HEAT TRANSFER TO FLOWING GAS-SOLIDS MIXTURES IN A VERTICAL CIRCULAR DUCT (thesis)

Technical Report · Mon Jul 11 04:00:00 EDT 1960

OSTI ID:4144551

Depew, C A

The problem of heat transfer to an air stream laden with solid spherical particles fiowing up a vertical tube with constant heat flux was examined. Two different particle sizes were used, 30 and 200 mu . The air rate was held constant at Reynolds number = 13,500 and 27.400 while solids were added up to gravimetric ratios of seven. The analytical treatment parallels the solution for single-phase flow. An approximate solution is obtained when it is assumed that the difference in the temperature of the two phases is small, and that the radial temperature profiles of the two phases in the fully developed region are similar. Nusselt numbers are based on the local tube wall and bulk meanmixture temperatures. Qualitative agreement with the experimental results was obtained. The analysis predicts that when solid glass particles are added to the air stream in increasing numbers, the asymptotic Nusselt number decreases to a minimum and then increases. The experimental results show that the Nusselt number remains constant for loading ratios (0.5 and decreases to a minimum which occurs between 1.0 and 1.5. The length of the thermal entry region increases with increasing solids to gas ratios and was found to be longer thsn the heat-transfer tube (46.4 pipe diameters) at a loading ratio of unity. Although the analysis predicts an increasing Nusselt number at ratios greater than 2, the experiments with 200- mu particles show that the Nusselt number is independent of the solids loading. Friction.factors calculated from over-all pressure-drop measurements predict heat- transfer coefficients, according to Reynolds analogy, that agree with experimental values within 20% for solids loadings less than 0.5. (auth)

• Research Organization: California. Univ., Berkeley. Lawrence Radiation Lab.
• DOE Contract Number: W-7405-ENG-48
• NSA Number: NSA-14-024234
• OSTI ID: 4144551
• Report Number(s): UCRL-9280
• Country of Publication: United States
• Language: English

Related Subjects

AIR
DISTRIBUTION
ENGINEERING AND EQUIPMENT
FLUID FLOW
FRICTION
GAS FLOW
GASES
GLASS
HEAT TRANSFER
MATHEMATICS
MIXING
NUSSELT NUMBER
PARTICLES
PRESSURE
QUANTITY RATIO
REYNOLDS NUMBER
SOLIDS
SPHERES
TEMPERATURE
TESTING
TUBES
TURBULENCE
VOLUME