Analysis on the influences of atomization characteristics on heat transfer characteristics of spray cooling. (November 2019) - Bao, Jun
Highlights: An open-loop spray cooling system combining with the PIV system was designed and established. The nozzle and medium factors affecting the heat transfer coefficient of heat source were discussed. As the diameter of the nozzle increases, the heat transfer effect can be improved. The better the uniformity of the droplets velocity distribution, the better the heat transfer of the surface. When the concentration of nano-alumina is 0.08％, the heat transfer coefficient reaches the optimal value. Abstract: The development of big data leads to the increasing heat dissipation of data center chips. As an efficient pattern to remove high heat flux, spray cooling has huge potential for data center cooling. Spray cooling system was established combined with PIV (Particle Image Velocimetry) system. The PIV was used to measure the flow pattern distribution of different nozzle sprays, while the surface heat flux and heat transfer coefficient were obtained by the thermocouples. The results show that as the spray diameter decreases, the outlet pressure and outlet velocity of the droplet increase, and the spray cone angle increases, causing only a small amount of droplets actually participate in the heat exchange, resulting in a higher velocity and a smaller heat transfer coefficient. It is also inferred that better uniformity of droplets velocity is beneficial for the heat transfer performance. Moreover, to further enhance the heat transfer performance, nano-alumina solution with five different fractions was applied to the experimental system. It is found that the heat transfer coefficient of the surface reaches an optimum value with a maximum velocity obtained by the PIV when the mass fraction of the solution is 0.08%.