A Painting Technique to Enhance Pool Boiling Heat Transfer in Saturated FC-72

Abstract

A benign method of generating a surface microstructure that provides pool boiling heat transfer enhancement is introduced. Pool boiling heat transfer results from an enhanced, horizontally oriented, rectangular surface immersed in saturated FC-72, indicate up to an 85 percent decrease in incipient superheat, a 70 to 80 percent reduction in nucleate boiling superheats, and a ∼ 109 percent increase in the critical heat flux (CHF = 30 W/cm2), beyond that of the nonpainted reference surface. For higher heat flux conditions (19 to 30 W/cm2), localized dryout results in increased wall superheats (8 to 48°C). The enhanced surface heat transfer coefficients are four times higher than those from the reference surface and similar to those from the Union Carbide High Flux surface. Photographs that identify differences in bubble size and departure characteristics between the painted and reference surfaces are presented.

Quantitative Evaluation of the Dependence of Pool Boiling Heat Transfer Enhancement on Sintered Particle Coating Characteristics

“…A number of studies have since explored various processing methods and geometric modifications for this structure, such as modulated porous copper coatings with periodic variations in layer thickness [2], a silver flake-based boiling enhancement paint [3], spray-coated alumina particulate layers [4], and porous graphite layers with randomly interconnected microscale pores [5,6], and observed significant enhancement of the heat transfer coefficient and critical heat flux (CHF).…”

Effect of particle size on surface-coating enhancement of pool boiling heat transfer

“…Compared to a smooth surface, the particle-coated surface decreased the incipience wall superheat by ~44% and increased CHF by ~36%. In a subsequent study, O'Connor and You [14] painted a mixture of silver flakes and epoxy over an aluminum surface to form a coating with 1 µm cavities; the incipience superheat was reduced by ~85% and CHF was increased by ~109%. Parker and El-Genk [15,16] studied nucleate boiling of HFE-7100 and FC-72, respectively, from porous graphite layers containing randomly interconnected microscale pores (60% porosity).…”

Confined Jet Impingement With Boiling on a Variety of Enhanced Surfaces

“…In a study of porosity on boiling enhancement from dendritic copper surfaces, rather than particle-based coatings, El-Genk and Ali [20] found that the surface with the largest porosity produced the lowest nucleate boiling wall superheat. Besides the metallic coatings considered above, paintable porous coatings that use an epoxy binder were investigated by You and coworkers [21][22][23][24][25][26][27]. O'Connor and You [22] created a paintable coating that consisted of 3-10 lm silver flakes, Omegabond 101 thermal epoxy, and isopropyl alcohol.…”