Cocoa drying on a platform type dryer with and without drying air recirculation
AbstractCocoa was dried under controlled field conditions, using a platform type unit with and without recirculation of the drying air. A value known as the ·overall thermal efficiency' was defined to enable the results presented here and elsewhere to be compared. By the application of a reduced air now to the non-recirculation runs, efficiencies at least as high as those obtained with recirculation could be obtained when drying at or near 60ºC. At 70°C the application of recirculation resulted in some increases in efficiency. Overall thermal efficiency values for the no-recycle runs, over the range of condition tested, was independent of drying air temperature. With recirculation, however, the degree of cocoa loading and to a lesser extent the drying air temperature were important in determining system efficiency. The drying rate curve of the run carried out showed three distinct periods, corresponding well with previously published results. Drying rates during the initial two periods were lower than expected though during the final period the usual exponential fall in drying rate took place.