Correction of cavitation with thermodynamic effect for a diaphragm pump in organic Rankine cycle systems
Correction of cavitation with thermodynamic effect for a diaphragm pump in organic Rankine cycle systems
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DOI：
10.1016/j.egyr.2020.10.013
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发表时间：
2020-11-01
期刊：
影响因子：
5.2
通讯作者：
Yu, Zhibin
中科院分区：
文献类型：
--
作者：
Li, Wenguang;Mckeown, Andrew;Yu, Zhibin
隔膜泵是一种防泄漏往复泵，具有低流量、高扬程和更高的效率，并且可以在有机朗肯循环（ORC）系统中作为有机流体到蒸发器的进料泵找到应用。当泵输送有机流体时，ORC系统中的隔膜泵不可避免地会在泵吸入室中遭受气蚀。然而，迄今为止，对于有机流体，泵的空化性能还知之甚少。文中根据泵厂提供的现有性能图表，从泵转速和冷水入口液体压力等方面确定了具体隔膜泵的性能。当泵以 480rpm 的转速将有机液体 R245fa 输送到 ORC 系统中的蒸发器时，通过考虑空化中的热力学效应来预测所需的净正吸头 (NPSHr)。计算入口液体压力为 100 kPa 和 141 kPa 时的可用净正吸头 (NPSHa)，并解决相应的空化安全裕度。计算出 NPSHr 和 NPSHa 的过冷度以及安全裕度。建立了吸入阀运动的两个一维 (1D) 机械模型，并在 480rpm、100 kPa 和 141 kPa 入口压力下求解。进行了初步实验以验证分析结果。结果表明，由于空化的热力学效应，冷水的NPSHr从3.02m NPSHr降低到2.02m，相应的过冷度从12.38℃降低到8.28℃。100kPa但141kPa的入口压力会导致泵中出现空化。一维机械模型受到吸入室流场粗略空间分辨率的影响，因此需要对流场进行三维（3D）数值模拟。 (C) 2020 作者。由爱思唯尔有限公司出版
Diaphragm pumps are a sort of leakage-proof reciprocating pumps with low flow rate but high head and better efficiency, and can potentially find their applications in organic Rankine cycle (ORC) systems as the feed-pump of organic fluid to the evaporator. A diaphragm pump in an ORC system may suffer from cavitation in the pump suction chamber inevitably when the pump delivers an organic fluid. However, the cavitation performance of the pump has been a little known for organic fluids so far. In the article, the performance of a specific diaphragm pump was determined based on the existing performance charts provided by the pump manufactory in terms of pump rotating speed and inlet liquid pressure for cold water. The net positive suction head required (NPSHr) was predicted by involving thermodynamic effect in cavitation when the pump feeds the organic liquid R245fa to the evaporator in an ORC system at 480rpm rotational speed. The net positive suction head available (NPSHa) was calculated at 100 kPa and 141 kPa inlet liquid pressures, and the corresponding cavitation safety margins were addressed. The subcooling for the NPSHr and NPSHa as well as the safety margin were figured out. Two one-dimensional (1D) mechanical models for motion of the suction valve were built and solved at 480rpm and 100 kPa and 141 kPa inlet pressures. A preliminary experiment was performed to verify the analytical results. It turned out that the NPSHr is reduced to 2.02m from 3.02m NPSHr of cold water due to the thermodynamic effect in cavitation, and the corresponding subcooling is lowered to 8.28 degrees C from 12.38 degrees C. 100 kPa but 141 kPa inlet pressure can result in cavitation in the pump. The 1D mechanical models are subject to a rough spatial resolution for the flow field in the suction chamber, hence three-dimensional(3D) numerical simulations of the flow field are desirable. (C) 2020 The Author(s). Published by Elsevier Ltd.