Experimental and numerical analysis of the influence of the nozzle-to-plate distance in a jet impingement process

Abstract

Jet impingement is a complex heat transfer technique which involves several process variables, such as nozzle-toplate distance, jet diameter, Reynolds number, jet temperature, among others. To understand the effect of each variable, it is important to study them separately. In industrial applications that use forced convection by air jet impingement, such as reflow soldering, the correct analysis of the flow structure and accurate definition of the variables values that affect the heat transfer over the target surface leads to an increase of the process performance decreasing the manufacturing costs. To reduce costs and time, the introduction of numerical methods has been fundamental. Using a Computational Fluid Dynamics software, the number of experiments is highly reduced, being possible to focus on the phenomena that are highly relevant for the purpose of the study. In this work, the nozzle-to-plate distance (H/D) variable is analyzed. This is considered one of the most important parameters since it influences the entire structure of the jet flow as well as the heat transfer coefficient over the target surface. The results present a comparison between different H/D under isothermal and non-isothermal conditions for a Reynolds number of 2,000.

Experimental and Numerical Study of Multiple Jets Impinging a Step Surface

“…From the mixing between the jet flow and the ambient air, a shear layer was generated leading to high lateral velocity gradients. As mentioned by [53], jet impingements characterized by 0.5 < H/D < 5 are within the length of the potential core. This means that no decaying or fully developed regions were expected to be identified.…”