Trapezoid vapour compression heat pump cycles and pinch point analysis

• We introduce trapezoid shaped thermodynamic cycles.
• We describe an example case of pinch point analysis.
• Two possibilities of integration of heat pumps are shown.
• The heat exchanger and storage tank setups are derived for the two methods.

Trapezoid Cycles are thermodynamic cycles, which basically adapt to the heat source curve and the heat sink curve in a temperature–entropy diagram (T–S-diagram). The name trapezoid cycle refers to the shape of these cycles in the T–S-diagram describing heat sources with sensible heat. It was shown earlier that trapezoid cycles are feasible when storage devices are added to the cycle setup. Two cases of an improved pinch analysis are shown in which trapezoid cycles can be implemented in plants for heat recovery. This methods lead to drastic improvement of cycle efficiency.In this article, the valve, heat exchanger and storage tank setup are derived for an example plant. The two methods of extended pinch analysis are described and compared to each other. For both methods the storage tank setup is derived.The second method differs from the first through an innovative integration of heat pumps in pinch analysis and consequently offers improved efficiency.