Shot Peening, Coating And Boiling Heat Transfer

Author:  Nadkarni, MC Sharma, S. Sharma
Source:  Conf Proc: ICSP-4, (p. 57-62)
Doc ID:  1990074
Year of Publication:  1990
Abstract:  
Effect of shot/grit peening on surface heat transfer coefficients of Boiler quality steel tube was studied. It was found that grit peening was beneficial in improving heat transfer characteristics, than shot peening. But when surfaces are coated with M-Seal compound, the heat transfer rate differed in a different way. It was observed that for heat flux up to 3 x 10(4) k cal/h M(2) effect of coating and peening was equally beneficial, but for higher heat flux both coating and grit peening processes have shown lesser benefits. Similarly it was also observed that coating with M-Seal (Thermoset Polymer Coat) of 0.1mm thick coat has shown lesser improvement in heat transfer at higher heat flux as compared to grit peened tube. It is evident that if peening is done with shots using pressure peening system and then coated with thinner coat, there will be duel advantage of better corrosion fatigue resistance and higher heat transfer rates. Adverse effect of sharp notches produced by grits will be reduced by sperical shots which will not only reduce stress concentration but at high velocity it will give appreciable roughness and adequate adhesion of coat with similar improvement in heat transfer rate as that of grits. Descriptors: Shot/grit peening; Nucleate boiling; Film boiling, Surface heat transfer co-efficient and wettability.