Pool Boiling: Effect of pool depth, polymer nano-textured heater surface and self-rewetting fluids*

Pool boiling of ethanol and self-rewetting fluids were studied on bare copper surface and surface with polymer nanofibers. Experiments with different pool depths of ethanol revealed insignificant differences in heat removal rate indicating that the heat transfer in the liquid microlayer is the important factor. Also, several alcohol solutions at 0.1% (v/v) concentration including self-rewetting fluids were investigated as working fluids. It was found that only the high carbon-alcohol improved boiling performance considerably at 0.1% (v/v) concentration. Further, boiling performances on polymer nano-textured copper surface were compared to the cases with bare copper heater. Two different polymer [polyacrylonitrile (PAN) and polystyrene (PS)] nanofibers were deposited on the copper surface. Measurements of boiling curve revealed a detrimental effect of PAN nanofibers in the case of ethanol and self-rewetting n-heptanol solutions. However, PS nanofibers revealed significant improvement in boiling heat transfer with n-heptanol and water. The reason for this contrast is attributed to the increased wettability of the corresponding working fluids on PAN and the decreased one on PS fibers compared to the bare surface.