Journal of Thermal Spray Technology

, Volume 28, Issue 1–2, pp 144–160 | Cite as

Pin Fin Array Heat Sinks by Cold Spray Additive Manufacturing: Economics of Powder Recycling

  • J. PerryEmail author
  • P. Richer
  • B. Jodoin
  • E. Matte
Peer Reviewed


As a result of the rise in processing power demands of today’s personal computers, water-cooled pin fin heat sinks are increasingly being employed for the cooling of graphical processing units. Currently, these high-performance devices are manufactured through high-cost, high-waste processes. In recent years, a new solution has emerged using the cold gas dynamic spray process, in which pin fins are manufactured onto a base plate by spraying metallic powder particles through a mask allowing for a high degree of adaptability to different graphics processing unit shapes and sizes. One drawback of this process is reduced deposition efficiency, resulting in a fair portion of the feedstock powder being wasted as substrate sensitivity to heat and mechanical residual stresses requires the use of reduced spray parameters. This work aims to demonstrate the feasibility of using powder recycling to mitigate this issue and compares coatings sprayed with reclaimed powder to their counterparts sprayed with as-received powder. The work demonstrates that cold gas dynamic spray is a highly flexible and economically competitive process for the production of pin fin heat sinks when using powder recycling. The heat transfer properties of the resulting fins are briefly addressed and demonstrated.


cold spray economics heat sink pin fin powder recycling 

List of symbols


Inlet temperature difference (°C)


Outlet temperature difference (°C)


Log-mean temperature difference (°C)


Fin efficiency


Surface efficiency


Fin base angle (°)


Dynamic viscosity (Pa s)


Density (kg/m3)


Nozzle throat area (m2)


Fin area (m2)


Total heat transfer area (m2)


Un-finned area (m2)


Transverse fin base width (m)


Side fin base width (m)


Cost of copper ($/kg)


Cost of electricity ($/kW-h)


Cost of labor ($/h)


Cost of nitrogen ($/kg)


Specific heat of nitrogen (kJ/kg K)


Linear spray distance (m)


Hydraulic diameter (m)


Mask deposition efficiency


Substrate deposition efficiency


Total electricity cost ($)


Total gas cost ($)


Fin height (m)


Convection coefficient (W/m2 K)


First-order modified Bessel function


Second-order modified Bessel function


Specific heat ratio


Conductivity of copper (W/m K)


Length of the finned area (m)


Total labor cost ($)


Fin parameter (m−1)


Mass flowrate of nitrogen (kg/s)

\(\dot{m}_{{\rm water}}\)

Mass flowrate of water (kg/s)


Number of fins widthwise


Pressure at the nozzle throat (Pa)


Perimeter of the flow area (m)


Stagnation pressure (Pa)


Total powder cost ($)


Total powder cost lost on the mask ($)


Total powder cost lost on the substrate ($)


Total powder cost un-deposited ($)


Powder feed rate (kg/s)


Heat rate through copper (W)


Total heat into nitrogen (J)


Heat rate into nitrogen (W)


Heat rate into water (W)


Ideal gas constant (J/mol-K)


Resistance of copper (K/W)


Equivalent resistance (K/W)


Resistance of fins (K/W)


Thermal contact resistance (K/W)


Resistance of un-finned area (K/W)


Reynolds number


Distance between fins (m)


Time of spray (s)


Temperature at nozzle throat (°C)


Inlet temperature of nitrogen (°C)


Outlet temperature of nitrogen (°C)


Temperature of the block (°C)


Stagnation temperature (°C)


Surface temperature (°C)


Water inlet temperature (°C)


Water outlet temperature (°C)


Thermal conductance (W/K)


Maximum flow velocity (m/s)


Traverse velocity (m/s)


Width of the finned area (m)



The authors would like to acknowledge the financial support of NSERC.


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Copyright information

© ASM International 2018

Authors and Affiliations

  1. 1.University of Ottawa Cold Spray Research LaboratoryOttawaCanada
  2. 2.Ironside Engineering Inc.OttawaCanada

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