Flow and heat transfer of hot impinging jets issuing from lobed nozzles

Abstract

This article studies the aerodynamic and thermal characteristics of impinging jets issued from lobed injections. They are compared to “traditional” jets issuing from tube. All nozzles have the same free area Ao, and the equivalent diameter for a tube is D = 14 mm. Experiments have been conducted for injection Reynolds numbers from 23,000 to 45,000, for orifice-to-plate distances from H/D = 1–5 and for an injection jet temperature: T∞ ≤ Tj ≤ 50 °C. Flow measurement has shown very specific tridimensional flows particularly for small injection-to-plate spacing (H/D = 1 or 2) and resulting heat transfer rates are very different from those of a jet issuing from a tube. For higher impinging distances, flows and heat transfer become more axisymmetric and more similar to those due to tubular injection.