A Calorimetric Approach for Evaluation of Fluid-to-Particle Heat Transfer Coefficient Under Tube-Flow Conditions

A calorimetric approach was used to evaluate the bulk temperature of moving particles, and the convective fluid-to-particle heat transfer coefficients (hfp) were evaluated under continuous tube-flow conditions. The technique consisted of introducing a particle at an upstream location into a holding tube, through which a carrier fluid circulated under prestabilized temperature and flow conditions, and retrieving it from a downstream location at a known time interval. The particle was transferred immediately into a specially constructed calorimeter and its bulk temperature was determined upon equilibration. The technique was calibrated using thermocouple equipped particles subjected to various time-temperature treatments. Since the medium temperature, particle initial temperature, exposure time and thermophysical properties were known, the associated hfpcould be computed using an iterative numerical technique for the evaluated bulk temperature of the particle. The hfpvalues obtained from using the calorimetric approach were comparable to those obtained from traditional techniques involving thermocouple equipped particles. Higherhfp values were associated with moving particles, as compared with stationary particles, particles of larger size and fluid flowing at higher rates.