A Generalised Assessment of Working Fluids and Radial Turbines for Non-Recuperated Subcritical Organic Rankine Cycles
A Generalised Assessment of Working Fluids and Radial Turbines for Non-Recuperated Subcritical Organic Rankine Cycles
复制标题
DOI：
10.3390/en11040800
复制
发表时间：
2018-03
期刊：
影响因子：
3.2
通讯作者：
M. White;A. Sayma
中科院分区：
文献类型：
--
作者：
M. White;A. Sayma
本文的目的是进行全面的评估，最佳的工作流体和径向涡轮机设计的小规模有机朗肯循环（ORC）系统在一系列的热源温度。前者是通过将亚临界、非再循环循环的热力学模型与Peng-Robinson状态方程耦合，并针对80 ° C至360 ° C的热源温度范围优化工作流体和循环参数来实现的。工作流体的临界温度被发现是一个重要的参数，管理工作流体的选择。此外，当热源温度低于300 ° C时，发现热源温度与实现最大功率输出的最佳临界温度之间存在线性相关性（T cr = 0.830 T hi + 41.27）。这种相关性已被验证对循环计算完成了九个预定义的工作流体，使用Peng-Robinson状态方程和使用REFPROP程序。最终，这种简单的相关性可用于识别特定热源温度的工作流体候选者。本文的后半部分研究了热源温度对25 kW亚临界ORC系统向心涡轮机转子优化设计的影响。随着热源温度的升高，最佳叶片载荷系数增大，而最佳流量系数减小。此外，通道损失在用于低温应用的涡轮机中占主导地位。然而，在较高的热源温度下，由于叶片高度的降低，间隙损失变得更占主导地位。这些信息可用于确定提高这些机器效率的最直接途径。最后，观察到从传统收敛定子到收敛-发散定子的过渡发生在大约165 ° C的热源温度下，而当热源温度超过250 ° C时，径向纤维涡轮机似乎不合适;这些结论可用于在早期阶段通知膨胀机设计和选择。
The aim of this paper is to conduct a generalised assessment of both optimal working fluids and radial turbine designs for small-scale organic Rankine cycle (ORC) systems across a range of heat-source temperatures. The former has been achieved by coupling a thermodynamic model of subcritical, non-recperated cycles with the Peng–Robinson equation of state, and optimising the working-fluid and cycle parameters for heat-source temperatures ranging between 80 ° C and 360 ° C . The critical temperature of the working fluid is found to be an important parameter governing working-fluid selection. Moreover, a linear correlation between heat-source temperature and the optimal critical temperature that achieves maximum power output has been found for heat-source temperatures below 300 ° C ( T cr = 0.830 T hi + 41.27 ). This correlation has been validated against cycle calculations completed for nine predefined working fluids using both the Peng–Robinson equation of state and using the REFPROP program. Ultimately, this simple correlation can be used to identify working-fluid candidates for a specific heat-source temperature. In the second half of this paper, the effect of the heat-source temperature on the optimal design of a radial-inflow turbine rotor for a 25 kW subcritical ORC system has been studied. As the heat-source temperature increases, the optimal blade-loading coefficient increases, whilst the optimal flow coefficient reduces. Furthermore, passage losses are dominant in turbines intended for low-temperature applications. However, at higher heat-source temperatures, clearance losses become more dominant owing to the reduced blade heights. This information can be used to identify the most direct route to efficiency improvements in these machines. Finally, it is observed that the transition from a conventional converging stator to a converging-diverging stator occurs at heat-source temperatures of approximately 165 ° C , whilst radially-fibered turbines seem unsuitable as the heat-source temperature exceeds 250 ° C ; these conclusions can be used to inform expander design and selection at an early stage.