Experimental investigation of five parallel plane jets with variation of Reynolds number and outlet conditions

Tomas Daubner,Mircea Dinulescu,Jens Kizhofer,P Dančová

doi:10.1051/epjconf/201818002018

Abstract

This article describes an experimental investigation in the near field of five parallel plane jets. The study applies 2D Particle Image Velocimetry (PIV) for ventilated and unventilated jets, where ventilated means exiting into a duct with expansion ratio 3.5 and unventilated means exiting to the free atmosphere. Results are presented for Reynolds numbers 1408, 5857 and 10510. The Reynolds number is calculated for the middle channel and is based on the height of the nozzle (channel) equivalent diameter 2h. All characteristic regions of the methodology to describe multiple interacting jets are observed by the PIV measurements - converging, merging and combined. Each of the five parallel channels has an aspect ratio of 25 defined as nozzle width (w) to height (h). The channels have a length of 185 times the channel height guaranteeing a fully developed velocity profile at the exit from the channel. Spacing between the single plane jets is 3 times the channel height. The near field of multiple mixing jets is depended on outlet nozzle geometry. Blunt geometry of the nozzle was chosen (sudden contraction).

Highlights

Main focus of the Apex Research Laboratory is the improvement of plate type heat exchangers, the reduction of the pressure drop through the ductwork and the mixing effectiveness in various industrial processes, for example mixing of ammonia in DENOx applications
Further paper continues in the discussion about multiple jet and its main focus is on the difference in the outlet conditions for multiple jets and its effect on mixing performance
We assume that outlet conditions will have influence on mixing effectiveness express as magnitude – Reynolds stress or as turbulence intensity. This implies that for this paper we have identified following parameters for jet formation: boundary conditions influencing the jet formation are Reynolds number based on channel height, nozzle aspect ratio, velocity profiles at exit including mean velocity profile as well as turbulence characteristics and nozzle geometry and spacing between the jets

Summary

Introduction

Main focus of the Apex Research Laboratory is the improvement of plate type heat exchangers, the reduction of the pressure drop through the ductwork and the mixing effectiveness in various industrial processes, for example mixing of ammonia in DENOx applications. This implies that for this paper we have identified following parameters for jet formation: boundary conditions influencing the jet formation are Reynolds number based on channel height (nozzle), nozzle aspect ratio, velocity profiles at exit including mean velocity profile as well as turbulence characteristics and nozzle geometry and spacing between the jets.

Results

Conclusion