Presentation on agricultural marketing trade and price

1. University of agricultural Sciences, Dharwad
College of agriculture, Hanumanamatti
AEG 202
Topic : Important engineering properties( Thermal, aero and
Hydrodynamic properties of cereals, pulses and oilseeds)
Submitted by:
PARVATI D U
UGS20AGR9918
Submitted to:
Dr Neelakanth
Dept of agricultural
Engineering

2. • The thermal properties like specific heat, thermal
conductivity, thermal diffusivity, enthalpy, surface heat
transfer coefficient, emissivity etc. are important for the
development of any thermal processing system. The thermal
processing may include heating, cooling, freezing, drying,
etc.
• There are some other thermal properties like melting,
freezing points, heat of adsorption, heat of respiration etc,
but these are not of much importance for the most heat
transfer application.
A) Thermal properties:

3. • The heat treatment to cereals (wheat, maize etc.) and
some of the pulses is given for stimulating
germination. The heat treatment given to cereals like
wheat, maize, sorghum and few millets for thermal
killing of insect pest in storage has been proved to be
a promising technology in recent years.

4. 1) Specific Heat:
• The specific heat may be defined as the amount of
heat (in kilocalories) must be added to or removed
from 1 kg of a substance to change temperature by
1oC.
• The specific heat is measured by calorimeter,
generally a simple thermos vacuum bottle. The
differential scanning-calorimeter (DSC) is suitable
for measuring the specific heat

5. 2) Thermal conductivity:
• The thermal conductivity may be defined as the rate of heat
flow through unit thickness of material per unit area normal
to the direction of heat flow and per unit temperature
difference. It is a measure of ability of the material to
conduct heat.
• K =Q L/A (T2-T1)
Where K =thermal conductivity
Q =amount of heat transfer
L =thickness of material
A =area of material
(T2-T1) =temperature gradient

6. 3) Enthalpy:
• Enthalpy is the total heat content or energy level of a
material. The enthalpy data are required for frozen foods
that freeze over a range of temperatures below 0oC and not
for those substances that freeze in a narrow temperature
limit, as the case of pure substances like water.
• H= E+PV
Where, H =Enthalpy
E =Internal Energy
P =Pressure
V =volume

7. 4) Thermal Diffusivity:
•The Thermal diffusivity is a thermal conductivity of a
substance over a product of density and specific heat
capacity. It is important in determination of heat
transfer rates in solid food materials of any shape.
• Physically it shows the relationship between the ability
of a material to conduct heat to its ability to store heat.
The common method of determination thermal
diffusivity is to calculate from experimentally measured
values of thermal conductivity, specific heat and mass
density.

9. B) Aero and Hydrodynamic properties:
• The aero and hydrodynamic properties such as
terminal velocity of agricultural products are
important and required for designing of air and water
conveying systems and separation equipment.
• The physical properties such density, shape and size,
drag coefficient etc, are required for calculating the
terminal velocity of the material. For example, in
pneumatic conveying and separation processes,the
material is lifted only when air velocity is greater
than its terminal velocity.

10. 1) Terminal Velocity:
• The terminal velocity of a particle may be defined as
equal to the air velocity at which a particle remains in
suspended state in a vertical pipe. In the steady state
conditions, after attaining the terminal velocity.
• If the density of the particle is greater than the
density of the fluid, the particle will move downward.
• If the density of the particle is lesser then the density
of the fluid, the particle will rise upward.

11. •The drag coefficient of the material and its resistance
to air flow depend upon,
(1) the bed thickness of the material,
(2) type, shape and size of grain,
(3) the air velocity and
(4) orientation and packing of the material.
In the design of blowers for aeration and drying
gadgets, the resistance exerted by the grain bed to air
current blown through must be known.

12. 2) Drag Coefficient:
•In fluid dynamics, the drag coefficient is a
dimensionless quantity that is used to quantify
the drag or resistance of an object in a fluid
environment, such as air or water.

13. Thank you