If a closed system undergoes an isochoric process, the thermodynamic work for this process is always zero. A closed system undergoes a process inside a rigid container. During this process, the thermodynamic work can only be zero. If a closed system undergoes an adiabatic process, the thermodynamic work for this process is always zero.

Air expands adiabatically in a piston-cylinder assembly from an initial state where p₁ = 100 lbf/in.², v₁ = 3.704 ft³/lb, and T₁ = 1000 °R, to a final state where p₂ = 30 lbf/in.²2 The process is polytropic with n = 1.4. The change in specific internal energy, in Btu/lb, can be expressed in terms of temperature change as Au = (0.171)(T₂ - T₁). Determine the final temperature, in °R. Kinetic and potential energy effects can be neglected. T₂ = i °R

A gas is contained in a vertical piston-cylinder assembly by a piston with a face area of 60 in2 and weight of 100 lbf. The atmosphere exerts a pressure of 14.7 lbf/in² on top of the piston. A paddle wheel transfers 3 Btu of energy to the gas during a process in which the elevation of the piston increases slowly by 2 ft. The piston and cylinder are poor thermal conductors, and friction between the piston and cylinder can be neglected. Determine the work done by the gas on the piston, in Btu, and the change in internal energy of the gas, in Btu. Step 1 Determine the expansion work done by the gas on the piston, in Btu. Wexp = i Btu

Some unknown gas undergoes a polytropic process, pV^1.5 = constant, the initial pressure, p1, is 1 bar, and the initialvolume, V1, is 1 m3. We also know the final volume, V2, is 4 m3. Please determine 1) the final pressure of the gas, p2, inbar; and the total work done by the gas, W, in kJ; 2) judge the direction of energy flow for the work: into the system or outof the system.