采用二元非共沸工质的有机朗肯循环热力学分析

Thermodynamic Analysis of Organic Rankine Cycle Based on Binary Zeotropic Mixtures

摘要:

建立了亚临界混合工质有机朗肯循环热力学模型，基于沸点差法提出了混合工质筛选方案，以净输出功为目标函数优化了蒸发参数和质量配比，针对不同热源温度筛选出了最佳混合工质；比较分析了最佳混合工质和最佳纯工质的系统性能参数、损分布.结果表明，各热源温度下最佳混合工质的净输出功均超过了同热源温度下的最佳纯工质，增长幅度为0.13%~5.04%.较小的汽化潜热和接近冷却水温升的冷凝温度滑移是混合工质净输出功大于纯工质的主要原因；混合工质的膨胀机进口处压力、温度均低于纯工质，最大降低幅度分别达到了27.08%和9.93%；混合工质的膨胀机损和冷凝器损均小于纯工质，总损也低于纯工质.

Abstract:

In order to explore the feasibility of using binary zeotropic mixtures to replace pure fluids, a subcritical organic Rankine cycle thermodynamic model based on mixtures was established. A screening method of mixtures was proposed on the basis of the boiling point difference. The net power output was selected as the optimization target for the evaporation parameter and mass ratio. For different heat source temperatures, the best mixtures were selected. The system performance parameters and energy loss distribution of the best mixtures and pure fluids are compared. The results show that the net power output of the best mixture is greater than that of the best pure fluid at the same heat source temperature with an increment ranging from 0.13% to 5.04%, which mainly results from mixtures’ smaller latent heat of vaporization and cooling temperature glide closing to cooling water temperature rise. The inlet temperature and pressure of the expander with mixtures are lower than those of pure fluids, and the decrement can reach up to 9.93% and 27.08% respectively. Compared with the best pure fluids, the best mixtures have lower exergy loss in the expander and condenser, which makes the total exergy loss of mixtures lower than that of pure fluids.