Determination of heat transfer coefficients on the surfaces of plastic tubes
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The paper discusses the statistical steady heat and momentum transfer problem in the inlet section of the plastic tubes. The modified two equation k–ɛ turbulent model utilizing variability of turbulent Prandtl number, Prt, was used for the analysis. Considering the thermophysical anisotropy of the tube material, a balance of local temperatures and local heat fluxes on the boundary between the fluid and the tube wall was assumed (conjugate heat transfer problem). The thermal boundary condition on the external surface of the tube (temperature) measured in the experiment was taken into account. The boundary problem described was solved by the control volume method. The values of the parameters of Pr and Re obtained from the experiments were included in the numerical calculations. Based on the results obtained, profiles of mean fluid temperatures, local Nusselt numbers on the internal and external surface of the tube, and profiles of temperatures on the internal surface of the tube and inside of the tube wall were determined. The analysis shows that changes in Prtand turbulence intensity, Tu, influence the local values of Nusselt numbers, and it also shows that the results for the local Nusselt numbers inside the tube obtained from numerical calculations are of great accuracy in comparison with results published in the available literature.
KeywordsHeat Transfer Heat Flux Heat Transfer Coefficient Nusselt Number Prandtl Number
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