Research on thermophoretic and inertial aspects of ash particle deposition on heat exchanger surfaces in coal-fired equipment
Little is yet known (theoretically or experimentally) about the simultaneous effects of particle inertia, particle thermophoresis and high mass loading on the important engineering problem of predicting deposition rates from flowing dusty'' gases. For this reason, we investigate the motion of particles present at nonnegligible mass loading in a flowing nonisothermal gaseous medium and their deposition on strongly cooled or heated solid objects by examining the instructive case of steady axisymmetric dusty gas'' flow between two infinite disks: an inlet (porous) disk and the impermeable target'' disk -- a flow not unlike that encountered in recent seeded-flame experiments. Since this stagnation flow/geometry admits interesting self-similar solutions at all Reynolds numbers, we are able to predict laminar flow mass-, momentum- and energy-transfer rate coefficients over a wide range of particle mass loadings, dimensionless particle relaxation times (Stokes numbers), dimensionless thermophoretic diffusivities, and gas Reynolds numbers. As a by-product, we illustrate the accuracy and possible improvement of our previous diffusion model'' for tightly coupled dusty gas systems. Moreover, we report new results illustrating the dependence of the important critical'' Stokes number (for incipient particle impaction) on particle mass loading and wall/gas temperature ratio for dust-laden gas motion towards overheated'' solid surfaces. The present formulation and insulating transport coefficients should not only be useful in explaining/predicting recent deposition rate trends in seeded'' flame experiments, but also highly mass-loaded systems of technological interest.
- Research Organization:
- Yale Univ., New Haven, CT (United States). High Temperature Chemical Reaction Engineering Lab.
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-86PC90756
- OSTI ID:
- 6945420
- Report Number(s):
- DOE/PC/90756-T11; ON: DE93003898
- Country of Publication:
- United States
- Language:
- English
Similar Records
Research on thermophoretic and inertial aspects of ash particle deposition on heat exchanger surfaces in coal-fired equipment. Quarterly report No. 9, September 1, 1988--November 30, 1988
Research on thermophoretic and inertial aspects of ash particle deposition on heat exchanger surfaces in coal-fired equipment
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