Aj. Fletcher et Wd. Griffiths, MODEL OF HEAT-TRANSFER DURING QUENCHING IN SODIUM POLYACRYLATE SOLUTIONS, Materials science and technology, 11(3), 1995, pp. 322-326
A model is proposed to describe heat transfer during the later stages
of a quench in sodium polyacrylate solutions. These quenchants exhibit
characteristics similar to those of an oil quench, with a maximum rat
e of heat transfer at temperatures much higher than that normally obta
ined from aqueous quenchants. This is associated with a pronounced ran
ge of temperature (400-100 degrees C) where the surface heat transfer
coefficient is very low and the surface of the component is covered wi
th a viscous slurry laden with almost stationary bubbles. The present
work demonstrates that the heat transfer during this stage of the quen
ch may be explained in terms of a heat conduction model, with heat flo
w through the vapour layer similar to that found during the vapour bla
nket stage at the start of the quench. Thus, in both instances the vap
our acts a a layer of insulation, in contrast to the nucleate boiling
stage, where rapid heat flow is associated with the release of individ
ual bubbles.