Scraped-surface heat exchange

An experimental study was made to test a theory developed for scraped-surface heat exchange. The apparatus was a cylindrical vessel equipped with two blades and baffles, cooled in an ice bath. The experiments showed the approach of dimensionless temperature deviated greatly from the theoretical prediction. It was found that part of this effect was the result of a change in temperature of the scraped wall, which could be accounted for by using the overall heat transfer coefficient between the cooling medium and the apparatus. Measurements on water showed the cooling rate to be much faster than the theory would predict. For a Cabosil-toluene mixture the cooling rate was slower. Scraped-surface heat-transfer coefficients of 45.7, 79.4, and 150.4 B.t.u./hr.-sq. ft\u27--\u27F. were obtained for the Cabosil-toluene mixture at shaft speeds of 10.5, 30, and 60 r.p.m. These experimental coefficients were lower by 29.1% to 2.34% than the theoretical values --Abstract, page ii