Drag Reduction Characteristics Using Aloe Vera Natural Mucilage: An Experimental Study

Drag Reduction Characteristics Using Aloe Vera Natural Mucilage: An Experimental Study

Hayder A. Abdul BariKumaran Letchmanan and Rosli Mohd. Yunus

Abstract
In the present study, a new natural and environmentally friendly drag reducing agent is introduced as a flow improver in pipelines carrying liquids in turbulent flow mode. The new drag reducing agent is extracted from the Aloe Vera leaves. The extracted mucilage drag reduction performance was tested using a closed loop liquid circulation system. The experimental work was carried out in 0.0254 m I.D. pipe with 100 to 400 ppm addition concentrations, four testing sections lengths and five different flow rates. It was found that the Aloe Vera mucilage was an effective drag reducing agent. A maximum drag reduction percentage of 63% could be achieved by adding 400 ppm of mucilage to the main flow. Drag reduction was found to increase with increasing Reynolds Numbers, additive concentrations and pipe lengths. Finally, a new correlation equation representing the experimental data is introduced.

INTRODUCTION

Liquids, especially crude oils, refinery products and raw water, are always transported under turbulent conditions in strategic pipelines. Massive amounts of pumping power are lost during transportation due to the power dissipation, which is caused by the turbulent structures that are formed in the flow media. Due to the velocity difference between the laminar sub layer and the core of the turbulent flow system, eddies are formed. Their shapes result from energy absorptions from the main flow. Such energy absorptions lead to losses in the pumping power that can be sensed as pressure drops across the piping system.

A solution to pumping power losses during transportation through pipelines is the addition of certain soluble chemicals to the main flow. These chemicals, which have viscoelastic properties, interfere with turbulent structures and eventually suppress eddies. More specifically, they prevent eddies from absorbing more energy from the main flow to reach their final shapes.

The drag reduction phenomenon is a combination of effects of various factors that happen at a same time and at a given position. Examples of such factors include pipe geometry, transported liquid properties and the degree of turbulence inside the pipe. It is known that none of the above-mentioned factors act individually but that many variables and factors may interact at a given moment to develop certain turbulent flow structures inside the pipe. The mission of the additive is to overcome the effect of turbulent flow structures and stop pumping power dissipation.

Toms (1949) was the first to report the drag reduction phenomenon and observed that the addition of few parts per million of long-chain polymers in a turbulent flow produces a dramatic reduction of the friction drag. This phenomenon has been the subject of extensive reviews by Mowla and Nadari (2006)Ling and Hassan (2006)Li et al. (2007)Wan et al. (2008)Safri and Bouhadef (2008)Riccoa and Quadrio (2008)Bari and Yunus (2009) Kamela and Shah (2009)Al-Sarkhi (2010) and many others.

Drag Reducing Agents (DRAs) can be classified into three major categories: polymers, surfactants and suspended solids (fibres). In general, polymers are most effective from the industrial point of view and the most usable in the industrial applications. It is known that, polymers are divided into two categories: synthetic polymers and natural polymers. Synthetic polymers are derived from petroleum oil, while natural polymers can be extracted from resources in nature. Although synthetic polymers possess good mechanical propertiesand thermal stability when used as flow improvers in pipelines, these materials biodegrade very slowly, which is an environmental concern. Moreover, for similar molecular weights, synthetic polymers are more expensive than natural polymers. On the other hand, natural polymers are biodegradable and easily obtained. Indeed, these materials are produced in the form of polysaccharides by microorganisms and plants.

Aloe Vera is an example of plant that contains a high amount of natural polymers. It is often assumed that Aloe Vera belongs to the cactus family because of the rosette-like arrangement of the long spiked leaves on the central stem. In fact, Aloe Vera is a perennial plant from the lily family (Liliaceae), not the cactus family. There are over 300 species of Aloe known and Aloe Vera L. is known as the true Aloe Vera and is famous for its various applications and purported healing virtues. Aloe Vera gel is the commercial name given to the fibre-free, mucilaginous exudates that are extracted from the hydroparenchyma of the succulent leaves of Aloe Vera. The viscous, pseudo plastic nature of Aloe Vera gel is mainly due to the presence of polysaccharides. These polysaccharides are a mixture of acetylated glucomannans that are lost shortly after extraction, apparently due to enzymatic degradation.

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