ASHRAE LO-09-031-2009 Discussion of Design Method and Optimization on Airflow Distribution in a Large-Space Building with Stratified Air-Conditioning System
ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
Scope
INTRODUCTION Stratified air-conditioning is used to air-condition the lower zone of an indoor space (occupied zone)@ as shown in Figure 1@ wherein the thermal parameters of the air-conditioned occupied zone can fulfill thermal environment design standard. With an energy-saving strategy@ stratified air-conditioning system removes the heat/thermal load in the occupied zone only; as a result@ the refrigeration capacity will be reduced efficiently. The level of the height@ where supply air nozzles are installed@ is taken as the stratified surface of the airconditioned zone. The stratified height is defined as the height from the stratified surface to the ground. Generally speaking@ as long as it meets the requirement of thermal environment design standard@ a lower stratified height will be beneficial so as to provide a lower cooling load and improve energy-saving. However@ a lower stratified height might cause an unreasonable air distribution in the air-conditioned zone@ which would bring about such side effects as non-uniform temperature distribution@ air draft and thermal discomfort in the partial airconditioned zone. Furthermore@ since the indoor air distribution is affected by the temperature and velocity of supply air@ the quantity and position of the blast nozzles@ as well as the size and type of the nozzles should also be considered. To achieve a design with optimal air distribution@ these factors should be taken into account. Based on the analysis of the large-space building space studied in this paper@ an optimized design methodology is proposed.