Extracting ________________ moisture proves easier during drying operations ?
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Answer: C. Unbound
Explanation
Unbound moisture resides on external particle surfaces or within large macroscopic voids of the wet solid. It exerts the full vapor pressure of free liquid at the operating temperature during the drying process. Because it requires no internal diffusion, extracting unbound moisture proves much easier than bound moisture. Total moisture in a solid equals the sum of bound moisture and unbound moisture content. Equilibrium moisture represents the moisture content where vapor pressure equals the partial pressure in air. Free moisture is any moisture content exceeding the equilibrium moisture value under given conditions.
Drying times for granular solids depend heavily on the initial fraction of unbound surface moisture present. Removing unbound moisture occurs rapidly during the constant-rate drying period of solid materials. Agricultural grain storage requires drying crops until unbound surface moisture is completely eliminated. Option A is incorrect because equilibrium moisture cannot be removed by standard air drying methods. Option B is incorrect because critical moisture marks the transition to slower internal diffusion rates. Option D is incorrect because bound moisture is held tightly in capillaries and is very difficult to extract.
- Subject
- Engineering
- Category
- Chemical Engineering
- Topic
- —
- Difficulty
- medium
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