Faculty Publications
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Item Experimental Transient Analysis of Radial Flow Clay Desiccant Packed Bed(Springer Science and Business Media Deutschland GmbH, 2021) Boche, A.; Kadoli, R.In this work, an experimental investigation on the desiccant bed with radial flow is discussed. The spherical clay balls with the average diameter of 11 mm is used as desiccant in the radial bed. Two sizes of radial test section are developed based on the diameter of the inner cylinder and outer cylinder. The diameter ratio is evaluated based on the space needed to accommodate the spherical clay desiccant as a single layer and two layered. For the present work, the behavior of 850 g of clay desiccant in the single layer and double layer radial packed bed is being compared. Both the experimental test units were kept at nearly same relative humidity during the process of adsorption and nearly same temperature during desorption process. The parameters such as exit air humidity, exit air temperature, mean bed temperature during the process of adsorption, and desorption are being compared. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Bed depth service time model for the biosorption of reactive red dye using the Portunus sanguinolentus shell(2010) JagadeeshBabu, P.E.; Krishnan, R.; Singh, M.Biosorption is an efficient and regenerative technique that often uses low-cost adsorbent materials, particularly for the treatment of wastewaters containing dyes and heavy metals. This study investigates the ability of crab shell (Portunus sanguinolentus) to remove reactive red dye in a packed bed up-flow column (internal diameter 2 cm; height 35 cm). Crab shell has high surface area (after proper size reduction) and high regenerative capacity. The experiments were performed with different bed heights (20 and 30 cm) and using different flow rates (12 and 17 ml/min) in order to obtain experimental breakthrough curves. The bed depth service time (BDST) model was used to analyze the experimental data and the model parameters were evaluated. The column regeneration studies were carried out for five different sorption-desorption cycles. The elutant used for the regeneration of the sorbent was 0.01 M EDTA (disodium) solution at pH 9.8 adjusted using NH4OH. This solution was found to have the best bed regeneration capacity and could be reused for several sorption-desorption cycles. The elution efficiency was greater than 99.1% in all seven cycles. Continuous use of the crab shell leads to a decrease in the adsorptive performance, as observed by the breakthrough curves becoming flatter and also because of a broader mass transfer zone. © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.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.Item Improved utilization of desiccant material in packed bed dehumidifier using composite particles(2011) Ramzy K, A.; Kadoli, R.; Ashok Babu, T.P.Solid desiccant dehumidifiers are widely used in drying processes. In most of these dehumidifiers, the desiccant material is used as packed bed of granule or spherical particles. Investigations of intra-particle heat and mass transfer processes has shown that the entire portion of the particle is not participating effectively during adsorption as well as desorption processes [Pesaran AA, Mills F. Moisture transport in silica gel packed beds-I. Theoretical study. International Journal of Heat and Mass Transfer 1987; 30: 1037-49]. This is because the diffusion rate is very small compared to that of convection. In the present work, a new desiccant composite particle, in which the unutilized portion of the spherical desiccant particle is replaced with an inert particle, is proposed. By replacing the conventional particles with composite particles for the same mass of desiccant material, the available area for heat and mass transfer increases and more amount of desiccant material is effectively utilized. Further, in order to ascertain the improvement in the performance of the desiccant bed using the composite particles, various factors like thermo-physical properties of the inert material, composite particle thickness ratio, bed configuration, bed volume, the pressure drop and the increase in total adsorbed or desorbed mass have to be considered. In view of this, a theoretical investigation of the operation of vertical solid desiccant packed bed dehumidifier, using both conventional silica gel particles as well as the new proposed composite silica gel particles has been reported. A modified solid side resistance (MSSR) model is developed for the prediction of intra-particle temperature and water content profiles. Results of the present theoretical models, when applied to packed bed of conventional silica gel particles, agree well with the experimental results from the literature for both desorption and adsorption processes. From the theoretical results, more utilization for the desiccant material is obtained when ordinary silica gel particles are replaced by composite silica gel particles. For the same amount of desiccant material and same mass flow rate of air, using particles