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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1970

A review on film boiling

Film boiling covering drops and puddles, pool boiling for various geometries and forced convective film boiling

Hsu, Y. Y.↗
NASA NTRSDate not supplied

Numerical Predictions of the Flow and Heat Transfer Characteristics in the Film Boiling Regime During Tube Quenching

Cryogenic fluid management plays a major role in refueling of spacecrafts while in space for NASA’s future human space exploration missions. Due to the low boiling points of cryogens, storage, transport and handling of these fluids becomes difficult and may result in inefficient operation of the space propulsion systems. For refueling applications in space, the cryogenic fluids have to be transported across different locations and hence, the transfer of cryogenic fluids through pipes become critical. The cryogenic chill-down process is characterized by different regimes of flow boiling, viz., film boiling, transition boiling and nucleate boiling. The prediction of these regimes in a single CFD framework available in the literature is challenging and the present work attempts to address this challenge by initially modeling the film boiling regime accurately and to incorporate an user-defined function for transition and nucleate boiling at a later stage. Hence, the aim of the present work is to numerically model and validate the film boiling regime of the chilldown curve for liquid nitrogen experiments available in the literature. The validations are carried out at different inlet mass fluxes to have a robust simulation methodology. A dispersed mixture model is used to predict the vapor-liquid interface dynamics with the phase change phenomena modeled using the Lee model.

line chilldown↗
NASA NTRS1972

A review of film boiling at cryogenic temperatures.

Film boiling occurs in the quenching of metals, the chilling of biological species, the regenerative cooling of rockets, and the cooling down of a cryogenic fuel tank. Occasionally film boiling is also found in a nuclear reactor or in a cryomagnet. Aspects of film boiling involving an unconstrained liquid mass are considered, giving attention to the evaporation time, the Leidenfrost temperature, solid-liquid contacts, the thermal properties of the solid, effects of coating or scale, wettability, the metastable condition, and the velocity effect on drops. Developments discussed with regard to pool boiling are related to vertical surfaces, film boiling from horizontal surfaces, film boiling from a horizontal cylinder, film boiling from a sphere, and film boiling of helium. Processes of film boiling in a channel are also analyzed.

Hsu, Y. Y.↗
NASA NTRS1972

Film boiling on vertical surfaces.

Film boiling of a saturated liquid on a vertical surface is analyzed to determine the local heat-transfer rates as a function of height and heater-surface superheat. Experiments show that the laminar-flow model is inadequate. A turbulent-vapor-flow model is used, and the influence of the interfacial oscillations is incorporated on a semiempirical basis. Measurements of local film boiling were obtained with a transient technique using saturated liquid nitrogen.

Suryanarayana, N. V.↗
NASA NTRS1975

Film boiling of mercury droplets

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. Diffusion from the upper surface of the drop appears as a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

Baumeister, K. J.↗
NASA NTRS1975

Film boiling of mercury droplets

Vaporization times of mercury droplets in Leidenfrost film boiling on a flat horizontal plate are measured in an air atmosphere. Extreme care was used to prevent large amplitude droplet vibrations and surface wetting; therefore, these data can be compared to film boiling theory. For these data, diffusion from the upper surface of the drop is a dominant mode of mass transfer from the drop. A closed-form analytical film boiling theory is developed to account for the diffusive evaporation. Reasonable agreement between data and theory is seen.

Baumeister, K. J.↗
NASA NTRS1972

Diffusive and radiative effects on vaporization times of drops in film boiling

Diffusive and radiative effects are incorporated into an analysis for the vaporization time of drops in film boiling. The momentum, energy, and continuity equations are solved with some appropriate simplifications so as to obtain a simple closed form solution for the overall film boiling heat transfer coefficient. Next, a theoretical expression for the droplet vaporization time is developed and compared to the measured vaporization times of water droplets vaporizing into air, argon, nitrogen, and helium. The agreement between experiment and theory is good. Under the helium blanket, the diffusive evaporative component is significant in comparison to the film boiling component.

Baumeister, K. J.↗
NASA NTRS1977

Effect of ice contamination of liquid-nitrogen drops in film boiling

Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. Experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation is presented. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

Schoessow, G. J.↗
NASA NTRS1977

Effect of ice contamination on liquid-nitrogen drops in film boiling

Previously reported vaporization time data of liquid nitrogen drops in film boiling on a flat plate are about 30 percent shorter than predicted from standard laminar film boiling theory. This theory, however, had been found to successfully correlate the data for conventional fluids such as water, ethanol, benzene, or carbon tetrachloride. This paper presents experimental evidence that some of the discrepancy for cryogenic fluids results from ice contamination due to condensation. The data indicate a fairly linear decrease in droplet evaporation time with the diameter of the ice crystal residue. After correcting the raw data for ice contamination along with convection, a comparison of theory with experiment shows good agreement.

Schoessow, G. J.↗
NASA NTRS1962

STABILITY OF FILM BOILING TWO-PHASE FLOW IN CRYOGENIC SYSTEMS

The stability of film boiling two phase flow is investigated referring in particular to saturated cryogenic liquids. This type of fluid motion is unstable, such that a range of wave numbers will always be present in which disturbances are amplified. Further the mode of operation of the energy supply system may favour temperature fluctuations of large amplitude if the circuit does not provide feed-back compensation. The theoretically predicted stabilization due to capillarity is reduced considerably in liquefied gases with low surface tension, such as hydrogen. This effect causes the transition to turbulent flow to occur at low Reynolds numbers, and increases the heat transport in the turbulent regime. A comparison with experimental data, (horizontal cylinder), shows that the "critical" film Reynolds number ūδ/𝜈, at which instabilities become effective, is lowered from approximately 200, (O2), to about 30, (H2). Similar results have been found with other configurations. Therefore application of laminar film boiling solutions is restricted to small objects, entrance regions, or stagnation points. Turbulent correlations given so far are valid only for a certain group of substances with similar behavior.

LIQUID FLOW↗