Prediction of thermal comfort levels in a rectangular shape room with basic heat transfer theories

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Prediction of thermal comfort levels in a rectangular shape room with basic heat transfer theories

 

Author: Mak, Cheuk Wai
Title: Prediction of thermal comfort levels in a rectangular shape room with basic heat transfer theories
Degree: M.Eng.
Year: 2007
Subject: Hong Kong Polytechnic University -- Dissertations.
Temperature -- Physiological effect.
Buildings -- Environmental engineering.
Temperature measurements.
Department: Dept. of Building Services Engineering
Pages: xiv, 137 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2117582
URI: http://theses.lib.polyu.edu.hk/handle/200/1651
Abstract: This study employs the fundamental knowledge of radiant heat transfer theories to develop a useful box model with quantitative research technique to suit Hong Kong situation for the prediction of the thermal comfort levels based on different locations under natural ventilation condition for a single office room with windows at one side. Measurement on environmental parameters such as air temperature, mean radiant temperature, relative humidity and air velocity. Other factors like human factors, clothing insulation value, metabolic rate and room surface temperatures were also monitored continuously for three days during the summer time. The results generated from the box model were compared with the actual measurement by using a statistical technique to analyze their goodness of fit. An application of the box model was implemented for illustrating the prediction of thermal comfort levels at different locations in a single glazed office room and also for determining the best location for working desk inside the room. A simple questionnaire survey was also carried out. The survey aims at providing useful information on user's habit with respect to the thermal comfort sensation and the preference on energy saving issue to air conditioning system during the unoccupied periods inside a single glazed office room. In addition, this survey can link up the box model to the balancing between energy conservation (i.e. by natural ventilation or during unoccupied period) and thermal comfort. The results of the measurement show that mean radiant temperature could be a dominant factor influencing the thermal comfort levels inside a single glazed office room. On the other hand, the results of the agreement between the box model and actual measurement showed a good correlation. The results also show that different locations would have different thermal comfort levels. Therefore, it raises a question to engineers or designers. The indoor thermal comfort issue should be considered during the design stage. The results of the questionnaire show that most of users are willing to contribute to energy saving. They would switch off the air conditioning system during long unoccupied periods if the saving is significant. However, they also have some misunderstanding about the energy saving issue as well as the usage of air conditioning system. It can be proved that most of users did not realize that switching off the air conditioning system for a shorter period can also save a lot of energy. On the other hand, most of users often or in many occasions wear heavy clothes in their office rooms, and they prefer setting a relatively low indoor temperature. Obviously, it will consume more energy for the air conditioning systems. Furthermore, most users think that the time for resumption of temperature back to normal one was very long and they did not fell uncomfortable. In the meantime, most of users agreed that it is worthwhile to switch off the air conditioning system during the overnight or lunch time period for energy conservation purpose. The results of this project can supplement the concept of using free cooling in some months.

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