Effect of nano-particles for pool boiling heat transfer of refrigerant 141B on horizontal tubes

Fluids with nano-sized particles have been proved that may effectively enhance the single-phase convective heat transfer performance. For pool boiling heat transfer, the published test results seems conflicted to each other. Some measured heat transfer coefficient decreased with increasing particle concentration but some showed no apparent difference.This study provides an experimental investigation on pool boiling heat transfer performance of refrigerants R-141b with and without nano-sized Au particles on horizontal plain tubes. The change of surface roughness and fluid particles condition were also observed for further understanding of the mechanisms that affect the pool boiling heat transfer performance. The test results show that the boiling heat transfer coefficients increase with increasing nano-particles concentration. At particles concentration of 1.0 %, the heat transfer coefficients are more than twice higher than those without nano-particles. The SPM investigation shows that the test tube surface roughness decreased from 0.317 μm before boiling test to 0.162 μm after test. Further investigation by TEM and Dynamic Light Scattering particle analyzer shows that the nano-particles aggregated from the average size of 3 nm before test to 110 nm after test. This results show that the nanosized Au particles are able to significantly increase pool boiling heat transfer of refrigerant R-141b on plain tube surface. The tube surface roughness and particle size changed after boiling test. Both of these effects degrade the boiling heat transfer coefficients.