An ideal cycle is simple to analyze and consists of:
# TOP (A) and BOTTOM (C) of the loop: a pair of parallel isobaric processes
# RIGHT (B) and LEFT (D) of the loop: a pair of parallel isochoric processes
If the working substance is a perfect gas,  is only a function of  for a closed system since its internal pressure vanishes. Therefore, the internal energy changes of a perfect gas undergoing various processes connecting initial state  to final state  are always given by the formula
Assuming that  is constant,  for any process undergone by a perfect gas.
Under this set of assumptions, for processes A and C we have  and , whereas for processes B and D we have  and  .
The total work done per cycle is , which is just the area of the rectangle. If the total heat flow per cycle is required, this is easily obtained. Since , we have .
Thus, the total heat flow per cycle is calculated without knowing the heat capacities and temperature changes for each step (although this information would be needed to assess the thermodynamic efficiency of the cycle).