The elevator compartment is made to rise by electrically heating the air contained in the piston and cylinder drive mechanism, and the elevator is lowered by opening a valve at the side of the cylinder, allowing the air in the cylinder to slowly escape. Once the elevator compartment is back to the lower level, a small compressor forces out the air remaining in the cylinder and replaces it with air at 20 C and a pressure just sufficient to support the elevator compartment. The cycle can then be repeated. There is no heat transfer between the piston, cylinder, and the gas; the weight of the piston, elevator, and elevator contents is 4000 kg; the piston has a surface area of 2.5m²; and the volume contained in the cylinder when the elevator is at its lowest point level is 25 m³. There is no friction between the piston and the cylinder, and the air in the cylinder is assumed to be an ideal gas with Cp = 30 J/mol K.
Required:
a. What is the pressure in the cylinder throughout the process?