An apparatus for measuring thermal conductivity employs an electrical heater sand- wiched between two identical samples of diamter 30 mm and length 60 mm which are pressed between two plates maintained at a uniform temperature To=77 C by a circulating fluid. good thermal contact is ensured. Differential thermocouples are imbedded with a spacing a 15 mm in the samples. The lateral sides of the samples
are insulated to ensure one-dimensional heat transfer through the samples. (a) With two samples of SS316 in the apparatus, the heater draws 0.353 A at 100V and the differential thermocouples read ?T1 = ?T2 = 25 C. What is the thermal conductiv- ity of the stainless steel sample material? (b) By mistake an Armco iron sample is placed in the lower position of the apparatus. The heater now draws 0.601 A at 100 V and the thermocouples read ?T1 = ?T2 = 15 C. What is the thermal conductivity of the iron sample?