Advanced heat exchangers for thermal energy storage (TES) systems utilize a range of materials designed to optimize energy storage density, thermal conductivity, mechanical strength, and durability under various operating conditions.
Materials Used and Approaches in Advanced TES Heat Exchangers
Phase Change Materials (PCMs):
- PCMs serve as the core material in many TES heat exchangers to exploit latent heat for higher energy storage density compared to sensible heat systems.
- Common PCMs in these applications include solid-to-liquid phase change substances, which have large latent heat capacity, enhancing the compactness and efficiency of TES devices.
- However, most PCMs inherently suffer from low thermal conductivity, which slows the charging and discharging processes (melting and freezing of the PCM).
Thermal Conductivity Enhancements:
- To overcome the low conductivity, additives are incorporated into PCMs. These include:
- Metallic particles
- Boron nitride
- Carbon fibers
- Carbon nanotubes
- Expanded graphite
- These additives improve heat transfer but present challenges such as uniform mixing, reduced latent heat capacity, filler fragility (e.g., carbon nanotubes), and increased cost (notably for boron nitride).
Structural and Heat Exchanger Materials:
- Heat exchanger structures, especially on the hot side exposed to high temperatures (up to 650°C), are typically made from high-performance metals like stainless steel and Inconel alloys. These materials provide:
- High heat flux capability
- Structural strength to withstand thermal expansion and mechanical stress
- Long-term durability in harsh environments.
- Advanced designs also aim to reduce thermal expansion and pressure drop while improving thermal performance and lowering weight, benefiting applications such as thermoelectric generators and industrial processes.
Emerging and Organic PCMs:
- Research is ongoing into biobased and fatty acid PCMs for improved environmental compatibility and thermal properties, especially in building applications focusing on thermal comfort.
Summary Table:
| Material Type | Examples/Details | Purpose/Benefits | Challenges |
|---|---|---|---|
| Phase Change Materials | Solid-liquid PCMs (organic/inorganic) | High latent heat storage density | Low thermal conductivity |
| Additives to PCMs | Metallic particles, boron nitride, carbon fibers/tubes, expanded graphite | Enhance heat transfer | Mixing uniformity, cost, latent heat reduction, fragility |
| Heat Exchanger Metals | Stainless steel, Inconel alloys | High-temp durability, high heat flux | Weight, cost |
| Novel/Organic PCMs | Fatty acids, biobased organics | Environmental friendliness, tailored melting points | Stability and performance variability |
In conclusion, advanced TES heat exchangers use composite PCM materials enhanced with nanoparticles or fibrous additives to improve heat conduction, combined with high-temperature metals like stainless steel or Inconel alloys for structural components. This material combination enables compact, durable, and efficient TES systems suitable for modern energy-saving and decarbonization goals.
Original article by NenPower, If reposted, please credit the source: https://nenpower.com/blog/what-materials-are-being-used-in-advanced-heat-exchangers-for-thermal-energy-storage/
