Electric Field and Surfactant Enhanced Boiling

Applications

This technology enhances boiling heat transfer, which can be used for steam generation, distillation, heat dissipation, or any other application where a controlled heat transfer rate is desired. Fields of use range from domestic cooking to power plants.

Problem Addressed

A heat transfer coefficient (HTC) is defined between a hot surface and boiling fluid. To increase boiling efficiency the HTC should be increased; however, as the superheat increases a critical heat flux (CHF) is reached, where coalescence of bubbles at the surface causes a vapor film to form that impedes the heat transfer. Typically, the CHF is maximized by increasing surface roughness and wettability; however, highly wetting behavior suppresses nucleation. Thus superheats are larger for a highly wetting surface, which is non-ideal from an HTC and energy efficiency standpoint. This technology increases the HTC and energy efficiency by adding surfactants to the fluid and applying an electric field to the system.

Technology

The system consists of a boiling surface, a fluid, a charged surfactant in the fluid, and a counter-electrode. The surfactant increase the HTC and decreases the wettability through solid-liquid adsorption, rendering the surface less wettable and promoting nucleation. In order to maximize capacitance (adsorption of the surfactant) at the boiling surface, the counter-electrode should have a much higher surface area than the boiling surface area. It was observed that the HTC increased with an applied electric field. For negatively charged surfactants a negative field and for positively charged surfactants a positive field increased the HTC. The tunability of the HTC was ±10%. This means that by adding surfactants and applying an appropriate electric field the efficiency of boiling is increased which can decrease the operation cost.  

Advantages

  • Increases HTC during boiling
  • Increases energy efficiency of boiling