Question

3. A thermocouple is used to measure the surface temperature of an object. The center of a thermocouple bead of diameter D-100 μm is positioned at a distance 10 μm from the surface of interest. The two thermocouple wires, each of diameter d = 1 mm and length L-250 mm, are held by a large manipulator that is at a temperature of Tm-25 °C. The thermal conductivities of the Nicrosil and Nisil thermocouple wires are Kvic respectively. We can neglect radiation and convection effects in this problem, but there is conduction heat transfer by air with the thermal conductivity kAir 0.02 W/m-K. If the thermocouple registers a temperature of Te 50 °C, what is the surface temperature Ts (in °C)? s 27 Wm-1K-1, Bead т,с 50 °C D 100 μm Wireproperties KNic 13 Wm-1K-1 KNis27 Wm-1K-1 Nicrosil wire Surface Manipulator Tm 25 °C L0.25 m Nisil wire

Answer 1

3 iven the effaut of roaliahion and ten vechon b can neg lecled The lempenahu of he srface wo be move than f bead. Takina stead stat mdihons, balontina huat aethe bead ti na 23 23 t12 rojeukd aa which is and is distenee ot sulace fum enter Subshituhing tht values, 냐 we get |T5=136, 39° C. Sol«Ang diren uem ot ai layer between bead and al bnelt, the d net woit etwod bend hee as te rmalt, the cnduc hon etfect oitt i-e beod Sa. ths projeeled aea is takun