(102a) Residence Time Distribution Studies in Microchannels with Staggered Herringbone Structures
AIChE Spring Meeting and Global Congress on Process Safety
2008
2008 Spring Meeting & 4th Global Congress on Process Safety
IMRET-10: 10th International Conference on Microreaction Technology
Characterization and Simulation - Part 1
Tuesday, April 8, 2008 - 8:30am to 8:55am
Characterisation of residence time distribution (RTD) in microchannels is important since RTD has an impact on conversion and selectivity of reactions. This work focuses on numerical simulations and experiments to obtain the RTD for a rectangular microchannel. It also investigates the impact of using staggered herringbone structures on the bottom of the channel in the RTD [1]. The Navier Stokes equations are solved using a commercial finite element method (FEM) software. The RTD is obtained with a particle tracking algorithm in which a random-walk model is incorporated to simulate the effect of diffusion. Experiments are carried out by injecting a small quantity of a tracer dye and the outlet concentration is recorded as a function of time by means of a UV detector. The results indicate that the structured channel has a narrower RTD, which may be approximated by a model of axial dispersion exchanging mass with a stagnant zone [2]. Both simulations and experiments show that the difference between the RTD of a structured and unstructured channel is not substantial at short channel lengths, however this difference becomes more pronounced at longer lengths. The improved features of the structured microchannels open the possibility of using larger structured channels that behave in similar way to smaller unstructured channels. This can potentially eliminate some of the problems associated with smaller channels like higher pressure drop and susceptibility to clogging.
References
1. Stroock, A. D.; Dertinger, S. K.; Ajdari, A.; Mezic, I.; Stone, H. A.; Whitesides, G. M. Chaotic mixer for microchannels. Science 2002, 295 (5555), 647-651.
2. Castelain, C.; Berger, D.; Legentilhomme, P.; Mokrani, A.; Peerhossaini, H. Experimental and numerical characterisation of mixing in a steady spatially chaotic flow by means of residence time distribution measurements. International Journal of Heat and Mass Transfer 2000, 43 (19), 3687-3700.