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Title: Operation Guidelines for Under Floor Air Distribution Systems with Respect to Occupants’ Thermal Comfort—A Case Study
Authors: Faisal Azzam Baddar 
Supervisor: Dr. Raed Bourisli
Keywords: Under Floor : Occupants
Issue Date: 2012
Publisher:  Kuwait university - college of graduate studies
Abstract: The purpose of this research is to two-fold. In the first stage, the occupants’ thermal comfort in buildings air-conditioned by under floor air distribution (UFAD) systems in The State of Kuwait is investigated experimentally. The UFAD system is fairly new in Kuwait, in-use only in the Kuwait Audit Bureau building in Kuwait City. A questionnaire was distributed on the occupants of the building in order to measure the thermal comfort subjectively. As perceived by the occupants, results showed that close to 80% of the occupants feel between slightly cool and cool. A physical experiment, using a Bruel and Kjaer type 1221 thermal comfort analyzer, was done in one of the typical rooms where an occupant performs typical office work during typical hours. The device gave an average predicted mean vote (PMV) of - 0.7 for that occupant based on a supply air diffuser temperature of 18ºC and a supply air velocity of 1.5 m/s, validating the subjective questionnaire results of a slightly cool feeling. Then, a CFD model of the room was constructed using the Design BuilderTM software, using the exact parameters and properties for the actual room were used. The actual tested room data was used to construct and validate the CFD model, thereby setting the stage for the second stage of the research. This second stage consisted of carrying out a parametric study of operating conditions as they relate to thermal comfort. In all, eleven numerical simulations were done, changing the supply air temperature and velocity in all the diffusers. A general picture of the optimum operating points emerged from the analyses showing the relationship between the temperature and velocity of the supply air and the level of thermal comfort of occupants. The Air Distribution Performance Index was used to measure the relative level of thermal comfort in tested configurations. Conclusions were drawn to aid in setting up operation conditions for this and other buildings of this type. Air stratification for all studied cases was analyzed to better understand the operation for the UFAD system. It was noticed that the best stratification occurs at low to moderate supply air velocities. Applied to the tested room used for validation, the new guidelines improved the ADPI by more than 90% when the optimum set of the parameters were used, which happened to be 21°C and 1 m/s for the supply air temperature and velocity, respectively. The proposed methodology of experimental validation followed by parametric (numerical) simulations is believed to enable designers of UFAD systems to make better decisions with regards to design variables and operation settings that give optimum thermal comfort for occupants.
Appears in Programs:0630 Mechanical Engineering

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