| Four methods of measuring liquid-to-particle convective heat transfer coefficients (h$sb{rm fp}$) in continuous flow were compared: moving thermocouple, liquid crystal, relative velocity, and temperature pill. Except the relative velocity method, all other methods involved measurement of the time-temperature history of a moving particle using different approaches. The relative velocity method involves indirect determination of h$sb{rm fp}$ from measurements of relative velocity between fluid and particle.;The moving thermocouple method yielded the lowest estimation of h$sb{rm fp}$, possibly due to restrictions in particle movement. The liquid crystal method (which accounted both for particle translational and rotational motion) yielded the highest estimates of h$sb{rm fp}$. The relative velocity method yielded lower h$sb{rm fp}$ values in comparison with that of liquid crystal method, since measured relative velocities were only translational and not rotational. The temperature pill in its intact form was found to be not well conditioned for h$sb{rm fp}$ determination.;Measured values of relative velocities for different experimental conditions ranged from 0.02 m/s to 0.29 m/s. The presence of significant relative motion between the fluid and the particle does not mean that the particle lags or leads the fluid, since the relative velocity is a localized phenomenon. Experimentally determined relative velocities were consistently higher than those predicted from average fluid velocities. Calculated Nusselt numbers (ranged from 7.7 to 64.2) were far greater than the limiting value of 2.0 (for zero relative velocity) as favored for process evaluation by FDA.;Significant parameters influencing h$sb{rm fp}$ values in continuous tube flow were found to be carrier medium viscosity, flow rate, particle-to-tube diameter ratio, radial location of the particle, and fluid-particle density difference. In scraped surface heat exchanger, h$sb{rm fp}$ values were found to be influenced by carrier medium viscosity, flow rate, particle-to-annulus clearance ratio, and mutator rotational speed. |
