222 Temperature measurement

The properties of air are functions of temperature. The pressure and density of naphthalene vapor are also sensitive to the naphthalene surface temperature, which in turn affects the sublimation rate and the accuracy of local mass transfer coefficient. The refore, it is important to attain high accuracy and precision in the temperature measurement, especially near the surface of naphthalene layer.

The temperature in the wind tunnel room is obtained from a thermometer with a 0.2°C reading precision, which is located near the barometer. The temperature in the data acquisition system room is also monitored by a thermometer with the same reading precision. These temperatures are used for naphthalene natural convection loss estimation.

The incoming main flow temperature in the wind tunnel (T), the naphthalene surface temperature at two different locations (Tw) around the mid-blade on the pressure and the suction side, respectively, are measured by three T-type thermocouples. The signals are then transfered to a multiple scanner (Keithly 7001) and a Keithly 196 digital multimeter, from which the voltage readings are collected by a Linux workstation through an IEEE-488 (GPIB) bus during the testing. All of the thermocouples were calibrated in a previous study (Goldstein et al., 1999).

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