HEAT TRANSFER IN A THIN LIQUID FILM IN THE PRESENCE OF AN ELECTRIC FIELD

Heat transfer enhancement in an evaporating thin liquid film utilizing a electric field under isothermal interfacial condition is presented. A new mathematical model subjected to van der Waals attractive forces, capillary pressure, and an electric field is developed to describe the heat transfer enhancement in the evaporating thin liquid film. The effect of the electrostatic field on the curvature of the thin film, evaporative flux, pressure gradient distribution, heat flux, and heat transfer coefficient in the thin film is presented. The results show that applying an electric field can enhance heat transfer in a thin liquid film significantly. In addition, utilizing electric fields on the evaporating film will be a way to expand the extended meniscus region to attain high heat transfer coefficients and high rates of heat flux.     

Synthesis and characterization of nanosized-silica gels formed under controlled conditions

Silica gel has been synthesized by the refluxing of rice husk ash with 1 M NaOH and subsequently adjusting the pH using 1 M H₂SO₄. The high purity of the silica gel has been found to be dependent on: (i) reflux time, (ii) water loading by addition of boiling DI water to the silica gel prior to titration with 1 M H₂SO₄ and (iii) rinse time on removal of impurities prior to drying. The surface area, pore size and volume of the silica gel were measured; XRD peaks of Na₂SO₄ impurity were absent after rinsing > 4 times. FTIR spectra showed that all the silica gels made by different schedules had a similar functional composition. The advantages of the present synthesis route are (i) a cost reduction due to the absence of pre-treatment for the rice husks before calcination below 700 °C, and (ii) the formation of a pure high surface area mesoporous amorphous silica gel.