In a tubular photobioreactor, microalgae cells obscure one another (Self-shading), leading to the microalgae at the bottom of the tube getting less light. The objective of this research was to design and develop Tubular Photobioreactor with 93.5 liters for microalgae cultivation. The experiments had two steps. The first step was designing the solar receiver by inserting the fin into each tube wall as follows: 12-34, 1-2-3-4, 1234, and 13-24. Then, FLUENT software was used to simulate flow behavior inside the tube by Computational Fluid Dynamics by observing the pressure drop, the amount of energy consumption, and the swirling velocity to select the best fin-type. The best fin-type with the growth rate equation is introduced in the next step to simulate the microalgae's growth and movement using the user-defined function technique. The comparison of a tubular photobioreactor is investigated between fin and without fin by observing biomass production. The results showed that algae's optimum inlet velocity is 0.15 meters per second with the tubes containing fin-type 13-24. When simulating the growth behavior of microalgae, results show that the tubes without fins had lower biomass content than the 13-24 fin-type, which were 0.675 and 0.806 grams per liter, respectively, because the 13-24 fin-type will make well microalgae distribution leading to increase the light distribution too. Tubular photobioreactor fins type 13-24 had more biomass production, up to 19.4 percent.

A tubular photobioreactor is one of the most effective methods of microalgae cultivation because of the high solar receiver area and better biomass productivity. However, the pressure drop along the tubular solar receiver induces a relatively high dead zone. An optimal design is necessary to maximize biomass productivity. In this article, the proposed model can reduce the dead zone by up to 15% under a pressure drop of 106 Pa. To optimize the area requirement, three configurations with different stacking angles of 30, 45, and 60°, are simulated. The optimal 60° stacked-layer model is then connected to an airlift device to demonstrate the complete system. This model can circulate seawater inside the reactor at an average velocity of 0.188 m/s with 0.07 m/s of air inlet velocity. The radial flow can force the microalgae from the inner part of the tube to the outer part and back again throughout the entire stacked section. This turbulence will enhance biomass productivity because the microalgae are moved from the darker interior of the tube to the periphery where they are exposed to solar radiation. The optimal stacked-layer tubular photobioreactor has a slope of 60° with four stacked layers. This modification promotes the circulation of microalgae in both axial and radial directions.

The flow behavior of liquid-solid particles in mixing tanks using a modified Rushton impeller, called a Rushton V-cut impeller, was studied. Both the Rushton and Rushton V-cut impellers were compared at a 300 rpm stirring speed and a 10 % wt solid concentration. Hydrodynamic behaviors, such as solid volume fraction, velocity, pressure, and shear stress, in both the Rushton and Rushton V-cut impellers were investigated. Computational fluid dynamics (CFD) software able to understanding of hydrodynamics of stirring liquids which contain solid particles. CFD programme was to predict the mixing flow of the highly viscous system. Therefore, the present work was carried out using CFD software with the Eulerian-Eulerian approach with a turbulent k-ε model. The simulation of mixing tanks was consisted of moving and stationary zones by using moving references frame method or MFR. The results were observed that Rushton V-cut can dramatically reduce pressure up to 20% and the shear stress up to 64.38% while keeping the liquid-solid mixing at a considerable degree. Therefore, this design can reduce the power consumption.