Nurudeen Yusuf - Academia.edu (original) (raw)

Papers by Nurudeen Yusuf

Abstract: Biodiesel is gaining more and more importance as an alternative fuel due to the depleti... more Abstract: Biodiesel is gaining more and more importance as an alternative fuel due to the depleting fossil fuel resources. Chemically biodiesel is monoalkyl esters of long chain fatty acids derived from renewable feedstock like vegetable oils and animal fats. It is produced by transesterification in which oil or fat is reacted with a monohydric alcohol in the presence of a catalyst. In this research, biodiesel was produced from groundnut oil under varying operating conditions (considering only temperature, catalyst concentration and reaction time being more prominent factors affecting the reaction). The optimum temperature, catalyst concentration and reaction time were found to be 70o C, 1% (wt of oil) and 1 hr respectively. Also propertiesthere should be comma in between viscosity, specific gravity and flash point of the biodiesel produced were investigated and the results obtained shows agreement with international standards. Part II of this paper will discuss the kinetics of the reaction.

In this study, a HMW anionic co-polymer of 40:60 wt/wt NaAMPS/acrylamide was used as a drag reduc... more In this study, a HMW anionic co-polymer of 40:60 wt/wt NaAMPS/acrylamide was used as a drag reduc- ing polymer (DRP) for oil–water flow in a horizontal 25.4 mm ID acrylic pipe. The effect of polymer con- centration in the master solution and after injection in the main water stream, oil and water velocities, and pipe length on drag reduction (DR) was investigated. The injected polymer had a noticeable effect on flow patterns and their transitions. Stratified and dual continuous flows extended to higher superficial oil velocities while annular flow changed to dual continuous flow. The results showed that as low as 2 ppm polymer concentration was sufficient to create a significant drag reduction across the pipe. DR was found to increase with polymer concentration increased and reached maximum plateau value at around 10 ppm. The results showed that the drag reduction effect tends to increase as superficial water velocity increased and eventually reached a plateau at Usw of around 1.3 m/s. At Usw > 1.0 m/s, the drag reduction decreased as Uso increased while at lower water velocities, drag reduction is fluctuating with respect to Uso. A maximum DR of about 60% was achieved at Uso = 0.14 m/s while only 45% was obtained at Uso = 0.52 m/s. The effectiveness of the DRP was found to be independent of the polymer concentration in the master solution and to some extent pipe length. The friction factor correlation proposed by Al-Sarkhi et al. (2011) for horizontal flow of oil–water using DRPs was found to underpredict the present experimental pressure gradient data.

In this paper, experiments were conducted to understand the influence of a small change of pipe d... more In this paper, experiments were conducted to understand the influence of a small change of pipe diam- eter in the effectiveness of drag reducing polymer (DRP) in horizontal oil–water flow. Two pipe diameters were used in this study; 19 and 25.4 mm pipes. The results showed a remarkable influence of pipe diam- eter on the polymer efficiency in modifying flow patterns and drag reduction. The results from both pipes showed that only 10 ppm polymer concentration is needed to achieve the maximum drag reduction for each investigated condition. The presence of DRP extended the region of stratified and dual continuous flows. However, the percentage increase in the stratified region is more significant in the 25.4-mm pipe while the extent of the dual continuous pattern in the 19-mm pipe is larger than that in the 25.4-mm pipe. Regardless of the pipe diameter, annular flow changed for all the investigated conditions to dual continuous flow. The dispersed region (water continuous or oil continuous) decreased after introducing DRP but the decrease is larger for the 19-mm pipe especially for dispersion of oil in water. The results for both pipes revealed that the maximum drag reduction is achieved when the flow is dispersed oil in water; however, higher drag reduction was obtained in the larger pipe diameter. Drag reductions up to 60% were observed in the 25.4-mm pipe in comparison with up to 45% achieved in the 19-mm pipe.

The effect of oil and water velocities, pipe diameter and oil viscosity on the transition from st... more The effect of oil and water velocities, pipe diameter and oil viscosity on the transition from stratified to non-stratified patterns was studied experimentally in horizontal oil–water flow. The investigations were carried out in a horizontal acrylic test section with 25.4 and 19 mm ID with water and two oil viscosities (6.4 and 12 cP) as test fluids. A high-speed video camera was used to study the flow structures and the transition. At certain oil velocity, stratified flow was found to transform into bubbly and dual continuous flows as superficial water velocity increased for both pipe diameters using the 12 cP oil viscosity. The transition to bubbly flow was found to disappear when the 6.4 cP oil viscosity was used in the 25.4 mm pipe. This was due to the low Eo}tvo}s number. Transition to dual continuous flow occurred at lower water velocity for oil velocity up 0.21 m/s when 6.4 cP oil was used in the 25.4 mm ID pipe, while for Uso > 0.21 m/s, the transition appeared at lower water velocity with the 12 cP oil.
The effect of pipe diameter was also found to influence the transition between stratified and non-strat- ified flows. At certain superficial oil velocity, the water velocity required to form bubbly flow increased as the pipe diameter increased while the water velocity required for drop formation decreased as the pipe diameter increased. The maximum wave amplitude was found to grow exponentially with respect to the mixture velocity. The experimental maximum amplitudes at the transition to non-stratified flow agreed reasonably well with the critical amplitude model. Finally, it was found that none of the available models were able to predict the present experimental data at the transition from stratified to non-stratified flow.

The flow patterns and pressure gradient of immiscible liquids are still subject of immense resear... more The flow patterns and pressure gradient of immiscible liquids are still subject of immense research interest. This is partly because fluids with different properties exhibit different flow behaviours in different pipe’s configurations under different operating conditions. In this study, a combination of oil–water properties (􏰂 = 20.1 mN/m) not previ- ously reported was used in a 25.4 mm acrylic pipe. Experimental data of flow patterns, pressure gradient and phase inversion in horizontal oil–water flow are presented and analyzed together with comprehensive comments. The effect of oil viscosity on flow structure was assessed by comparing the present work data with those of Angeli and Hewitt (2000) and Raj et al. (2005). The comparison revealed several important findings. For example, the water veloc- ity required to initiate the transition to non-stratified flow at low oil velocities increased as the oil viscosity increased while it decreased at higher oil velocities. The formation of bubbly and annular flows and the extent of dual contin- uous region were found to increase as the oil–water viscosity ratio increased. Dispersed oil in water appeared earlier when oil viscosity decreased.
The effect of oil viscosity on pressure gradient was also investigated by comparing the results with Angeli and Hewitt (1998) and Chakrabarti et al. (2005). One of the main findings is the large difference between the pressure gradient results which is attributed to the difference in oil viscosity. The differences between the results become bigger at higher oil velocities. The largest difference in pressure values was observed in flow region where oil is the continuous phase. On the contrary, for dispersed oil in water (Do/w), the pressure gradient values observed at the same conditions are approximately the same. A simple correlation was developed to predict the pressure gradient in this regime. The correlation was validated using new experimental data.
Finally, the effect of oil viscosity on pressure gradient prediction was investigated using the two flow model for stratified flow and the homogenous model for oil dispersed in water. Both models showed better prediction for the low oil viscosities.