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A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks. III. Unsteady-state conditions (evacuation period).

Author(s) : REISS H.

Type of article: Article

Summary

This paper analyses the evacuation period of a 300 L super-insulated cryogenic storage tank for liquid nitrogen. Storage tank and radiation shields are the same as in part I of this paper. This analysis extends application of stationary fluid networks to unsteady-states to determine local, residual gas pressures between shields and the evacuation time of a multilayer super-insulation. Parameter tests comprise magnitude of desorption from radiation shields, spacers and container walls and their influence on length of the evacuation period. Calculation of the integrals over time-dependent desorption rates roughly confirms weight losses of radiation shields obtained after heating and out-gassing the materials, as reported in the literature. After flooding the insulation space with dry N2-gas, the evacuation time can enormously be reduced, from 72 to 4 h, to obtain a residual gas pressure of 0.01 Pa in-between shields of this storage tank. Permeation of nitrogen through container walls is of no importance for residual gas pressures. The simulations finally compare freezing H2O-layers adsorbed on shields, spacers and container walls with flooding of the materials. [Reprinted with permission from Elsevier. Copyright, 2006]. See also the Bulletin of the IIR, reference 2005-1097 and this Bulletin, reference 2007-0011.

Details

  • Original title: A coupled numerical analysis of shield temperatures, heat losses and residual gas pressures in an evacuated super-insulation using thermal and fluid networks. III. Unsteady-state conditions (evacuation period).
  • Record ID : 2007-0012
  • Languages: English
  • Source: Cryogenics - vol. 46 - n. 12
  • Publication date: 2006/12

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