Experimental study of the sintered multi-walled carbon nanotube/copper microstructures for boiling heat transfer

• Influences of MWCNTs contents and coating method were studied.
• The heat transfer performance improved as the content increased up to 20 vol.%.
• A worst boiling performance was observed from the 30 vol.% MWCNT/Cu coating.
• A better enhancement was performed by double-layer coating.

Due to the mesh surface and intrinsic thermal conductivity of multiwalled carbon nanotubes (MWCNTs), a variety of MWCNT growth techniques are applied to boiling heat transfer enhancement. In this study Cu powders and MWCNTs were ball milled to produce composite powders. These composite powders were applied on Cu plate substrates by electrostatic spraying and were consolidated by sintering in an electric furnace. The resulting surface coatings that were fabricated from the MWCNT/Cu composite powders were considered and studied for the enhancement of the boiling heat transfer under a pool of saturated R134a. The thermophysical properties of the surface coatings were investigated. It was found that the pore density was a major factor that influenced the boiling heat transfer performance. The 20 vol.% MWCNT/Cu coating exhibited the best boiling performance. The single-layer coating was found to be less efficient in its boiling performance as compared to the double-layer coating due to the lack of the mechanical support from the Cu powder based layer.