Investigation on low delta-T symptom and building energy performance

Pao Yue-kong Library Electronic Theses Database

Investigation on low delta-T symptom and building energy performance

 

Author: Shang, Jingfang
Title: Investigation on low delta-T symptom and building energy performance
Degree: M.Eng.
Year: 2010
Subject: Hong Kong Polytechnic University -- Dissertations
Commercial buildings -- Energy consumption
Heat -- Transmission
Department: Dept. of Building Services Engineering
Pages: x, 68 leaves : ill. ; 31 cm.
InnoPac Record: http://library.polyu.edu.hk/record=b2356383
URI: http://theses.lib.polyu.edu.hk/handle/200/5809
Abstract: Nowadays, energy saving is an important issue receiving wide attention. For the commercial buildings, the energy consumption of HVAC systems contributes a large amount to the total energy consumed in buildings. The main aim of this study is therefore to examine the heat transfer performance of air handling units and investigate the low chilled-water temperature difference between the chilled water supply and return occurred in the operation of chilled water distribution systems. Based on the outputs of this study, a set of recommendations and guidelines are made for achieving high chilled-water temperature difference and improving the overall system operating efficiency. This study is mainly focused on the investigation of the performance of air handling units. A transient system simulation program, TRNSYS, is used to simulate the components and process controllers in the chilled water loop, such as the pipelines, air handling units and PID controllers. The simulation tests were carried out under various working conditions in order to find the possible causes of the low chilled water temperature differences. Based on the test results, it is found that an increase in chilled-water temperature differentials result in a low water flow rate which can save energy. The common causes of the low chilled-water temperature differentials include the improper coil selection, improper control valve selection, coil fouling, laminar coil flow, mismatched design conditions, improper sensor calibration, the use of three-way valves, the use of improper control settings, system pressure difference above the valve shut-off head, and plant chilled water mixing. It is believed that proper system design of air handling units could help to increase the chilled-water temperature differentials, and thus to enhance the overall system performance.

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