Liquid piston compression efficiency with droplet heat transfer
Liquid piston compression efficiency with droplet heat transfer
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DOI：
10.1016/j.apenergy.2013.10.005
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发表时间：
2014-02-01
期刊：
影响因子：
11.2
通讯作者：
Loth, Eric
中科院分区：
文献类型：
--
作者：
Qin, Chao;Loth, Eric
风力涡轮机和其他不稳定的发电系统可以通过集成廉价且易于定位的压缩空气能量存储（CAES）来提供更连续的能量供应而大大受益。然而，传统的CAES还没有与离岸风力涡轮机相结合。此外，典型的CAES系统是低效的，因为压缩功还产生热能，当加压空气长时间储存时，热能通常损失到环境中。为了使离岸风能存储，液滴喷雾传热的概念进行了研究，以建立一个近等温的高效压缩过程。特别地，使用小水滴和高质量负载可以允许用于热传递的大界面表面积。与这种液体引入相关联的问题可以用液体活塞来缓解，这也允许可变的活塞横截面以进一步提高效率。为了研究液滴喷雾传热的概念，开发了详细的多相热力学模型，并用实验数据进行了验证。基于这种方法，一维模拟进行了使用正弦驱动的活塞在5千瓦的第一级气缸与各种压缩比，以及预混合和直接喷射的情况。结果表明，在液体活塞中，高空液滴的总表面是实现高性能的关键。这最好通过小液滴和高质量负载与直接喷射相结合来实现。例如，对于十倍压力，压缩效率（定义为等温储存能量与真实的压缩功的比率）从绝热压缩的71%增加到喷雾喷射的98%。然而，液滴碰撞（与其他液滴和腔室壁），三维，喷射器动力学和壁热传递的影响，应考虑下一步，以帮助改善设计和理解这样的系统。(C)2013爱思唯尔有限公司保留所有权利。
Wind turbines and other unsteady power producing systems can benefit substantially by integrating inexpensive and easily sited Compressed Air Energy Storage (CAES) to provide a more continuous energy supply. However, traditionally CAES has not been combined with off-shore wind turbines. In addition, typical CAES systems are inefficient since the compression work also generates thermal energy, which is generally lost to the ambient when pressurized air is stored over a long period of time. To enable off-shore wind energy storage, a droplet spray heat transfer concept is investigated to establish a near-isothermal high-efficiency compression process. In particular, the use of small water droplets and high mass loading can allow for a large interfacial surface area for heat transfer. Issues associated with this liquid introduction can be mitigated with a liquid piston, which also allows variable piston cross-sections to further improve efficiency. To investigate the droplet spray heat transfer concept, a detailed multiphase thermodynamic model was developed and validated with experimental data. Based on this approach, one-dimensional simulations were performed using a sinusoidally driven piston in a 5 kW first-stage cylinder with various compression ratios, as well as both pre-mixed and direct injection scenarios. The results show that the total surface of aloft droplets is critical to achieve high performance in a liquid piston. This is best achieved with small droplets and high mass loadings combined with direct injection. For example, the compression efficiency (defined as a ratio of isothermal stored energy to real compression work) increased from 71% for adiabatic compression to as much as 98% with spray injection, for a tenfold pressure. However, the effects of droplet collision (with other droplets and the chamber walls), three-dimensionality, injector dynamics, and the wall heat transfer should next be considered to help improve design and understanding of such systems. (C) 2013 Elsevier Ltd. All rights reserved.