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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Extended hydrodynamic theory of the peak and minimum pool boiling heat fluxes

The hydrodynamic theory of the extreme pool boiling heat fluxes is expanded to embrace a variety of problems that have not previously been analyzed. These problems include the prediction of the peak heat flux on a variety of finite heaters, the influence of viscosity on the Taylor and Helmoltz instability mechanisms with application to film boiling and to the peak heat flux in viscous liquids, the formalization of the analogy between high-current-density electrolysis and boiling, and the description of boiling in the low-gravity limit. The predictions are verified with a large number of new data.

Linehard, J. H.↗
NASA NTRS1972

Hydrodynamic prediction of peak pool-boiling heat fluxes from finite bodies.

Previous theoretical models are considered, giving attention to the original formulation proposed by Zuber (1959), an infinite horizontal flat plate, a horizontal cylinder, and a sphere. Some general features of any hydrodynamic prediction are inferred by examining the characteristics of the models. It is found possible to eliminate the need for observed values of the vapor-blanket thickness. The concepts obtained are utilized in the derivation of expressions for the prediction of the peak pool-boiling heat flux in the case of some new configurations.

Lienhard, J. H.↗
NASA NTRS1974

Peak pool boiling heat flux in viscous liquids

The stability of a gas jet in a surrounding viscous liquid is studied. An expression is developed for the critical velocity at which the jet becomes unstable in a returning viscous liquid. The stability analysis is made to correspond with the geometrical configuration of gas jets and liquid columns similar to those observed near the peak pool boiling heat flux. The critical velocity of the gas jet is then used to obtain the functional form of the peak heat flux on flat plates and cylindrical heaters. The expressions are compared with original observations of the peak heat flux in very viscous liquids on flat plate, and cylindrical, heaters at both earth-normal, and elevated, gravities.

Dhir, V. K.↗
NASA NTRS1977

Burning of liquid pools in reduced gravity

The existing literature on the combustion of liquid fuel pools is reviewed to identify the physical and chemical aspects which require an improved understanding. Among the pre-, trans- and post-ignition processes, a delineation was made of those which seem to uniquely benefit from studies in the essential environment offered by spacelab. The role played by the gravitational constant in analytical and experimental justifications was developed. The analytical justifications were based on hypotheses, models and dimensional analyses whereas the experimental justifications were based on an examination of the range of gravity and gravity-dependent variables possible in the earth-based laboratories. Some preliminary expositions into the questions of feasibility of the proposed spacelab experiment are also reported.

Kanury, A. M.↗
NASA NTRS1977

'Chain pooling' model selection as developed for the statistical analysis of a rotor burst protection experiment

A statistical decision procedure called chain pooling had been developed for model selection in fitting the results of a two-level fixed-effects full or fractional factorial experiment not having replication. The basic strategy included the use of one nominal level of significance for a preliminary test and a second nominal level of significance for the final test. The subject has been reexamined from the point of view of using as many as three successive statistical model deletion procedures in fitting the results of a single experiment. The investigation consisted of random number studies intended to simulate the results of a proposed aircraft turbine-engine rotor-burst-protection experiment. As a conservative approach, population model coefficients were chosen to represent a saturated 2 to the 4th power experiment with a distribution of parameter values unfavorable to the decision procedures. Three model selection strategies were developed.

Holms, A. G.↗
NASA NTRS1979

Feasibility study of liquid pool burning in reduced gravity

The feasibility of conducting experiments in the Spacelab on ignition and flame spread with liquid fuel pools which are initially at a temperature lower than the fuel's flash point temperature was studied. Theories were developed for the ignition and flame spread processes, and experiments were conducted to understand the factors influencing the ignition process and the spread rate. The results were employed to devise a conceptual Spacelab experiment which is expected to be feasible for a safe conduct and to be suitable for obtaining crucial data on the concerned processes.

Kanury, A. M.↗