On the Heat-Transfer of Laminar Flow in the Circular Pipe

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  • 円管内層流熱伝達の近似解法
  • エン カンナイ ソウリュウ ネツ デンタツ ノ キンジカイホウ

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This paper describes a solution for the heat-transfer in a circular pipe of constant temperatur, in which the velocity distribution of fluid is the Poiseuille's flow. The basic equations are the same as that of Graetz or Nusselt, and as a mathematical method we applied the Karman-Pohlhousen's method which is used on the boundary layer problems. We derived an equation from the bsic equations, which correspond to the momentum equation of the bouodary layer problems, and used the conception of thermal boundary layer, in which we assume dthat the temperature distribution varies as the 4th degree equation with respect to the distance from the pipe wall. As a result we obtained the following equations, for the relation of dimensionless mean temperature of fluid θm and Graetz number Wc/kL, [numerical formula][numerical formula] Where ti is an initial temperature of fluid, and tw is a temperture of pipe wall, tm is a mean temperature of fluid after passed the pipe length L, Wc/kL is a Graetz number. And δ is a dimensionless thickness of the thermal boundary layer at the pipe end. We can δ between equations (1) and (2), but practically it is more advantageous to draw θm-Wc/kL curve by calculate the values of equations (1) and (2) corresponding δ=0.1, 0.2 etc.. This solution will be used over a range between the ranges in which Nusselt-Groeber-Yamagata's solution and Leveque's solution were used respectively. And moreover for the range of Leveque's solution, perhaps this solution will be more exact than the Leveque's solution.

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