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Simulation of Critical Heat Flux in Vertical Tubes

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Technical Report,03 Feb 2020,18 Jun 2020

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C5ISR Center Aberdeen Proving Ground United States

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Boilingtwo phase heat transfer is an attractive cooling mechanism due to the possibility of very high heat transfer coefficients, giving high heat flux at low temperature difference. The drawback is the possibility of dry-out. This occurs when too much of the liquid is vaporized, and the remaining liquid cant rewet the surface to absorb the heat. The heat transfer coefficient suddenly decreases by an order of magnitude, causing the surface temperature to rapidly rise. This critical heat flux CHF condition damages the systems being cooled. Location of CHF is a function of geometry, heat flux, and fluid flow rate. Increasing the fluid flow rate can insure that critical heat flux does not occur however, doing so increases the required pumping power and fluid mass. Correctly predicting the CHF location gives the minimum weight to meet cooling requirements. Simulations of the critical heat flux in a vertical tube are presented. The location of the predicted critical heat flux is shown to have good agreement with experimental values.

Subject Categories:

  • Thermodynamics
  • Fluid Mechanics

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