Construction of vapor compression cycle with composite pressure-regulating components using GraPHsep method

Abstract

Developing efficient vapor compression systems is a technical approach that effectively achieves low-carbon cooling and heating. An effective method for constructing vapor compression cycles is key to further improving the system’s energy efficiency. In our previous study, an integrated optimization method, called GraPHsep, was proposed for constructing the vapor compression cycle and heat exchange network. The method can synchronously optimize the structure and parameters of the cycle as well as the layout of the heat exchanger network. Composite pressure-regulating components that perform multiple adiabatic pressure-regulating processes, such as vapor-injected compressors, ejectors, and supersonic two-phase expanders, have the potential to improve the energy efficiency of the vapor compression cycle. In this study, the adaptability of the GraPHsep method is expanded to construct vapor compression cycles with composite pressure-regulating components. The general method consists of two steps: (1) solving the cycle topologies composed of pressure-regulating components using graph theory and (2) optimizing the heat exchanger network integrated with refrigerant and thermal fluids based on pinch analysis. The method is applied to construct a zeotropic vapor compression cycle with an ejector used for a high-temperature heat pump. The constructed cycle increases the coefficient of performance by 10.1% and 34.6%, respectively, compared to a single-stage compression cycle with a recuperator and that with an ejector using pure refrigerant.