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Indoor Air Quality Investigation and Mitigation
Published in Benjamin Alter, Environmental Consulting Fundamentals, 2019
The HVAC system includes all heating, cooling, and ventilation equipment serving a building. The heating and cooling systems generally run independently of each other, although they and the ventilation system, use a central component known as the air handler (see Figure 17.1). The air handler brings in outdoor air which often is mixed with air that has circulated through the building, heats or cools the air as needed, sends it into the building, and then retrieves it for re-conditioning and reuse.
Characterizing the performance of a do-it-yourself (DIY) box fan air filter
Published in Aerosol Science and Technology, 2022
Rachael Dal Porto, Monet N. Kunz, Theresa Pistochini, Richard L. Corsi, Christopher D. Cappa
Three filter-based air cleaners were tested: the Corsi-Rosenthal Box and two commercial HEPA-based air cleaners. The Corsi-Rosenthal Box was originally proposed by Richard Corsi on Twitter and with Jim Rosenthal making the first prototype (Rosenthal 2020). The CR Box used here is constructed using three 20” x 20” x 2” and two 16” x 20” x 2” MERV-13 filters (Air Handler, LEED/Green Pleated Air Filter, total cost $34.75) and a 20” box fan (Air King Model 4CH71G, $23.68). (See Figure S3 and the Supplemental Material for a full description and discussion of cost). The CR Box here sits on legs that hold it about 4” (10 cm) off the ground and with the fan pointed upwards or sideways. In one variation, we tested the CR Box inverted such that the fan pointed at the floor, sitting about 4” (10 cm) off the floor. An inverted CR Box would potentially be more robust against potential foreign objects being dropped into the fan. One of the HEPA-based air cleaners (HEPA #1) has a stated tobacco smoke CADR = 300 ft3 min−1 (510 m3 h−1) when operated at maximum speed while the other (HEPA #2) has a stated tobacco smoke CADR = 141 ft3 min−1 (240 m3 h−1) when operated at maximum speed.
Cost- and Risk-Based Seismic Design Optimization of Nuclear Power Plant Safety Systems
Published in Nuclear Technology, 2021
Chandrakanth Bolisetti, Justin Coleman, William Hoffman, Andrew Whittaker
In order to examine the effect of cost functions on the optimized design, a separate design optimization is performed in this section with modified cost functions presented in Fig. 10. These cost functions are modified such that the total initial capital cost is almost the same, but the rate of increase of the capital cost is modified for all components, except for the duct and air handler. The initial design of the system, that is, the median fragilities of the SSCs, are kept unchanged. A higher rate of capital cost increase indicates a larger seismic design penalty for the component. Figure 10 shows that the rate is increased for the MCC, battery, and CRDM, whereas it is reduced for the structure and the rest of the NSSS components, coolant pump, reactor vessel, steam generator, and piping. These modifications are intended to counter the design changes made by the optimization algorithm in Sec. V.C, where the costs and median fragilities of the NSSS components and the structure are reduced, whereas battery and CRDM are strengthened and their capital costs are increased. With the modified cost functions, a reduction in the median fragilities of the structure and the NSSS components will not reduce the cost as much, and an increase in the median fragility of the MCC, battery, and CRDM will result in a larger increase in the cost than those from the original cost functions.
Development of control quality factor for HVAC control loop performance assessment I—Methodology (ASHRAE RP-1587)
Published in Science and Technology for the Built Environment, 2019
Yanfei Li, Zheng D. O'Neill, Xiaohui Zhou
Heating, ventilation, and air-conditioning (H`VAC) systems in buildings are used to provide the desired built environment, such as temperature and humidity. In addition to HVAC components such as a chiller, pump, fan, and so on, many control loops are applied to ensure a functional HVAC system. For example, there are various control loops in a typical HVAC system: room air temperature control served by a variable air volume (VAV) box or fan coil unit, water loop differential pressure control for hot and chilled water systems, supply air static pressure control for an air handler unit (AHU) in a VAV system, and so on. The control loops are pivotal to guarantee that the HVAC systems are working well toward the desired states. The most commonly used controllers for HVAC systems are the proportional-integral (PI) controllers (Zhao et al. 2013). However, improperly tuned PI control loops often result in poor control performance, and numerous studies show that the poor performance of control loops can lead to multiple consequences: energy waste, unsatisfied human comfort, rising operational cost due to the wear of valves, dampers, and more (Barwig et al. 2002). How to evaluate the control loop performance within the controller and in real time remains a big challenge for the HVAC field.