The role of surface conditions in nucleate boiling

Abstract

Nucleation from a single cavity has been stuied indicating that cavity gemtry is aportant in two ways. The mouth diameter determines the superheat nmeded to initiate boiling and its shape determines its stability one boiling has begun. Contact angle is shown to be important in bubble nucleation primarity thrugh its effect on cavity stability. Contact angle measurements made on "clean" and paraffin coated stainIess steel murftces with water shcw that the contact angle varies between 20 and 110* for tenperatures from 20[degree] to 170[degree] C. On the basis of single cavity nucleation theory, it is proposed to characterie the gross nucleation properties of a given surface for all fnds under all conditions with a single group having the dmnions of length. Finally, it is shown experimentally that this characterization is adequate by boiling water, methmnol and ethanol different copper surfaces finished with 3/0 emry, and showing that the number of active centers per unit area is a function of this variable alone.