Cooling load reduction with stratified air distribution system in office

Pao Yue-kong Library Electronic Theses Database

Cooling load reduction with stratified air distribution system in office

 

Author: Lai, Chun Chung
Title: Cooling load reduction with stratified air distribution system in office
Degree: M.Eng.
Year: 2013
Subject: Displacement ventilation.
Cooling load -- Measurement.
Office buildings -- Air conditioning.
Hong Kong Polytechnic University -- Dissertations
Department: Dept. of Building Services Engineering
Pages: xii, 109 leaves : ill. (some col.) ; 30 cm.
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b2641103
URI: http://theses.lib.polyu.edu.hk/handle/200/7103
Abstract: The stratified air distribution (STRAD) system can achieve energy saving, reduce cooling load and improve indoor air quality in the breathing zone, compared with the traditional mixed ventilation (MV) system. Concerning the current situation that it is still not widely used in Hong Kong in spite of its potential benefits, this research aims to provide the fundamental knowledge of the cooling load reductions with the presence of different types of heat loads. It will also serve as a base for comparing or verifying CFD simulation results in previous work. This study has been undertaken through an experimental approach. A full-scale office room environment was simulated in a laboratory chamber located in the Building Services Engineering Laboratory in the Hong Kong Polytechnic University. Since lighting load, occupant load and external solar heat gain through fenestration were the major heat loads in office rooms, cooling load reductions in each load simulation has been studied independently. The combined effects of the three loads have also been examined. Besides, the reductions in three exhaust locations have been calculated, which include luminaire slot, supply-side exhaust and window-side exhaust. The split return-exhaust configuration was adopted to reflect its further energy saving potential. Cooling load reduction has been estimated according to the algebraic expressions derived by Cheng and Niu. The use of common parameters like air temperatures and flow rates facilitated experimental measurements. Results indicated that the space air temperatures increased with height. This is consistent with the inherent characteristic of temperature stratification. Moreover, cooling load can be reduced most in lighting load simulation, but the least in occupant load simulation. This suggests that the significance of the ECLF outweighs that of the radiant heat portion. A more significant finding is that window-side exhaust tends to be the most effective option in heat removal when the three loads were switched on simultaneously. Cooling load was reduced by as much as 24.2%, which was 6.3% greater than that by supply-side exhaust. Based on the findings of this study, it can be concluded that a larger portion of heat exhausted directly by a close exhaust outlet could cause a greater reduction.

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