Increasing Boiling Heat Transfer using Low Conductivity Materials.
We report the counterintuitive mechanism of increasing boiling heat transfer by incorporating low-conductivity materials at the interface between the surface and fluid. By embedding an array of non-conductive lines into a high-conductivity substrate, in-plane variations in the local surface temperature are created. During boiling the surface temperature varies spatially across the substrate, alternating between high and low values, and promotes the organization of distinct liquid and vapor flows. By systematically tuning the peak-to-peak wavelength of this spatial temperature variation, a resonance-like effect is seen at a value equal to the capillary length of the fluid. Replacing ~18% of the surface with a non-conductive epoxy results in a greater than 5x increase in heat transfer rate at a given superheat temperature. This drastic and counterintuitive increase is shown to be due to optimized bubble dynamics, where ordered pathways allow for efficient removal of vapor and the return of replenishing liquid. The use of engineered thermal gradients represents a potentially disruptive approach to create high-efficiency and high-heat-flux boiling surfaces which are naturally insensitive to fouling and degradation as compared to other approaches.
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Md Mahamudur
MM
Rahman
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Jordan
J
Pollack
Department of Mechanical Engineering and Mechanics, Drexel University, Philadelphia, PA, USA.
Matthew
M
McCarthy