This paper describes the behavior of the long packed bed heat regenerator in terms of the simple axial dispersion model which has so ?occeasfully accounted for nonideal Row of Auida. Thus Instead of trying to determme the Fhape of the evolving temperature front by ngorous or sun-ngorous analytical methods this model charactenzea the spreading phenomenon by lhe moments of Its associated tiaussran distribution. This procedure, though approximate, allows one to account for all the factors which contribute to the spreading of the temperature front: axial dispersion of gas, film heat transfer and conduction into the particles.
Efficiencies of heat recovery are directly calculable with this model for all sorts of operations: single pass, periodic cocurrent and periodic countercurrent, using either equal Rows of hot and cold gas, or unequal flows. This approach also gives the optimal switching time, the favored contacting patterns, and shows how changes in the design parameters affect the heat recovery efficiency. An example i> worked out to illustrate thin design method.
Practically all pasl analyws of the regenerator assumed that film heat transfer was the dominant mechanism in causing a lowering in performance of these exchangers. However the worked-out example shows that this assumption can be incorrect and shows that one should consider the action of all three of the spreading mechanisms.