Raining Particles Heat Exchanger

Thus a single stage, NH= 1, corresponds to a solids temperature rise (or drop) equal to the average gas-solids temperature difference, as shown in the lower left-hand side of Fig. 10. On this basis, it is convenient to define equipment efficiency in terms of a unitary heat transfer stage  

For good equipment performance, it is, therefore, desirable to look for alow height z/Nh and low pressure drop AP/NH.. 

The fractional heat recovery rj is defined as the ratio of the actual temperature rise of the gas (or of the solids) to that for complete heat transfer between the gas and the solids, that is, according to Fig. 10 

Comparison with the integrated form for N, given yields the following expressions for G/S heat exchange 

The particles, while exchanging heat with the flowing gas stream, are in accelerative motion in accordance with the equation 

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The disadvantage of employing coarse particles in raining-bed operations dpe to short retention and insufficient heat exchange is evident from Fig. 44, as described in Section VIII.C. For countercurrent operation, this may be improved by breaking the fall of these particles during their descent by means... 

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