Lee, Sang Won (2007-08). Heat transfer characteristics of a two-pass trapezoidal channel and a novel heat pipe. Doctoral Dissertation. Thesis uri icon

abstract

  • The heat transfer characteristics of airflows in serpentine cooling channels in stator vanes of gas turbines and the novel QuTech(R) Heat Pipe (QTHP) for electronic cooling applications were studied. The cooling channels are modeled as smooth and roughened two-pass trapezoidal channels with a 180? turn over a range of Reynolds numbers between about 10,000 and 60,000. The naphthalene sublimation technique and the heat and mass transfer analogy were applied. The results showed that there was a very large variation of the local heat (mass) transfer distribution in the turn and downstream of the turn. The local heat (mass) transfer was high near the end wall and the downstream outer wall in the turn and was relatively low in two regions near the upstream outer wall and the downstream edge at the tip of the divider wall in the turn. The variation of the local heat (mass) transfer was larger with ribs on two opposite walls than with smooth walls. The regional average heat (mass) transfer was lower in the turn and higher in the entire channel with the flow entering the channel through the larger straight section than when the flow was reversed. The pressure drop across the turn was higher with the flow entering the channel through the larger channel than when the flow was reversed. Thermal performance of the QuTech(R) Heat Pipe was identified over a range of inclination angles between 90? and -90? and thermal mechanism of the QTHP was studied with GC-MS, ICP-OES, XRD, XPS, and DSC. This study resulted in the following findings: the performance of the QTHP was severely dependent on gravity; the QTHP utilizes water as working fluid; there were inorganic components such as Na, K, P, S, and Cr, etc.; and the vaporization temperature of the working fluid (mostly water) was lower than the boiling temperature of pure water. This was due to the presence of inorganic salt hydrates in the QTHP. It may be concluded that thermal performance of heat pipes increases with additional latent heat of fusion energy and energy required to release water molecules from salt hydrates.
  • The heat transfer characteristics of airflows in serpentine cooling channels in
    stator vanes of gas turbines and the novel QuTech(R) Heat Pipe (QTHP) for electronic
    cooling applications were studied. The cooling channels are modeled as smooth and
    roughened two-pass trapezoidal channels with a 180? turn over a range of Reynolds
    numbers between about 10,000 and 60,000. The naphthalene sublimation technique and
    the heat and mass transfer analogy were applied. The results showed that there was a
    very large variation of the local heat (mass) transfer distribution in the turn and
    downstream of the turn. The local heat (mass) transfer was high near the end wall and
    the downstream outer wall in the turn and was relatively low in two regions near the
    upstream outer wall and the downstream edge at the tip of the divider wall in the turn.
    The variation of the local heat (mass) transfer was larger with ribs on two opposite walls
    than with smooth walls. The regional average heat (mass) transfer was lower in the turn
    and higher in the entire channel with the flow entering the channel through the larger
    straight section than when the flow was reversed. The pressure drop across the turn was higher with the flow entering the channel through the larger channel than when the flow
    was reversed.
    Thermal performance of the QuTech(R) Heat Pipe was identified over a range of
    inclination angles between 90? and -90? and thermal mechanism of the QTHP was
    studied with GC-MS, ICP-OES, XRD, XPS, and DSC. This study resulted in the
    following findings: the performance of the QTHP was severely dependent on gravity; the
    QTHP utilizes water as working fluid; there were inorganic components such as Na, K, P,
    S, and Cr, etc.; and the vaporization temperature of the working fluid (mostly water) was
    lower than the boiling temperature of pure water. This was due to the presence of
    inorganic salt hydrates in the QTHP. It may be concluded that thermal performance of
    heat pipes increases with additional latent heat of fusion energy and energy required to
    release water molecules from salt hydrates.

publication date

  • August 2007