Transport phenomena

2) A copper-constantan thermocouple with the configuration shown in the diagram was exposed to an airstream with h=28.4J/sm2C. Given that the air temperature is 121C and the initial temperature of the thermocouple is 21c and the thermal conductivity is 100J/smC. a) Calculate the Biot number of the system and say whether it can be treated as a lumped system. b) What is the time required for the temperature to drop to 115C ? Data: (rho) =8,960kg/m3; Specific heat capacity of copper, C=385kJ/KgC