Alternative Approaches for Real-time Monitoring of the Effectiveness of Hydrogenerator Heat Exchangers

Abstract

Heat exchangers require periodic maintenance. Offline cleaning scheduled shutdowns are usually needed to restore the exchanger effectiveness, drastically reduced when fouling accumulation occurs. An online real-time alternative for monitoring the effectiveness of exchanger (during a period of eleven months of continuous operation) and an adapted version of the ε-NTU method to calculate its effectiveness are discussed. The experimental difficulties of measuring the mass flow rate and the hot air temperature at the exit of the exchanger is examined. Detailed analysis confirmed that the outlet temperature of the hot fluid could introduce errors of up to 30% in the calculation of the exchanger effectiveness. A skillful treatment of the energy balance is proposed to address the issue. The associated uncertainties are estimated by two independent approaches, the so-called classic method, i.e., the Guide to the Expression of Uncertainty in Measurement and the Monte Carlo method. Both confirmed that measurements of the air outlet temperature accounts for more than 50% of the uncertainty associated with the calculation of the exchanger effectiveness. It is suggested that the conventional method (based on measurements of the outlet air temperature) is not suitable for traditional everyday practices to monitor the effectiveness of the heat exchangers of hydrogenerators.

Acknowledgements

The authors are grateful to the Brazilian Electricity Regulatory Agency (Aneel) and the electric power concessionaire, Light Energia S/A, for financial support under grant 5161-010/2016 (Project Light-Aneel R&D). Thanks are also due to the Brazilian Research Funding Agency CAPES (Coordination for the Improvement of Higher Education Personnel) for financial support under grant code 001. The second author gratefully acknowledges financial support from the Vice Rectorate of Science, Technology, and Innovation (VCTI) of the Universidad Antonio Narino/Colombia under Project Grant 2022008.

Disclosure statement

The authors have no conflicts of interest. All co-authors have seen and agree with the contents of the publication, certifying that the submission reflects an original work, not submitted to any other journal.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

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Notes on contributors

Maurício N. Frota

Maurício Nogueira Frota has a Ph.D. in Mechanical Engineering (Stanford University, 1982). In the past, he held the positions of Director of Scientific and Industrial Metrology of the National Institute of Metrology of Brazil, President of the Inter-American Metrology System of the Americas (SIM) and Vice President of the International Measurement Confederation (IMEKO). Currently he is Emeritus Professor of the Postgraduate Metrology Programme of the Pontifical Catholic University of Rio de Janeiro, Brazil.

José Daniel Hernández-Vásquez

José Daniel Hernández Vásquez holds a master’s degree in Metrology and a Doctoral Degree in Mechanical Engineering from the Pontifical Catholic University of Rio de Janeiro Brazil. He is currently the Research Coordinator at Facultad de Ingeniería Mecánica, Electrónica y Biomédica (FIMEB) of the Mechanical Engineering Program at the Universidad Antonio Nariño. His areas of interest are thermodynamics, heat transfer and fluid mechanics, uncertainty analysis, and experimental methods in thermosciences.

Rui Pitanga Marques da Silva

Rui Pitanga Marques da Silva holds a Ph.D. in Mechanical Engineering from the City University of London (England, 1989) and a D.E.A in Mechanical Engineering from the École Nationale Supérieur de Mécanique et d’Aérotechnique (France, 1981). He is currently an Associate Professor at the Department of Mechanical Engineering of the Celso Suckow da Fonseca Federal Center for Technological Education (Rio de Janeiro, Brazil). His areas of interest are thermodynamics and fluid mechanics, reservoir engineering, and numerical methods in thermosciences.

Sergio Bragantine Germano

Sergio Bragantine Germano has a master’s degree in Metrology (Pontifical Catholic University of Rio de Janeiro. 2013). He is a researcher at the Research and Development Institute of the Brazilian Army, with experience in defense projects, automated manufacturing processes and industrial equipment development. Collaborating researcher of the Metrology Programme. His areas of interest are automation, servo-controlled equipment, and experimental methods in thermosciences.

Sergio de La Hoz Truyoll

Sergio de La Hoz Truyoll is a Mechanical Engineer (Universidade del Atlantico/Colombia, 2021). He is a researcher of the Institute of the CONFOMAT group of the Universidad del Atlántico, with experience in metal-mechanical projects and execution of civil works. Collaborating researcher of the Metrology Programme. His areas of interest are thermodynamics, heat transfer and fluid mechanics. Currently he is working on his master’s degree in Measurement Science (Metrology) in area directly related to the topic of this paper (effectiveness of heat exchangers).