UNIT OPERATIONS IN FOOD PROCESSING
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Introduction
Material and energy
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Fluid-flow theory
Fluid-flow applications
Heat-transfer theory
Heat-transfer
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Drying
Evaporation
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separation processes

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separations

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Mixing
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CHAPTER 7

DRYING

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Introduction
Basic Drying Theory
Three States of Waterphase diagram for water
       vapour pressure/temperature curve for water

Heat Requirements for Vaporization latent heat of vaporization          latent heat of sublimation
Heat Transfer in Drying
Dryer Efficiencies
Mass Transfer in Dryingmass transfer coefficient
Psychrometryabsolute humidityrelative humidity
       dew pointhumid heat

Wet-bulb Temperaturesdry bulb temperatureLewis number
Psychrometric Charts
Measurement of Humidityhygrometers
Equilibrium Moisture Content
Air Dryingdrying rate curves
Calculation of Constant Drying Rates
Falling rate Drying
Calculation of Drying Times
Conduction Drying
Drying Equipment
Tray Dryers
Tunnel Dryers
Roller or Drum Dryers
Fluidized Bed Dryers
Spray Dryers
Pneumatic Dryers
Rotary Dryers
Trough Dryers
Bin Dryers
Belt Dryers
Vacuum Dryers
Freeze Dryers
Moisture Loss in Freezers and Chillers
Summary
Problems

Examples in this Chapter:
7.1. Heat energy in air drying
7.2. Heat energy in vacuum drying
7.3. Heat energy in freeze drying
7.4. Efficiency of a potato dryer
7.5. Partial pressure of water vapour
7.6. Relative humidity
7.7. Relative humidity, enthalpy and specific volume of air
7.8. Relative humidity of heated air
7.9. Water removed in air drying
7.10. Humidity of air leaving a dryer
7.11. Reheating of air in a dryer
7.12. Air conditioning
7.13. Rate of evaporation on drying
7.14. Heat transfer in air drying
7.15. Temperature and RH in air drying of carrots
7.16. Lewis relationship in air drying
7.17. Time for air drying at constant rate
7.18. Time for drying during falling rate
7.19. Moisture content of breakfast food after drum drying

Figures in this Chapter:
7.1 Phase diagram for water
7.2. Vapour pressure/temperature curve for water
7.3 Psychrometric chart
7.4 Equilibrium moisture contents
7.5 Drying rate curves
7.6 Drying curve for fish
7.7 Generalized drying curve
7.8 Dryers



Drying > INTRODUCTION, BASIC DRYING THEORY


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Unit Operations in Food Processing. Copyright © 1983, R. L. Earle. :: Published by NZIFST (Inc.)
NZIFST - The New Zealand Institute of Food Science & Technology