Refrigerant Charge Fault Detection and Diagnosis Algorithm for Water-to-Water Heat Pump Unit

Boahen, Samuel; Choi, Jong Min

doi:10.3390/en12030545

Cited by 15 publications

(9 citation statements)

References 14 publications

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“…Given simultaneous OFRF and refrigerant charge faults at 60% OFRF and 70% 270 RCR, capacity and COP reduced by 28.2% and 30.9%, respectively. Nonetheless, at 60% 271 OFRF, 70% RCR and 80% IFRF, capacity and COP reduced by 31…”

Section: Refrigerant Underchargementioning

confidence: 96%

“…According to Boahen et al [24] and Boahen et al [31], the compressor discharge temperature, brine temperature difference in the IDHX and ODHX have direct relations with the refrigerant charge fault, IFRF and OFRF, respectively. As a result that these operating parameters can be easily measured using temperature sensors when operating the heat pump, they were selected as independent variables for the FDD algorithm.…”

Section: Development Of Fault Detection and Diagnosis Algorithmmentioning

confidence: 98%

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Fault Detection Algorithm for Multiple-Simultaneous Refrigerant Charge and Secondary Fluid Flow Rate Faults in Heat Pumps

et al. 2021

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The detection and diagnosis of faults is becoming necessary in ensuring energy savings in heat pump units. Faults can exist independently or simultaneously in heat pumps at the refrigerant side and secondary fluid flow loops. In this work, we discuss the effects that simultaneous refrigerant charge faults and faults associated with the flow rate of secondary fluids have on the performance of a heat pump operating in summer season and we developed a correlation to detect and diagnose these faults using multiple linear regression. The faults considered include simultaneous refrigerant charge and indoor heat exchanger secondary fluid flow rate faults (IFRFs), simultaneous refrigerant charge and outdoor heat exchanger secondary fluid flow rate faults (OFRFs) and simultaneous refrigerant charge, IFRF and OFRF. The occurrence of simultaneous refrigerant charge fault, IFRF and OFRF caused up to a 5.7% and 8% decrease in cooling capacity compared to simultaneous refrigerant charge and indoor heat exchanger secondary fluid flow rate faults, and simultaneous refrigerant charge and outdoor heat exchanger secondary fluid flow rate faults, respectively. Simultaneous refrigerant charge fault, IFRF and OFRF resulted in up to an 11.6% and 5.9% decrease in COP of the heat pump unit compared to simultaneous refrigerant charge fault and IFRF, and simultaneous refrigerant charge fault and OFRF, respectively. The developed FDD correlations accurately predicted the simultaneous refrigerant charge and faults in the flow rate of the secondary fluid within an error margin of 7.7%.

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Section: Refrigerant Underchargementioning

confidence: 96%

Section: Development Of Fault Detection and Diagnosis Algorithmmentioning

confidence: 98%

Fault Detection Algorithm for Multiple-Simultaneous Refrigerant Charge and Secondary Fluid Flow Rate Faults in Heat Pumps

et al. 2021

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“…Three fault conditions will be investigated: working fluid leakage from the heat pump, compressor failure, and fouling inside of the gas cooler on the water side. These fault conditions are seen as the main fault categories in heat pumps [36,37].…”

Section: Fault Conditionsmentioning

confidence: 99%

“…Compressor failure may occur when the seal and mechanisms inside a compressor wear with use [36]. Compressor failure was simulated by assigning a fixed value for isentropic efficiency and gradually decreasing it as input parameter from 0.6527 to 0.5027 in increments of 0.05.…”

Section: Compressor Failurementioning

confidence: 99%

An Energy Graph-Based Approach to Fault Diagnosis of a Transcritical CO2 Heat Pump

