Ventilation schemes for high-temperature buoyancy-driven plumes from spherical surfaces of a large-scale experimental facility

Abstract

Abstract A large-scale sphere-shaped experimental facility for neutrino detection is designed as a 23-latitudinal layer composite by using organic glass as the major raw material and is assembled via mass polymerization through a top-to-bottom approach. Heating belts at 4200 W/m2 are used to anneal the bonding joints of external and internal spherical surfaces and produce high-temperature thermal plumes. Buoyancy-driven plumes should be effectively mitigated using ventilation to ensure the near-surface air temperatures above the finished layers can be delicately controlled within 21±1 °C to minimize the deformation of the facility. Schemes to control plumes on both surfaces were investigated using Computational Fluid Dynamics (CFD) method by following a performance-based approach. First, an independent field study was conducted to measure surface temperature and heat flux of mass polymerization and provide references for simulations. Second, dynamic buoyancy-driven plumes produced along the external and internal spherical surfaces were simulated under a no-ventilation scenario. After contacting with the plumes, three periods, in which buoyancy, convection, and advection, were dominating, can be observed according to the changes of near-surface air temperature. Moreover, the temperature and Ra number of the surface-attached plumes were used as indicators to assess the intensity of the plumes quantitatively. Third, three major ventilation schemes, i.e., general, push-pull, and sphere-attached ventilations (with three subdesigns), were compared under the same air change rate level on the basis of the following perspectives: (1) air temperature distributions above the polymerizing layer, (2) overall heat exhaust efficiency, and (3) total spaces where temperature was higher than 22 °C. Results indicated that the combination of push-pull and side-supply ventilations, by which the heat exhaust efficiencies were up to 1.87–3.24, was found to be most effective to control thermal plumes, with approximately 0.1% of the total surrounding air exceeding 22 °C.