Heat transfer coefficients for condensation of N-heptane in the presence of methane
Defriece, Allen N
Akers, W. W.
Master of Science
In this investigation, condensing heat transfer coefficients for the n-heptane-methane system were studied as a function of concentration of methane in the vapor at two condenser temperatures, 224 and 247 F. It was estimated that the effective condenser tube surface temperature was within the range of 85 to 95 F. The condensing heat transfer coefficients were obtained by means of the Wilson graphical method as modified by Beatty and Katz. Data secured for this method of obtaining condensing heat transfer coefficients were overall heat transfer coefficients at a series of cooling water velocities for constant condenser temperature, constant methane concentration in the vapor, and an average cooling water temperature that varied within the narrow range 82 to 84 F. Under the conditions just enumerated, the reciprocal of the 0.8 power of the cooling water velocity to obtain a straight line which was extrapolated to zero value for the abscissa, the 0.8 power pf the water velocity. The condensing heat transfer coefficient was calculated for the intercept thus obtained. The apparatus used for the investigation was a closed combination condenser-vaporizer containing a horizontal condensing tube. There was no oriented bulk flow of the vapor-gas mixture past the condensing element. Methane vapor concentrations varied from 0 to 18 mol percent. The condensing heat transfer coefficients varied from 180 to 6.3 BTU/hr/ft2/F. It was concluded that under the conditions of the investigation, a single curve is obtained when the condensing heat transfer coefficient is plotted versus mol percent methane in the vapor.