LIQUID‐TO‐PARTICLE HEAT TRANSFER DURING CONTINUOUS TUBE FLOW: INFLUENCE of FLOW RATE and PARTICLE to TUBE DIAMETER RATIO¹

Abstract

Liquid‐to‐particle convective heat transfer coefficients were measured during continuous flow through tubes, using an experimental technique in which a thermocouple was moved at the same speed as the particle. Water was used as the carrier fluid and transducer particles were made hollow to approximate densities of real food particles. Results from over 250 experimental runs over a fluid Reynolds number range from 7300 to 43600, showed that the convective coefficient was increased significantly with increasing fluid flow rate and particle to tube diameter ratio. Convective coefficient values ranged from 688 to 3005 w/m20C depending on the experimental conditions. Dimensionless correlations obtained between the Nusselt number, particle Reynolds number, particle to tube diameter ratio, and the particle Froude number yielded R2 values ranging from 0.82 to 0.92 depending on the complexity of the relation.

DETERMINATION of CONVECTIVE HEAT TRANSFER COEFFICIENT BETWEEN FLUID and CUBIC PARTICLES IN CONTINUOUS TUBE FLOW USING NONINVASIVE EXPERIMENTAL TECHNIQUES1

“…More recent work from this laboratory (Balasubramaniam and Sastry 1994) has found that under laminar flow conditions, the effect of particle-to-pipe dimension ratio was not clear cut; this was attributed to variation in particle trajectories (which were not controlled). Zitoun and Sastry (1994) determined convective heat transfer coefficients for cubic particles in non-Newtonian carrier fluids in laminar flow using the moving thermocouple approach of Sastry et al (1990). Results indicated increasing heat transfer coefficients with increasing flow rate, decreasing viscosity and decreasing particle-to-tube dimension ratio.…”

Liquid‐to‐particle heat transfer in continuous tube flow: Comparison between experimental techniques

“…Since time has a large error coefficient value, longer residence times are desirable (although not practical). Other precautions and sources of experimental error are described by Sastry et al (1990).…”

“…The presumption of zero relative velocity, while conservative, is contradicted by most measurements of h fp under continuous flow conditions (Heppell, 1985;Sastry et al, 1989Sastry et al, , 1990Mwangi et al, 1993). Most such studies have indicated that h fp is significantly greater than expected from the zero relative velocity conjecture.…”

“…A limited number of studies (Heppell, 1985;Sastry et al, 1989Sastry et al, , 1990Stoforos & Merson, 1991;& Mwangi et al, 1993) have involved measurement of h fp with moving particles. Heppell (1985) reported h fp values for 3.1 mm diameter alginate beads in a continuous flow system using Bacillus stearothermophilus.…”

Elastic behavior of syrups

“…Ultrasonic energy has successfully been exploited in the past two decades for medical diagnosis and industrial purposes (Chernikova, 1977;Floros & Liang, 1994;Gallego, 1998;Satstri, Lima, Brim, Brunn, & Heskitt, 1990). However, relatively lesser attention have been paid by agricultural scientists to its application in agriculture and food industry.…”