A thermocouple junction is a small ball of solder with diameter D=0.71 mm. The thermocouple is used to gauge the temperature of a gas stream. Under the conditions employed, the convective heat transfer coefficient is h=400 W/m2 -K. The junction is initially at Ti=25 °C and is abruptly placed in a Tg=200 °C gas stream. Material properties are k=20 W/m-K, Cp=400 J/kgK, and =8500 kg/m3 .
1. How can one speed up the response of the thermocouple?
2. How long will it take for the thermocouple to reach Tf=199.0 °C?
3. How long will it take for the thermocouple to reach Tf=199.5 °C?