Trapezoid Cycles and Extended Pinch Analysis

• Trapezoid shaped thermodynamic cycles are introduced.
• Calculation methods for cycle COP of Trapezoid Cycles are shown.
• The Pinch Analysis is transferred into the T-S-diagram.
• Trapezoid Cycles are introduced into the Extended Pinch Analysis.

Trapezoid Cycles are thermodynamic cycles, mainly vapour compression cycles, which simply spoken adapt to the heat source curve and the heat sink curve in the temperature – entropy – diagram (T-S-diagram). The name of the cycles refers to the case of sensible heat, where the shapes of these cycles is similar to trapezoids. It was shown before that trapezoid cycles are feasible by adding storage devices to the cycle setup.In this article exact and simplified theoretic equations for the calculation of the COP of different cases of Trapezoid Cycles both with and without influence of dissipation are presented. These equations allow a mathematically simple prediction of the COP with very small error.Further the use of Trapezoid Cycles in the well-known Pinch Analysis is derived on a graphical basis (T-S-diagram). Heat which is usually lost in the Pinch Analysis will become usable with the highest thermodynamic possible efficiency.