Bikash Mohanty

Supercritical extraction of sunflower oil: A central composite design for extraction variables.

Supercritical carbon dioxide (SC-CO2) extraction of sunflower seed for the production of vegetable oil is investigated and compared to conventional methods. The effects of extracting variables, namely pressure, temperatures, particle size, SC-CO2 flow rate and co-solvent, on SC-CO2 extraction are investigated. The maximum yield for sunflower oil is found to be about 54.37 wt%, and is obtained when SC-CO2 extraction is carried out at 80 °C, 400 bar, 0.75 mm particle and 10 g/min solvent flow with 5% co-solvent. A central composite design is used to develop the model and also to predict the optimum conditions. At optimum conditions obtained based on desirability function, 80.54 °C, 345 bar, 1.00 mm, 10.50 g/min and 7.58% ethanol, SC-CO2 extraction has performed and found that extraction yield dropped by 2.88% from the predicted value. Fatty acid composition of SC-CO2 and hexane extracted oil shows negligible difference and found high source of linoleic acid.

Prediction of heat transfer coefficient during condensation of water and R-134a on single horizontal integral-fin tubes

Abstract This paper presents a few salient features of an investigation carried out to study the heat transfer augmentation during condensation of water and R-134a vapor on horizontal integral-fin tubes. The experimental investigation was performed on two different experimental set-ups for water and R-134a. The test-sections were manufactured by machining fins over plain copper tubes of 24.4 ± 0.6 mm outside diameter. The performance of two types of finned tubes viz. circular integral-fin tubes (CIFTs) and spine integral-fin tubes (SIFTs) was studied for the condensation of water and R-134a. These tubes were positioned one by one inside the test-condenser to perform the experiments. All together the experiments were conducted for the condensation on 10 different test-section tubes. With the help of the experimental results, authors have developed an empirical equation. This equation predicts the condensing heat transfer coefficient from their own experimental data for the condensation over CIFTs and SIFTs within a range of ± 15% and experimental data of other thirteen investigators in a range of ± 35% for condensation of water and different refrigerants.

Selection of optimal feed flow sequence for a multiple effect evaporator system

Abstract A nonlinear model is developed for a SEFFFE system employed for concentrating weak black liquor in an Indian Kraft Paper Mill. The system incorporates different operating strategies such as condensate-, feed- and product-flashing, and steam- and feed-splitting. This model is capable of simulating a MEE system by accounting variations in τ, U, Qloss, physico-thermal properties of the liquor, F and operating strategies. The developed model is used to analyze six different F including backward as well as mixed flow sequences. For these F, the effects of variations of input parameters, T0 and F, on output parameters such as SC and SE have been studied to select the optimal F for the complete range of operating parameters. Thus, this model is used as a screening tool for the selection of an optimal F amongst the different F. An advantage of the present model is that a F is represented using an input Boolean matrix and to change the F this input matrix needs to be changed rather than modifying the complete set of model equations for each F. It is found that for the SEFFFE system, backward feed flow sequence is the best as far as SE is concerned.

Review Article: Recycling of Polystyrene

Recycling of polystyrene can be done by mechanical, chemical, and thermal methods. High impact polystyrene is a promising material for mechanical recycling since its properties are not extremely affected even after multiple processing of upto nine cycles. Production of liquid products and gaseous products are highly dependent on the reaction condition. The catalysts used are highly selective for the production of liquid as well as gaseous products. In this article we have reviewed the various types of methods followed so far for recycling of polystyrene.

Augmentation of heat transfer during filmwise condensation of steam and R-134a over single horizontal finned tubes

Abstract An experimental investigation has been carried out to augment the heat transfer rate by enhancing the heat transfer coefficient during the condensation of pure vapours of steam and R-134a over horizontal finned tubes. The study was conducted for plain tubes, circular integral-fin tubes (CIFTs), spine integral-fin tubes (SIFTs) and parially spined circular integral-fin tubes (PCIFTs). The SIFT out performed the CIFT for the condensation of R-134a by approximately 16%. However, the spines were found most effective in the bottom side of the CIFT. The PCIFTs with the spines only in the bottom side of the tube augmented the heat transfer coefficient by 20% and 11% for the condensation of steam and R-134a, respectively, in comparison to the CIFT.

Development of a new model for multiple effect evaporator system

Abstract A new simplified scalable mathematical model, based on concepts of stream analysis, temperature paths and internal heat exchange, has been developed for synthesis of a multiple effect evaporator systems. In this model, fresh feed is assumed to be composed of product and number of condensate streams, which come out from different effects and these are treated as separate streams. For the present work a septuple effect flat falling film evaporator system, used for concentrating black liquor in an Indian Kraft Pulp and Paper mill, has been considered. This system is being operated under backward sequence with condensate-, feed- and product-flashing as well as steam splitting in first two effects. The set of linear algebraic equations for this model are self-generated through programming and is solved simultaneously using Gaussian Elimination Method with partial pivoting. Results of the present approach are validated with published model and industrial data.

