Pool boiling of enhanced heat transfer surfaces in refrigerant-oil mixtures and aqueous calcium sulfate solutions

摘要

Pool boiling data of structured surfaces in R113/3GS oil mixtures show a general decrease in heat transfer with oil concentration, degradation in performance of all surfaces at 10% oil, no change in enhancement of the structured surfaces over plain surface, and restoration of performance of the enhanced surfaces upon cleaning in denatured alcohol. Fouling data of structured surfaces in pool boiling of sat. aq. CaSO(sub 4) solution show that effects of fouling (wall superheat changes, deposit weight) are more pronounced at 80 kW/m(sup 2) than at 10 kW/m(sup 2) heat flux; precipitation fouling show an effect within the first 2 h exposure. High flux surfaces have lower deposition weight than other surfaces; thus the deposition rate may depend strongly on wall superheat. The numerous nucleation sites of the enhanced surfaces provide more turbulent motion near the boiling surface than for the plain surface; thus the removal rate should be greater for an enhanced surface, although no removal of a deposit was ever observed.