60 



MISC. PUBLICATION" 540, U. S. DEPT. OF AGRICULTURE 























































^ 



8% 



7% 



6% 









2 3 



TIME (HOURS) 



Figure 26. — A typical drying curve. 



Effect of Wet-Bulb Depression 



Other things being equal, drying will proceed faster if the wet-bulb 

 depression of the air is high (relatively dry air) than if it is low 

 (relatively moist air). Figure 27 compares drying curves for potato 

 strips in three experiments ; in all of them the wet-bulb temperature 



TIME (HOURS) 

 Figure 27. — Drying curves for potato strips at varying dry-bulb temperatures. 



of the air was 90° F., but dry-bulb temperature was 105° in one case, 

 130° in another, and 150° in the third, so that wet-bulb depressions 

 were 15°, 40°, and 60°, respectively. The very great effect of 

 this factor is apparent. 5 



5 In this figure and the other drying curves which follow it, a logarithmic scale for mois- 

 ture content is used, in order to show differences at low moistures more effectively. 



