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Austin, TX, United States

Zhao X.,Nodal Partners LLC | Yang M.,University of Nebraska at Omaha | Li H.,University of Nebraska at Omaha
HVAC and R Research | Year: 2012

Monitoring the water flow rate through chillers is necessary and important for safety and optimal operation of a chiller system. Conventional measuring methods are reluctantly accepted by end users due to high implementation cost and continuous maintenance requirements. In this study, a cost-effective virtual sensing method was developed to determine the water flow rate in chillers using generally available chiller onboard measurements. The method was implemented, evaluated, and demonstrated in both a laboratory test environment and a field test environment. The test results show that the method is capable of accurately monitoring the water flow rate in the condenser loop and evaporator loop using low-cost and noninvasive measurements obtained while the system is operating. In terms of application, the proposed method is promising for embedment within a chiller onboard controller or a monitor system to monitor actual water flow rate in the chiller system. © 2012 Copyright Taylor and Francis Group, LLC. Source


Zhao X.,Nodal Partners LLC | Yang M.,Nodal Partners LLC | Li H.,University of Nebraska at Omaha
Energy and Buildings | Year: 2014

Most existing Fault Detection and Diagnostic (FDD) methods for chillers are primarily tested and evaluated in a controlled laboratory environment. The controlled laboratory environment is usually configured and installed to satisfy the requirements of the FDD methods and therefore contain rich data sets. However, some measurements required by the FDD methods may not be commonly available on the field chillers. Therefore, field demonstrations and commercialization of chiller FDD is a big challenge since many practical issues must be addressed. In this study, a decoupling-based FDD method which can deal with multiple simultaneous faults was fully implemented online and evaluated in the field test environment. A step by step process of implementing the evaluated FDD method for the real application is described to aid readers to apply and use the method. Several occurrences of multiple simultaneous faults were found on the test chiller. The field test results show that the decoupling-based FDD method has potential to be incorporated within commercial FDD products or embedded into the control system onboard the chiller to monitor the health of the chiller's operation. © 2014 Elsevier B.V. All rights reserved. Source


Zhao X.,Nodal Partners LLC | Yang M.,Nodal Partners LLC | Li H.,Nodal Partners LLC
Energy and Buildings | Year: 2012

In the field, almost every condenser suffers from some kind of fouling problems. The chiller performance degrades naturally and gradually as fouling increases. Early identification of fouling in the condenser is essential to maintain an optimal chiller operation. In this paper, a method (virtual fouling monitor sensor) using low cost and commonly available onboard chiller measurements for monitoring the fouling status of the condenser is presented. The performance of the proposed virtual fouling monitor sensor was evaluated using lab data over a wide range of operating conditions in both normal and faulty conditions. Moreover, the proposed virtual fouling monitor sensor was also implemented and evaluated on a field chiller. The laboratory and field test results show that the proposed method gives a good and robust performance in terms of detecting the condenser fouling faults in chillers. In terms of possible applications, the proposed method has the potential to be implemented as an individual fouling monitor sensor/tool, incorporated within the commercial chiller FDD tool, or embedded in the control systems onboard the chiller to automatically monitor the condenser fouling status. © 2012 Elsevier B.V. All rights reserved. Source

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