Computational and Experimental Investigation of Heat Transfer Within a Column Photobioreactor

Abstract

The goal of this research is to investigate heat transfer effects of two phase gas-liquid flows in a column photobioreactor (PBR) experimentally as well as computationally using Computational Fluid Dynamics (CFD). The authors have completed a preliminary study on bubble formation, rise and resulting circulation patterns using lab-scale experiments and CFD simulations. This study extends on this previous work by investigating the relationships of bubble drag coefficient and bubble Reynolds number with superficial gas velocity and a study of heat transfer within the PBR. It is hypothesized that a greater understanding the bubble movement patterns will aid in predicting heat transfer rates within the PBR. Dispersed gas–liquid flow in the rectangular column PBR are modeled using the Eulerian–Lagrangian approach. The heat transfer process has been considered for the case of a steady state three dimensional PBR. A low Reynolds number k–epsilon CFD model is used for the description of flow pattern near the wall. The velocity profiles and eddy diffusivity obtained by the model are utilized to predict heat transfer coefficients for different superficial gas velocities. The information on heat transfer effects between cooling or heating surfaces and a gas-liquid dispersed bed is essential for designing a PBR. Carbon dioxide, which is necessary for photosynthetic microalgae growth, is added to the system. Bubble size distribution measurements are carried out using a high-speed digital camera. The main interaction forces, i.e. the drag force, the added mass force, and lift force are considered. Heat transfer and internal hydrodynamics of a column reactor are studied and the numerical simulations results are presented for heat transfer and hydrodynamics in column PBRs. The results are validated with experimental data and with data from current literature.