Design of Bulk-Solids Moving-Bed Heat Exchangers

Presented here are equations governing heat transfer in a moving-bed heat exchanger, along with a numerical method for solving them Moving-bed heat exchangers (MBHE) represent an efficient method for heating or cooling bulk-solid materials compared to other technologies, such as screws and fluidized beds. This article describes the equations governing heat transfer in an MBHE, and provides information on a numerical method to solve the equations. In a bulk-solids moving-bed heat exchanger, a flowing bed of solid particles indirectly exchanges energy with a secondary heating or cooling medium across a separating wall. MBHEs typically consist of hollow parallel plates. The bulk material flows, driven by gravity, between adjacent plates, while the heat-transfer fluid flows inside the plates. Beneath the heat-exchanger plate bank is a mass-flow hopper, followed by a feeder that modulates the solids flowrate and keeps the channels between the plates filled with bulk material. In a mass-flow hopper, all the solids are in motion during discharge. Refer to Ref. 1 for procedures for designing mass-flow hoppers. Heat transfer between plates Consider the streams of bulk solids and heating or cooling fluid moving countercurrently inside the…