Browsing by Author "Jalal Uddin, Md."

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Applicability of alluvial roughness predictors for Gumti, Kushiyara and Mohananda rivers
(Department of Water Resources Engineering, 1999-12) Jalal Uddin, Md.; Halim, Dr. M. A.
This study has been performed to determine the applicability of alluvial roughness predictors for Gumti, Kushiyara and Mohananda rivers. Eleven roughness predictors are evaluated- six are based on division of roughness and five are based on overall roughness. The selected methods are evaluated on the basis of Manning's n, Chezy's C and Darcy-Weisbach friction factor f and, where possible, on the basis of depth and/or velocity. To predict the roughness characteristics of alluvial rivers, hydrological data, e.g. discharge, cross-sectional area, mean velocity, river width, water surface slope and grain size data of bed materials are needed. The discharge stations Jibanpur, Sherpur and Chapai Nawabganj are selected for the rivers Gumti, Kushiyara and Mohananda, respectively. The required hydrological and grain size data of the selected rivers have been obtained from BWDB and SWMC, respectively. The Manning, Chezy and Darcy-Weisbach formulae are applied to calculate the roughness coefficients n, C and f, respectively. The roughness coefficients are also predicted by using the selected roughness predictors and then these values were compared with the values obtained by Manning, Chezy and Darcy-Weisbach formulae. Accuracy of different predictors has been determined on the basis of MNE and the standard deviation ofthe MNE. Out of the eleven selected roughness predictors, the Einstein and Barbarossa (1952) is the only method, which can satisfactorily predict roughness coefficients for full range of discharges for all the rivers. Some of the roughness predictors seem to predict Manning's n satisfactorily for the full range of discharge of a particular river, e.g. the Shen (1962) method for Gumti river. Shen (1962) method for the Kushiyara river predicts Manning's n about 100% higher than the calculated values for all discharges. Simons' and Richardson (1966) method predicts Manning's n about 48% higher for the Gumti river and 87% higher for the Kushiyara river than the calculated values for all discharges. Some methods predict Manning's n satisfactorily only for moderate to high range of discharge of a particular river, e.g. Haque and Mahmood (1983) and Shen et al. (1990) methods for the Kushiyara river. Some of the methods, e.g. Engelund and Hansen (1967), Van Rijn (1993), Garde and Ranga Raju (1977), Brownlie (1983), White et al. (1987) and Karim (1995) methods predict roughness coefficients of poor quality for any discharges and all the rivers. The Einstein and Barbarossa (1952), Shen (1962) and Brownlie (1983) methods for the river Gumti and Brownlie (1983) and Karim (1995) methods for the river Kushiyara predict depth satisfactorily. During analyses of the hydrological data collected from BWDB for the river Mohananda, the data did not seem reliable, because the calculated Manning's n from observed data vary from 2.316 to 0.081 which are about 30 to 3 times higher than from its normal ranges. So no conclusion could be drawn for the predictors in case of the Mohananda river. But Einstein and Barbarossa (1952) and Shen (1962) methods seem to predict resonable roughness coefficients for the full range of discharges and Haque and Mahmood (1983) method seems to predict resonable results for moderate to high discharges of the Mohananda river. The Manning's n for the Gumti and the Kushiyara rivers is ma.ximum when the discharge is low and decreases with increasing discharge. For the river Gumti detail analyses indicate the presence of bed forms in all discharges, i.e. throughout the year. For the river Kushiyara; bed forms are only present in the range of low to medium discharges but at high discharges the river bed becomes plane. The response of grain roughness to the change in discharge is relatively less than that for form roughness. The variation of grain roughness is responsive to that of the total roughness but the variation of form roughness is similar to the total roughness. The Manning's n for the river Gumti is maximum during the month of March when discharge is low; and attains minimum value during the months of May to October when high flow takes place. The Manning's n for the river Kushiyara is maximum during the month of February when the discharge is low and minimum during the month of July to September when the discharge is high. The Mohananda river attains the maximum discharge in the month of September and the minimum discharges in the months of December to May.
