1-ft3 of air is contained in the spring-loaded piston cylinder device shown in figure below. The spring constant is 5 lbf/in, and the piston diameter is 10 in. When no force is exerted by the spring on the piston, the state of the air is 250 psia and 460°F. This device is now cooled until the volume is one-half its original size. Determine the change in the specific internal energy and enthalpy of the air.

 

Spring -D FIGURE P4-61E