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

Proceedings of the 9 th SIRWEC Conference 15-17 March 1998, Luleå, Sweden 276
temperature was measured at the center of the surface of the probe, i.e. at the bottom of the
water, by a thermocouple.
H2O
Figure 2 : schematic representation of the cooling system.
T
thermocouple
cooler
body
insulator (plastics)
thermoelectric cooler
heat sink
Table 1 gives an example of computed cooling performances obtained with a
commercial TEC. i is the current supplied to the TEC, U the voltage 3 , Qin the electric power,
Qc the cooling power, Qh the rejected heating power and COP the coefficient of performance.
Heat power and COP depend of course on the temperatures Tc and Th of the cold and hot sides
of the TEC. In this example, Tc = - 19.1 °C and Th = 5.9 °C. The operation principle of
electronic refrigeration is described in Appendix A.
i [A] U [V] Qin [W] Qc [W] Qh [W] COP
1.5 1.4 2.1 1.7 3.8 0.80
2 1.8 3.5 2.6 6.2 0.74
2.5 2.1 5.3 3.4 8.7 0.63
3 2.5 7.5 3.9 11.5 0.53
3.3 2.7 9.0 4.2 13.2 0.47
3.9 3.2 12.3 4.5 16.8 0.37
Table 1 : cooling performances of a commercial TEC 4 .
3 Note that the symbol U is used for the internal energy (§ 2.1.2) as well as for the voltage!
4 MELCOR CP 1.0-31-05L.