Experimental and Computational Fluid Dynamics Studies on Straight and U-Bend Double Tube Heat Exchangers with Active and Passive Enhancement Methods

Abstract

In this work, the authors wanted to demonstrate the possibility to increase the heat transfer efficiency by using simple wire coil inserts to create turbulent flow in the boundary layer as well as air blowing into the annulus of the pipe. Experimental investigations were carried out for four heat exchanger constructions, i.e., plain double tube, turbulized double tube, plain U-bend double tube, U-tube with turbulator, plain double tube and U-bend double tube working with two-phase flow conditions (air-water mixture). For these geometries, the values of pressure drop and heat flux were determined. The comparison of heat transfer efficiency was performed based on NTU-ε method. The computational fluid dynamics (CFD) technique was also employed to investigate the influence of coiled wire inserts and air bubbly injection at heat transfer, pressure drops and overall efficiency in double tube heat-exchangers. For this purpose, six configurations of heat exchangers were meshed and simulated at various flow conditions by using the CFD package Autodesk CFD 2016 (Students & Educators version).

Additional information

Funding

The work presented in the paper was partially funded by statuary activity of faculty of Mechanical Engineering of Gdansk University of Technology.

Notes on contributors

Rafał Andrzejczyk

Rafal Andrzejczyk works as a scientist in Gdansk University of Technology, Poland. He received his Ph.D. degree in Technical Sciences, the discipline of Machinery Construction and Exploitation in 2014. His research interests are: active and passive methods of heat transfer intensification of compact mini and micro heat exchangers, heat transfer enhancement in two-phase closed thermosiphons, heat transfer and pressure drops in two-phase flow boiling and condensation in minichannels, designing of conventional heat exchangers, designing of mini and microchannel heat exchangers, recovery systems for utilization of waste heat from technological and energy processes, performance enhancement techniques of heat pump and refrigeration units, simulation of buildings and HVAC systems, and energy analysis.

Tomasz Muszynski

Tomasz Muszynski works as a scientist in Gdansk University of Technology, poland. He has received his PhD degree in Technical Sciences, the discipline of Machinery Construction and Exploitation in 2013. His research interests are: microjet technology, blowing of inert gases, baffles and flow turbulators, a variation of the shape of the flow channel, use of centrifugal force, expansion of the heat transfer surface, use of nanopowders with hydrophobic and hydrophilic properties.

Przemysław Kozak

Przemysław Kozak is a Ph.D. student at Gdansk University of Technology (GUT), Department of Energy and Industrial Apparatus, Poland, under the supervision of Prof. Janusz T. Cieśliński. He received M.Sc degree in 2009 in mechanical engineering from the same university and currently works as an engineer at GUT. He is working on heat transfer issues, especially focused on the applicability of nanofluids.