Performance evaluation of extra low temperature air-conditioning system

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Performance evaluation of extra low temperature air-conditioning system


Author: Ng, Ting Fung
Title: Performance evaluation of extra low temperature air-conditioning system
Degree: M.Eng.
Year: 2015
Subject: Air conditioning
Air conditioning -- Design and construction.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: vii, 67 pages : color illustrations
Language: English
InnoPac Record:
Abstract: Over the last decades, disease such as avian flu, SARS (severe acute respiratory syndrome) have occurred in some places such as Hong Kong. The safety of AC systems grows more crucial. Typical conventional air conditioning system is usually a multi-zone system which the conditioned air will be distributed to different zone by an air handling unit (AHU). This would cause cross contamination which may increase the chance of disease transmission. In this study, a novel DOAS (dedicated outdoor air system) with extra-low temperature with heat pipe heat exchanger (ETHP) was proposed. This study aimed to investigate the energy performance and thermal comfort of the novel DOAS and compare the novel system with conventional air conditioning system. Simulation software Energyplus was used to simulate and evaluate the energy performance and thermal comfort environment of the ETHP. The influence of various selected parameters such as no.of stage of cooling, pre-treated outdoor air temperature and supply temperature was investigated.It was found that the energy saving achieved by adopting ETHP over conventional CAV is 10.9% which is due to the absence of reheater in the ETHP. Also, the non-comfortable hours of ETHP is 7.4% less than conventional CAV. This is because ETHP adopts higher supply air temperature and provides better humidity control. In additions, in the parametric study, it was found that pre-treated outdoor air temperature and no. of stage are closely related to energy consumptions of the system while the non-comfortable hours was related to supply air temperature and pre-treated outdoor air temperature. The optimum operating condition was found to be a three-stage cooling system with supply air temperature of 18℃ and pre-treated outdoor air temperature of 4℃. It was concluded that ETHP with the optimum operating condition can best achieve energy saving and thermal comfort among all studied cases.

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