The existing theoretical research concerned with thermal creep at fluid/solid interfaces is briefly reviewed, and the importance of microgravity-based experimental data is then discussed. It is noted that the ultimate goal of this research is a rational molecular level theory that predicts the dependence of a dimensionless thermal creep coefficient, Ctc, on relevant dimensionless parameters describing the way fluid molecules interact with the solid surface and how they interact among themselves. The discussion covers thermophoresis of isolated solid spheres and aggregates in gases; solid sphere thermophoresis in liquids and dense vapors; thermophoresis of small immiscible liquid droplets; and applications of the direct simulation Monte Carlo method.

: This annual technical report summarizes Yale High Temperature Chemical Reaction Engineering Laboratory research activities (under Grant AFOSR 91-0170) for the one-year period ending 14 February 1992. Among our research results described in detail in the cited references (Section 5). Perhaps the most notweworthy are the development of: Rl rational correction factors to account for the effects of suspended particle morphology on convective diffusion mass deposition rate's R2 quantitative criteria for influence of particle thermophoresis on the structure of two-phase laminar counterflow diffusion flames (potentially useful to predict IR radiation from such flames and optimize particle properties in synthesis applications) R3 quantitative methods for predicting/correlating the effects of particle inertia on thermophoretic deposition across laminar boundary layers on targets with streamwise curvature (experimentally verified by our seeded micro-combustor experiments on concave ribbon targets) 15 presentations and 2 PhD dissertations have resulted from this research program. Copies of 3 reprints appearing during this period are included in the Appendices (Section 6) of this report.

Two marine bluegreen algae, Oscillatoria sp. Miami BG 7 and Synechococcus sp Miami 041511 have been selected as the result of over 10 years continuous and intensive effort of isolation, growth examination, and the screening of hydrogen photoproduction capability in this laboratory. Both strains photoproduced hydrogen for several days at high rates and a quantity of hydrogen was accumulated in a closed vessel. Overall hydrogen donor substance of the hydrogen photoproduction was found to be salt water. Using strain Miami BG 7, a two step method of hydrogen photoproduction from salt water was successfully developed and this was recycled several times over a one month period using both free cells and immobilized cells in both indoor and outdoor under natural sunlight. According to these experiments, a prototype floating hydrogen production system was designed for further development of the biosolar hydrogen production system.

The present work has placed emphasis on the detailed kinetic and mechanistic study of selected fluorine/ceramic reactions. The results of our program include work on fluorine reaction with Al2O3 (38, 39), B4C (33, 37), Re (61, 64), Gd (61, 65), LaB6 (37, 50, 61, 63) and LaB6-C, LaB6-MoSi2 composites (61, 63). One application of materials resistant to fluorine attack at high temperature is the HF chemical laser. Nickel and nickel alloys are useful in fluorine to ca. 1000K, but higher temperatures are required in CW HF lasers. Since the number of candidate materials decrease and fluorine corrosion rates increase with temperature it is useful to set upper bounds on the temperatures required for this application. Our analysis of this problem (61, 66) is presented. Given the temperature range of interest, the mechanisms by which fluorine gasifies solids limit the number of possible fluorine resistant materials.

A combined experimental-theroretical attack on the problem of multicomponent deposition of condensible inorganic materials (present in combustion gases) on immersed solids (turbine blades, duct walls, heat exchanger surfaces) is outlined. With the help of seeded laboratory burner data on Na/sub 2/SO/sub 4/ and B/sub 2/O/sub 3/ deposition, a comprehensive but tractable convective diffusion deposition rate theory, based on the assumption of a multicomponent chemically frozen boundary layer (CFBL), has been developed for making self-consistent salt/ash deposition rate predctions over a wide variety of environmental conditions of gas turbine and magneto-gas-dynamic (MGD) interest. Under the conditions of these experiments (highly undersaturated mainstream), particle formation and transport are evidently negligible; however, our CFBL theory is sufficiently general to embrace the transport of particles present in the mainstream, provided they are small enough to be considered heavy molecules. Interesting corollaries of the present CFBL theory are: (1) a dew point is not a purely thermodynamic quantity, but rather is influenced by Soret and multicomponent diffusion phenomena, as well as (gas phase and interfacial) nonequilibrium phenomena; and (2) in any particular situation there is more than one dew point, depending upon its operational definition. We conclude with an assessment of the onset and rolemore » of boundary layer condensation processes and a summary of research needs highlighted by this program.« less