Thermal comfort and indoor air quality in rooms with integrated personalized ventilation and under-floor air distribution systems

A comprehensive study comprising physical measurements and human subject experiments was conducted to explore the potential for improving occupants’ thermal comfort and indoor air quality (IAQ) using a personalized ventilation (PV) system combined with an under-floor air distribution(UFAD) system. The integrated PV-UFAD system, when operated at relatively high temperature of the air supplied from the UFAD system, provided comfortable cooling of the facial region, improved inhaled air quality, and decreased the risk of “cold feet,” which is often reported in rooms with UFAD alone. This article explores associations between the physical measurements and human responses in a room served with a PV-UFAD system. The experiments were conducted in a field environmental chamber served by two dedicated systems—a primary air-handling unit (AHU) for 100% outdoor air that is supplied through the PV air terminal devices and a secondary AHU for 100% recirculated air that is supplied through UFAD outlets. Velocity and temperature distribution in the chamber were measured. A breathing thermal manikin was used to measure the heat loss from 26 body segments and to determine the equivalent temperature. The responses of 30 human subjects were collected. The experiments were performed at various combinations of room air and PV air temperatures. The results reveal improved overall thermal sensation and decrease of cold feet complaints, as well as improved inhaled air quality (including perceived air quality) with PV-UFAD in comparison with the reference case of UFAD alone or mixing ventilation with a ceiling supply diffuser. Increase of predicted draft rating with the decrease of the local thermal sensation at the feet was identified. The manikin-based equivalent temperature determined for the face was positively correlated with thermal sensation at the face region. The measured inhaled air quality indices (personalized exposure effectiveness and personalized exposure index) were improved by decreasing PV supply air temperature. The perceived inhaled air freshness increased with the decrease of the inhaled air temperature and increase of facial velocity.

[1]  S. Tanabe,et al.  Development and application of an underfloor air-conditioning system with improved outlets for a 'smart' building in Tokyo , 1995 .

[2]  A. Melikov,et al.  Protection of Occupants from Exhaled Infectious Agents and Floor Material Emissions in Rooms with Personalized and Underfloor Ventilation , 2007 .

[3]  Takashi Akimoto,et al.  Experimental study on the floor-supply displacement ventilation system , 1995 .

[4]  Arsen Krikor Melikov,et al.  Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate , 2010 .

[5]  Hui Zhang,et al.  Testing and optimizing the performance of a floor-based task conditioning system , 1995 .

[6]  Qingyan Chen,et al.  Floor-Supply Displacement Ventilation in a Small Office , 2003 .

[7]  A. Melikov.  Indoor air quality assessment by a breathing thermal manikin , 2000 .

[8]  P. Fanger,et al.  Human response to personalized ventilation and mixing ventilation. , 2004, Indoor air.

[9]  K. W. D. Cheonga,et al.  Local thermal sensation and comfort study in a field environment chamber served by displacement ventilation system in the tropics , 2005 .

[10]  S. Sekhar,et al.  Indoor air quality and thermal comfort studies of an under-floor air-conditioning system in the tropics , 2002 .

[11]  Arlindo Tribess,et al.  Analysis of Thermal Comfort in an Office Environment with Underfloor Air Supply in a Tropical Climate , 2006 .

[12]  L. P. Johnston,et al.  Performance testing of a floor-based, occupant-controlled office ventilation system , 1991 .

[13]  A. Melikov.  Personalized ventilation. , 2004, Indoor air.

[14]  F. Bauman.  Underfloor air distribution (UFAD) design guide , 2003 .

[15]  P. Fanger,et al.  Impact of Temperature and Humidity on the Perception of Indoor Air Quality , 1998 .

[16]  Hui Zhang,et al.  Modeling thermal comfort in stratified environments , 2005 .

[17]  Standard Ashrae.  Thermal Environmental Conditions for Human Occupancy , 1992 .

[18]  Arsen Krikor Melikov,et al.  Performance of Personalized Ventilation in Conjunction with Mixing and Displacement Ventilation , 2006 .

[19]  Povl Ole Fanger,et al.  Findings of Personalized Ventilation Studies in a Hot and Humid Climate , 2005 .

[20]  C. Chao,et al.  Airflow and air temperature distribution in the occupied region of an underfloor ventilation system , 2004 .

[21]  Arsen Krikor Melikov,et al.  Air Quality and Thermal Comfort in an Office with Underfloor, Mixing and Displacement Ventilation , 2006 .

[22]  W. Snow,et al.  Ventilation of buildings , 1906 .

[23]  Qingyan Chen,et al.  Floor-supply displacement ventilation for workshops , 2007 .

[24]  A. Melikov,et al.  Personalized ventilation: evaluation of different air terminal devices , 2002 .

[25]  L. G. Harriman,et al.  Underfloor air distribution: thermal stratification , 2002 .