Experimental and numerical study of the additive layer manufactured inter-layer channel heat exchanger

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

doi:10.1016/j.applthermaleng.2020.116501

Evaldas Greiciunas, Duncan Borman + Show 2 more

Open Access

https://doi.org/10.1016/j.applthermaleng.2020.116501

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Abstract

In this paper the performance of a recently patented additive layer manufactured (ALM) concept inter-layer heat exchanger (HE) is evaluated experimentally and numerically. Two numerical HE models are developed using the conjugate heat transfer (CHT) methodology. The first is an idealised HE core model, consisting of a single period width HE corrugation section (termed superchannel). The second approach uses a fully detailed HE unit model which resolves the flow and heat transfer inside the complete HE unit. A close agreement was found between the HE unit simulations and the experimentally obtained results, such that the fully detailed HE model could be validated. It was also shown that, a full CHT approach is necessary to accurately evaluate complex inter-layer ALM HE core flow and heat transfer behaviour and can serve as an approach for optimising HE designs. The results also reinforce the occurrence of the inter-layer flow mixing inside the HE core of the same flow streams and allows the mass flow to redistribute inside the HE core which is impossible with the current HE generation geometries. The superchannel model results in a slight over-estimation in heat transfer (ΔT≈4 K on average) making the simplified model acceptable as a conservative estimate. Using validated simulations a parametric study was conducted by changing the solid properties of the full CHT HE model to aluminium to investigate the effects of a significantly more conductive material. This resulted in ≈3% higher heat transfer effectiveness (ϵ) of the HE unit. All the simulations were carried out using CFD package OpenFOAM.

Highlights

Heat Exchangers (HE) are the devices in which the heat is transferred between two or more fluid streams separated by a solid and are critical components in many industries, such as aerospace, automotive, power generation or chemical & process industry [1]
Additive Layer Manufacturing Computational Fluid Dynamics Direct Metal Laser Sintering Heat exchanger(s) Powder Bed Fusion Selective Laser Melting Diameter of the inlet to heat exchanger, m hydraulic diameter, m surface area density, Asurface∕Vflow, m2∕m3 velocity vector, m∕s Density, kg∕m3 thermal conductivity, W∕(mK) heat transfer effectiveness Pressure drop coefficient Pressure, Pa Pressure drop, Pa Heat balance (Qhot∕Qcold × 100) viscosity, Pa s Turbulent viscosity, Pa s Temperature, K specific heat capacity, J/(kgK) Reynolds number defined as Recorrug =∕μ Reynolds number defined as Reinlet =∕μ brazing or welding
Two HE models were developed using a conjugate heat transfer (CHT) methodology: firstly, a fully detailed HE unit model was developed in order to capture the complex flow and heat transfer in full detail

Summary

Introduction

Heat Exchangers (HE) are the devices in which the heat is transferred between two or more fluid streams separated by a solid and are critical components in many industries, such as aerospace, automotive, power generation or chemical & process industry [1]. Additive Layer Manufacturing Computational Fluid Dynamics Direct Metal Laser Sintering Heat exchanger(s) Powder Bed Fusion Selective Laser Melting Diameter of the inlet to heat exchanger, m hydraulic diameter, m surface area density, Asurface∕Vflow, m2∕m3 velocity vector, m∕s Density, kg∕m3 thermal conductivity, W∕(mK) heat transfer effectiveness Pressure drop coefficient Pressure, Pa Pressure drop, Pa Heat balance (Qhot∕Qcold × 100) viscosity, Pa s Turbulent viscosity, Pa s Temperature, K specific heat capacity, J/(kgK) Reynolds number defined as Recorrug = (ρU dh)∕μ Reynolds number defined as Reinlet = (ρU Dinlet)∕μ brazing or welding This can provide improved structural integrity and a reduced likelihood of current HE manufacturing flaws, shown in [3]. Inter-layer HE unit model a parametric study is undertaken to evaluate the HE performance with aluminium as the HE material to investigate whether any thermal gains are obtained

Experimental approach

Numerical solution methodology

Computational domains and grid independence

Validation of the numerical results with the experiments

Effect of higher conductivity material for the heat transfer efficiency

Conclusions