Author: Tang, Hou Man
Title: Numerical study on sleeping thermal comfort using bed-based task/ambient air conditioning (TAC) system
Advisors: Chan, Ming Yin (BSE)
Degree: M.Eng.
Year: 2020
Subject: Air conditioning
Human comfort
Hong Kong Polytechnic University -- Dissertations
Department: Department of Building Services Engineering
Pages: viii, 60 pages : color illustrations
Language: English
Abstract: The numerical study of the bed-based task/ambient air-conditioning system for a single-bed bedroom was conducted. The study is heavily based on two standards, namely ASHRAE Standard 55: Thermal Environmental Conditions for Human Occupancy and ISO 7730: Ergonomics of the Thermal Environment, where both standards provide the requirement of a thermally comfortable environment at daytime. The study primarily focuses on the thermal and energy performance of the TAC system at night time, in which the lower metabolic rate of occupant, bedding insulations and heat gain at the external wall from the sun at day time must not be overlooked. The TAC system is equipped with a double supply air inlet, in which the numerical study was conducted to investigate the performance of such unique design at different heights, namely H800mm, H1100mm, H1400mm, H1700mm and H2000mm. The study shows that ANSYS FLUENT is an effective tool to simulate the system and perform comprehensive study. Especially when defining the appropriate turbulent model, the CFD program is capable to generate result with more details. In the study, the details of the result contour improved when adopting the SST transition model from the standard k-ε turbulent model. Among all the settings, the H800, H1100 and H1400 shows an excellent performance in thermal comfort, around 7% of the occupants are predicted to dissatisfy with the thermal environment under the setting. However, the PMV of H1700 and H2000 are 1.15 and 1.52 respectively, therefore they don't fulfil the minimum requirement of the standard and are not recommended due to their poor energy saving potential. The energy saving capability is essential, as the ability to save energy is another major property the TAC uniquely possesses, hence this study further analysis the performance of the TAC based on the index called EUC that indicated the energy performance of the system. This helps to distinguish which settings is optimal in term of energy saving and thermal comfort. The result shows that the EUC of H800 is 1.43 and could potentially save the most energy compared to other settings. Moreover, the double air supply inlet design doesn't improve the thermal comfort and energy efficiency compared to the results of previous study, therefore this design of inlet for TAC system is not recommended, unless there are further studies on the design under different boundary conditions in the future. The PMV and EUC of the study overall suggests that the bed-based TAC is a thermal comfort system with excellent energy-efficiency, which has high potential to be adopted in the near future.
Rights: All rights reserved
Access: restricted access

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