of 0.2 thickness ratio the pressure drop decreases by about 60% for the case investigated. In addition, an increase of about 11.07% and 20.46% in total mass adsorbed and desorbed respectively are obtained. At the time when adsorption process ends, an increase of 15.5% in the bed effectiveness has been obtained. In addition, the expected improvement in total mass adsorbed and desorbed is observed to be dependent on the inert material thermo-physical properties for thickness ratio less than 0.5. An optimization technique relating the composite particle design, resulting savings in pressure drop and bed volume increase is proposed. © 2010 Elsevier Ltd.Item Performance studies on the desiccant packed bed with varying particle size distribution along the bed(2012) Ramzy K, A.; Kadoli, R.; Ashok Babu, T.P.The transient heat and mass transfer in a desiccant packed bed containing varying particle diameter distribution along the axial direction has been investigated using the pseudo gas controlled approach that considers the heat conduction in the bed. The numerical results of the present model and the experimental data from literature show good agreement with a maximum root of mean square of errors of 3% and 2% for exit air temperature and humidity ratio, respectively. The improvement in the total mass adsorbed and/or reduction in pressure drop has been investigated for various cases of packed bed namely, uniform particle diameter, linear, parabolic and cubic ascending and descending distributions. It has been found that there is a 25.7% reduction in pressure drop with negligible reduction in the total mass adsorbed for a desiccant bed with cubic type particle size distribution when compared to the bed with uniform particle diameter of 1.0 mm. A threshold flow velocity exists below which the total mass adsorbed is independent of particle diameter distribution type. © 2012 Elsevier Ltd and IIR. All rights reserved.Item Experimental and theoretical investigations on the cyclic operation of TSA cycle for air dehumidification using packed beds of silica gel particles(Elsevier Ltd, 2013) Ramzy K, A.K.; Kadoli, R.; Ashok Babu, T.P.Dehumidification using desiccant beds provide a good alternative for the conventional vapor compression cooling system. Desiccant material in the desiccant dehumidification system should undergo both adsorption and desorption processes. In the present work, experimental tests have been carried out for thermal swing adsorption (TSA) cycle utilizing two packed beds of silica gel spherical particles. The pseudo gas side controlled (PGC) mathematical model has been presented for predicting the cycle performance. The mathematical model has been validated using the experimental results. The root mean square of errors ranges from 1.15% to 9.03% for the exit air humidity ratio and from 1.08% to 9.68% for exit air temperature. The dynamics of desiccant bed during the cyclic operation has been investigated numerically. In addition, it has been found from the parametric study that the cycle efficiency is maximum for a regeneration temperature of 90-95°C when the bed length varies from 50 to 300mm and for desiccant particle diameter ranging from 2 to 5mm. A sensible cooling for the process air before undergoing the dehumidification period is recommended for increasing the cycle efficiency and the dehumidification time which is an added advantage. © 2013 Elsevier Ltd.Item Hydrous Cerium Oxide Nanoparticles Impregnated Enteromorpha sp. for the Removal of Hexavalent Chromium from Aqueous Solutions(American Society of Civil Engineers (ASCE) onlinejls@asce.org, 2016) Selvasembian, S.; Selvaraju, N.; Raj Mohan, B.; Muhammed Anzil, P.K.; Amith, K.D.; Ushakumary, E.R.A novel nanobiocomposite, hydrous cerium oxide nanoparticles impregnated Enteromorpha sp. (HCONIE) was used effectively for the adsorption of Cr(VI) from aqueous solutions. The chemical and structural characteristics of the nanobiocomposite were investigated using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) analysis. Adsorption studies were determined as a function of pH, contact time, initial concentration of Cr(VI), HCONIE dose, and temperature. The equilibrium adsorption data were modeled using two parameter isotherms, including Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Jovanovic, Halsey, and Harkin-Jura. Adsorption data were well described by the Freundlich and Halsey isotherm. The kinetics data were analyzed using adsorption kinetic models like the pseudo-first-order, pseudo-second-order and intraparticle diffusion equation. Kinetic data showed good agreement with the pseudo-second-order kinetic model. The obtained thermodynamic parameters showed that the adsorption of Cr(VI) onto the HCONIE was exothermic in nature. The presence of foreign ions showed a decreased effect on the adsorption capacity of HCONIE towards Cr(VI) removal. The desorption study was carried out with 0.1 and 0.5 M of three different desorbing agents. The study suggests that HCONIE nanobiocomposite could be used for the removal of Cr(VI) from aqueous solution. © 2015 American Society of Civil Engineers.Item