The study on the effect of hydrodynamic flow on the photocatalytic performance of photocatalytic reactors

The scalability of photocatalytic reactor is the major challenge due to the inability of the light penetration when the laboratory scale reactors are ascended. It is well known that the characteristic length of photocatalytic reactor is one of the influential parameters determining the efficiency of light penetration and also affects the hydrodynamic fluid flow behaviour inside the reactor. This study visualizes hydrodynamic flow behaviour of three differently configured photocatalytic reactors through numerical simulation of the fluid mass transport inside the reactors. The three photocatalytic reactors are (1) concentric cylindrical glass tube micro-reactor (CGTR), (2) UV-LED strip photocatalytic reactor (STR) and (3) classical annular reactor (CAR) from our previous work. The simulations of flow behaviour confirmed that CGTR exhibited plug flow regime, STR exhibited arbitrary flow (in-between continuously stirred tank reactor and plug flow reactor) and CAR behaved like continuously stirred tank reactor. Also, interpretations of numerical modelling were validated through plotting experimental residence time distribution curve. Furthermore, the comparison of performance parameters revealed that the highest modified space time yield (STY_modified) 225 s^-1and highest modified photocatalytic space time yield (PSTY_modified) 9.375 s^-1/kW/m³ was obtained for plug flow reactor when compared to continuously stirred tank reactor (CAR) and arbitrary flow reactor (STR). The study confirms that decrease in characteristic length of photocatalytic reactor onsets plug flow regime, which has highest photocatalytic performance efficiency.