EPRI: Collaborative Research: autoFlutter: Efficient, Waterless Power Plant Cooling

CBET-1357819Mittal电厂冷却系统用水的消耗率和回收率由于供水和成本有限、监管限制和环境问题而变得难以为继。然而，目前常规凝汽器系统的干风冷却效果一直受到冷风热阻高、空气热容量差等问题的阻碍。显然，为了能够显著降低发电用水量，必须显著加强冷凝蒸汽和空气侧介质之间的换热。早期改进空气侧换热的尝试集中于增加表面特征(凹陷等)。在散热片上取得了有限的成功，但风扇功率显著增加。该程序通过利用冷却气流和微型自主颤动簧片(AFR)之间的相互作用来诱导凝汽器翅片表面附近小尺度涡流运动的形成和平流，从而克服了空气侧热传输的限制。这种方法的一个独特之处是，通过利用嵌入冷却气流的机械能以极低的压力损失惩罚产生簧片颤振。这些低成本的薄簧片可以为冷凝器的不同区域量身定做，并可以作为外部冷凝器表面的整体制造，也可以作为现有冷凝器的翻新组件。簧片组件易于安装和维护，无需修改厂级基础设施。初步的强化换热和压降分析结合凝汽器设计和发电厂模拟表明，与湿法冷却相比，采用AFR技术的空冷凝汽器可以提高工厂效率，同时显着降低水耗。该研究计划将重点放在使热电厂冷凝器技术的进步能够克服目前通过干燥空气冷却的限制，从而显著减少蒸发冷却的用水量。该方法通过利用冷却气流和微型自主颤动簧片之间的相互作用来诱导冷凝器翅片附近的小尺度涡流运动的形成和平流，从而克服了空气侧热传输的局限性。这种方法的一个独特之处是，通过利用嵌入冷却气流的机械能以极低的压力损失惩罚产生簧片颤振。该计划包括综合的实验/建模/数值调查，重点是实施、设计和优化AFR所需的基本知识，并展示它们在改善发电厂配置和运行条件下凝汽器翅片空气侧通道的换热特性方面的有效性。佐治亚理工学院的研究将集中于AFR强化换热特性的实验研究，以及AFR技术实现的新型冷凝器配置的建模、设计和测试。约翰霍普金斯大学将专注于小规模换热的CFD研究，以及AFR增强型冷凝器配置的性能评估和优化。最近在佐治亚理工学院的风冷加热管道中证明了AFRs的小规模强化换热，具有显著的换热强化作用。这些低成本的薄簧片可以为冷凝器的不同区域量身定做，并可以作为外部冷凝器表面的整体制造，也可以作为现有冷凝器的翻新组件。簧片组件易于安装和维护，无需修改厂级基础设施。

CBET-1357819MittalThe rate of consumption and withdrawal of water for use in power plant cooling systems has become untenable in light of limited water supply and cost, as well as regulatory restrictions, and environmental concerns. However, the effectiveness of dry air cooling of current, conventional condenser systems has been hindered by the high thermal resistance and poor air thermal capacity of the cooling air. It is clear that in order to enable an appreciable decrease in water consumption for power generation, the heat transfer between the condensing steam and the air-side medium must be significantly enhanced. Earlier attempts to improve the air-side heat transfer focused on the addition of surface features (dimples, etc.) on the cooling fins with limited success and significant increase in fan power. The proposed program overcomes the limits of air-side heat transport by exploiting interactions between the cooling air flow and miniature, autonomously-fluttering reeds (AFRs) to induce the formation and advection of small-scale vortical motions near the condenser fin surfaces. A unique aspect of this approach is that reed flutter is generated by harnessing mechanical energy from the embedding cooling air flow at exceedingly low penalty in pressure losses. These low-cost thin reeds can be tailored for different regions of the condenser and fabricated either integral to the external condenser surfaces or as drop in retrofit assemblies for existing condensers. The reed assemblies are easy to install and maintain without plant level infrastructure modifications. Preliminary heat transfer enhancement and pressure drop analyses coupled with condenser designs and power plant simulations have shown that air-cooled condensers using AFR technology can increase plant efficiency while significantly reducing water consumption compared to wet cooling. The research program will focus on enabling advances in thermoelectric power plant condenser technology to overcome current limits of cooling by dry air and thereby significantly reduce water usage for evaporative cooling. The present approach overcomes the limits of air-side heat transport by exploiting interactions between the cooling air flow and miniature, autonomously-fluttering reeds (AFRs) to induce the formation and advection of small-scale vortical motions near the condenser fins. A unique aspect of this approach is that reed flutter is generated by harnessing mechanical energy from the embedding cooling air flow at exceedingly low penalty in pressure losses. The program encompasses integrated experimental/modeling/numerical investigations that will focus on the fundamental knowledge needed to implement, design, and optimize the use of the AFRs, and demonstrate their efficacy in improving the heat transfer characteristics of finned air-side passages of condensers in power plant configurations and operating conditions. The research at Georgia Tech will focus on experimental investigations of the heat transfer characteristics enhanced by the AFRs along with the modeling, design, and testing of novel condenser configurations enabled by the AFR technology. Johns Hopkins University will focus on CFD investigations of small-scale heat transfer and performance evaluation and optimization of AFR-enhanced condenser configurations. Small-scale heat transfer enhancement by AFRs was recently demonstrated in air-cooled heated ducts at Georgia Tech with significant heat transfer enhancement. These low-cost thin reeds can be tailored for different regions of the condenser and fabricated either integral to the external condenser surfaces or as drop in retrofit assemblies for existing condensers. The reed assemblies are easy to install and maintain without plant level infrastructure modifications.