Pool boiling visualization of Novec-649 and FC-72 on copper microchannels

Abstract

Saturated pool boiling from copper microchannel surfaces was examined using Novec-649 and FC-72 as working fluids. Parallel microchannels fabricated by machining were about 0.2 mm wide, and 0.2 to 0.4 mm deep and spaced every 0.4 mm. The experiments were carried out at atmospheric pressure. The images of the growing and departing bubbles for the entire surface of the specimen were taken with a Photonfocus PHOT MV-D1024-160-CL camera and an EX-FH20 (Casio) camera. At low superheats, the bubbles departing from enhanced surfaces were spherical in shape and did not coalesce. At higher superheats, the bubbles interacted with each other intensively, forming flattened spherical, funnel-shaped bubbles at the bottom. The visualization study aimed at identifying nucleation sites of the departing bubbles and determining their diameters and frequency at various superheats.

Hydrophilic and Hydrophobic Nanostructured Copper Surfaces for Efficient Pool Boiling Heat Transfer with Water, Water/Butanol Mixtures and Novec 649

“…So far, only a few studies were performed using environmentally friendly dielectric fluid 3M™ Novec™ 649, which has an ultra-low global warming potential (GWP) in comparison with the well-known dielectric 3M™ Fluorinert™ FC-72, which has similar thermophysical properties [63,64]. Kaniowski et al [65][66][67] published several papers on boiling heat transfer enhancement using Novec™ 649 as the working fluid. They obtained HTCs up to approx.…”