申論題

2. (15%) An experimental apparatus for measuring thermal conductivity of test piece is shown in the following figure. At the steady state, the current and voltage provided to the heater are 4A and 20V, respectively. The surrounding of test piece is completely adiabatic. The cross-sectional area and length of test piece are 20cm X 20 cm and 20cm, respectively. One thermocouple is installed at the interface of test piece and heater and the other is installed at the interface of test piece and heat sink, shown as the thermocouple wires in the figure. The EMF values of right-hand side thermocouple and left-hand side thermocouple are 0.6mV and 0.3m Y, respectively. The measured EMP values of both thermocouples at ice point and boiling point of water at I atmosphere are 0.0mV and 1.0mV. Please assume that the EMF value and the temperature are linearly dependent.ㆍ Please determine the thermal conductivity of test piece (Free-Standing Bridge). The unit of thermal conductivity is W/m•K ㆍ