TY - JOUR
T1 - Indoor airflow and contaminant transport in a room with coupled displacement ventilation and passive-chilled-beam systems
AU - Shi, Zhu
AU - Lu, Zechao
AU - Chen, Qingyan
N1 - Funding Information:
The authors are grateful for the support by American Society of Heating, Refrigerating and Air-conditioning Engineers (ASHRAE) on this research through research project 1666.
Publisher Copyright:
© 2019 Elsevier Ltd
PY - 2019/8/15
Y1 - 2019/8/15
N2 - Displacement ventilation (DV) is now widely used in enclosed environments such as office buildings. Although DV can provide good indoor air quality, its ability to remove heat is limited. On the other hand, passive chilled beams (PCBs) can have a high heat-removal capability. Therefore, this investigation evaluated a coupled DV and PCB system in terms of air quality and thermal comfort. This study first conducted experiments in a full-scale environmental chamber with the DV-PCB system to obtain airflow velocity, temperature and contaminant concentration data. A computational fluid dynamics (CFD) model was developed to simulate air distribution in an enclosed environment with the DV-PCB system, which was then validated by the measured data. The validated CFD model was employed to analyze thermal comfort and indoor air quality in the enclosed environment with the DV-PCB coupled system using four indices: vertical temperature gradient, draft rate, normalized contaminant concentration and age of air. The results indicate that PCBs were quite effective in reducing the temperature gradient created by DV. However, the cold downward jet generated by the PCBs created a “zone with high draft” under the PCBs, and the magnitude of the draft was strongly correlated with the cooling load removed by the PCBs and the size of the PCBs. In addition, the downward air jet generated by the PCBs could disrupt the contaminant stratification and increase the mean age of air in the occupied zone.
AB - Displacement ventilation (DV) is now widely used in enclosed environments such as office buildings. Although DV can provide good indoor air quality, its ability to remove heat is limited. On the other hand, passive chilled beams (PCBs) can have a high heat-removal capability. Therefore, this investigation evaluated a coupled DV and PCB system in terms of air quality and thermal comfort. This study first conducted experiments in a full-scale environmental chamber with the DV-PCB system to obtain airflow velocity, temperature and contaminant concentration data. A computational fluid dynamics (CFD) model was developed to simulate air distribution in an enclosed environment with the DV-PCB system, which was then validated by the measured data. The validated CFD model was employed to analyze thermal comfort and indoor air quality in the enclosed environment with the DV-PCB coupled system using four indices: vertical temperature gradient, draft rate, normalized contaminant concentration and age of air. The results indicate that PCBs were quite effective in reducing the temperature gradient created by DV. However, the cold downward jet generated by the PCBs created a “zone with high draft” under the PCBs, and the magnitude of the draft was strongly correlated with the cooling load removed by the PCBs and the size of the PCBs. In addition, the downward air jet generated by the PCBs could disrupt the contaminant stratification and increase the mean age of air in the occupied zone.
KW - Displacement ventilation
KW - Indoor air quality
KW - Passive chilled beam
KW - Thermal comfort
UR - http://www.scopus.com/inward/record.url?scp=85068519281&partnerID=8YFLogxK
U2 - 10.1016/j.buildenv.2019.106244
DO - 10.1016/j.buildenv.2019.106244
M3 - Journal article
AN - SCOPUS:85068519281
SN - 0360-1323
VL - 161
JO - Building and Environment
JF - Building and Environment
M1 - 106244
ER -