Sustainable thermal comfort

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Sustainable thermal comfort


Author: Leung, Suet-ha
Title: Sustainable thermal comfort
Degree: Ph.D.
Year: 2008
Subject: Hong Kong Polytechnic University -- Dissertations.
Air conditioning.
Buildings -- Thermal properties.
Buildings -- Environmental engineering.
Department: Dept. of Building Services Engineering
Pages: xx, 207, [70] leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record:
Abstract: Ex-Premier Hon. Lee Guan Yew at the end of last Century, voted the invention of air-conditioning system as the greatest invention in 20th Century for Far East Asians because these systems keep indoor users comfortable in indoor spaces. The thermally comfortable environment helps to boost up the economy in Asia. ASHRAE Standard 55 on 2004 which is based on the late Professor Fanger's comprehensive thermal comfort theory provides the engineers a model to design and control the indoor thermal environment optimally. In geographically temperate regions, indoor cooling is the main issue for keeping an optimum thermal comfort environment. A survey conducted by Chan et al (1996) in the Hong Kong air-conditioned offices revealed that the thermal environment is not satisfactory. Two main reasons are identified in this project - distributive nature of the thermal environmental parameters and local culture. The former is not, and probably in many situations, cannot be properly controlled to match the thermal loading with the cooling capacity. The later influences the thermal comfort management protocol inducing unacceptability. In this thesis, two approaches are used to rectify the situation. Firstly, from further analysis of the large data base compiled by Chan et al., the most influential distributive natures are found to be the spatial and temporal distribution of the air temperature and the distribution of clo. It is further found that the Hong Kong people are almost 2 oC lower indulged as compared to ASHRAE Standard thermal comfort zone. The findings lead to a new sequence of design, test and commissioning and operation of the air-side systems in setting the optimum air temperature for control, fine tuning of the air distribution and control, and operation of the systems. An envelop of air temperature which is formed by the two extreme distribution functions at air temperature linked by the range of temperature swing is proposed as a new target of air temperature control function. In this integrated approach, education, space air lightness, air and water balances and company culture on clothing clo are all taken into account. Secondly, this study explores the feasibility of raising the air temperature in indoor space. Thermal comfort is maintained by increasing the velocity. Energy saving by replacing chilled water energy with fan energy is not the main target. In traditional thermal comfort management, cooled supply air is the main tool. In this study, loss of thermal comfort satisfaction due to the raised supply air temperature is compensated by higher air velocity and room air by-pass. A higher air velocity is produced by a special design of the fan coil system which is an integration of a traditional fan coil and an inverter control fan. The inherent deficiency of wall mounted thermostat can be reduced. Furthermore, a periodic fluctuation of air velocity is rendered possible which further enhances the thermal comfort. Hence, the new system is named "Harmonious Fan Coil System". The system is analyzed and found feasible by site testing and ample computational fluid dynamic computations.

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