Thermal Endurance Of Solar Fluids.pdf

- Investigations into the thermal long-term durability of solar fluids
- Solar fluids must meet various requirements for reliable, trouble-free operation
- Modern thermal solar systems with heating support often experience stagnation during summer months, leading to high temperatures (up to 200°C in flat collectors, 300°C in vacuum tube collectors)
- The "Craft Joule" project studied stagnating systems, including Tyforop as a solar media manufacturer
- Experiments on selected flat collector and vacuum tube collector systems revealed a general schema for the stagnation process
- Solar fluids must have efficient heat transfer, frost protection, good corrosion protection, compatibility with seal materials, thermal stability, non-flammability, low toxicity, environmental compatibility, and a good price-performance ratio
- Water is the optimal heat transfer medium but requires an antifreeze component for use in cold climates
- Propylene glycol (PG) has been used exclusively in solar media for about ten years due to its toxicological safety compared to ethylene glycol
- Inhibitors are necessary to prevent corrosion of metal materials in solar systems
- A standard heat transfer concentrate consists of solid components dissolved in PG with water
- Reserve alkalinity (RA) is crucial for the lifespan of solar fluids, as it neutralizes acidic reaction products that could otherwise cause corrosion
- When the medium's boiling point is reached, water and PG evaporate, but inhibitors crystallize and decompose, leading to reduced corrosion protection and potential blockages
- Tyforop introduced Tyfocort LS, a solar fluid designed for high thermal loads, with an inhibitor system consisting almost entirely of liquid, evaporable components
- Field tests were conducted on problematic flat collector combination systems and reduced vacuum tube collector systems using Tyfocort LS
- The results from the "Tuttner" and "Scheucher" systems, operated exclusively with LS from July 1999 to October 2000, were discussed.