The underfloor air distribution (UFAD) system has attracted great attention from many researchers and designers due to its advantages of energy conservation and air quality enhancement. In a UFAD system, the conditioned air is directly delivered to the occupied zone, causing thermal stratification from the lower zone to the upper zone. This flow pattern provides better distribution of temperature and airflow than the overhead air conditioning system for its improved ventilation and indoor air quality at the breathing level. This paper focuses on a new and unconventional way of conditioning the interior zones in UFAD buildings by employing large-area grille diffusers in a full-scale experimental room. The influences of swirl diffusers and grille diffusers on the temperature distribution in the UFAD system are compared. The effects of supply air temperature, airflow rates, and number of diffusers on the performance of the UFAD system with grille diffusers are discussed in details. The results show that the large-area grille diffusers can create stratification comparable to the more traditional swirl diffusers and thus provide an alternative way of configuring a UFAD system.
BaumanFWebsterT. Outlook for underfloor air distribution. ASHRAE J2001; 43(6): 18–27.
2.
BaumanFDallyA. Underfloor air distribution (UFAD) design guide, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, 2003.
3.
XueGLeeKJiangZChenQ. Thermal environment in indoor spaces with under-floor air distribution systems: Part 2. Determination of design parameters (1522-RP). HVAC&R Res2012; 18(6): 1192–1201.
4.
KongQYuB. Numerical study on temperature stratification in a room with underfloor air distribution system. Energy Build2008; 40(4): 495–502.
5.
ASHRAE/ANSI 113-2013. Method of testing for room air diffusion, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, 2013.
6.
LeeKJiangZChenQ. Air distribution effectiveness with stratified air distribution system. ASHRAE Trans2009; 115(2): 322–338.
7.
LeeKZhangTJiangZChenQ. Comparison of airflow and contaminant distribution in rooms with traditional displacement ventilation and under-floor air distribution systems. ASHRAE Trans2009; 115(2): 306–326.
8.
ASHRAE. UFAD guide: Design, construction, and operation of underfloor air distribution systems, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, 2013.
9.
ZhangKZhangXLiSJinX. Review of underfloor air distribution technology. Energy Build2014; 85: 180–186.
10.
AlajmiAEl-AmerW. Saving energy by using underfloor-air-distribution (UFAD) system in commercial buildings. Energy Convers Manage2010; 51(8): 1637–1642.
11.
ZukowskiM. A new formula for determining a minimum recommended value of inlet air velocity from UFAD system to prevent occupants from draught risk. Build Environ2007; 42(1): 171–179.
12.
KimGSchaeferLLimTSKimJT. Thermal comfort prediction of an underfloor air distribution system in a large indoor environment. Energy Build2013; 64: 323–331.
13.
LimTSSchaeferLKimJTKimG. Energy benefit of the underfloor air distribution system for reducing air-conditioning and heating loads in buildings. Indoor Built Environ2012; 21(1): 62–70.
14.
XuHNiuJ. Numerical procedure for predicting annual energy consumption of the under-floor air distribution system. Energy Build2006; 38(6): 641–647.
15.
Inatomi TAH, Abe V and Leite BCC. Energy consumption of underfloor air distribution systems: A literature overview. In: Proceedings of the 23th conference on passive and low energy architecture, Geneva, Switzerland, September 6–8 2006; pp.685–690.
16.
BaumanFWebsterTLindenPBuhlF. Energy performance of underfloor air distribution systems, Los Angels: California Energy Commission (CEC) Public Interest Energy Research (PIER) Program, State of California, 2007.
17.
BaumanFJinHWebsterT. Heat transfer pathways in underfloor air distribution (UFAD) systems. ASHRAE Trans2006; 112(2): 567–580.
18.
Bauman F, Schiavon S, Webster T and Lee KH. Cooling load design tool for UFAD systems. ASHRAE J 2010; September: 62–71.
19.
SchiavonSLeeKHBaumanFWebsterT. Simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems. Energy Build2011; 43(2): 517–528.
20.
ChengYNiuJGaoN. Stratified air distribution systems in a large lecture theatre: a numerical method to optimize thermal comfort and maximize energy saving. Energy Build2012; 55: 515–525.
21.
ChengYNiuJLiuXGaoN. Experimental and numerical investigations on stratified air distribution systems with special configuration: thermal comfort and energy saving. Energy Build2013; 64: 154–161.
22.
LiRSekharSCMelikovAK. Thermal comfort and indoor air quality in rooms with integrated personalized ventilation and under-floor air distribution systems. HVAC&R Res2011; 17(5): 829–846.
23.
WebsterTBaumanF. Design guidelines for stratification in UFAD systems-guidance for sizing interior and perimeter zones of underfloor-air-distribution systems. HPAC Eng2006; 78(6): 6–27.
24.
Webster T, Bauman F, Shi M and Reese J. Thermal stratification performance of underfloor air distribution (UFAD) systems. In: Proceedings of Indoor Air 2002, the ninth international conference on indoor air quality and climate, Monterey, CA, June 30–July 5 2002; pp.1–6.
25.
WebsterTBaumanFReeseJ. Underfloor air distribution: thermal stratification. ASHRAE J2002; 44(5): 28–33.
26.
Schiavon S, Webster T, Dickerhoff D and Bauman F. Stratification prediction model for perimeter zone UFAD diffusers based on laboratory testing with solar simulator. In: Proceedings of Indoor Air 2014, the 13th international conference on indoor air quality and climate, Hong Kong, July 7–12 2014; pp.1–7.
27.
WangXPepperDW. Numerical simulation for under-floor air distribution system with swirl diffusers. J Heat Transf2007; 129(4): 589–594.
28.
ANSI/ASHRAE 55-2013. Thermal environmental conditions for human occupancy, Atlanta, GA: American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc, 2013.
29.
Zhang H, Huizenga C, Arens E and Yu T. Modeling thermal comfort in stratified environments. In: Proceedings of Indoor Air 2005, the 10th international conference on indoor air quality and climate, Beijing, September 4–9 2005; pp.133–137.
