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Suche nach „[Y.-G.] [Lei]“ hat 2 Publikationen gefunden
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    NachhaltigF: Angewandte Naturwissenschaften und WirtschaftsingenieurwesenF: Europan Campus Rottal-Inn

    Zeitschriftenartikel

    Rui Li, Y.-L. He, Y.-G. Lei, Y. Tao, P. Chu

    A Numerical Study on Fluid Flow and Heat Transfer Performance of Internally Roughened Tubes with Dimples

    Journal of Enhanced Heat Transfer, vol. 16, no. 3, pp. 267-285

    2009

    DOI: 10.1615/JEnhHeatTransf.v16.i3.40

    Abstract anzeigen

    In this paper, 3D numerical simulations are conducted in heat transfer enhanced tubes with internally roughened dimples in the range of Re = 2000 to 11,000. The fluid flow and heat transfer characteristics are fully understood by the local and overall friction factors, Nusselt number, and Colburn j factor. The local mean friction factor has a periodic change due to the periodic dimple distribution, the eddy zone and high-pressure region of every dimple greatly influence the working fluid for heat transfer enhancement. In this numerical simulation, five samples are employed to study the detailed heat transfer characteristics. The results show that the dimpled tube is a new kind of heat transfer enhanced tube with the excellent heat transfer performance and low resistance. It is found that the effects of dimples on the heat transfer performance can be well described by the field synergy principle. The effect of different dimple arrangements is very little, which is always within 2%. But the effect of dimple size on heat transfer and fluid flow performance is very significant, thus there exists a tube with an optimum dimple size among the tubes investigated in this paper. By integrated performance evaluation of NUF0/NU0F, a maximum of about 60% heat transfer enhancement with the same friction penalty can be gained by the optimal dimpled tube.

    NachhaltigF: Angewandte Naturwissenschaften und WirtschaftsingenieurwesenF: Europan Campus Rottal-Inn

    Zeitschriftenartikel

    Y.-G. Lei, Y.-L. He, Rui Li, Y.-F. Gao

    Effects of baffle inclination angle on flow and heat transfer of a heat exchanger with helical baffles

    Chemical Engineering and Processing: Process Intensification, vol. 47, no. 12, pp. 2336-2345

    2008

    DOI: 10.1016/j.cep.2008.01.012

    Abstract anzeigen

    Numerical simulations were carried out to study the impacts of various baffle inclination angles on fluid flow and heat transfer of heat exchangers with helical baffles. The simulations were conducted for one period of seven baffle inclination angles by using periodic boundaries. Predicted flow patterns from simulation results indicate that continual helical baffles can reduce or even eliminate dead regions in the shell side of shell-and-tube heat exchangers. The average Nusselt number increases with the increase of the baffle inclination angle α when α < 30°. Whereas, the average Nusselt number decreases with the increase of the baffle inclination angle when α > 30°. The pressure drop varies drastically with baffle inclination angle and shell-side Reynolds number. The variation of the pressure drop is relatively large for small inclination angle. However, for α > 40°, the effect of α on pressure drop is very small. Compared to the segmental heat exchangers, the heat exchangers with continual helical baffles have higher heat transfer coefficients to the same pressure drop. Within the Reynolds number studied for the shell side, the optimal baffle inclination angle is about 45°, with which the integrated heat transfer and pressure drop performance is the best. The detailed knowledge on the heat transfer and flow distribution in this investigation provides the basis for further optimization of shell-and-tube heat exchangers.