Identification of air conditioning energy conservation technologies and measures（2）: some uncertain points in UFAD system design(Ⅰ)

Analyses the main problems of load and total supply air rate calculation in the actual underfloor air distribution (UFAD) systems based on literature consulting, experimental studies and engineering surveys. Laboratory experiments and engineering practice reveal that it is difficult to form the room air stratification in ordinary offices in which the UFAD system is adopted, and the supply air rate depends on whether the room air stratification forms or not and the supply air rate in turn influences formation of the stratification; and that there is little essential difference between the UFAD system and conventional overhead (OH) system in load and total supply air rate calculation and considering human comfort，the supply air by an UFAD system provides higher temperature and the total air flow rate is generally larger than that of OH system significantly. The calculation of air conditioning load and the total air flow rate as the key issue in UFAD system designing, its correctness will affect the  economic results and the practicability of the system, therefore needing deepened research and discussion.