On-line performance evaluation of balancing variable flow secondary chilled water loop

Pao Yue-kong Library Electronic Theses Database

On-line performance evaluation of balancing variable flow secondary chilled water loop


Author: Chan, Kin-hung
Title: On-line performance evaluation of balancing variable flow secondary chilled water loop
Degree: M.Sc.
Year: 1999
Subject: Water -- Distribution
Refrigeration and refrigerating machinery -- Automatic control
Hong Kong Polytechnic University -- Dissertations
Department: Multi-disciplinary Studies
Dept. of Building Services Engineering
Pages: viii, 84 leaves : ill. ; 31 cm
Language: English
InnoPac Record: http://library.polyu.edu.hk/record=b1471906
URI: http://theses.lib.polyu.edu.hk/handle/200/1461
Abstract: Balancing of variable water flow system has aroused different opinions or viewpoints on the advantages and the disadvantages of control performance and energy performance of the systems. Based on those discussions about such issue, variable water flow system has been presumed to work better using dynamic balancing by means of the flow limiting valves. Hence, dynamic models of secondary chilled water loop including the distribution network, the cooling coil, the actuator, the sensor, the variable speed pump, the DDC controller and the flow limiting valve are so developed to simulate the dynamics of the secondary loop chilled water system. On-line performance evaluations can then be carried out under different loads, different operating conditions and different configurations. This dissertation presents the literature findings, the models, the system simulation of the secondary chilled water system and the on-line flow control performance evaluation of the flow limiting valves on the system. Using dynamic balancing but not necessarily installing manual balancing valves, the performance of system can be improved under full loads and part loads conditions. Although the flow limiting valve also has certain limitations in improving the control performance of the system, the installation of those valves at some selective/critical locations is worth recommending.

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