evaluated. Laterized mortars with Zone III and Zone IV fine aggregates, at all replacement levels, result in the same compressive strengths as those of control mortars. Suitable strength enhancement technique has been attempted to achieve strengths of Zone I and Zone II lateritic fine aggregates based mortars at 100 wt% replacement, to achieve strength at least equal to or more than those of control mortars. Laterized concretes have achieved nearly the same strengths as those of control concretes, at all replacement levels and for all fineness levels (Zone I to Zone IV). © 2018 Elsevier Ltd
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    The effect of load and addition of MWCNTs on silicone based TIMs on thermal contact heat transfer across Cu/Cu interface
    (Institute of Physics Publishing helen.craven@iop.org, 2019) Pathumudy, R.; Narayanprabhu, K.
    In the present work, the effect of thermal interface material (TIM) and load on contact heat transfer between hot and cold cylindrical copper specimens was assessed. Pristine silicone grease and multi walled carbon nanotubes (MWCNT) impregnated silicone grease was used as TIM. Copper specimens with L/D ratios of 1 and 5 were used. For copper specimens with L/D ratio of 1, the interfacial heat transfer was quantified by estimating the peak heat flux and integral heat flow using a lumped heat capacitance approach. An inverse solution to heat conduction equation was adopted for estimating heat flux transients for copper specimens with L/D ratio of 5. As the applied load increased from a no load condition to 5 kg, the peak heat flux and the corresponding integral flow increased significantly. Increasing the load above 5 kg did not result in any significant changes in the peak heat flux and integral heat flow for both sets of specimens. The effect of load on the contact heat transfer was significant in the absence of TIM. The use of 0.1 wt% MWCNT- silicone grease as TIM significantly increased the heat flow for no load condition. At higher loads, the effect of MWCNT was insignificant and caused deterioration in the heat flow parameters. Further, increasing the MWCNT content to 1 wt% in silicone grease decreased the heat flux transients at all loading conditions. The thermal contact resistance (RT) was calculated and it increased exponentially with the peak temperature difference (?Tmax) between hot and cold specimens irrespective of the L/D ratio. © 2019 IOP Publishing Ltd.
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    Structural damage identification of bridge using high dimensional model representation
    (Bellwether Publishing, Ltd., 2021) Naveen, B.O.; Balu, A.S.
    Any engineering structure under the action of various internal and external factors like changes in the material properties, inadequate design, faulty construction, deterioration due to malfunctioning are susceptible to damages. In the past, many methods have attempted to identify damage by solving an inverse problem, which inevitably needs an analytical model. However, often the construction of these analytical model requires considerable effort in building a mathematical framework with acceptable level of accuracy and reliability which makes these approaches less attractive. To circumvent this complexity, this work presents a computationally efficient approach in structural damage identification using high dimensional model representation. © 2020 Taylor & Francis Group, LLC.
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    Sonar mapping of abandoned water-logged underground coal mine and backfilling operation using underwater camera
    (Inderscience Publishers, 2021) Pal, S.K.; Tripathi, A.K.; Panda, S.; Palaniappan, S.K.
    The paper describes mine mapping and backfilling work carried out during field experimentations on simple hydraulic gravity blind backfilling method for the stabilisation of ground above old abandoned waterlogged underground coal mine of Eastern Coalfields Limited (ECL), India. The section of the abandoned mine to be backfilled was explored using the underwater remote operated vehicle (ROV) camera before actual backfilling work. The use of sonar imaging facility of the ROV camera for mapping of the underground waterlogged area to be backfilled is described. The plotting of gradual progress of sand bed as the filling progressed in different stages through different boreholes as monitored from surrounding camera boreholes is also described. © © 2021 Inderscience Enterprises Ltd.
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    Freeze casting of lamellar-structured porous lead-free (Na0.52K0.48)(Nb0.95Sb0.05)O3 piezoceramic with remarkable enhancement in piezoelectric voltage constant and hydrostatic figure of merit
    (Springer, 2021) Dixit, P.; Seth, S.; Rawal, B.; Kumar, B.P.; Panda, H.S.
    The study reports the development of lamellar-structured, porous lead-free (Na0.52K0.48)(Nb0.95Sb0.05)O3 ceramics, abbreviated as NKNS, using the freeze-casting method with water as pore-forming agent. The effect of directional porosity on the microstructure, dielectric, and piezoelectric properties of the lead-free porous material is investigated. Furthermore, the effects of conventional and microwave sintering on microstructure and piezoelectric properties have also been analyzed. In addition, the study compares conventional and corona poling too. The results depicted no deterioration of piezoelectric properties (d33:130 pC/N), despite being ~ 50% porosity, along with reasonably good hydrostatic piezoelectric strain coefficient (dh: 60pC/N). The samples exhibited hydrostatic piezoelectric voltage coefficient (gh) of 58.70 mV.m/N providing a significant value of the hydrostatic figure of merit (HFOM = dh?gh: 3522 × 10–15 Pa?1) for the porous NKNS ceramic which is nearly 39 times more than the dense ceramic. Considering its unique advantages such as environmental friendly, less dense, wide performance range with enhanced figure of merit, the lamellar-structured NKNS ceramic is a promising material for sensor and transducer applications. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.