The Effect of Dissolving Salts in Water Sprays Used for Quenching A Hot Surface : Part 1-Boiling of Single Droplets  

Oleh:

McCahan, Susan ; Chandra, Sanjeev ; Qiang, Cui

Jenis: Article from Bulletin/Magazine
Dalam koleksi: Journal of Heat Transfer vol. 125 no. 2 (Apr. 2003), page 326-338.
Topik: droplets; dissolving salts; water spray; quenching; hot surface; boiling; single droplets

Ketersediaan

Perpustakaan Pusat (Semanggi) Nomor Panggil: JJ90.6 Non-tandon: 1 (dapat dipinjam: 0) Tandon: tidak ada

Lihat Detail Induk

Isi artikel

We conducted experiments on the effect of dissolving three different salts sodium chloride (NaCl), sodium sulfate (Na(2)SO(4)) and magnesium sulfate (MgSO(4)) in water droplets boiling on a hot stainless steel surface. Substrate temperatures were varied from 90° C to 220° C. We photographed droplets as they evaporated, and recorded their evaporation time. At surface temperatures that were too low to initiate nucleate boiling all three salts were found to reduce droplet evaporation rates because they lower the vapor pressure of water. In the nucleate boiling regime, low concentrations (< 0.1 mol / l) of Na2SO4 and MgSO4 enhanced heat transfer because they prevented coalescence of vapor bubbles and produced foaming in the droplet, significantly reducing droplet lifetimes. Increasing the salt concentration further did not produce a corresponding increase in droplet boiling rate. Dissolved salts prevent bubble coalescence because they increase surface tension and stabilize the liquid film separating bubbles, and because electric charge that accumulates on the surfaces of bubbles produces a repulsive force, preventing them from approaching each other. Na(2)SO(4) and MgSO(4), which have high ionic strengths, produced a large amount of foaming in droplets and increased their boiling rate significantly. NaCl, which has low ionic strength, had little effect on droplet boiling.

Opini Anda

Klik untuk menuliskan opini Anda tentang koleksi ini!

Kembali