Heat transfer characteristics of mechanically-stimulated particle beds

The characteristics of mechanically-stimulated particle beds are reviewed with particular attention to the transfer of heat at atmospheric pressure. A mass of granular material, when vibrated in the frequency range of 20-100 Hz at an amplitude of up to 5 mm, can serve as an excellent heat transfer medium. The particles engage both in a local minor motion and an overall streaming motion which facilitates higher transfer rates than those normally encountered in gas-fluidized beds, because of the absence of the relatively low conductivity gas bubbles. Preliminary experimental findings at atmospheric pressure indicate high heat transfer coefficients of up to 1100 W/m(2) K for particle diameters of 50 < d(p) < 170 mu m, these values being much greater than those achievable by gas fluidization, and heat transfer coefficients as high as 280 W/m(2) K at 20 mbar. (C) 1998 Elsevier Science Ltd. All rights reserved.