Inhaltszusammenfassung

Tubes with corrugated surfaces can clearly increase the overall heat transfer coefficient in comparison with smooth tubes. Due to the additional influence of different curved surfaces, the analytical calculation of the overall heat transfer coefficient and pressure drop fails for those tubes. Numerical simulations using turbulence models with two or three differential equations appropriate for isotropic turbulence are not satisfactory in this case. Since corrugated walls cause anisotropic tu...Tubes with corrugated surfaces can clearly increase the overall heat transfer coefficient in comparison with smooth tubes. Due to the additional influence of different curved surfaces, the analytical calculation of the overall heat transfer coefficient and pressure drop fails for those tubes. Numerical simulations using turbulence models with two or three differential equations appropriate for isotropic turbulence are not satisfactory in this case. Since corrugated walls cause anisotropic turbulences in the near wall region, the secondary flow must be considered in the numerical simulation. Within the time averaging turbulence models (Reynolds Averaged Navier Stress Model =RANS) the Reynolds Stress Model (RSM) is the only model solving all six components of the Reynolds Stress Tensor and thus enabling a simulation of secondary flow. Most turbulence models are developed and calibrated for smooth wall boundary conditions. As a consequence, simulations of corrugated tubes based on isotropic turbulence models provide inadequate results when compared with measured values. This article describes the calibration of the RSM for the simulation of corrugated tubes using the values of a shel and tube heat exchanger test facility for adaptation. To calibrate the heat transfer rate the dimensionless variable Prt is modified. For the pressure drop calculation, the pressure strain coefficient is adjusted varying the dimensionless coefficient C1. Moreover, the local flow behavior in the near wall region is validated by local measurements by Laser Doppler velocimetry. » weiterlesen» einklappen

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Klassifikation

DFG Fachgebiet:
Strömungsmechanik, Technische Thermodynamik und Thermische Energietechnik

DDC Sachgruppe:
Ingenieurwissenschaften