Investigation of Multiple Miniature Axial Fan Cooling Solutions for Confined Thermal Management

This paper investigates the thermal and fluid dynamic characteristics due to multiple miniature axial fans with blade chord and span length scales less than 10 mm, impinging air onto finned surfaces. The proposed arrangement is intended for local package cooling in space-constrained electronic systems, where large single fan and high profile heat sink cooling solutions can be impractical. A coupled approach, utilising both experimental and numerical techniques, has been devised to examine in detail the interaction between cooling fans within an array. The findings demonstrate that fans positioned adjacently in an array can influence heat transfer performance both positively and negatively by up to 35% compared to an equivalent single fan - heat sink unit operating standalone. Numerical simulations, modelled using experimental inputs, have provided an insight into the flow fields produced by the interaction between adjacent fans and also the interaction with fixed fan motor support structures downstream. It was determined that the significance of motor support structures on thermofluid characteristics should be carefully considered during thermal design of fan cooled systems, particularly as fan length scales are reduced. A novel experimental approach utilising infrared thermography has been developed to locally assess the validity of the numerical models. Thermofluid characteristics which compliment the numerical observations have been confirmed using this assessment and considerations for modelling fan cooled devices have been outlined. Overall, the study provides an insight into fan cooled heat sinks utilising multiple miniature axial fans and recommendations for improving current numerical modelling approaches.