Relation between Moisture regain and Moisture content

Relation between Moisture regain and Moisture content:

Moisture regain 
Moisture regain is defined as the weight of water in a material as a percentage of the oven dry weight. 

Let,

 Oven dry weight of a material = D 

Weight of water in this material = W 

                                   W 
Moisture regain, R = …… X 100 %                             …….(A) 
                                   D

Moisture content: 
Moisture content is defined as the weight of water in a material express as a percentage of the total weight of the material. 

                                       W 
Moisture content, C = ……….. X 100 %       ……………(B) 
                                    W+D 

From equation (1) we get, 

         W 
D = …… X 100 
         R 

Putting the value of D in equation (B) we get, 

                         W 
C = …………………………  X 100 
         W + { (W/R) X 100} 

                      W 
=>  C = …………………
              W (1+100/R) 

                    100 
=> C = ………………
               1 + 100/R 

               100R 
=> C = …………                         ………..(C) 
              R+100 

Again from equation (C) we get, 

          RC + 100C 
R = ………………
              100 

=> R = C + RC/100 

=> R – RC/100 = C 

=> R (1-C/100) = C 

                  C 
=> R = …………
             1-C/100 

               100C 
=> R = ……….              ………..(D) 
              100-C 

Equation (C) and (D) express the relation between Moisture regain and Moisture content.

v Standard moisture regain:

   The moisture absorbed by a particular weight sample in standard atmosphere after treating at 105+3 or 105-3 degree celsius is called standard moisture regain. It is also called Official regain.

Standard Testing Atmosphere

R.H.%= 65%+2% or 65%-2%

Tropical and subtropical countries  Standard Testing Atmosphere 27+2 or 27-2 degree celsius .

For cold countries 20+2 or 20-2 degree celsius.

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