Abstract:
Heat transfer coefficients for agitated liquids in a flat bottomed vessel equipped with finned tube helical coil were determined over the 125-500r.p.m range of agitator speeds by using a flat paddle turbine impeller in order to examine the effect of finned coil geometry. The heat transfer experiments have been carried out in two sets using three finned coils.with different spacing. In the first set heat transfer coefficients were calculated for each coil using the Wilson graphical method by changing the, hot stream flow rate and the temperature at constant agitator speed. In the second set only agitator speed was varied while hot and cold stream flow rates and temperatures were maintained constant. The overall conductance was determined from the heat transfer rate and log mean temperature difference by calculating the tube side heat transfer coefficient from theSieder-Tate correlation, the outside heat transfer coefficient was found. In addition to these experiments, the heat transfer coefficients in one type of finned coiled agitated vessel were also observed under unsteady state oonditions. The experimental data were compared with smooth tubes. As a result of this investigation the finned coils were found to be more heat transfer effective than the smooth coils. The values of the mixing coefficients were in agreement with previously published data. Unsteady state experiments showed that the correlation derived to find outside heat transfer coefficients under steady state conditions could be used also for unsteady state conditions. Higher heat transfer coefficients were obtained at higher agitator speeds.
