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Equilibrium Moisture Content (EMC) in Drying

Equilibrium Moisture Content (EMC) in Drying. Muanmai Apintanapong. Moisted air. At equilibrium : determine Moisture content Temperature RH EMC : Loss of water = desorption Gain of water = adsorption. Constant T, RH. sample. Heated air. Ideally Desorption and Adsorption. Desorption.

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Equilibrium Moisture Content (EMC) in Drying

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  1. Equilibrium Moisture Content (EMC)in Drying MuanmaiApintanapong

  2. Moisted air • At equilibrium : determine • Moisture content • Temperature • RH • EMC : • Loss of water = desorption • Gain of water = adsorption Constant T, RH sample Heated air

  3. Ideally Desorption and Adsorption Desorption EMC Time Adsorption

  4. Practically Desorption and Adsorption Desorption EMC Time Adsorption

  5. Relationship between EMC and RH • EMC Isotherms EMC Desorption Adsorption RH

  6. Relationship between EMC, T and RH Low Temp High Temp

  7. Types of Equations (Models) used to represent EMC Data or Isotherm • 3 variables : RH, MC and T • MC = f (RH, T) • EMC = f (ERH, T) at equilibrium • RH = f (MC, T)

  8. Henderson’s equation • Use in grain and food materials 1 – RH = exp(-c.T.Mn) Where c, n = constant RH = relative humidity in decimal M = moisture content in %db T = temperature in Rankin

  9. Modified Henderson’s equation • For desorption isotherms (drying) 1 – RH = exp[-K.(T+C)(100.M)N] Where c, n = constant RH = relative humidity in decimal M = moisture content in %db T = temperature in Rankin

  10. Modified Henderson’s equation

  11. Chung’s equation • For desorption isotherms (drying) RH = exp[-A/(T+c) exp(-B.M)]

  12. Chung’s equation

  13. Example of EMC Model

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