Laszlo Csanyi writes:
I'm Laszlo Csanyi and I would like to ask for some help, opinion of the engineers reading this site.
I'm working on the "new generation" of flat-plate solar collectors, where the main idea is to replace the air inside the collector with a low-conducting gas, such as Argon, thus reducing the gas convection and molecular conduction losses.
Of course vacuum would be the perfect solution, however with flat-plate solar collectors this would cause serious technical problems, such as more intensive air-leakages and "large" aperture would need support also.
Hence, the main idea I have to deal with is the proper sealing of the collector. The major requirements of the sealant are to withstand elevated temperatures (+200°C), possible to create air and also diffusion tight sealing. Silicon rubber sealing would be applicable; however gases like Helium can diffuse through it, thus the collector needs re-filling after a certain period of time. We would like to avoid this, and also it would be more likely to find the material which accommodates different coefficients of thermal expansions and contractions.
There are many possibilities to create a sealing with Butyl tapes, high bond tapes, different sealants such as butyl, latex, polyurethane, silicon and from one company I got the suggestion of using epoxy. However I do hope there is someone who has experience with advanced sealants which would fulfill our requirements.
Each suggestion is very welcomed.
I also have a little bit different design from the conventional one, however to seal this I would like to get some information about gradient materials. Is it possible to find a gradient cermet layer with a high metal content on the one side and a high ceramic content on the other side in order to overcome the problem of coefficient of thermal expansion mismatch with a ceramic to metal seal?
Can it be possible to find these materials for commercial applications…I wouldn't like to go to NASA and get some tiles from the space shuttles! : )
In this project my concern is mainly the design of the collectors and material considerations, however if someone has experience with different methods of gas filling, please get in touch with me!
Thank you to everyone for reading this, and please share your opinions and suggestions with me!
Best wishes,
Laszlo
thermal coefficients
