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Buildings 2018, 8(7), 84; https://doi.org/10.3390/buildings8070084

Mathematical Explanation and Fault Diagnosis of Low Delta-T Syndrome in Building Chilled Water Systems

College of Urban Construction, Nanjing Tech University, No. 200, North Zhongshan Road, Nanjing 210009, China
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Received: 29 April 2018 / Revised: 14 June 2018 / Accepted: 20 June 2018 / Published: 21 June 2018
(This article belongs to the Special Issue Innovative Approaches to Achieving Building Energy Efficiency)
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Abstract

Low delta-T syndrome often occurs in building chilled water systems, which makes systems fail to operate as efficiently as originally anticipated. Extensive studies have been conducted on the subject of low delta-T syndrome with the aims of investigating the potential causes behind and the ways to keep delta-T high. This paper addresses to explain the causes of degrading delta-T from a mathematic perspective and to analyze the impacts of important operational parameters on the delta-T quantitatively. A simplified global cooling coil model representing the relationship between the total cooling load and the total water flow rate of chilled water systems is developed, which can be used to predict the system delta-T under different load distribution and system operation conditions. It is proved mathematically that the load distribution characteristic is an important factor in influencing the system delta-T of a chilled water system. This finding explains why the system delta-T is always lower than the delta-T of individual coils, particularly under low partial load conditions. A system-level fault detection and diagnosis (FDD) method is proposed for identifying the possible causes of the low delta-T problem. A case study is conducted to validate the proposed global model and FDD method in a real building. View Full-Text
Keywords: low delta-T syndrome; chilled water system; global cooling coil model; mathematical explanation; fault diagnosis low delta-T syndrome; chilled water system; global cooling coil model; mathematical explanation; fault diagnosis
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Yan, C.; Yang, X.; Xu, Y. Mathematical Explanation and Fault Diagnosis of Low Delta-T Syndrome in Building Chilled Water Systems. Buildings 2018, 8, 84.

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