Modelling of high-temperature tube heat exchangers operating at supercritical pressure

Jan Taler, Dawid Taler, Katarzyna Węglarz, Mateusz Marcinkowski and Marek Węglarz

Energy, 2025, vol. 317, issue C

Abstract: A new analytical-numerical method for modelling supercritical crossflow superheaters is presented. Steam flows inside the tubes, while flue gas flows perpendicularly outside. The heat exchanger is divided into finite volumes. Analytical formulas were derived to calculate fluid temperatures within a control volume, significantly reducing computation time. The specific heat of steam is a function of pressure and temperature, and the specific heat of flue gas depends on temperature. Steam pressure distribution was determined by solving the momentum conservation equation. A new formula for calculating the friction factor in rough tubes was proposed, along with equations to identify the Reynolds number, above which the friction factor depends only on relative roughness. Convective and radiative heat transfer, including the effects of ash deposits on tube surfaces, are considered. The total circumferential stress from pressure and thermal load in the tube wall was calculated. The method accurately predicts steam and flue gas temperatures in a two-pass live steam supercritical superheater working at 100 % load. Considering that steam at supercritical pressure is a real gas causes an increase in the heat flow rate from exhaust gases to steam by about 2.5 % compared to isobaric steam superheating at a constant average pressure in the superheater.

Keywords: Supercritical steam superheater; Friction factor; Convection and radiation heat transfer; Thermal-hydraulic modelling; Thermal stresses (search for similar items in EconPapers)
Date: 2025
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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:317:y:2025:i:c:s0360544225003718

DOI: 10.1016/j.energy.2025.134729

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