Spray Cooling Enhancement by Addition of a Surfactant

Abstract

An experimental study was done on the effect of dissolving a surfactant in water sprays used to cool a hot surface. A copper surface was heated to an initial temperature of 240°C and then rapidly cooled using a spray of either pure water or an aqueous solution containing 100 ppm by weight of sodium dodecyl sulfate. The variation of surface temperature was measured during cooling, and spray impact was photographed. Addition of the surfactant was found to enhance nucleate boiling heat flux by up to 300 percent. The surface temperature required to initiate vapor bubble nucleation was reduced from 118°C to 103°C. These effects were attributed to the surfactant promoting bubble nucleation and foaming in spray droplets. Nucleate boiling heat transfer enhancement was observed at all liquid mass fluxes and droplet velocities in the range of our experiments. The surfactant slightly reduced transition boiling heat transfer, and also reduced the temperature at which spray droplets started to wet the surface. Changing the orientation of the surface with respect to gravity had no effect on heat transfer.

Characterization and identification of super-effective thermal fire extinguishing agents :

“…In the work of Qiao and Chandra [107] on nucleate boiling enhancement using a surfactant/water solution, the heat flux measurements could also be correlated well by scaling with T^rf-T f in a form similar to Eq. (31), q'^OSÖxlO-'iT^-Tf) 6 .…”

Spray Cooling Trajectory Angle Impact Upon Heat Flux Using a Straight Finned Enhanced Surface

“…Other topics researched to date include the effect of surfactant addition [12,13], and secondary nucleation [9,14,17]. This work is a continuation of the enhanced surface study by Silk et al [ 181, with emphasis on straight fins as the featured surface structure geometry.…”

Heat-transfer dynamics during cryogen spray cooling of substrate at different initial temperatures

“…As a result, constant heat-transfer coefficient (h) is used in all analyses regardless of surface temperature. Previous studies on water spray cooling of metal substrates have shown that h is dependent on surface temperature (Qiao and Chandra 1998, Ciofalo et al 1999, Jia and Qiu 2003 and suggest that the assumption of constant h may be incorrect during transient CSC. In order to explore the heat-transfer mechanisms during CSC and to provide data at elevated initial substrate temperatures, experiments herein were performed with a Plexiglas R skin phantom coupled with a fast-response thermal sensor.…”