Question

A spherical thermocouple junction of diameter 0.706 mm is to be used for the measurement of temperature of a gas stream. The convective heat transfer co-efficient on the bead surface is 400 w/m^2k. The thermo-physical properties of thermocouple material are k = 20 w/mk, c =400 j/kg, k and Ď = 8500 kg/m^3. If the thermocouple initially at 30°c is placed in a hot stream of 300°c, then the time taken by the bead to reach 298°c, is ______________ s.

Answer 1

2 isto 1ans is 24 if the