Experimental Investigation of the Effects of Inlet Cooling Air Temperature on the Occupants’ Local Thermal Sensation in the Under-Floor Air Distribution System

Document Type : Research Article

Authors

University of Birjand

Abstract

In the present study, the effects of inlet cooling air temperature from the diffusers of under-floor air distribution system have been experimentally investigated on the occupants’ local thermal sensation. In the experiments, the inlet air temperature is controlled at 12°C, 16°C and 20°C, and the inlet velocity is kept constant. Also, the room thermal conditions have been controlled at the mean temperature of 24±0.5°C and mean relative humidity of 25±2%. During the experiment, 8 healthy male subjects with common office clothing and metabolic rate were exposed to an under-floor air distribution system for 30 min and their thermal sensation and satisfaction were assessed on the basis of thermal comfort standards. Based on the results, the head and chest thermal sensations are not significantly depended on inlet temperature. But, by decreasing the inlet temperature, the thermal sensation and satisfaction of hands and feet are decreased. Moreover, the results indicated that the overall body thermal sensation is significantly depended on the sensation of the body parts with extreme thermal conditions. Also, the results show that the feeling of air movement can be increased during the time; so, the subjects reported about 75% draught discomfort after 30 min exposure to under-floor air distribution system.

Keywords

Main Subjects

References

[1] Q.A. Liu, P. F.  Linden The fluid dynamics of an underfloor air distribution system, 2006.
[2] R. Li, S.C. Sekhar, A.K. Melikov, Thermal comfort and IAQ assessment of under-floor air distribution system integrated with personalized ventilation in hot and humid climate, Building and Environment, 45(9) (2010) 1906-1913.
[3] T. Arghand, T. Karimipanah, H.B. Awbi, M. Cehlin, U. Larsson, E. Linden, An experimental investigation of the flow and comfort parameters for under-floor, confluent jets and mixing ventilation systems in an open-plan office, Building and Environment, 92 (2015) 48-60.
[4] Y. Xue, Q. Chen, Influence of floor plenum on energy performance of buildings with UFAD systems, Energy and Buildings, 79 (2014) 74-83.
[5] M. Zukowski, A new formula for determining a minimum recommended value of inlet air velocity from UFAD system to prevent occupants from draught risk, Building and Environment, 42(1) (2007) 171-179.
[6] A. Alajmi, W. El-Amer, Saving energy by using underfloor-air-distribution (UFAD) system in commercial buildings, Energy Conversion and Management, 51(8) (2010) 1637-1642.
[7] S.H. Ho, L. Rosario, M.M. Rahman, Comparison of underfloor and overhead air distribution systems in an office environment, Building and Environment, 46(7) (2011) 1415-1427.
[8] S. Schiavon, K.H. Lee, F. Bauman, T. Webster, Simplified calculation method for design cooling loads in underfloor air distribution (UFAD) systems, Energy and Buildings, 43(2) (2011) 517-528.
[9] K. Zhang, X. Zhang, S. Li, X. Jin, Experimental study on the characteristics of supply air for UFAD system with perforated tiles, Energy and Buildings, 80 (2014) 1-6.
[10] M.H. Fathollahzadeh, G. Heidarinejad, H. Pasdarshahri, Prediction of thermal comfort, IAQ, and energy consumption in a dense occupancy environment with the under floor air distribution system, Building and Environment, 90 (2015) 96-104.
[11] G. Heidarinejad, M.H. Fathollahzadeh, H. Pasdarshahri, Effects of return air vent height on energy consumption, thermal comfort conditions and indoor air quality in an under floor air distribution system, Energy and Buildings, 97 (2015) 155-161.
[12] M.H. Fathollahzadeh, G. Heidarinejad, H. Pasdarshahri, Producing a better performance for the under floor air distribution system in a dense occupancy space, Energy and Buildings, 126 (2016) 230-238.
[13] M. Afzalian, S.A. Zolfaghari, A. Foadadini, Effects of air change rate on comfort, air quality and energy consumption in an amphitheater with under-floor air distribution system, Modares Mechanical Engineering, 17(2) (2017) 284-294.(In persian)
[14] Y.H. Yau, K.S. Poh, A. Badarudin, A numerical airflow pattern study of a floor swirl diffuser for UFAD system, Energy and Buildings, 158 (2018) 525-535.
[15] F.S. Bauman, A. Dally, R. American Society of Heating, A.-C. Engineers, Underfloor Air Distribution (UFAD) Design Guide, American Society of Heating Refrigerating and Air-Conditioning Engineers, 2003.
[16] T. Webster, F.S. Bauman, Design guidelines for stratification in underfloor air distribution (UFAD) systems,  (2006).
[17] H. Zhang, E. Arens, C. Huizenga, T. Han, Thermal sensation and comfort models for non-uniform and transient environments: Part I: Local sensation of individual body parts, Building and Environment, 45(2) (2010) 380-388.
Amirkabir Journal of Mechanical Engineering
Volume 53, Issue 3
June 2021
Pages 1537-1548

Files

Share

How to cite

Statistics