Cooling in poor air quality environments -- Impact of fan operation on particle deposition

TL;DR

This study examines how fan operation affects particle deposition in cooling systems within polluted environments, using simulations to identify factors influencing particle transport and proposing mitigation strategies.

Contribution

It provides detailed insights into particle transport mechanisms under various fan conditions and introduces a simple flow control method to reduce deposition on electronic equipment.

Findings

Deposition velocities vary significantly with fan operating conditions.

Flow impingement and vortices influence particle deposition patterns.

A mitigation strategy effectively reduces particle deposition.

Abstract

Environmental pollutants are a source for reliability issues across data center and telecommunications equipment. A primary driver of this is the transport and deposition of particle matter (PM$_{2.5}$, PM$_{10}$) on printed circuit boards, electronic components and heat exchange surfaces. This process is enhanced by turbulent air flows generated from cooling fans. Particle pollutants can persist after contemporary filtering, highlighting the importance of elucidating particle transport mechanisms and utilising this information to design robust equipment. This study investigates particle transport behaviour arising from axial fans operating under varied aerodynamic conditions. Transient, multi-phase numerical simulations were performed to model the flow of millions of microscale particles in air and determine their fate. Across a comprehensive range of fan operation conditions, from aerodynamic stall to free delivery, non-dimensional deposition velocities spanned an order of magnitude. Deposition profiles vary from monotonic to non-monotonic behaviour, influenced by local flow impingement, blade tip vortices, and shear velocity. A simple flow control solution that mitigates the factors influencing deposition has been demonstrated for equipment already deployed. The findings and numerical methods can be applied for the optimization of fan-cooled equipment intended for indoor and outdoor environments where air quality is poor, or pollution levels are high.