Off-design performance analysis of a combined cooling and power system driven by low-grade heat source

Abstract

The combined cooling and power (CCP) system integrating the organic Rankine cycle with the ejector refrigeration cycle is a modern solution for low-grade geothermal water. This paper conducts a quantitative analysis of the off-design performance of a CCP system based on a specially designed combination of a radial inflow turbine, an ejector and plate heat exchangers. The CCP system operating at a vapor split ratio of 0.5 is studied, and a novel preliminary design and off-design simulation process are presented. The sliding pressure operation strategy is used to achieve good off-design performance. The results indicate that the CCP system produces 153.76 kW cooling and has a cooling to net power ratio of 1.58 at the design point. The increasing geothermal water mass flow rate ratio could lower thermal efficiency, exergy efficiency and cooling to net power ratio. Higher geothermal water inlet temperature results in lower thermal efficiency. Among the geothermal water inlet temperature, the saturated condensing temperature and the evaporator saturated temperature, the net power is affected mostly by the saturated condensing temperature while the cooling and thermal efficiency are mostly influenced by the evaporator saturated temperature.