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Hofmann R.,Josef Bertsch GmbH and Co. KG | Walter H.,Vienna University of Technology
Journal of Thermal Science and Engineering Applications | Year: 2012

In this study, a heat transfer and pressure drop correlation are determined for helically I- and U-shaped finned tubes as well as for solid I-finned tubes at constant transverse and longitudinal spacing. In the heat transfer correlation, the influence of the number of tube rows arranged in flow direction is taken into consideration. A detailed description of the test rig and the data reduction procedure is presented. A thorough uncertainty analysis was performed to validate the results. The investigation has shown that the influence of the fin geometry on the heat transfer of the helically segmented I- and U-shaped tubes can be disregarded. The heat transfer correlation, which is valid for the helically segmented I- and U-shaped tubes in a staggered arrangement, can describe 90% of all measurement data within ±15%. All measurements are performed for constant transverse and longitudinal spacing. For the pressure drop coefficient, two new correlations, which are only valid for helically segmented U shaped finned tubes in a staggered arrangement, show an average deviation of approximately ±13% for 90% of all measurement results. All new correlations are compared with correlations from open and established literature for industrial boiler applications. The new heat transfer and pressure drop correlations show a relative deviation of ±20% in comparison with correlations in open literature. The new pressure drop correlations show the same characteristic as most correlations in the open literature. © 2012 American Society of Mechanical Engineers. Source


Hofmann R.,Josef Bertsch GmbH and Co. KG | Walter H.,Vienna University of Technology
ASME 2012 11th Biennial Conference on Engineering Systems Design and Analysis, ESDA 2012 | Year: 2012

In the present work, a comparison between numerical and experimental gas side heat transfer and pressure drop for a tube bundle with solid and segmented circular finned tubes in a staggered arrangement is investigated. For the numerical simulations a three dimensional model of the finned tube are applied. Rormalization group theory (RNG) based k-s turbulence model was used to calculate the turbulent flow. Experiments have been carried out to validate the numerical predictions. The numerical results for the Nu-number and pressure drop coefficient show a good agreement with the data from measurement. A comparison between solid and segmented finned tubes from the global calculation of the Nu-numbers within the analyzed Re-range shows an enhancement by applying segmented finned tubes rather than finned tubes with solid fins. Copyright © 2012 by ASME. Source


Hofmann R.,Josef Bertsch GmbH and Co. KG | Walter H.,Vienna University of Technology
Journal of Thermal Science and Engineering Applications | Year: 2012

The heat transfer and pressure drop behavior of segmented circular and helical as well as solid finned tubes are investigated in a three-dimensional numerical study. The simulation is carried out using a finite volume method for calculating the steady-state temperature and flow field of the fluid as well as the temperature distribution of the tube material. For modeling the turbulence, the k-ε turbulence model based on the renormalization group theory (RNG) is used to resolve the near-wall treatment between adjacent fins. All simulations are performed in the Re range between 3500 ≤ Re ≤ 50,000. The influence of Reynolds number and fin geometry (segmented or solid and circular or helical) on the local and global averaged heat transfer and pressure drop was studied. A comparison between solid and segmented finned tube has shown that the heat transfer and pressure drop for the segmented finned tubes is higher. The numerical results are compared with experimental data. © 2012 American Society of Mechanical Engineers. Source


Hofmann R.,Josef Bertsch GmbH and Co. KG | Walch T.,Josef Bertsch GmbH and Co. KG | Kolbitsch A.,Josef Bertsch GmbH and Co. KG | Walter H.,Institute For Energietechnik Und Thermodynamik | Von Eichhain C.D.,Geschaftsfuhrung KED
VGB PowerTech | Year: 2012

The study was aiming at the examination of empirical values for operating. and load change behaviour of a combined cycle power plant. The analysed vertical heat recovery steam generator (HRSG) with top supporting heating surfaces and multi-pressure construction method with natural circulation evaporators is described. The exhaust gas is supplied to a boiler from two Siemens gas turbines SGT-800 with an approximately exhaust mass flow of 132 kg/s each and an exhaust gas temperature of approximately 563°C (at full load). An inevitable high demand for optimisation of the gas-side is particularly required to ensure an even flow behaviour upstream of the heating surfaces and provide an even heat absorption of the bundle heating surfaces as well as to avoid any flow inclinations. Therefore, the flue-gas channel was numerically optimised between the two gas turbines and the heat recovery steam generator. In the second part of the study, measurement data from a cold start-up process of the HRSG are compared with simulation calculations. Source

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