3. In setting up an experiment, a steel rod (k = 60 W/m K) with radius r = 10 cm and length L, = 2L= 2 m is placed into a hollow aluminium tube (K= 150 W/m.K, LAI = 2 m) whose outer radius r2 = 20 cm. The steel-aluminium composite cylinder is placed between a heater and a cylindrical rod (Trod = 12 = 20 cm, Lrod=L= 1 m) labelled as rod X which is made of unknown material as shown in figure below. A uniform volumetric heat is generated at q = 1000W/m within the heater. To ensure one- dimensional heat transfer condition, the bottom of the heater, the outer surfaces of both aluminium tube and the cylindrical rod X are perfectly insulated. It is also assumed that the heat transfer from the aluminium cylinder to the steel rod or vice versa is negligible. The other end of the cylindrical rod X is exposed to a radiation heat flux rad 25 W/m and surrounding air at T = 25C and convection coefficient of h = 200 W/m.K. Assuming no contact resistances and isothermal condition at all interfaces, constant properties and steady state condition: (a) Construct an appropriate thermal circuit that can be used to calculate temperatures at the interface of the heater and the steel-aluminium composite cylinder, TA. (b) Express the equations in terms of krod that can be used to calculate TA. (c) In selecting a suitable material of rod X for such experiment, it is restricted that the temperature of the steel-aluminium cylinder must not exceed 100C, what is the appropriate range of the thermal conductivity, Krod, for rod X? grad = 25W/m 2L L Surrounding air Too, h rod X, Krod Perfectly insulated Steel rod Aluminum tube Heater, 11 12 kr> 18.45 W/m.K