Photon Absorption in Modified Taylor-Couette Flow: Theory and Experiment

The modified Taylor-Couette device operating at large rotation rates and with UV absorption through the transparent stator has the characteristics of a continuous stirred tank reactor or CSTR. In particular, the modifications include holes in the rotor that produce cavitation at large rotation rates. Experiments with the UV-induced oxidation of iodide I- to triiodate I3- agree well with the trends predicted by a CSTR. For the maximum rotor frequency covered, there were no effects of cavitation alone on the latter chemistry in the absence of UV. Moreover, greater than a two log reduction or 99.4% was observed for active E. coli in water. The inactivation levels of E. coli were reduced to ~50% with the addition of a water-soluble dye due to photon absorption. The modified Taylor-Couette device in the present study should be particularly useful for applications that require both mass transfer in two-phase flow containing either bubbles or droplets and the simultaneous application of UV. The large shear provided by the cavitating flow at large rotation rates would reduce the bubble or drop size, thus significantly increasing the rate of mass transfer.