NANOPARTICLE DEPOSITION AND CONVECTIVE TRANSPORT IN HEAT EXCHANGER SYSTEMS. A thesis by Joshua Coleman; research funded by the Purdue Water Institute.

This thesis investigates the transport, deposition, and distribution of nanoparticles in laminar fluid flow within microchannel heat exchanger systems, focusing specifically on transient conditions influenced by Brownian diffusion and thermophoresis.

Context and Objectives: As nanofluids (fluids containing nanoparticles) are increasingly utilized in thermal management applications, from microscale electronics cooling to larger-scale power plant systems, it becomes critical to understand how nanoparticles behave when flowing through channels. Specifically, nanoparticle deposition onto channel walls can significantly alter heat transfer rates, fluid dynamics, and device efficiency. This study aims to analytically predict distribution and deposition behaviors to optimize system design and operation.

Methodology:

The research comprises two main components:

1. Theoretical Analysis:

• Developed a modified analytical model based on Buongiorno’s two-component model.
• Incorporated Brownian diffusion, thermophoretic diffusion, and transient particle deposition.
• Derived mathematical expressions for nanoparticle distribution within laminar flow channels under transient conditions.

1. Experimental Investigation:

• Conducted controlled experiments to measure actual nanoparticle deposition while varying Brownian to Thermophoretic diffusion ratios.
• Used experimental results to validate and refine the theoretical predictions.

Techniques Used:

• Analytical modeling (partial differential equations, boundary conditions).
• Dimensional analysis and non-dimensional parameter evaluation.
• Experimental setups involving heat exchangers and nanoparticle suspensions.
• Data analysis and validation using numerical simulation and experimental comparison.

Key Findings:

• Particle deposition shown analytically to transiently impact particle distribution
• Identified conditions under which Nbt ratios significantly impact heat exchanger deposition.
• Demonstrated correlation between theoretical predictions and experimental data

Reproducibility and Practical Application:

The thesis includes detailed modeling equations, boundary conditions, and experimental setups clearly documented to allow replication and further research. Findings support future designs and optimizations in industries using microchannel heat exchanger technologies.