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The Building Survey
Published in Kenneth F. Cherry, Asbestos, 2020
Individual spaces or zones in a building are served by supply and return air and a thermostat to activate the HVAC system. The supply and return may be in ductwork or in a plenum. Plenums are spaces; for example, the space above a dropped acoustical ceiling and below the roof or floor above. In most cases, the plenum is used for return air, that is, the air leaves the room, enters the plenum, and is drawn into the mechanical room from the plenum.
Plumbing, Electrical, and Mechanical Systems
Published in Kathleen Hess-Kosa, Building Materials, 2017
Plenums are often exposed to high humidity and condensate spray from the cooling coils. In many commercial units, the mixing plenum and sometimes the AHU insulation is waterproofed with an asphalt/polymer coating. Due to the elevated temperatures inside an HVAC system during the colder seasons, asphalt emissions are unlikely.
Operator Action–Induced Two-Phase Flow Condition Resulting in Performance Degradation of Interfacing Passive System
Published in Nuclear Technology, 2021
Natural circulation in parallel flow channels connected to common plena is important to many NPP applications (see Chap. 4 of Ref. 18 for an introduction). The eight SG modules and bypass flow paths of the SMART integral-type PWR RCS are a special case of vertical, parallel, cooled flow channels connected to common plena. Reverse flow can occur in some channels when the condensation or cooling increases fluid density along the normal direction of flow. Downward flow (of primary RCS fluid through the shell side) is the normal direction in the SMART configuration. The density increase creates a static pressure head, such that a net pressure gain exists between the two common plena in the normal direction of flow. The pressure head at the outlet can sustain reverse flow in some channels, transferring outlet plenum fluid to the inlet plenum. If cooling or heating is occurring in some channels, the fluid states in the plena are different and mixing occurs in the inlet plenum.
Numerical simulation and experimental research on CHF characteristics of AP1000 nuclear reactor
Published in Journal of Nuclear Science and Technology, 2018
Jianquan Liu, Jiguo Zhang, Jingda Shi, Baomin Sun, Huimin Ji
In order to facilitate the analysis of the calculation results, the region from the reactor inlet pipe to reactor core inlet plate was defined as the inlet channel, and region from reactor core inlet plate to its upper grid plate was defined as central channel, while the region from upper grid plate to reactor outlet was defined as outlet channel. The downcomer, lower plenum and upper plenum were set as fluid domains. The reactor internals (e.g. core barrel, core shroud, RV, etc.) were set as solid domains. The boundaries between different domains were set as interface. In the steady state simulation, total amount of coolant for the reactor remained as 2 × 35,772m3/h and two loops are evenly distributed. The reactor’s four inlets were set as mass flow inlet with 3761 kg/s at 280.7°C (normal operating condition) and the two outlets were set as pressure outlet, and the reactor reference pressure was set to 15.4MPa.
Numerical study of the radiation effect on the jet array impinging heat transfer in a feeding pipe
Published in Numerical Heat Transfer, Part A: Applications, 2018
Junkui Mao, Tian Yao, Xingsi Han, Zhenzong He, Kang He
The numerical domain, as shown in Figure 3, consists of both the fluid and solid domains. The fluid domain consists of a single feeding manifold that discharges in a plenum. The solid domain considered contains the pipe in which a number of impinging holes exist. The structured hexahedral mesh is applied in the present study, which was generated by ANSYS ICEM. Taking the case A (see Table 1, i.e., H/d = 4) as an example, the grid of the whole domain and the details of grids at the pipe inlet and one impinging hole are shown in Figure 4. The grids have been finely clustered in the near-wall region, with the aim of capturing the sharp pressure and temperature gradients in those regions.