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Thermal Environment Design Strategies
Published in Chitrarekha Kabre, Synergistic Design of Sustainable Built Environments, 2020
Several energy conservation techniques can be integrated with air-conditioning systems. Building energy management system (BEMS) can control and coordinate all the building’s energy-using equipment responsively, to optimize energy use. An economy cycle can increase out air supply without running the chiller plant when the outdoor air is cooler than the indoors. A night flush of (cool) outdoor air may be provided to remove the heat stored in the building fabric, thus reducing the following day’s cooling requirement; see Section 3.3.3. An underfloor air distribution (UFAD) system or displacement ventilation using a large number of low-volume supply air outlets (floor diffusers) create laminar flow at the bottom of the room, where people are, instead of conditioning the whole space. The NOAA Daniel K. Inouye Regional Centre features displacement ventilation; see Section 6.2 for more information.
Air Tempering and Distribution
Published in Herbert W. Stanford, Adam F. Spach, Analysis and Design of Heating, Ventilating, and Air-Conditioning Systems, 2019
Herbert W. Stanford, Adam F. Spach
Expanding on this concept, some buildings in the United States and United Kingdom have used this type of system to provide floor level supply air sufficient for ventilation and to offset space heat gains and losses. In this case, air is supplied via an unducted underfloor air distribution (UFAD) system that uses a raised floor plenum concept. But, performance by these systems have been mixed, for several different reasons.
An investigation of thermal comfort, IAQ, and energy saving in UFAD systems using a combination of Taguchi optimization algorithm and CFD
Published in Advances in Building Energy Research, 2021
Ghassem Heidarinejad, Samaneh Shokrollahi, Hadi Pasdarshahri
Underfloor air distribution (UFAD) systems can improve thermal comfort conditions, ventilation efficiency, and indoor air quality (IAQ) by distributing fresh supply air from the floor (Bauman & Webster, 2001). The use of these systems leads to a reduction in energy consumption compared to conventional overhead air distribution (OHAD) systems and improves the productivity and health of occupants (Bauman & Webster, 2001). The examination of improving energy efficiency is usually accompanied by an investigation of IAQ in the studies related to the built environment (Bakhtiari et al., 2019). In this way, UFAD systems are able to create smaller vertical differences of air temperature and a more comfortable environment than OHAD systems (Nada et al., 2016). Given the advantages of UFAD systems, their application has been considerably expanded (Bauman & Webster, 2001), and so examining the effective parameters on the performance of these systems is essential.
Modelling of contaminant dispersion in underfloor air distribution systems: comparison of analytical and CFD methods
Published in Journal of Building Performance Simulation, 2019
Underfloor air distribution (UFAD) systems have been a matter of cynosure to researchers in the field of air conditioning for the few last decades because of their edge in providing thermal comfort and good indoor air quality at relatively lower energy cost (Wang, Zhang, and Qi 2019). The UFAD concept is to introduce fresh and cool air through underfloor plenum and then through diffusers mounted in the floor. The supply air can be then at the desired temperature or slightly lower since it is provided in the vicinity of occupants, which reduces notably the cooling coil power. The air supplied at the floor level gets warm and displaces upward transporting air contaminants to the upper zone of the space leaving the lower zone cool and clean. Another factor that makes UFAD systems competitive is the space provided beneath the floor as air supply plenum that can be used to accommodate the wires and cables in intelligent buildings. Moreover, UFAD systems make built environments flexible to any changes in the interior design or floor plan modifications according to occupants’ needs and preferences (Alajmi, Badda, and Bourisli 2015). UFAD systems were firstly used in the 1950s in computer rooms with cooling load up to 1000 W/m2 and they were introduced to office spaces in the late 1970s (Hui and Li 2002). Nowadays, more than 130 UFAD systems are installed in North America and this number is growing (Sodec 1990).
Impact of chilled ceiling in a high sensible cooling load room with underfloor air distribution
Published in Science and Technology for the Built Environment, 2019
Xiaozhou Wu, Jie Gao, Haichao Wang, Fenghao Wang, Zhen Tian
An underfloor air distribution (UFAD) system, which is regarded as one of the most energy efficient ventilation systems, has been extensively utilized in modern office buildings (Alajmi et al. 2015; Alajmi et al. 2013; Alajmi and El-Aer 2010; Mai and Yan 2003). The sensible cooling load in a modern office includes the internal sensible cooling load and external sensible cooling load. The internal sensible cooling load is mainly caused by the heat dissipation of internal heat sources, such as computers, printers, and lighting. The external sensible cooling load is caused by heat transfer of the external building envelope. The sensible cooling load increases greatly with the extensive application of IT equipment and glass-walls (Zhang et al. 2017; Ohsumi et al. 2011). However, the supply air temperature and velocity should be limited to avoid cold drafts and for the UFAD, which may result in limited cooling capacity and less competency in removing the high sensible cooling load in modern office buildings (Kim et al. 2013; Xue et al. 2012; Bauman and Daly 2003; Schiavon et al. 2015).