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Renin Angiotensin Mechanism.

Important Concepts Related to Drying.

 

Definition

  • Drying is defined as the removal of liquid from a product usually with application of heat.

Important Concepts Related to Drying.

Total moisture content (TMC): 

  • It is the total amount of liquid associated with a wet solid.

Bound moisture: 

  • It is a liquid in a solid that exerts a vapour pressure less than that of the pure liquid at the same temperature. 

  • Liquid retained in small capillaries in the solid adsorbed at the solid surfaces, solution in cell or fibre walls and water of crystallization is bound moisture. 

  • It is difficult to remove bound water from solid than unbound water 

Unbound moisture: 

  • It is a liquid in a solid that exerts a vapour pressure equivalent to that of the free liquid at the given temperature.

  •  It is the easily removable water from the solid.

Free moisture: 

  • The moisture content of solids in excess of the equilibrium moisture content is called free moisture.

Equilibrium moisture content (EMC): 

  • The moisture content of a wet solid in equilibrium with air of given humidity and temperature is termed the equilibrium moisture content (EMC).

Desorption: 

  • It is the phenomenon when air of constant temperature and humidity is passed over the solid containing more moisture than EMC, then solid loses moisture until EMC is reached.

Sorption: 

  • It is the phenomenon when air of constant temperature and humidity is passed over the solid containing moisture less than EMC, then moisture gets attached to the solid until EMC is reached.

Sorption Isotherm: 

  • Sorption isotherm of a product describes its ability to adsorb or release water vapour from or into the surrounding atmosphere until an equilibrium state is reached.

Humidity:

  • Amount of the water vapour present in the air.

Relative Humidity(RH):

  • It is the ratio of the partial pressure of water vapour to the equilibrium vapour pressure of water at a given temperature. 

  • It is normally expressed as percentage; a higher percentage means air-water mixture is more humid.

Absolute Humidity:

  • It is the mass of water vapors divided by the mass of dry air in a certain volume of air at a specific temperature.

  • Expressed as grams of moisture per cubic meter of the air. (g/m3)

Dew Point:

  • It is the temperature at which air becomes saturated with water vapour.

  • Below this point the moisture in air condenses to form dew.

Dry Bulb Temperature:

  • It is the surrounding temperature measured by an ordinary thermometer.

Wet Bulb Temperature:

  • Used to measure adiabatic saturation temperature, measured by using a thermometer with bub wrapped in a muslin cloth.

Psychrometrics: 

  • It is the study of the thermodynamic properties of air–vapour mixtures.
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