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Geothermal
Scanning Electron Microscope ( SEM ) image of tested samples . On the left side is a carbon steel substrate and on the right side is Amorphous 1 coated on stainless steel .
Based on the heat transfer , microstructural analysis , and mechanical results , the following conclusions can be summarised for the single phase GeoHex coatings :
• Amorphous 1 shows great potential in silica removal where 80 % of silica scaling was removed at 15.86 MPa but only 40-50 % was removed on 245SMO and 316L at 27.03 MPa and 18.1 MPa respectively .
• TSA and ENP show a 45 % and 35 % increase in heat transfer coefficient respectively with low scaling accumulation compared to reference materials .
• 316L-Amorphous 2 sample had 4.9 % lower heat transfer coefficient compared to the nanoporous- Amorphous 2 sample indicating better heat transfer performance , indicating better heat transfer performance by using the nanoporous coating .
Advantages of amorphous over crystalline structures Amorphous materials do not have a well-defined crystalline structure , giving coatings based on them unique physical and chemical properties making them ideal for protective coatings . The lack of a crystalline structure means they can be deposited in a variety of ways ( sputtering , ARCdeposition ,), at mild and very scalable conditions giving precise control of thickness and properties .
Other advantages :
• Hardness and wear resistance
• Corrosion resistance
• Smoothness
• Can be designed to have enhanced properties , such as high or low reflectivity
• Electrical properties – can be designed to have high conductivity or insulation
David Ingvi Snorrason ( R & D Engineer and Project Manager from GREIN research , another member of the GeoHex consortium ) explains further : “ Corrosion tends to occur on grain boundaries and amorphous materials lack such boundaries meaning that the oxide scale which inherently forms on the material is uniform which hopefully makes the coatings more corrosion resistant . Also , with regards to the polymeric reaction of silica scaling , the smoothness of metallic glass could potentially hinder formation of scaling and / or make it easier to get rid of silica scaling . The focus of this project is on heat exchangers , but we also see possible application in different parts of geothermal systems .”
Future applications and overcoming issues When asked about the future of such coatings , and prospects of their real-life application to geothermal heat
The image on the left is the experimental setup . The test rig is fitted with temperature , flow , and pressure sensors and the data was used to calculate the heat transfer coefficient of tested materials . On the right side is the heat exchanger where a plate is place into the slot as shown . During the test , a working fluid flows on one side and a geothermal brine on the other side .
www . heat-exchanger-world . com Heat Exchanger World May 2023
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