A. Rashid Hasan
University of North Dakota
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Featured researches published by A. Rashid Hasan.
Spe Production Engineering | 1988
A. Rashid Hasan; C. Shah Kabir
This paper presents a physical mode for predicting flow pattern, void fraction, and pressure drop during multiphase flow in vertical wells. The hydrodynamic conditions giving rise to various flow patterns are first analyzed. The method for predicting void fraction and pressure drop is then developed. In the development of the equations for pressure gradient, the contribution of the static head, frictional loss, and kinetic energy loss are examined. Laboratory data from various sources show excellent agreement with the model.
Spe Production Engineering | 1988
A. Rashid Hasan; C. Shah Kabir
In deviated wells of an offshore producing environment, flow of two- or three - phase mixtures are invariably encountered. While large number of investigators have studied vertical multiphase flow behavior, there are few studies, often entirely empirical, that deal with deviated well systems. The main objective of this work is to present a model that predicts both flow regime and pressure gradient in a deviated wellbore. In modeling flow pattern transition and void fraction, an approach similar to that for vertical flow is taken; that is, four principal flow regimes are recognized - bubbly, slug, churn and annular.
Spe Production Engineering | 1988
A. Rashid Hasan; C. Shah Kabir; Rehana Rahman
This work proposes a hydrodynamic model for estimating gas void fraction, f/sub g/, in the bubbly and slug flow regimes. The model is developed from experimental work, involving an air/water system, and from theoretical arguments. The proposed model suggests that prediction of f/sub g/, and hence the bottomhole pressure (BHP), is dependent on such variables as tubing-to-casing-diameter ratio, densities of gas and liquid, and surface tension. Available correlations do not include these variables as flexible inputs for a given system. Computation on a field example indicates that slug flow is the most dominant flow mechanism near the top of liquid column at the earliest times of a buildup test. As buildup progresses, transition from slug to bubbly flow occurs in the entire liquid column. Beyond the afterflow-dominated period, the effect of bubbly flow diminishes as gas flow becomes negligibly small. Comparisons of BHPs are made with the proposed and available correlations. Because the proposed model predicts f/sub g/ between these of the Godbey-Dimon and Podio et al. correlations, BHP is predicted accordingly.
Spe Production Engineering | 1990
A. Rashid Hasan; C. Shah Kabir
This work presents the results of an experimental and theoretical investigation of two-phase oil/water flow behavior in vertical pipes. Bubbly flow is observed to be the predominant flow pattern, although at high flow rates, slug flow as noted. The proposed method, developed from the drift-flux principle, is validated by experimental data and those obtained from other sources. Limited study indicates the proposed methods superiority over others available in the literature. This work further shows the error involved when oil/water flow behavior is predicted by homogeneous, gas/liquid, and constant-slip models. Application of the model for production log interpretation is also documented.
Chemical Engineering Communications | 1988
A. Rashid Hasan
This paper presents a flow pattern approach to estimating void fraction during vertical upward recurrent two-phase flow recognizing the four major flow regimes—bubbly, slug, churn and annular. Expressions for void fraction in bubbly, slug and churn flow regimes are derived from the relationship between the phase velocities. Recirculation effect in large diameter pipes during bubbly flow and modifications to account for this effect are established. The differences in the predictive procedure for bubbly-slug flow transition between large and small diameter pipes are pointed out. The similarities between slug and churn flow and the modifications needed for void fraction prediction during churn flow are demonstrated. The predictions of the proposed model for flow pattern transition and void fraction are compared with experimental data gathered for this work as well as from independent sources. Good agreement between the data and the predictions of the model is noted.
Fuel | 1993
S.Farid Ahmed; A. Rashid Hasan
Abstract Combustibility of coal-water fuel (CWF) slurries in pressurized systems is influenced by the apparent viscosity of the slurry at shear rates range of 10 4 –10 5 s −1 that are estimated to arise during atomization. Fuel slurries of beneficiated low rank coals and a bituminous coal were tested with a Haake rotational viscometer and a capillary extrusion rheometer at shear rates up to 10 5 s −1 . Real time acquisition of flow rate and pressure data and use of a Coriolis-type mass flow meter contributed to accurate determination of power law flow parameters. Coefficient of variation of the flow behaviour index was less than 0.2% in all cases. Most low-rank-fuel slurries displayed some degree of increased pseudoplasticity with increasing shear rate, especially for slurries of lower average particle size. Fuel slurries of micronized Taggart bituminous coal exhibited increased dilatancy as the rate of shear increased. This difference in flow behaviour at shear rates over 10 4 s −1 helps to explain the reported higher combustion efficiency of beneficiated low-rank CWFs as compared to bituminous CWF.
Chemical Engineering Communications | 1991
A. Rashid Hasan
Abstract This paper discusses the simultaneous prediction of mass flux and steam quality from two measurements, critical flow lip pressure and pressure drop across an orifice. The James equation for predicting mass flux during two-phase critical flow of steam and water in geothermal wells from lip pressure and stagnation enthalpy data is used. For two-phase flow across an orifice, the separated flow model proposed by Chisholm is used, with modification to account for the upstream fluid momentum. These predictions are compared with the data gathered by James and with the predictions of the James orifice correlation. The study indicates that for low qualities (quality < 40%), the modified separated flow model is as good as the James correlation in predicting the James data. However, the prediction accuracy of both the approaches are unacceptably low at higher steam quality. A sensitivity analysis is done which indicates that the inaccuracy in prediction arises from the coupled nature of the critical flow eq...
Energy Sources | 1987
A. Rashid Hasan; Dorab N. Baria
Abstract The flow of lignite-water slurry through a 2-in. pipe was investigated over a wide range of flow rates and solid concentrations. The pressure drop data gathered were compared with various correlations. In general, the simpler correlations were found to be less accurate than the more elaborate models. The Gasseler model was found to fit our data best, with the optimum value of the parameter β∗ = 0.243. The widely used Durand correlation as well as the Newitt model also performed satisfactorily without parameter adjustments. The three venturimeters used in the flow loop proved the suitability of such an inexpensive instrument for metering slurry flow. The discharge coefficient for slurry was found to be very similar to that for single-phase flow, although a slight dependency of the discharge coefficient on the solid concentration was observed.
Chemical Engineering Communications | 1984
A. Rashid Hasan; E. Rhodes
A horizontal boiling water loop was used to obtain pressure drop and heat transfer data for two-phase steam-water flow for pressures of up to 825 kPa. The data were used to examine the predictions of the separated flow model using the Lockhart-Martinelli method of estimating the two-phase friction multiplier. The influence of mass flux on the two-phase friction multiplier has been reported for high pressure systems by many workers. The present work confirms the existence of this influence at low pressures as well. System pressure is also found to be a parameter. A correlation for the two-phase friction multiplier, incorporating the effects of mass flux and pressure, is presented here. The correlation has been tested against data from two independent sources. The predictions have been found to be in very good agreement with the data.
Journal of Petroleum Technology | 1983
A. Rashid Hasan; C. Shahjahan Kabir