Influence of geometric and environmental parameters on air-cooled steam condenser performance

["Numerical modeling", "Wind effects", "Fan performance", "Dissertations -- Mechanical engineering", "Theses -- Mechanical engineering", "Power-plants -- Cooling", "Air-cooled steam condensers"]

Joubert, Retief ; Kroger, D. G.

Stellenbosch University

Others  :  https://scholar.sun.ac.za:443/bitstream/10019.1/4153/1/joubert_influence_2010.pdf

瑞士|英语

来源: Stellenbosch University

【 摘 要 】

ENGLISH ABSTRACT: Air-cooled steam condensers (ACSCs) are used in the power generation industry to directlycondense turbine exhaust steam in areas where cooling water is expensive or unavailable.Large axial flow fans force ambient air through A-frame heat exchanger bundles made up of anumber of rows of finned tubes through which the steam is ducted and consequentlycondensed during the heat transfer process to the air. The heat rejection rate or performanceof an ACSC is proportional to the air mass flow rate, determined by fan volumetricperformance, and the temperature difference between the finned tubes and the air.The air flow through a 30 fan ACSC (termed the generic ACSC) operating under windyconditions is solved using the commercial computational fluid dynamics (CFD) code FLUENTand the required data is extracted from the solution to calculate performance trends. It isfound that fan performance is reduced due to a combination of factors. The first is additionalupstream flow losses caused by separated flow occurring primarily at the leading edge of theACSC and secondarily at the fan bellmouth inlets. The second factor leading to reduced fanperformance is the presence of distorted flow conditions at the fan inlets. Hot plume airrecirculation is responsible for decreased ACSC thermal performance due to increased fan inletair temperatures. It is found that reduced fan performance is the greater contributor toreduced ACSC performance.The performance effects of varying two geometrical parameters of the generic ACSC, namelythe fan platform height and the windwall height, are investigated under windy conditions. It isfound that each parameter is linked to a specific mechanism of performance reduction withthe fan platform height affecting fan performance and the windwall height affectingrecirculation. The respective platform and windwall heights specified for the generic ACSC arefound to provide acceptable performance results.To mitigate wind induced performance reductions a number of modification and additions tothe ACSC are investigated. These primarily aim at improving fan performance and included theaddition of walkways or skirts, the addition of wind screens beneath the fan platform,removing the bellmouth fan inlets, using different types of fans and increasing fan power. Theaddition of a periphery walkway and windscreens is considered to be the most practicalmethods of improving ACSC performance under windy conditions. The generic ACSC ismodified to include both modifications and under high wind conditions the performance isfound to increase measurably. The modifications also resulted in the ACSC performance beingless sensitive to wind direction effects.