LOCAL HEAT TRANSFER COEFFICIENTS IN SCRAPED-FILM HEAT EXCHANGER

Abstract

The instantaneous heat transfer coefficients in a scraped-film heat exchanger have been determined using the electrochemical technique for a two-bladed, 78.7mm I.D. exchanger. The time-averaged local heat transfer coefficients were found to agree fairly well with previous work of Azoory and Bott, though some variation in liquid flow rate was detected. The timeaveraged local Nusselt number was found to be represented by
Nu=Q.15(Re_r•Pr)^1/2Re^a_w
with a=(l-3.74×10^-2N)/9. The variation of heat transfer coefficient with time was observed to be very different from that predicted by the accepted model for the phenomena based upon unsteady state conduction.