rate
The misting system as the most important part of the mist bioreactor has
a significant effect on the growth performance and the production of
hairy roots culture. The most effective factor which influences misting
rate is the viscosity, density, surface tension and height of medium
(Barreras et al., 2002; Knorr et Al., 2004; Avvaru et al., 2006). The
ANOVA results of experimental factors are presented in table 3. The
results showed that the ultrasonic misting rate (MistUS ) was influenced by medium and heights, either
individually or in combination (P = 0.01(.
The effect of liquid height on mist generation (total and ultrasonic),
surface evaporation rate, the power consumption of various media are
shown in Fig. 4. The results showed that the ultrasonic mist generation
rate increased with increasing liquid height, and after that reached to
a maximum value and then decreased, this trend is similar for all media.
When the liquid height is low on the piezo surface. The mist
characteristics change. Instead of forming a relatively homogeneous
mist, the diameter of particles are not uniform. In this case, larger
diameter droplets form on the liquid surface. (Barreras et al., 2002).
The droplets return to the liquid surface after detachment again and a
few change of mass reduction was recorded by mass balance. Therefore,
the only mass loss of vessels is due to the small fraction of misting.
This result had been reasoned by the capillary wave hypothesis by
researchers (Lang, 1962). Lang (1962) demonstrates that exciting
vibration caused a wave. The peaks of wave tears and the collision and
agglomeration of the droplets shortly after leaving the surface caused
this uniformity (Lang, 1962). Due to bubble detection in bulk of liquid,
Barreras et al., (2002) suggested that the other possible mechanism of
misting (cavitation) should be considered for describing of atomization
process (Barreras et al., 2002). At a high level of liquid, it seems
that the wave damp and the surface stack formation fail to result again
low misting rate generation. The maximum misting generation rate (total
and ultrasonic) was obtained at the heights of 4, 3, 3, and 3 cm for
water, B5, MS, and ½ MS respectively. The highest value of\(\text{Mist}_{\text{US}}\) rate was belonged to MS
(\(2.78\times 10^{-2}\ \text{gr}/s\)), on the other hand, the lowest
value was obtained for B5 (\(0.52\times 10^{-2}\text{gr}/s\)) at a
height of 1 centimeter above piezoelectric. The power consumption
analysis was depicted for water and MS as media with the highest misting
rate (Fig. 4-A & 4-B). The power consumption increased with the
increasing height of liquid above the piezo. The trends are not the same
for MS and water due to different chemical compounds. The power
consumption for a specified amplitude is proportional to the viscosity
of the fluid (Figura & Teixeira, 2007).