Transient Behaviors of Gas in Thermal Insulation Media at Rapid Depressurization

Abstract

Thermal insulation systems are often used to high-temperature gas cooled reactors.

In this paper, transient behavior of the gas flow in thermal insulation media was systematically analyzed in the case of sudden decrease in a coolant pressure. The structure of these systems is capable of substituting for the simplified model that the gas in a containment filled with porous insulation media exhausts from a balancing hole to main flow duct. In the case of rapid depressurization, these behaviors were calculated by using equations of continuity and motion based on the Darcy flow model with area ratio of a balancing hole and permeability of porous insulation media as parameters. The transient pressure difference of a hot liner wall between the main flow helium and the insulation layer induced at depressurization was numerically analyzed. It was revealed from analytical results that transient behaviors were strongly influenced by prescribed parameters, and experimental results can be explained by using the analytical model.

KEYWORDS:

• transient behavior
• thermal insulation
• rapid depressurization
• coolant pressure
• porous insulation media
• Darcy How model
• permeability
• area ratio
• HTGR type reactors