Boiling heat transfer enhancement by impurities deposition of tap water

We studied the effectiveness of using tap water and deionized water as working fluids in enhancing critical heat flux levels. During boiling processes, impurities from tap water formed a thin film deposit on a substrate. This thin film layer substantially improved the wettability of the surface and reduced the contact angle of the surface from 90° to <10°. To investigate the properties of the thin film layer, we used a scanning electron microscope equipped with an X-ray energy dispersive spectrometer, and the results confirmed that the surface was composed of impurities.