(421c) Heat Exchange in the Rotated Arc Mixer: Experiment, Theory, and Plant Trials

The Rotated Arc Mixer (RAM) is a continuous mixer for highly viscous Newtonian or shear sensitive fluids. By using programmed boundary motions to generate chaotic advection instead of internal obstructions means the RAM's pressure drop is the same as an open pipe. Previous work demonstrated the RAM's efficacy as a mixer [1]. By adding a thermal jacket the RAM becomes a heat exchanger for highly viscous products. However, the change from solving the conservative kinematic equation to solving the dissipative advection-diffusion equation changes the basic nature of the optimization problem for designing the boundary motions to maximize heat transfer rates and global temperature equilibration. The thermal optimization problem for chaotic stirred flows typically results in a fractal distribution of the performance enhancement over the parameter space of the flow, and we have developed new methods to resolve this space and solve the optimization problem [2,3]. Lab experiments and theory achieve a nearly 80% reduction in total energy input over an equivalent pipe required to thermalize viscous Newtonian fluid. We will also present results from pilot trials done with a food processing company [4].

[1] Metcalfe et al. 2006. AIChE J., 52(1), 9--28, doi:10.1002/aic.10640.

[2] Lester et al. 2007. J. Comp. Phys., 227, 3032--3057, doi:10.1016/j.jcp.2007.10.015.

[3] Lester, Rudman & Metcalfe. 2009. Int. J. Heat Mass Trans., 52, 655--664, doi:10.1016/j.ijheatmasstransfer.2008.06.039.

[4] Metcalfe & Lester. 2009. J. Food Eng., in press, doi:10.1016/j.jfoodeng.2009.04.032