et al. 2020

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The objective of this paper is to describe an energy-based approach to visualize, identify, and monitor faults that may occur in a water-to-water transcritical CO 2 heat pump system. A representation using energy attributes allows the abstraction of all physical phenomena present during operation into a compact and easily interpretable form. The use of a linear graph representation, with heat pump components represented as nodes and energy interactions as links, is investigated. Node signature matrices are used to present the energy information in a compact mathematical form. The resulting node signature matrix is referred to as an attributed graph and is populated in such a way as to retain the structural information, i.e., where the attribute points to in the physical system. To generate the energy and exergy information for the compilation of the attributed graphs, a descriptive thermal-fluid model of the heat pump system is developed. The thermal-fluid model is based on the specifications of and validated to the actual behavioral characteristics of a physical transcritical CO 2 heat pump test facility. As a first step to graph-matching, cost matrices are generated to represent a characteristic residual between a normal system node signature matrix and a faulty system node signature matrix. The variation in the eigenvalues and eigenvectors of the characteristic cost matrices from normal conditions to a fault condition was used for fault characterization. Three faults, namely refrigerant leakage, compressor failure and gas cooler fouling, were considered. The paper only aims to introduce an approach, with the scope limited to illustration at one operating point and considers only three relatively large faults. The results of the proposed method show promise and warrant further work to evaluate its sensitivity and robustness for small faults.Energies 2020, 13, 1783 2 of 34 Zogg also refers to a field survey [2] that indicates that the average energetic efficiencies of the heat pumps installed in Swiss buildings were about 10% lower than the efficiencies measured under standard laboratory conditions. It was also found that for some installations the performance degradation was as high as 30%. A similar study in the United States of over 55,000 air conditioning units showed that more than 90% were operating with one or more kinds of faults [3]. Yet another study surveying roof-top units indicates an operating efficiency of 80% of designed performance with 63% of these units having performance degradation due to refrigerant leakage [4]. These observations motivate the need for diagnostic techniques which ideally can monitor these energy conversion systems during transient and steady-state operating conditions.In the review papers by Zhao et al., and Shi and O'Brien [5,6] the classification of fault detection methods for energy systems are presented. Fault detection methods can be classified into two subcategories: data-based and knowledge-based. The knowledge-based methods rely on domain and prior knowledge to deri...

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“…D. G. Down [16] developed an observer-based fault diagnosis method to detect and isolate sensor faults. In addition to pump and sensor failure, heat exchanger faults [17], valve faults [18], and refrigerant charge faults [19] are also discussed. While prior research has explored component-level physical failures in depth, few have considered how componentlevel failures affect MPLs system function from a system-level viewpoint Despite the significance of how cyber-attacks could affect MPLs performance, few studies have examined the impact.…”

Section: Introductionmentioning

confidence: 99%

Safety Impact Analysis Considering Physical Failures and Cyber-Attacks for Mechanically Pumped Loop Systems (MPLs)

Zhang

et al. 2022

Sensors

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As complex systems composed of physical and cyber components, mechanically pumped loop systems (MPLs) are vulnerable to both passive threats (e.g., physical failures) and active threats such as cyber-attacks launched on the network control systems. The impact of the aforementioned two threats on MPL operations is yet unknown, and there is no practical way to evaluate their severity. To assess the severity of the impact of physical failures and cyber-attacks on MPLs, a safety impact analysis framework based on Elman Neural Network (ENN) observers and the Gaussian Mixture Model (GMM) algorithm is suggested. The framework discusses three common attack and failure modes: sensor hard failure that occurs suddenly, sensor soft failure that occurs gradually over time, and denial-of-service (DoS) attacks that prevent communication between the controller and valve. Both sensor failures and DoS attacks render the system unsafe, according to simulation data. In comparison to DoS attacks, however, sensor failures, particularly soft failures, inflict the greatest harm to the MPLs. Furthermore, sensors engaged in global control, rather than those involved in local control, need additional protection.

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Refrigerant Charge Fault Detection and Diagnosis Algorithm for Water-to-Water Heat Pump Unit

Cited by 15 publications

References 14 publications

Fault Detection Algorithm for Multiple-Simultaneous Refrigerant Charge and Secondary Fluid Flow Rate Faults in Heat Pumps

Fault Detection Algorithm for Multiple-Simultaneous Refrigerant Charge and Secondary Fluid Flow Rate Faults in Heat Pumps

An Energy Graph-Based Approach to Fault Diagnosis of a Transcritical CO2 Heat Pump

Safety Impact Analysis Considering Physical Failures and Cyber-Attacks for Mechanically Pumped Loop Systems (MPLs)

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