Case Studies

E L I T E C H A N N E L PA R T N E R simulation@rand.com | RandSIM.com | 888.483.0674 Large Combined Cycle Power Plant Utilizes CFD Modeling to Predict the Negative Cross Wind Effects on a Large Air Cooled Condenser Rand Simulation Models Plant Airflows to Improve ACC Efficiency and Reduce Turbine Backpressure The Challenge Air cooled condensers (ACCs) cool the steam turbines, which are the primary component in generating power. ACCs condense exhaust steam and return condensate to the boiler without water loss. During the summer at a large power generation plant in the southwest, given particular wind patterns, hot air from huge fans blowing air off the condensers was found to re-entrain into the suction side of the ACC train. When the ACCs re-ingested this warmer air, it reduced their efficiency and introduced increased backpressure into the steam turbines. The company was experiencing unit derates in power generation plants when the summers were warm and the wind blew from a certain direction. And summer time was the peak period where the majority of profits were made given increased customer demand for electricity during those months. "We had been dealing with summer power output decreases due to hot weather winds for almost ten years," said the plant manager. "We tried various solutions through trial and error, but it was labor intensive and nothing completely solved the issue. We knew that a computational fluid dynamic (CFD) analysis of the airflow around the plant and across the ACCs could help better position air flow wind deflectors and make these units work better, but we had dismissed it as too costly." When a supplier introduced Rand Simulation's CFD team to the power plant's parent company, they discovered that CFD for plant-level analysis was not only cost effective, but also the ideal way to explore how to improve ACC and fan performance. After a recent project in the northeast, the plant engineers could see the clear ROI in CFD analysis so they began to work with the Rand Simulation CFD Analysis group as well. The Solution Plant engineers outlined their goals. They wanted to increase the overall fan flow rate and to improve flow uniformity across all the fans to improve efficiencies during the summer months. Working remotely via phone and desktop sharing, Rand Simulation CFD experts quickly built representative 3D CAD models of the plant from photographs and drawings. The team used the models to simulate existing airflows and air temperatures around the facility, including ACC and fan stack exhaust, as well as wind speed, direction and temperature. The models showed that changing the direction of the airflow on the inlet side of the ACC fans would provide greater fan throughput, thus improving power output. "Turbine derates due to increased backpressure caused by hot weather winds were costing us significant generation loss. With Rand Simulation's expert CFD analysis, we were able to identify problem areas to increase overall air cooled condenser effectiveness." —Plant Manager

• Cover