VEGETABLE AND FRUIT DEHYDRATION 



85 



Either of two approximate methods can be used satisfactorily. 

 With one method trucks are introduced into the drier at a faster rate 

 than is normal, and the time interval between trucks is progressively 

 increased until normal operating conditions are reached. Although 

 the method produces fairly uniform drying, it is limited in applica- 

 tion. For instance, a plant with a large number of driers will be 

 faced with a formidable scheduling and coordinating problem. In 

 order to keep up with the initial demand, the processing line must 



5 CABBAGE 

 10 POTATOES 



Figure 47. — Typical drying curves for counterflow tunnels. 



be speeded up temporarily, or the prepared product must be accumu- 

 lated over a period of time. If this first expedient is impossible, a 

 second may be used. This method consists of the application of a 

 modified drying schedule, and produces acceptable results. It is 

 apparent from figure 48 that the greatest drop in dry-bulb tempera- 

 ture occurs at the wet or loading end of the drier. Therefore, in 

 modifying the temperature schedule, most of the adjustment should 

 occur during the initial stages of the starting-up period. With this 

 as the basis and by reducing the number of temperature adjustments 

 to a minimum, a rough approximation of the time-temperature curve 

 is established as shown by the dotted graph. Since the drying curves 

 for all products are basically similar in shape, this simplified graph 

 can be used in starting most counterflow dehydrators. The success of 



