Optimization And Dynamic Simulation Of Subcritical Organic Rankine Cycle

Organic Rankine Cycle(ORC) power generation technology has a broad prospect for development in the field of low-temperature waste heat recovery and utilization. It draws attentions by simple structure, high thermal efficiency and environmentally friendly. This paper focuses on how to achieve effective and economical recycling of ORC power generation system at the given conditions of heat source. Therefore, it is so important for the analysis of the system performance under off-design conditions and dynamic simulation about the system. The main conclusions for this study are as follows:Firstly, R245 fa was chosen as working fluid at the given conditions of heat source in this study. Then, it takes the thermal efficiency, exergy efficiency and the initial investment cost as the optimization object, compared the comprehensive performance of ORC with Recuperator, Reheat ORC and Basic ORC power generation systems which using R245 fa as working fluid. The results show that the Reheat ORC has the worst performance compared to the other two systems. The Basic ORC power generation system is the best when choosing a low exergy efficiency in Pareto optimal value space. ORC with Recuperator and Basic ORC power generation system all can be selected at high exergy efficiency in Pareto optimal value space.It shows that whatever the system, there is no need for a large superheat temperature by analyze of the distribution of the decision variables within its range. It has a great impact for evaporating pressure, condensing pressure, mass flow rate of working fluid on the objective function. The sensitivity analysis shows that condensing pressure is the most significant effect on the objective function. The effectiveness of regenerator has a small impact on the investment costs in the range of 0.3 to 0.6.The decrease of reheat pressure results in the increase cost on reheat and evaporator. But thermal efficiency is decrease, while the exergy efficiency increase,.The goal is to maximize the output power for the energy recovery system and to select the best operating parameters which could make full use of remaining heat under off-design conditions operate as sliding pressure of the expander. In order to achieve maximum power output at the heat source load is reducing,the working fluid should heated to just the saturated vapor state at the evaporator outlet. The heat source temperature changes have a more significant impact than the heat source mass flow rate on the system optimal pressure, and the net power output and the thermal efficiency increased with increasing heat source’s temperature or mass flow rate. However, the heat recovery efficiency is increased with the increasing temperature of the heat source, while the heat recovery efficiency is decreased with the increasing of mass flow rate.The ORC systems with various components of the simulation module are developed. It is carried out by analysis of the dynamic response of the system main parameters when external conditions change. The results show that a response time for a step change of heat source temperature or cooling water mass flow rate is longer to reach equilibrium. The regenerator has a significant impact on the system response.