Geoscience Reference
In-Depth Information
calibrated at ice and steam points, and the calibration error was within
0.1
◦
C. The temperature difference between the two sensors within the vessel
remained within 0.1
◦
C, when a steady condition was reached.
One circulator was fixed at the roof of the cold room to keep the
temperature uniform inside the room. A light was also kept inside the room
for working purposes.
At first, the temperature of the room was brought to a pre-decided
value of low temperature, and then steam was passed into the vessel until a
steady temperature was reached. This steady condition can be controlled in
two ways, i.e. by fixing the temperature of the vessel when steam was passed
and controlling the flow of steam. The steady temperature can be retained
for about 5 min. The seeding was done at that steady temperature. The
entire experiment was performed within this steady condition. One should
note that, as steam was passed, the temperature of the room remained
almost constant, but that of the vessel underwent quick change. In all the
experiments the total water content of the vessel was kept fixed within a
narrow range of 130
10
−
3
kg.
Commercially available DMSO being used here is 99.5% chemically
pure. As the freezing point of DMSO is 17-18
◦
C, it remains in liquid state
at the normal temperature of the laboratory. A volume of 20
−
150
×
10
−
6
m
3
of
the liquid, brought quickly from room temperature, was sprayed inside the
vessel in one stroke. The syringe being used here had a nozzle and admitted
only droplets having diameter with a peak of 0.7
µ
m and standard deviation
of 0.21
×
m. It is expected that DMSO will form solid particulate inside the
chilled vessel.
To study the optical property, the laser beam was passed through a
port located in the middle of the vessel. Five other ports are located in the
same horizontal section of the vessel so that the directly scattered beam as
well as those scattered at angles 30
◦
,36
◦
, 144
◦
, and 150
◦
with respect to
the forward direction can be received. Five photodiodes are placed behind
the five ports to receive the scattered light. A current-regulated circuit then
amplifies the signal, and the amplified voltage output then goes to a data
logger. Finally, all the data registered in the data logger are transferred to a
PC for archiving. Immediately after the seeding the scattered intensities are
found to change with time. The scattered intensity is automatically noted
and archived at an interval of 1 s. When the voltage output returns to the
base value, one can assume that the medium has become clear of ice cloud.
Crystals formed within the ice cloud finally settle down at the base of
the vessel. To collect the falling-crystals formvar-coated glass slides were
µ