A Comprehensive Study of Modified Wilson Plot Technique to Determine the Heat Transfer Coefficient during Condensation of Steam and R-134a over Single Horizontal Plain and Finned Tubes

In the present investigation a comprehensive study of the modified Wilson plot technique has been made and a stepwise methodology has been evolved. This technique can be used to determine the condensing-side heat transfer coefficient during condensation of vapor over a horizontal tube. The necessary experimental data have been acquired by conducting experiments for the condensation of steam and R-134a over a plain tube and different finned tubes (CIFTs and SIFTs). The experimental heat transfer coefficient, based on the test-section wall temperature measurement (wall temperature was measured with thermocouples), ho, has been compared with that predicted by the modified Wilson plot technique, hmw. The modified Wilson plot technique underpredicted the condensing-side heat transfer coefficient for the condensation of steam in a range of 7.5-15%. The heat transfer coefficient for the condensation of R-134a is also underpredicted in a range of 13-25% by this technique.In the present investigation a comprehensive study of the modified Wilson plot technique has been made and a stepwise methodology has been evolved. This technique can be used to determine the condensing-side heat transfer coefficient during condensation of vapor over a horizontal tube. The necessary experimental data have been acquired by conducting experiments for the condensation of steam and R-134a over a plain tube and different finned tubes (CIFTs and SIFTs). The experimental heat transfer coefficient, based on the test-section wall temperature measurement (wall temperature was measured with thermocouples), ho, has been compared with that predicted by the modified Wilson plot technique, hmw. The modified Wilson plot technique underpredicted the condensing-side heat transfer coefficient for the condensation of steam in a range of 7.5-15%. The heat transfer coefficient for the condensation of R-134a is also underpredicted in a range of 13-25% by this technique.

Boiling heat transfer from a vertical row of horizontal tubes

Abstract An experimental investigation was carried out to measure the enhancement in the nucleate pool boiling heat transfer of upper heating tubes of copper having 32 mm outer diameter (OD), 18.2 mm internal diameter (ID), and 100 mm effective length, placed one over another in a vertical row as a function of heat flux, type of liquid, and tube material and surface characteristics. Based on the data of present work and similar experiment work of other investigators a model was developed to predict the heat transfer coefficient of individual tube in a multi-tube row and the bundle heat transfer coefficient. The heat flux and pressure range covered was 19– 45 kW/m 2 and 35.36–97.5 kPa, respectively. The developed model predicts the experimental data for benzene, toluene, distilled water, and R-113 within ±15%.

Growth of three bacteria in arsenic solution and their application for arsenic removal from wastewater

The present paper compares the arsenic removal capacities of three bacterial strains namely, Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 form wastewater (simulated acid mine drainage) containing arsenic (As(III):As(V)::1:1), Fe, Mn, Cu and Zn in the concentration of 15 mg/l, 10 mg/l, 2 mg/l, 5 mg/l and 10 mg/l respectively, in bulk liquid phase. Growth patterns of these bacteria in presence of arsenic in solution as well as under starvation have also been investigated as the acid mine drainage normally does not contain organic carbon and also contains high arsenic. At the nutrient broth concentration of 1.25 g/l and in presence of 15 mg/l arsenic sufficient growth of these strains have been observed. However, growth of Ralstonia eutropha MTCC 2487 has been found slightly more than Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374. Arsenic removal capacities of Ralstonia eutropha MTCC 2487, Pseudomonas putida MTCC 1194 and Bacillus indicus MTCC 4374 from simulated acid mine drainage are ∼67%, 60% and 61% respectively. It has also been observed that arsenic concentration of 15 mg/l prolongs the stationary phase of these strains. pH and temperature for the above studies have been maintained at 7.1 ± 0.1 and 29 ± 1 °C, respectively. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

MODELING AND SIMULATION OF MEE SYSTEM USED IN THE SUGAR INDUSTRY

In this work, a generalized steady-state mathematical model has been developed for simulation of the multiple effect evaporator (MEE) system, used in the Indian sugar industry. The developed model is capable of handling exhaust steam (saturated/superheated) inputs in more than one effect, vapor bleeding from desired effects, heat loss from each effect, and variations in boiling point rise as well as specific heat capacity with combination, heat transfer coefficient through external empirical correlations, and condensate flashing. The developed model has been solved by the globally convergent method. The results of present investigations have been validated against the data obtained from the Indian sugar industry with seven effects. The predicted exit liquor concentration, vapor body temperature, and amount of vapor bleed from each effect shows close agreement with the industry data within a maximum error band of ±2%. Further, a correlation has been developed for the prediction of overall heat transfer coefficient (OHTC) of each effect. The developed model can be further used to improve the steam economy of the MEE system by the incorporation of flash vapors from condensate stream.