Design study of configurations on system COP for a combined ORC (organic Rankine cycle) and VCC (vapor compression cycle)

The study introduced a novel thermally activated cooling concept – a combined cycle couples an ORC (organic Rankine cycle) and a VCC (vapor compression cycle). A brief comparison with other thermally activated cooling technologies was conducted. The cycle can use renewable energy sources such as solar, geothermal and waste heat, to generate cooling and power if needed. A systematic design study was conducted to investigate effects of various cycle configurations on overall cycle COP. With both subcooling and cooling recuperation in the vapor compression cycle, the overall cycle COP reaches 0.66 at extreme military conditions with outdoor temperature of 48.9 °C. A parametric trade-off study was conducted afterwards in terms of performance and weight, in order to find the most critical design parameters for the cycle configuration with both subcooling and cooling recuperation. Five most important design parameters were selected, including expander isentropic efficiency, condensing and evaporating temperatures, pump/boiling pressure and recuperator effectiveness. At the end, two additional cycle concepts with either potentially higher COP or practical advantages were proposed. It includes adding a secondary heat recuperator in the ORC side and using different working fluids in the power and cooling cycles, or so-called dual-fluid system.