Equilibrium and Kinetic Studies of Hexavalent Chromium Removal Using A Novel Biosorbent: Ruellia Patula Jacq(Springer Verlag, 2017) Saranya, N.; Nakkeeran, E.; Shrihari, S.; Selvaraju, N.The present work utilized Ruellia patula Jacq leaves as biosorbent for hexavalent chromium removal. Sulfuric acid modification was done and checked for enhanced biosorption capacity. Electron microscopy–energy-dispersive X-ray spectroscopy, Fourier transform infrared spectrometry, elemental analysis were performed for characterization of biosorbents. Batch experiments were conducted to optimize contact time, solution pH, initial Cr(VI) concentration, biosorbent dose, agitation speed and temperature for maximum Cr(VI) removal. Also, the study attempted to show polyphenols present in the biosorbent reduce Cr(VI) through adsorption. Equilibrium data were analyzed using Langmuir, Freundlich and Dubinin–Radushkevich isotherms. Monolayer adsorption capacities of raw and acid-modified biosorbents were found to be 37.03 and 62.50 mg/g, respectively. Pseudo-second-order kinetic model suited well than other models like pseudo-first-order and intraparticle diffusion models examined. Determination of ? H?, ? S? and ? G? from thermodynamic studies showed that the biosorption is exothermic, stable and thermodynamically feasible. Desorption studies using NaOH as desorbing agent showed considerable performances up to three cycles. These findings revealed that Ruelliapatula leaves serve as potent biosorbent for the removal of hexavalent chromium from aqueous solutions. © 2017, King Fahd University of Petroleum & Minerals.Item Adsorption and desorption through packed and fluidized clay-based composite desiccant beds: a comparison study(Springer Science and Business Media Deutschland GmbH, 2022) Hiremath, C.R.; Kadoli, R.The present study considers the composite desiccant employing horse dung, sawdust with clay and later impregnating CaCl2 into the host material. The microscopic and spectroscopic experimental methods such as scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to characterize the composite desiccants. The specific heat (Cp) quantification reveals higher values for clay-additives composite desiccants with lower pore volume and larger grain sizes, whereas lower values for clay composite desiccants with higher pore volume and smaller grain sizes. Adsorption–desorption experiments for moisture removal and addition are conducted in a vertical column in static and fluidized states. The desiccant beds are subjected to an initially set value of process air velocity, relative humidity, temperature and mass of bed. Moisture removal capacity, moisture addition capacity and mass transfer coefficient are the parameter indices adopted to measure the heat and mass transfer characteristics of vertical packed and fluidized bed comprising clay-additives-CaCl2 composite desiccants. Comparing packed and fluidized beds, a higher surface area of bed in fluidization improves dehumidification performance and results in higher desorption rates. Experimental results confirmed that clay and clay-additives-based desiccants have desired adsorption–desorption characteristics of a suitable desiccant. The interesting advantage of fabricated clay and clay-additives-based composite adsorbents is that the air exits the desiccant bed at a lower temperature, saving cooling energy requirements of sorption-based systems. © 2022, The Author(s), under exclusive licence to The Brazilian Society of Mechanical Sciences and Engineering.Item Sorption–desorption characteristics of dried cow dung with PVP and clay as composite desiccants: Experimental and exergetic analysis(Elsevier Ltd, 2023) Dasar, S.R.; Boche, A.M.; Yadav, A.K.; Anish, S.The present study investigates the sorption and desorption characteristics of a natural composite desiccant based on dried cow dung (DCD). Polyvinyl Pyrrolidone (PVP) and clay are used as binders with DCD. The moisture uptake capacity of composite desiccants is measured with an isotherm experiment under different DCD to binder ratios. Based on their isotherms, composite desiccants are chosen for characteristic study under different humid conditions and validated with available literature data. Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Halenda (BJH) analyses are carried out to understand the physical properties of DCD, DCD+PVP (3:1) and DCD+Clay (3:1). Total heat load reduction, exergy efficiency and power required for these dehumidification systems are calculated for different inlet conditions. Desorption characteristics are tested at 328 K and 6% RH. Results show the maximum moisture uptake capacity of DCD and DCD+PVP as 14.42 and 14.72 g/100 g, respectively. The maximum exergy efficiency of the DCD+PVP dehumidification system is found to be 55%. Desorption time for DCD+PVP desiccant is 17 min, which is 4 and 2 min higher compared to DCD, and DCD+Clay, respectively. With this experimental study, it is concluded that the DCD+PVP has the potential to become an alternative to chemical desiccants based on their exergy efficiency and moisture uptake capacity. © 2022 Elsevier Ltd