thermal properties related to agricultural engineering

1. THERMAL
PROPERTIESS
OF GRAINS
AND THEIR
APPLICATIONS

2. THERMAL PROPERTIES OF
GRAINS:
 Specific heat
 Thermal conductiity
 Latent heat of vaporiatioin of grain moisture
 Heat transfer coefficient of grain bed
 volumetric heat transfer coefficient

3. 1.SPECIFIC HEAT:
 The specific heat at constant pressure is
normally used for studying the heat transfer
problems drying and storage of agricultural
crop.
 Specific heat is a function of temperature
 Sieball proposed that specific heat of food
materials
 Specific heat is same both solid and liquid
matter but high pressure is needed

4. cont
 The specific heat of grain is usually determined by
the method of mixture using distilled water as
colorimeter fluid
 The technique consist in determining the temp
change of water contained in the colorimeter
when a known quantity of grain is added to it at a
known different temperature
 Heat loss by grain=heat gained by water and
colorimeter

5. THERMAL CONDUCTIITY:
 It is heat transfer property of grains
 Heat transfer is done between moisture of
grains and atmosphere depending on whether
condition
 Two methods
Steady state method-Cylinder apparatus
Transient heat flow method-linear

6. Latent heat of vaporization of
grains:
 Energy required to vaporize moisture from the
product
 its depends upon the type of the crop

7. Heat transfer coffecient of grain
bed:
 The rate of heat transfer between a solid and
a fluid may be computed from the following
relation
 Qc=hc A∆T

8. volumetric heat transfer
coefficient
 Grains are dried to equilibrium moisture
content,cooled to room temp
 Grains are filled in dummy insulated cylinderin
a same depth, air temp and RH used to dry
the original sample
 After air temp and RH are stablize ,the grains
are replaced to experimental cylinder and air
temp at different position as monitered

9. cont
 From the air temp at different position is used
to calculate the volumetric heat transfer
coefficient

10. Thank u,….