Effects of scrap addition on the physico-chemical properties of rigid polyvinyl chloride products
(Department of Materials and Metallurgical Engineering (MME), 2014-01) Jalal Uddin, Md.; Kurny, Dr. ASW
Raw material powder mixtures have been prepared with polyvinylchloride (PVC) resin, unplasticized polyvinylchloride (uPVC) scraps and additives by melt mixing method. A twin screw extruder has been used to make pipe for sample preparation from the mixture. Domestic and external uPVC scraps were formulated and blended with PVC resin to form melt compound. Domestic samples designated as DS-10, DS-20, DS-30, DS-40, DS-50 and DS-100 have been prepared by blending 10, 20, 30, 40, and 50phr and 100% uPVC domestic scrap with PVC resin and various additives followed by extrusion, flattening and machining. Following the similar procedure, external samples such as ES-10, ES-20, ES-30, ES-40, ES-50 and ES-100 have been prepared using external uPVC scraps. Effects of the proportions of uPVC scraps in the raw material mix on the properties of the recycled uPVC products have been investigated. The specific properties under studies include the (i) physical (ii) mechanical properties, (iii) chemical (iv) thermal properties, (v) surface morphology and (vi) structural properties of the recycled uPVC products. All the samples prepared have successfully satisfied the requirements of acetone test. Density of samples containing domestic scraps shows the minimum value of 0.64% for DS-50 and the maximum value of 1.91% for DS-20. On the other hand, in samples containing 10 and 40 phr external scraps the density increases by 0.64% while in sample containing 30 phr external scraps the density decreases by 4.46%. Mechanical properties, such as break stress and % elongation-at-break, impact strength, flexural strength and harness values vary with proportions of scraps in the samples. The maximum decrease in break stress is 11.40% for 20 phr domestic scraps, while in samples containing external scraps this decrease is 15.71% for 40 phr scraps. The decrease in break stress for sample containing 100% external scraps is 38.95%. The minimum decrease (9.48%) in viscosity number is found in sample containing 30 phr domestic scraps, while in sample containing external scraps the maximum decrease is 42.24% in sample containing 30 phr scraps. Fourier transform infrared (FTIR) spectroscopic investigation has been followed to detect new functional groups with the addition of different proportions of domestic and external scraps. Only a variation in IR light intensity has been observed. X-ray fluorescence investigation shows a decrease in the percentage of carbon revealing the maximum decrease of 15.53% in sample containing 50 phr domestic scraps. The amount of lead added to samples as a stabilizer from lead sulphate, increases with the amount of scraps in the sample. The maximum increase is 18.52% in sample containing 40 phr domestic scraps and 37.04% in sample containing 40 phr external scraps. Scanning electron microscopy together with energy dispersive spectroscopy (EDS) and x-ray diffraction (XRD) analysis show the same phases in all samples. However, variation in shape and distribution of the phases and interfaces has been observed in different samples. EDS spot analysis shows a variation in elemental composition. XRD analysis shows an amorphous polymer and crystalline calcium carbonate (CaCO3) phases. The relative intensities of the different peaks were different and these results can be attributed to the presence of different amount of CaCO3 in the different samples. Results of thermogravimetric analysis(TGA) and EDS are in good agreement with the observation suggesting that no new phases are formed due to the addition of different proportions of scraps. Differential scanning caloriemetry indicates two glass transition temperatures indicating a immiscibility of two components. In different samples, differences in thermal expansion or contraction have been detected by thermo-mechanical analysis (TMA). The observed values by TMA have been attributed to the difference in coefficient of thermal expansion of the different phases. TGA thermograms show that degradation temperature (around 300oC) is much higher than the processing temperatures used (around 200oC). Thermal analysis results have shown that the residue content left at 1000oC is in general higher in the samples containing external scraps. Vicat softening temperature values show that the resistance to heat increases with an increase in the amount of scraps in the samples, wherein the effect of external scraps is more pronounced. This has been attributed to the increased amount of CaCO3 in the sample containing external scraps.
Modified fast fourier transform technique in power system transient analysis
(Department of Electrical and Electronic Engineering (EEE), 1986-07) Jalal Uddin, Md.; Mujibur Rahman, Dr. Md.
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Study of pressure drop characteristics and heat transfer performance in an internally finned tube
(Department of Mechanical Engineering, 1998-08) Jalal Uddin, Md.; Aziz-ul Huq, Dr. A. M.
Heat exchangers have numerous applications in power plants, industries, automobiles and electrical and electronic equipmemts. In the present work steady state turbulent flow heat transfer performance of circular tube having integral internal longitudinal fins was experimentally studied. This report describes new experimental data for turbulent fluid flow and heat transfer in a tube having internal fins. An experimental set up was designed and installed to study the heat transfer performance and pressure drop characteristics in the entrance region as well as in the fully developed region of the finned tube. The tube and fin assembly was cast from brass to avoid contact resistance. Air was used as the working fluid. The Reynolds number based on inside diameter ranged from 1.86 x 104 to 3.97 X 104 . The heat transfer test section was heated electrically by wrapping nichrome wire providing an ... uniform heat flux around the tube periphery over the entire length of the test section. Results exhibited high pressure gradient and high heat transfer coefficients in the entrance region, approaching the fully developed values away from the entrance section. Nusselt numbers of the finned tube were compared with those for an unfinned tube for both constant Reynolds number and constant pumping power. The enhancement of heat transfer rate due to integral fins was found to be very significant over the entire range of the flow rates studied in this experiment. Heat transfer coefficient based on inside diameter and nominal area of finned tube exceeded unfinned tube values by as much as 76.69%. The results of this study indicate that significant enhancement of heat transfer is possible by using internal fins with sacrificing less additional pumping power. These experimental results are expected to be very useful for the design of pipe-lines and heat exchanger tubes.
Study of variables of anodizing
(Department of Materials and Metallurgical Engineering, BUET, 1994-12) Jalal Uddin, Md.; Kurny, Dr. A. S. W.
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