Physical bases of freezing point measurement using ... - Boschung

Proceedings of the 9 th SIRWEC Conference 15-17 March 1998, Luleå, Sweden 277
For the currents listed in table 1, measurements of the cooling of pure water are shown
in figure 3. The water thickness is 0.5 mm and its volume is about 80 mm 3 . As discussed in
§ 2.1.3, the peaks of the curves originate from freezing. They reach the temperature of 0 °C.
T [°C]
10
5
0
-5
-10
-15
-20
-25
-30
3.3 A
3.9 A
0 20 40 60 80 100 120 140 160 180
t [s]
1.5 A
2 A
Figure 3 : influence of the current on the cooling rate of pure water.
2.5 A
The times t-15 and t-20 necessary to lower the temperature of 15 °C, respectively 20 °C,
are reported versus the current in figure 4, as well as the temperature difference between T0
and Ta. With the low current of 1.5 A, cooling of more than 20 °C is reached. This means that
even with low supplied power, effective cooling can be achieved.
t [s]
140
120
100
80
60
40
20
0
1 1.5 2 2.5 3 3.5 4
i [A]
Figure 4 : performances of cooling of the probe.
34
32
30
28
26
24
22
20
T 0 - T a [°C]
3 A
t -15 [s]
t -20 [s]
T 0 - T a [°C]