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Question A1 a. Two surfaces of a 2 cm thick plate are maintained at 0°C and 100°C respectively. If heat is transferred through the plate at a rate of 500 W/m², calculate its thermal conductivity. [20%] Answer: 0.1 W/m.k b. A 1000 W iron is left on an ironing board with its base at a temperature of 674 °C exposed to air at 20 °C. The convection heat transfer coefficient between the base and its surrounding air is 35 W/m².°C. If the base has an emissivity of 0.6 and a surface area of 0.02 m², calculate the rate of heat transfer by convection and radiation from the base. [40%] Answer: convection 457.8 W, radiation 542.2 W C. Electrical power is to be generated by installing a hydraulic turbine generator at a site 70 m below the free surface of a large reservoir that can supply water at 1500 kg/s. The turbine converts power from the water to a mechanical power output of 800 kW and the final electrical power generation is 750 kW. Calculate the efficiency of the turbine, the generator and the combined plant. (40%) Answer: eff. turbine 77.7%, eff. generator 93.75%, overall eff. 72.8%