| Title | The Longevity of Self Assembled Mono-layer Coatings for Enhanced Steam Condensation and Their Applications in Geothermal Power Plants |
|---|---|
| Authors | Vemuri, S.; Kim, Kwang J.; Bell, Thomas W. |
| Year | 2006 |
| Conference | Geothermal Resources Council Transactions |
| Keywords | Geofluids; dropwise condensation, organic coatings, mono-layers |
| Abstract | Reported herein are the results of experimental investigations of the effect of using self assembled mono-layer (SAM) coated surfaces on steam condensation processes with a potential for use in geothermal power plants. Two different types of mono-layer coatings have been analyzed experimentally for their ability to promote dropwise condensation (DWC). For any technique used for promoting dropwise condensation, the longevity of the coating is critical. In the current research experiments were carried out using SAMs for more than 3,600 hrs of experimentation and it showed good dropwise phenomena. Stearic acid solution (SAM–1) and n-octadecyl mercaptan solution (SAM–2) were used to form an ultra-thin organic hydrophobic film on the surface. In general, a SAM system with a long-chain, hydrophobic group is nano-resistant, meaning that such a system forms a protective hydrophobic layer with negligible heat transfer resistance but a much stronger bond. When compared to complete filmwise condensation, the SAM–2 (n-octadecyl mercaptan) coating increased the condensation heat transfer coefficient by a factor of approximately 3 after 100 hrs of experimentation and by a factor of approximately 1.6 after 3,600 hrs of experimentation for copper alloy surfaces, under vacuum condition (33.86 kPa). The lifetime of maintaining dropwise condensation is greatly dependent on the bonding of SAM coating to the condensing surface. Contact angles were measured for all the SAM coated surfaces before and after experimentation, respectively. |