  The established microalgae growth models are semi-empirical or considerable
fitting coefficients exist currently. Therefore, the ability of the model
prediction is reduced by the numerous fitting coefficients. Furthermore, the
predicted results of the established models are dependent on the size of the
photobioreactor (PBR), light intensity, flow and concentration field. The
growth mechanism of microalgae has not clearly understood in PBR cultivation.
It is difficult to predict the microalgae growth by theoretical methods, owing
to the aforementioned factors. We developed an exploratory bridging microalgae
growth model to predict the microalgae growth rate in PBRs by using the
nondimensional method which is effectively in fluid dynamics and heat transfer.
The analytical solution of the growth rate was obtained for the parallel flow.
The nondimensional growth rate expressed as function of Reynolds number and
Schmidt number, which can be used for arbitrary parallel flow due to the
solution was expressed as nondimensional quantities. The theoretically
predicted growth rate is compared with the experimentally measured microalgae
growth rate on the order of magnitude. The nondimensional method successfully
applied to the microalgae growth problem for the first time. The general
nondimensional solution can unify the numerous experimental data for different
laboratory conditions, and give a direction for the disorder of the microalgae
growth problem. The nondimensional solution may be useful to explain the growth
mechanism of microalgae and design large-scale PBRs for microalgae biofuel
production. The significance of the work is to give a theoretical foundation
and methodology of biological theory of microalgae growth.
