Effect of axial conduction in integral rough friction stir channels: experimental thermo-hydraulic characteristics analyses

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Integral mini-channels fabricated in the metal substrate by friction stir channeling process are different from conventional mini-channels due to irregular shape, and large surface roughness. The effect of axial wall conduction on heat transfer in such mini-channels is significant, which could limit their utilisation as cooling channels in heat transfer based applications. Hence, in this study, we present an experimental analysis of the thermo-hydraulic performance of a friction stir channel to identify the axial wall conduction effect using de-ionized water as working fluid. The thermo-hydraulic performance parameters are analysed in the range of Reynolds number of 500 to 2100. The local wall temperature distribution along the length of the mini-channel is found to be non-uniform due to the significant axial wall conduction effect. The distinct pattern of numerical heat flux distribution is used as evidence to confirm the presence of axial wall conduction effect which is implied by the local wall temperature distribution. The higher average heat transfer and flow characteristics compared to the theoretical predictions for conventional mini-channels are observed as a result of simultaneously developing flow and the presence of surface roughness.

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A c :

Average mini-channel cross-section area (m2)

A s :

Heated side mini-channel surface area (m2)

A w :

Average wall cross-section area (m2)

c p :

Specific heat capacity (J/kg.K)

D h :

Hydraulic diameter (m)

f :

Darcy friction factor

H ch :

Average mini-channel height (m)

h g :

Heat transfer coefficient at glass wool surface (W/m2.K)

I :

Current supply (A)

i, j :

Index notations

K :

Thermal conductivity (W/m.K)

k :

Turbulent kinetic energy (J/kg)

K f :

Thermal conductivity of fluid (W/m.K)

K w :

Thermal conductivity of wall material (W/m.K)

L c :

Mini-channel length (m)

L h :

Hydrodynamically developing length (m)

L t :

Thermally developing length (m)

\( \dot{m} \) :

Mass flow rate (kg/s)

Nu :

Nusselt number

Nu avg :

Average Nusslet number

Nu x :

Local Nusselt number

P :

Electric DC power supply (W)

\( \overline{P} \) :

Time averaged pressure (Pa)

ΔP :

Pressure drop (Pa)

P c :

Average mini-channel perimeter (m)

Pe :

Peclet number

Pr :

Prandtl number

Pr t :

Turbulent prandtl number

Po :

Poiseuille number

q :

Heat transfer rate (W)

q conv :

Convective heat transfer rate (W)

q loss :

Heat loss (W)

Re :

Reynolds number

T :

Temperature (°C)

\( \overline{T} \) :

Time averaged temperature (°C)

T amb :

Ambient temperature (°C)

T f :

Bulk fluid temperature (°C)

T g :

Glass wool surface temperature (°C)

T in :

Inlet fluid temperature (°C)

T out :

Outlet fluid temperature (°C)

T w :

Wall temperature (°C)

T wx :

Local wall temperature along the mini-channel length (°C)

μ :

Dynamic viscosity (Pa.s)

\( \overline{u} \) :

Time averaged velocity component (m/s)

\( \overset{\hbox{'}}{u} \) :

Fluctuation in velocity component (m/s)

μ t :

Turbulent/ eddy viscosity (Pa.s)

ν t :

Kinematic eddy viscosity (m2/s)

V :

Voltage supply (V)

v :

Bulk flow velocity (m/s)

W ch :

Average mini-channel width (m)

x :

Axial distance from the mini-channel entrance (m)

x + :

Non-dimensional axial distance (x/ReDh)

X + :

Non-dimensional axial distance (x/ReDhPr)

ε :

Rate of dissipation of turbulent kinetic energy (m2/s3)

ν :

Kinematic viscosity of fluid (m2/s)

ρ :

Fluid density (kg/m3)

α :

Aspect ratio of mini-channel

ω :

Specific rate of dissipation of turbulent kinetic energy (1/s)


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The authors would like to thank Government Engineering College, Patan-384265, Gujarat, India for the financial support under TEQIP-II Initiative (MHRD, Govt. of India). Authors acknowledge Prof. Amit Agrawal, Department of Mechanical Engineering, Indian Institute of Technology Bombay, Mumbai- 400076, India, for providing support for this study. One of the authors would like to acknowledge the Board of Research in Nuclear Sciences (BRNS), (project number 57/14/05/2019-BRNS/).

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Correspondence to Amit Arora.

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Pandya, S., Gurav, S., Hedau, G. et al. Effect of axial conduction in integral rough friction stir channels: experimental thermo-hydraulic characteristics analyses. Heat Mass Transfer (2020) doi:10.1007/s00231-019-02788-7

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  • Friction stir channeling
  • Mini-channel
  • Axial wall conduction
  • Surface roughness
  • Nusselt number
  • Friction factor