Experimental verification of the self-condensing CO2 transcritical power cycle

Abstract

CO2 is an excellent natural working fluid for both power cycles and refrigeration cycles. However, it limits the actual application of the CO2 transcritical power cycle that subcritical CO2 is hard to be condensed by conventional cooling water. Aiming to search solutions for this condensing problem, this work carried out an experimental verification of a novel cycle named self-condensing CO2 transcritical power cycle and got some operation laws of the system. The results showed that the self-condensing CO2 transcritical power cycle can operate well with conventional cooling water around 30 °C. In most cases, the operation was steady and could be adjusted easily. The saturated liquid CO2 even as cold as 5 °C was generated for the pump. It is beneficial for the power sub-cycle to keep inlet pressure and outlet temperature of the throttle valve as high as possible. In the throttling process, the maximum pressure drop and temperature drop were about 3.6 MPa and 25 °C, respectively. A transcritical or near-critical throttling occurred in the experimental investigation and the pump usually experienced a transcritical compression under high pump inlet temperature. In summary, the self-condensing CO2 transcritical power cycle had been verified and is fully feasible in a practical application.