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Evaluation of Heat Recovery Steam Generator

serrated Finned Tube

Evaluation of Heat Recovery Steam Generator for Gas/Steam Combined Cycle Power Plants

Abstract The combined cycle power plant consists of topping cycle,bottoming cycles and heat recovery steam generators(HRSGs) as the integral systems.The main focus of this work is to predict and analyse fluid flow behaviour in HRSG.The heat transfer and pressure drop analysis are performed byusingcomputational fluid dynamics(CFD) model.The CFD model capability for predicting heat transfer and pressure drop performance of finned tube in cross-flow is analysed.The HRSGS having serrated tube and steady-state approach,with a two-equation turbulence model is employed to examine fluid flow having Reynolds numbers variation from 5000 to30,000. The external flow Nusselt number and overall pressure drop predicted by the CFD model are compared with those predicted by published empirical correlations.

Keywords Heat recovery steam generator·Serrated tubes·Heat transfer· Pressure drop·Combined cycle power plants

This work presents the comparative analysis for helically segmented finned tubes by using heat transfer and pressure drop model by using CFD tool for the economizer. Three tubes are compared with each other based on Nusselt number, pressure drop.temperature difference and overall heat transfer coefficient for the interaction of fluid.The water flows inside the tubes and the gas flows outside the tubes.The tubes are arranged in a shell in the horizontal directionwhile the flue gases are allowed to flow verticallyThe interaction of flue gases and feed water is noticed and how the serrated tube disrupts the boundary layer of flue gases thickened near the tubes. The thermal evaluation was analysed using properties of fluid tube and fin materials, tube geometry and operating conditions.The theoretical model was compared with the simulated model.The different tube geometry is analysed with different configurations such as solid tube,27-segmented tube and 30-segmented tube. These evaluations are based on different Reynolds numbers from 5000 to30,000 of flue gases. To study and compare the performance based on existing plant, the material used for HRSG(Economizer) has been considered similar to the one being currently used in the existing HRSG at combined cycle power plant of Delhi.India.The tube material considered in economizer section of the HRSGis detailed.The fluid properties (exhaust gases and water) and the material properties are taken from Sharma and Singh.

The CFD model used in this simulation is k-erealizablescalable viscous heating turbulence model.