ABSTRACT

CBET-1357819
Mittal

The 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.

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