Heat transfer characteristics of controlled droplet trains impacting solid surfaces

The unpredictable spray characterization caused by different manufacturing standards still limits the implementation of spray cooling. To obtain a predictable spray, a droplet generator was in-house designed and fabricated, which can generate predictable monodisperse droplets or multiple droplet trains at a certain droplet generation frequency (f_G). Based on the measurement of the droplet flux (N), the controlled droplet trains are classified into the controlled sparse spray and dense spray. In the experiments, deionized water was used as the liquid coolant, and heat transfer characteristics were analyzed in the controlled sparse spray and dense spray. The experimental results show at the same volumetric flow rate the heat transfer curve of dense spray is always above the heat transfer curve of sparse spray. In the cooling area of controlled dense spray, the average Nusselt number Nu‾_L was correlated as logNu‾_L∝−(f_G/N)^1/2. This study would benefit the application of controlled spray cooling technology in high-heat-flux thermal management.