Comparative Analysis of Hydrodynamics Behavior of Microalgae Suspension Flow in Circular, Square and Hexagonal Shape Photo Bioreactors

Mushfique Shahriar,Ujjwal Kumar Deb,Mohammad Iftekhar Monir

doi:10.4236/ajcm.2016.64033

Abstract

Microalgae based biofuel is an emerging natural source of energy alternative to the fossil fuel. As microalgae are photosynthetic microorganisms, light is one of the limiting factors for its culture. Though many researches have been carried out for findings behind suitable culture system for the proper growth of microalgae, those are confined only to tubular Photo-bioreactor (PBR). This paper aims to make comparison among the horizontal loop photo bioreactors with different cross sections based on the analysis of hydrodynamics behavior. Three different geometrical shapes having vertical cross sections of circular, square and hexagonal PBR, have been proposed taking into account light intensity for microalgae culture. In this study, we simulate the flow dynamics of three types of PBRs and discuss the velocity, pressure and shear stress properties as microalgae endurance capacity depends on them. For the dimension of the three PBRs we considered here, each of them have radius of about 0.05 m while the length together with bending portion is approximately 20.5 m for a single loop. From the study, the hydrodynamic behaviors are observed to be quite dissimilar in case of three PBR’s. In the straight portion the velocity profile is quite parabolic in tubular but distorted minimally in case of square and hexagonal PBRs. In the middle of the U-loop, a haphazard fluid distribution is noticed. The velocity magnitude and agitation of microalgae cells are higher in hexagonal than in square and tubular. The shear rate is less in case of tubular compared to square and hexagonal. A linear pressure drop is found from the inlet to the outlet for three PBR’s. From this comparison, it can be said that the tubular one would be the best option for microalgae culture in case of industrial purposes.

Highlights

Sustainable development and efficient use of energy goes on hand which results in environment pollution minimisation and better socio-economic conditions
For achieving better and comparative results, we ran the simulation for the seventh day of microalgae culture as microalgae growth can clearly be observed from this day
In the U-loop portion, higher velocity exists than any other parts but always the speed is less and moderate in tubular PBR than others

Summary

Introduction

Sustainable development and efficient use of energy goes on hand which results in environment pollution minimisation and better socio-economic conditions. Increasing consumption of petro-fuel with rapid growth of transportation and population compared to total deposited amount is leading it on the verge of gradual extinction as it is a depleted source of energy [1] [2]. In this context, oil extracted from organic matter (biofuel) has attracted the scientist and researchers as it is eco-friendly and sustainable. The developed countries of the world have emphasized and investing money to increase the productivity level of biofuel. It can be foreseen to be the fuel of future [3] [4] [5]

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