HOT AIR ASSISTED RADIO FREQUENCY DRYING

1. “HOT AIR ASSISTED RADIO FREQUENCY DRYING”
SEMINAR
ON

2. Introduction
• In many countries, open-air and hot air (HA) drying methods are in practice for drying paddy,
which have some inherent disadvantages, such as low thermal conductivity, long drying times and
degradation of quality.
• To overcome these disadvantages , an alternative drying practice should be investigated to reduce
the drying time meanwhile preserving nutrients in paddy processing.

3. Radio frequency drying machine

4. Paddy Tray

5. A: HA drying (T = 60 ◦C, v = 2.5 m/s);
B: HA-RF drying (T = 50 ◦C, v = 2.5 m/s & EG = 110 mm);
C: HA-RF drying (T = 55 ◦C, v = 2.5 m/s & EG = 110 mm);
D: HA-RF drying (T = 60 ◦C, v = 2.5 m/s & EG = 110 mm);
Damage Level

6. E: HA-RF drying (EG = 100 mm, T = 60 ◦C & v = 2.5 m/s);
F: HA-RF drying (EG = 120 mm, T = 60 ◦C & v = 2.5 m/s);
G: HA-RF drying (v = 0.5 m/s, T = 60 ◦C & EG = 110 mm);
H: HA-RF drying (v = 1.5 m/s, T = 60 ◦C & EG = 110 mm).
Damage Level

7. Factors affecting Damage Level
• Decrease of RF electrode gap, the damage level of HA-RF dried paddy increase
• Increase of temperature, the damage level of HA-RF dried paddy decrease
• Increase of velocity, the damage level of HA-RF dried paddy decrease
Damage Level

8. Industries and costumers are very sensitive to taste of paddy which has a significant effect on
paddy economic value in international market. The taste value was analyzed using a taste
value analyzer . This unit tests the paddy taste using several parameters such as taste, freshness
and hardness.
Taste Value
Taste values of HA-RF drying dried samples as compared with those of control and HA dried ones.

9. Factors affecting taste value
• increase in electrode gap (EG), taste value increase
• increase of hot air velocity, taste value increase
• Temperature had no significant effect
Taste Value

10. Drying curves at
(A) different temperatures
(B) different velocities
(C) different electrode gaps of paddy grains for
HA-RF drying.
Drying curve
Moisture Ratio = moisture content on dry basis at time t / initial moisture content on dry basis

11. Crack ratio (CR)
To estimate the number of cracked kernels, the method is selecting hundred dried
kernels randomly from the samples and placing them above a light source which
provides a transparent view on glass board and the cracks are shown in lines which
can be distinguished by naked eyes.
where c refers to number of cracked kernels per 100 paddy kernels.

12. Advantages of HA-RF Drying
• short process time
• uniform heating
• Reduce cracking of paddy
• Better taste value
• Better efficiency
• Accurate process control

13. Conclusions
•The experimental results demonstrated that HA-RF drying has significant
advantages over HA drying in both drying rate and quality of paddy grains.
•The introduction of RF causes 62.5% improvement in drying rate as compared to
HA drying under optimum combination of drying parameters.
•HA-RF drying is a good alternative strategy for industrial- scale drying of paddy
grains with improved heating uniformity and drying characteristics and qualities

14. • Effects of hot air assisted radio frequency drying on heating uniformity,
drying characteristics and quality of paddy (Jan 2022)
• Wikipedia
• Google scholars
References

15. THANK YOU