Abstract
Highly porous two-dimensional (2D) cellular metals have multifunctional attributes, with tailorable structures to achieve multifunctional performance. The focus of this study is to explore the optimal cellular topology of 2D cellular metals for heat dissipation, and to investigate the eligibility of different heat enhancement techniques for more efficient heat dissipation. An analytical approach for the optimal design of metallic 2D cellular materials, cooled by single-phase laminar forced convection in various flow configurations, is proposed and validated by comparison with full numerical simulations. The optimal design is characterized by two subsidiary dimensionless parameters: one reflecting the trade-off between convection and fluid friction, and the other reflecting the optimal balance between conduction and convection. A heat transfer enhancement technique––boundary layer redevelopment––is subsequently introduced and its feasibility examined experimentally. Future research directions in specific areas are discussed.
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Abbreviations
- A :
-
area
- c :
-
coefficient
- c p :
-
specific heat at constant pressure
- C:
-
perimeter
- D h :
-
hydraulic diameter
- e :
-
roughness
- E :
-
Young’s modulus
- \( \tilde{E} \) :
-
Young’s modulus of a cellular solid
- f :
-
friction factor
- \( f_{D_{h}} \) :
-
friction factor based on the size of a single duct
- f H :
-
friction factor based on the height of the 2D cellular core
- F :
-
function
- g :
-
acceleration due to Earth’s gravity
- Gr :
-
Grashof number
- h :
-
heat transfer coefficient
- \( \bar{h} \) :
-
overall heat transfer coefficient
- h(x):
-
local heat transfer coefficient
- H :
-
overall height of a 2D cellular solid
- Inf:
-
infinity
- k :
-
thermal conductivity
- k eff :
-
effective thermal conductivity of a 2D cellular solid
- k e,ax :
-
effective thermal conductivity of a 2D cellular solid in axial direction
- k e,r :
-
effective thermal conductivity of a 2D cellular solid in lateral direction
- K :
-
pressure loss coefficient
- l bottom :
-
length of the bottom parallel side in trapezoidal cells
- l top :
-
length of the top parallel side in trapezoidal cells
- L :
-
overall length of a 2D cellular solid
- L ch :
-
length of the inlet channel defined in the computation domain in Fig. 3.1(b)
- L hy :
-
hydrodynamic developing length
- M :
-
mass flow rate
- M :
-
dimensionless mass flow rate
- n :
-
normal direction
- N H :
-
the cell number along the height of a 2D cellular solid
- N L :
-
block number
- N W :
-
the cell number along the width of a 2D cellular solid
- Nu :
-
Nusselt number
- Nu H :
-
Nusselt number based on the height of the 2D cellular core
- p :
-
pressure
- p d :
-
dynamic pressure measured by the Pitot tube
- \( \Updelta p \) :
-
pressure loss
- \( {\mathbf{\Updelta p}} \) :
-
dimensionless pressure loss
- \( \Updelta p_{\text{l}} \) :
-
local pressure loss
- \( \Updelta p_{\text{f}} \) :
-
frictional pressure loss
- P :
-
pumping power
- P :
-
dimensionless pumping power
- Pr :
-
Prandtl number
- \( q^{\prime\prime} \) :
-
heat flux
- Q :
-
total heat transfer
- Q :
-
dimensionless heat transfer
- R :
-
thermal resistance
- Ra :
-
Rayleigh number
- Re :
-
Reynolds number
- \( Re_{{D_{\text{h}} }} \) :
-
Reynolds number based on the size of a single duct
- \( Re_{H} \) :
-
Reynolds number based on the height of the 2D cellular core
- t :
-
cell-wall thickness
- \( t_{\text{face}} \) :
-
face-sheet thickness
- T :
-
temperature
- u, v, w:
-
x, y, z components of a velocity vector in Cartesian coordinate
- U :
-
velocity vector
- U c :
-
centre line velocity in the inlet channel upstream of the specimen
- U m :
-
mean velocity in the inlet channel upstream of the specimen
- \( U^{\prime}_{\text{m}} \) :
-
mean velocity averaged over the specimen’s porosity
- W :
-
overall width of a 2D cellular solid
- x, y, z :
-
Cartesian coordinate (shown in Fig. 1)
- x + :
-
dimensionless axial distance in hydrodynamic developing region
- x*:
-
dimensionless axial distance in thermal developing region
- α:
-
thermal diffusivity
- β:
-
coefficient of thermal expansion
- ε :
-
porosity
- ϕ :
-
surface area density
- μ :
-
dynamic viscosity
- ν :
-
kinematic viscosity
- θ :
-
base angle in triangular, trapezoidal, and hexagonal cells
- ρ :
-
relative density
- \( \tilde{\rho } \) :
-
density of a cellular solid
- σ:
-
strength
- \( \tilde{\sigma } \) :
-
strength of a cellular solid
- \( \tau_{\text{w}} \) :
-
wall shear stress
- Ψ:
-
shape factor
- M :
-
flow configuration of fixed mass flow rate
- Δp :
-
flow configuration of fixed pressure drop
- P :
-
flow configuration of fixed pumping power
- Crt:
-
critical
- Eff:
-
effective
- F:
-
fluid
- In:
-
inlet
- Max:
-
maximum
- Min:
-
minimum
- N:
-
normal direction
- Opt:
-
optimal
- Out:
-
outlet
- Ref:
-
reference
- S:
-
solid
- W:
-
wall
- SC:
-
sudden contraction
- SE:
-
sudden expansion
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Acknowledgments
This work is supported by the Overseas Research Studentship (ORS) and Overseas Trust Scholarship of Cambridge University, the National Natural Science Foundation of China (10572111, 10632060), the National Outstanding Youth Foundation, the National 111 Project of China (B06024), and the National Basic Research Program of China (2006CB601202).
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Xu, F., Wen, T. & Lu, T.J. Two-dimensional cellular metals as multifunctional structures: topology optimization. Heat Mass Transfer 45, 485–501 (2009). https://doi.org/10.1007/s00231-008-0450-0
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DOI: https://doi.org/10.1007/s00231-008-0450-0