A multi-scale conjugate heat transfer modelling approach for corrugated heat exchangers

Evaldas Greiciunas,Duncan Borman,Jonathan Summers,Steve J Smith

doi:10.1016/j.ijheatmasstransfer.2019.05.086

Evaldas Greiciunas, Duncan Borman + Show 2 more

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https://doi.org/10.1016/j.ijheatmasstransfer.2019.05.086

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Abstract

The paper compares two serrated plate-fin Heat Exchanger (HE) corrugation modelling methods using Computational Fluid Dynamics (CFD). The first method follows closely recent literature studies and models a finite length single channel of a corrugation layer inside the HE core. The second method utilises the conjugate heat transfer methodology and models a section of the HE core with both cold and hot fluid streams separated by a solid conducting wall (HE corrugation). The results of latter model are then extrapolated for the full dimensions of a HE core layer to obtain flow and heat transfer characteristics. The conjugate heat transfer analysis methodology presented is novel and eliminates the need for analytical/empirical modelling currently widely used within industry. Furthermore, it provides more detailed information about the flow and heat transfer inside the HE core enabling potential for more efficient HE designs. Predictions at the corrugation level were carried out at 88⩽Recorrug⩽2957 with mesh independence studies completed for all the computational domains. The results obtained in the HE corrugation predictions were then implemented to the multi-scale HE unit model where the flow inside the HE core was modelled using two porous media simplifications whilst the heat transfer was simplified using the effectiveness source term. The HE unit predictions were validated against industrial experimental data with good agreement found between the numerical and experimental results. All the simulations were completed using the open-source CFD package OpenFOAM.

Highlights

Heat Exchangers (HE) are the devices used widely in aerospace, automotive and other industries in which heat is transferred between two or more fluid streams, provided there is a significant temperature gradient between them [1]
Results from the HE corrugation domains were used to generate the data for the pressure drop test validation, whilst the HE section model was employed to generate the data for the thermal performance test modelling
Single column HE section column domain predictions at Recorrug % 300. This is believed to coincide with the onset of the unsteady flow which was not resolved directly here due to the computational cost as identified earlier

Summary

Introduction

Heat Exchangers (HE) are the devices used widely in aerospace, automotive and other industries in which heat is transferred between two or more fluid streams, provided there is a significant temperature gradient between them [1]. Using a single column domain has been established in the literature, but has significant disadvantage because of the limitations in terms of only considering heat transfer via a constant temperature or heat flux boundary conditions through the walls of the domain These boundary conditions are not directly suitable in this case because the computations cannot account for the crossflow nature of the heat transfer between two fluid streams. These effects are of particular importance in many cross-flow HE applications where one of the streams does not remain at a constant temperature throughout the HE core. The predicted pressure drop from the single column computational domain were useful for verifying the HE section model described below

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Results

Conclusion