Photothermal conversion of biodegradable fluids and carbon black nanofluids

Area of Science:

• Solar Energy Engineering
• Materials Science
• Fluid Dynamics

Background:

• Direct absorption solar collectors (DASCs) utilize fluids to absorb solar radiation.
• Evaluating alternative heat transfer fluids is crucial for DASC efficiency.
• Nanofluids and biodegradable colloids are potential candidates for DASC applications.

Purpose of the Study:

• To compare the thermal performance of nanofluids (water with carbon black nanoparticles) and biodegradable coffee colloids as heat transfer fluids in DASCs.
• To analyze the solar absorption characteristics of these fluids.
• To develop and validate a theoretical model for DASC performance.

Main Methods:

• Indoor experiments using artificial light to measure temperature increase in static fluid samples.
• Experiments using a solar collector system to evaluate fluid performance under direct solar irradiation.
• Theoretical analysis of heat transfer and absorption processes.
• Model validation against experimental data and literature.

Main Results:

• Static indoor experiments showed similar temperature increases (46-50 °C) for both nanofluids and coffee colloids.
• In the solar collector system, nanofluids exhibited higher temperature rises due to intense absorption by carbon black nanoparticles.
• Theoretical analysis demonstrated good agreement with experimental findings.
• The developed model for flowing fluid in a DASC was validated.

Conclusions:

• Nanofluids, specifically water with carbon black nanoparticles, offer superior heat transfer performance in direct absorption solar collectors compared to coffee colloids.
• The enhanced absorption of solar radiation by nanoparticles is key to improved DASC efficiency.
• The validated theoretical model can predict DASC performance with flowing fluids.