Title
Experimental Studies of Vertical Mixing in an Open Channel Raceway for Algae Biofuel Production
Date of Award:
8-2012
Document Type:
Thesis
Degree Name:
Master of Science (MS)
Department:
Mechanical and Aerospace Engineering
Committee Chair(s)
Byard D. Wood
Committee
Byard D. Wood
Committee
Clair J. Batty
Committee
Leijun Li
Committee
Barton L. Smith
Abstract
Turbulent mixing plays an important role in the distribution of sunlight, carbon dioxide, and nutrients for algae in the raceway ponds. For large-scale raceway ponds the choice of mixing technology still needs to be evaluated in order to prevent algae sedimentation and to enhance light utilization efficiency. In open ponds, mixing the algae culture is of great significance in terms of input energy costs and particularly productivity. A very small amount of research has been performed previously using different vortex generators in the algal raceway ponds, but the quantification of mixing depth relationships is not defined well. By accepting the premise from the literature review that mixing increases algal production, delta wings were selected to study mixing characteristics in the raceway. The main objective of this research was to study algae-raceway hydrodynamics with an emphasis on increasing vertical mixing. A clear acrylic raceway was designed and constructed for flow visualization studies. Experimental investigations were performed to quantify the vertical mixing with and without delta wings in a lab-scale raceway at approximately the same power input to the paddle wheel. Velocity vector profiles and turbulence parameters were measured using an Acoustic Doppler Velocimeter (ADV) at various locations along the entire length of the raceway. The results indicated that the addition of delta wings increases the vertical mixing intensity or circulation of algae cells over the raceway depth. Vortices were observed in the raceway up to a distance of around 3 m downstream of the delta wing. This sort of systematic vertical mixing plays an important role to produce the flashing light effect (light-dark cycles) on algae mass culture. In addition, turbulence dissipation rates were evaluated to compare them with the published literature and to estimate the microscales using the Kolmogorov hypothesis. Also, an energy model was developed to operate the paddlewheel-driven raceway with the delta wing.
Checksum
7c053a14eb9def43c7f79fbc8986e0eb
Recommended Citation
Voleti, Ram Sudheer, "Experimental Studies of Vertical Mixing in an Open Channel Raceway for Algae Biofuel Production" (2012). All Graduate Theses and Dissertations. 1307.
https://digitalcommons.usu.edu/etd/1307
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Comments
This work made publicly available electronically on July 29, 2012.