Dynamic characteristics for evaporator in Organic Rankine Cycle

Organic Rankine Cycle (ORC) is suitable for recovering energy from low-grade heat sources. A moving boundary model is introduced to describe the transient phenomena of evaporator, which is an important component of ORC. Based on the partial-differential equations expressing the conservation principles of mass and energy, coupled with flue gas and tube wall energy equations, a set of ordinary-differential equations can be obtained by integrating separately over the three regions: unsaturated liquid, liquid-vapor mixture, and the superheat vapor. The state space equation of evaporator can be derived by linearizing the obtained equations at the operating point. Finally, the simulation results are presented to show the feasibility of the proposed method of modeling.