Unsteady temperature measurement in an enclosed thermoconvectively heated air

Thermally-induced convection in an enclosed fluid is investigated experimentally and applications and potential importance are briefly discussed. In the experiments described here, air enclosed between parallel plates is subjected to rapid heating from the top (along the gravity vector). The experimentally determined variables included the heated boundary temperature, the cavity pressure, and air temperature. The transient air temperature was measured using an optical method. For this purpose, the temperature along a cross section of the enclosure was found by measuring the refractive effects on a planar laser sheet that traverses the test volume inclined at an angle to the heated wall. The experimental results are compared with the computed results from a numerical model for this process. It is found that the agreement between the two results is very good, especially at shorter times following the initiation of heating.