Investigation on the elimination of geyser in a cryogenic pipe by a recirculation method

Abstract

• A recirculation structure is designed to successfully eliminate the geyser in a cryogenic pipe. • The geyser-elimination physics and the mechanism of recirculation formation are revealed. • A sine-wave-like oscillation process is found to exist in the initial process of the recirculation. • An improved approach is proposed to enhance the recirculation ability and reduce the oscillation amplitude by as much as 55%. A geyser elimination approach using recirculation methods is investigated in the present work, which is essential to guarantee the integrity of facilities. Both experimental and numerical methods are adopted in the investigation using LN 2 as working fluids. A recirculation pipe is designed to eliminate geysers in a cryogenic vertical pipe. The performance of the recirculation method is comprehensively explored involving its formation mechanism and oscillation physics. A deeper understanding of the liquid recirculation is achieved. The physics of the ambiguous oscillation phenomenon is revealed. It is concluded that by breaking down the energy storage pattern inside the cryogenic pipe, geysers can be perfectly eliminated by the recirculation method. Liquid recirculation in the pipeline is found to be initiated firstly by the liquid density difference between the vertical pipe and recirculation pipe and dominated by liquid flashing in the recirculation pipe. A negative feedback connection between void fraction and mass flow rate is the reason for the oscillation in its initial process. Besides, an effective method is proposed to enhance the recirculation ability as well as to attenuate the unstable oscillation by imposing a gradually increased heat flux. It is found that the oscillation amplitude could be reduced by as much as 55%.