Water spray heat transfer through a piezoelectric atomizer with a single-hole micronozzle

Abstract

We report an experimental study on the flow and heat transfer for a single microhole of water spray impingement on an indium tin oxide (ITO) heating plate using a piezoelectric atomizer. A microhole of dj = 35 µm was used and tested with a volumetric flow rate of 0.22 cm3/min for three different spray heights of 10, 20 and 30 mm and five heater initial temperatures of 25 °C, 50 °C, 100 °C, 150 °C, and 200 °C. Through the optical measuring techniques of the microparticle image velocimetry (μPIV) as well as interferometric particle imaging (IPI) and micro laser-induced fluorescence (μLIF), the velocity field, such as spray centerline velocity, droplet impact velocity and impact crater diameter, including impinged liquid film thickness and heat transfer performance (CHF) can be measured and calculated. The effects of the spray height and initial heater temperature on the flow and thermal characteristics are presented and discussed herein. The experimental results show that both the spray centerline velocity and spray droplet impact velocity were significantly influenced by the initial surface temperature as well as by the spray height. As a result, the cooling performance would be, in turn, affected by the aforesaid two parameters.