Yang Qichao

Theoretical and experimental research on scroll expander used in small-scale organic Rankine cycle system

Scroll expander is suitable for small-scale organic Rankine cycle system. In this article, a detailed mathematical model describing the stable and dynamic process of scroll expander is built, an experiment system is set up, and the performance of scroll expander is tested. The results show that the p−V diagram of simulation and experiment show good agreement. The volumetric efficiency of scroll expander increases with rotating speed, and the maximum value is 63% under the tested condition. The isentropic efficiency increases at low rotating speed but then decreases, and the maximum value is 36.4%. Both the stable rotating speed and stable time of scroll expander increase with the electric resistance; here the stable time is defined as the elapsed time when the scroll expander varies from one stable condition to another. Although the transient rotating speed varies periodically with running time when the scroll expander runs stably, the variable quantity can be ignored. The total efficiency of expander and system efficiency first increase with the rotating speed and then decrease, and the maximum values are 41% and 2.9%, respectively, when the Carnot efficiency is 21.2% and the maximum theoretical efficiency is 8%.