Empowered by: KU Leuven, VITO, imec & UHasselt Strategies ...
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Empowered by: KU Leuven, VITO, imec & UHasselt Strategies for the Design and Predictive Maintenance of Heat Exchangers Used in Geothermal Applications GeoWatt – Activity 2 - Deep Geothermal Energy to Produce Electricity and Heat Problems and Objectives • Geothermal brines have a high salinity and are at high temperatures • This is very corrosive to the heat exchangers (HEX) • Possible resistant materials (e.g. titanium) are expensive and reduce the profitability of the power plant -> Suitability of more economic materials is tested -> Existing HEX typologies are compared and possible alternatives are devised -> Predictive maintenance and intelligent monitoring strategies are evaluated Material Evaluation • Common steel types, both low-alloyed carbon steels as stainless steels, are tested • Exposure tests are performed to determine the uniform corrosion rates (figures left) • Cyclic polarisations experiments are done to assess the resistance to pitting and crevice corrosion (figures right) Heat Exchanger Design • The feasibility of existing HEX designs for a geothermal power plant is assessed and their pros and cons are compared • Important features are: cost, ease of cleaning, ease of replacing corroded parts, possibility of monitoring & thermohydraulic performance • Potential typologies are: shell-and-tube (a), plate (b), double-pipe & spiral HEX Monitoring and maintenance • A set-up is being built to test if sensors can monitor different aspects related to HEX performance and assess corrosion damage: • Alternatives to the existing design are considered: • Adapted versions of existing design where worn parts can readily be replaced or where corrosion can be tolerated (e.g. double wall plate HEX, c) • New designs with a focus on simple cleaning, maintenance, and monitoring A C B In- and outlet temperatures Pressure drop Wall thickness • Combining these inputs, a model will be developed to allow predictive maintenance • The model should predict which parts are likely to fail, eliminating the need for expensive preventive maintenance of the entire HEX • This should reduce the total cost of ownership (TCO) of the installation Conclusions • The corrosive conditions in geothermal power plants dictate the use of expensive materials for the HEX • Low cost materials could be used, taking uniform and localised corrosion into account • Optimal design can decrease construction and maintenance costs • With a proper set of sensors, the real-time state of the HEX can be evaluated References Kakac, Sadik, Hongtan Liu, and Anchasa Pramuanjaroenkij. Heat exchangers: selection, rating, and thermal design. CRC press, 2012. Plateflow - gasketed plate & frame heat exchanger DOUBLE-WALL - http://www. ittstandard.com
Transcript of Empowered by: KU Leuven, VITO, imec & UHasselt Strategies ...
Empowered by: KU Leuven, VITO, imec & UHasselt
Strategies for the Design and Predictive Maintenance of Heat Exchangers Used in Geothermal ApplicationsGeoWatt – Activity 2 - Deep Geothermal Energy to Produce Electricity and HeatProblems and Objectives• Geothermal brines have a high salinity and are at high temperatures• This is very corrosive to the heat exchangers (HEX)• Possible resistant materials (e.g. titanium) are expensive and reduce the profitability of the power plant
-> Suitability of more economic materials is tested-> Existing HEX typologies are compared and possible alternatives are devised -> Predictive maintenance and intelligent monitoring strategies are evaluated
Material Evaluation• Common steel types, both low-alloyed carbon steels as stainless steels, are tested• Exposure tests are performed to determine the uniform corrosion rates (figures left)• Cyclic polarisations experiments are done to assess the resistance to pitting and crevice corrosion (figures right)
Heat Exchanger Design• The feasibility of existing HEX designs for a geothermal power plant is assessed and their pros and cons are compared• Important features are: cost, ease of cleaning, ease of replacing corroded parts, possibility of monitoring & thermohydraulic performance• Potential typologies are: shell-and-tube (a), plate (b), double-pipe & spiral HEX
Monitoring and maintenance• A set-up is being built to test if sensors can monitor different aspects related to HEX performance and assess corrosion damage:
• Alternatives to the existing design are considered:• Adapted versions of existing design where worn parts can readily be replaced or where corrosion can be tolerated (e.g. double wall plate HEX, c)• New designs with a focus on simple cleaning, maintenance, and monitoring
A
C
B
In- and outlet temperaturesPressure dropWall thickness
• Combining these inputs, a model will be developed to allow predictive maintenance• The model should predict which parts are likely to fail, eliminating the need for expensive preventive maintenance of the entire HEX• This should reduce the total cost of ownership (TCO) of the installation
Conclusions• The corrosive conditions in geothermal power plants dictate the use of expensive materials for the HEX
• Low cost materials could be used, taking uniform and localised corrosion into account
• Optimal design can decrease construction and maintenance costs• With a proper set of sensors, the real-time state of the HEX can be evaluated
ReferencesKakac, Sadik, Hongtan Liu, and Anchasa Pramuanjaroenkij. Heat exchangers: selection, rating, and thermal design. CRC press, 2012.Plateflow - gasketed plate & frame heat exchanger DOUBLE-WALL - http://www.ittstandard.com
