TRANSIENT ANALYSIS AND PERFORMANCE STUDIES OF 2 TUBULAR PHOTOBIOREACTORS FOR OUTDOOR CULTURE OF SPIRULINA

A mathematical model to make a transient thermal analysis and to estim ate the incident solar energy for two designs of tubular photobioreact or installed outdoors is presented here. In the first photobioreactor design the tubes were arranged in one plane, whereas in the second the tubes were arranged in two planes. The model was validated by compari ng the experimental data and predicted values of culture temperature. Both the input solar energy and culture temperature in a tubular photo bioreactor may be predicted with a reasonable degree of accuracy by em ploying the model. The performance of the two photobioreactors for mas s culture of Spirulina was also studied in relation to their design an d culture temperature. The average biomass yield obtained in one-plane and two-plane photobioreactors were (dry weight) 23.7 g m(-2) day(-1) and 27.8 g m(-2) day(-1) respectively. Such biomass yields correspond ed to a volumetric productivity of (dry weight) 0.466 g litre(-1) day( -1) in the one-plane reactor and 1.5 g litre(-1) day(-1) in the two-pl ane reactor. We further observed that biomass yield could be increased by about 21% when the culture temperature was maintained at the optim al value of 35 degrees C compared to another culture in which temperat ure changed according to the ambient temperature from 20 to 39 degrees C during the day.