PIV and LDA help the Apex Group improve the performance of heavy duty heat exchangers

 The Apex Group is a manufacturer of heavy duty heat exchangers with a strong R&D department, who is optimizing their products in terms of efficiency and reduced power consumption by reducing the pressure drop in the system.

Heat exchanger design has always been a trade-off between having a turbulent flow for a proper heat exchange on one hand, and a low pressure drop for reducing the power consumption on the other.

Time resolved PIV studies help the researchers understand the transitional process from laminar to turbulent flow in rectangular channels. This work has a pioneering character as most available literature covers circular pipes.

apex flow ill
Vorticity in a rectangular heat exchanger duct at different Reynolds numbers – Click the image to see the video.

Simulation backed up by experiments

For optimizing the flow within the channels of the heat exchangers, the researchers analyze the transition to turbulence in the heat exchangers and focus on optimizing the drag efficiency of all components in the channels and ducts. The APEX Group uses computer simulations as well as up- and down-scaled models of heat exchanger channels and inlet geometries, in which the influence of different turbulence generating mechanisms can be studied with various laser-based measurement techniques such as LDA or PIV.

The experimental set-up

The time resolved PIV experiment uses a 30 mJ Laser to illuminate the measurement domain in the air duct behind different inlet geometries. The flow field is captured by Dantec Dynamic’s 4MP high-speed camera SpeedSense 340 with up to 810 frames per second.

By reducing the optical resolution, the temporal resolution can be increased to 2,000 fps to cover a Reynolds number range of up to 10,000. The observed plane typically has a length of 5 times the channel height and starts right after the inlet which could be a blunt, a bellmouth or an undulated geometry.

More information

Read more on Dantec Dynamics’ Particle Image Velocimetry solutions
Read more on the validation on CFD in industrial processes with Dantec’s LDA solution
Read more on the Apex Group