Abstract
Experiments were conducted on a liquid helium natural circulation loop with a 4 m long horizontal heated section. Wall temperatures on the heated section, mass flow rate and pressure drop were measured in steady and transient regimes. The stability of the loop has been studied and the power stability limits have been found. Also, different heating configurations were explored and their drawbacks and benefits were observed. The result is that the loop is stable only above a non-zero low power and below a certain upper power limit. The distance from the heating to the vertical riser affects the stability range. It has been found that instabilities at low power or transients following a low power step pulse can produce considerable temperature oscillations, potentially dangerous from the magnet protection point of view.
Highlights
Within the R&D program for the R3B-GLAD spectrometer, horizontally heated loops started beeing studied at low power
High temperature excursions at very low heat flux can take place during the first stage if initially the system is at rest, especially for long NHHL
Established flow and short NHHL can inhibit this transient feature, which gives us hints of how to protect devices from this undesired effect
Summary
Helium natural circulation loops are used for cooling large superconducting magnets. Within the R&D program for the R3B-GLAD spectrometer, horizontally heated loops started beeing studied at low power. We perform experiments on a big size helium natural circulation facility To explore other existing thermalhydraulic regimes during steady and transient power solicitation; To identify eventual heat transfer deterioration phenomena; To determine ways of mitigating harmful effects
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