# Example Problem with Complete Solution

1D-2 : Thermodynamic Cycles in Normal Life 3 pts
 List three common devices that make use of thermodynamic cycles and explain how you know they operate using a thermodynamic cycle. Read: Not much to say here. Given: Find: Assumptions: Equations / Data / Solve: Answers: 1- Refrigerator Work and heat cross the system boundary, but mass does not. The refrigerant undergoes a cyclic process involving changes in both T & P, but the refrigerant always returns to the same initial state to begin the cycle again. 2- Air conditioner Work and heat cross the system boundary, but mass does not. The refrigerant undergoes a cyclic process involving changes in both T & P, but the refrigerant always returns to the same initial state to begin the cycle again. 3- Automobile This one is a bit trickier. Work and heat cross the system boundary. Heat enters the working fluid (air) from the heat source (burning gasoline) and work leaves the system in the form of a rotating drive shaft or gear train. It is not as clear that the air undergoes a cyclic process. It may help to consider all the air in the world as the working fluid for the cycle. The engine draws in air at ambient temperature. It undergoes changes in T & P inside the engine and is exhausted back into the environment at a higher temperature. Eventually, the exhausted air cools back down and returns to its initial state to complete the cycle.