amafh-thermo

Problem 1:

Heat is transferred steadily through a 0.2-m thick, 8m x 2 m wall at a rate of 2.6 kW.  The inner and outer surface temperatures of the wall are 15 °C and 5 °C respectively.  Find the average thermal conductivity of the wall.

Problem 2: 

Consider a refrigerator that consumes 350 W of electric power when it is running.  If the refrigerator runs only one quarter of the time and the unit cost of electricity is $0.19/kWh, find the electricity cost of the refrigerator over a 30 day month.

Problem 3:

The elevator of a large building is designed to raise a net mass of 4,000 kg at a constant speed of 12 m/s using an electric motor.  Find the minimum power rating of the motor in kW.