Temperature
Pipette
Monitor
Air Pressure
Regulator
Extracted Water
Heater Regulator
and Readout
Glycol
To Campbell CR10
Ice Sample
PRT
To Hand Device
Precision
Tempe Cell
Temperature
Controller
Restance-Wire Heater
Refrigerator
Stirrer
Figure 1. Experimental setup.
meter. The full combination as shown in Figure 1 was
in place for the second experiment.
SAMPLE PREPARATION, INSTALLATION,
AND ANALYSIS
We prepared two ice samples, both seeded with
frazzle ice nucleated from singly distilled, supercooled
water. To grow the first sample (Sample A), we placed
a beaker of frazil slurry in a brine bath maintained at a
temperature near 20C in a coldroom. Continuous
agitation with a magnetic stirrer removed air bubbles
ahead of the freezing front. This procedure produced a
Figure 2. Ice sample is placed within a hermetically
heterogeneous sample of coarse to fine-grained ice (Fig.
sealed Tempe cell.
3a, b). Large crystals on the order of centimeters grew
in from the sides and bottom of the beaker and (at a
slower rate) at the top of the slurry. The central, fine-
initial run tested the viability of the experiment. For
grained portion was agitated by the magnetic stirrer,
this run we used a quickly prepared ice sample
which we removed for the final freezing. For the sec-
(described in the next section) and monitored tempera-
ond sample we sought a refined technique that would
ture of the ice bath with a single thermistor connected
produce a more homogenous and fine-grained sample.
to a manual readout. High sensitivity of water levels to
To prepare the second sample (Sample B), we placed a
bath temperature indicated the need for continual and
beaker of frazil ice on a 25C cold plate in a room
more accurate temperature monitoring. Thus, on the
where the temperature was kept slightly above 0C.
second experiment we added three thermistors and a
highly accurate ( 0.001C) platinum resistance ther-
Water froze from the bottom up while being stirred at 3
mometer (PRT). Data from the thermistors were con-
rpm with a motorized paddle held just above the freez-
tinuously collected on a Campbell CR10 and periodi-
ing front on an adjustable mount. This procedure grew
relatively fine-grained ice (Fig. 3cd) at a rate of approx-
cally transferred to a computer. The PRT was manually
imately 1 cm per hour. Both samples were disc-shaped,
monitored with a S1220 Systemteknik temperature
2
Previous Page
