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Cremers, C. J.

Publications and source records attributed to Cremers, C. J..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1999

The Three-D Flow Structures of Gas and Liquid Generated by a Spreading Flame Over Liquid Fuel

We developed a new experimental technique called: Combined laser sheet particle tracking (LSPT) and laser holographic interferometry (HI), which is capable of measuring the transient behavior of three dimensional structures of temperature and flow both in liquid and gas phases. We applied this technique to a pulsating flame spread over n-butanol. We found a twin vortex flow both on the liquid surface and deep in the liquid a few mm below the surface and a twin vortex flow in the gas phase. The first twin vortex flow at the liquid surface was observed previously by NASA Lewis researchers, while the last two observations are new. These observations revealed that the convective flow structure ahead of the flame leading edge is three dimensional in nature and the pulsating spread is controlled by the convective flow of both liquid and gas.

Tashtoush, G.↗
NASA NTRS1975

Thermophysical properties of Apollo 14 fines

The vacuum thermal conductivity of lunar fines sample 14163 was measured for the approximate temperature range 100 to 400 deg K. Several sample densities from 1100 to 1800 kg/cu m were used. The temperature dependence of the conductivity was found to be well represented by the relation k = A + BT cubed, which is predicted by elementary theory. The coefficients A and B were obtained by least squares analysis of the data. The thermal diffusivity was calculated for the various densities by using specific heat data from the literature along with the measured conductivities. The results are compared with those obtained for Apollo 11, Apollo 12, and terrestrial basalt samples.

Cremers, C. J.↗
NASA NTRS1974

Thermophysical properties of Apollo 14 fines

The vacuum thermal conductivity of lunar fines sample 14163 was measured for the approximate temperature range of 100 to 400 K. Sample densities of 1500 kg/cu m and 1800 kg/cu m were used. The temperature dependence of the conductivity was found to be well represented by the relation k = A + BT-cubed, which is predicted by elementary theory. The coefficients A and B were obtained by least-squares analysis of the data. The thermal diffusivity was calculated for the various densities using specific heat data from the literature along with the measured conductivities. The results are compared with those obtained for Apollo 11, Apollo 12, and terrestrial basalt samples.

Cremers, C. J.↗
NASA NTRS1974

Thermophysical properties of lunar media. II - Heat transfer within the lunar surface layer

Heat transfer within the lunar surface layer depends on several thermophysical properties of the lunar regolith, including the thermal conductivity, the specific heat, the thermal diffusivity, and the thermal parameter. Results of property measurements on simulated lunar materials are presented where appropriate as well as measurements made on the actual samples themselves. The variation of temperature on the moon with depth is considered, taking into account various times of the lunar day. The daily variation in temperature drops to about 1 deg at a depth of only 0.172 meters. The steady temperature on the moon below this depth is 225 K.

Cremers, C. J.↗
NASA NTRS1974

Thermal characteristics of Apollo 16 lunar fines

The vacuum thermal conductivity of the Apollo 16 fines is presented as a function of temperature for the approximate range of diurnal temperatures on the moon. The density used is 1500 kg/cu m, which is approximately the density of the core tube samples returned from the landing site. The thermal diffusivity was calculated from the conductivity, density and specific heat and is also presented. These properties along with the reflectance and emittance are used in a calculation of temperature in the lunar surface layer.

Cremers, C. J.↗
NASA NTRS1974

Thermal conductivity of Apollo 15 lunar fines

The moon is covered to a depth of several meters with fine material. Heat transfer calculations depend, therefore, for the most part on the properties of the fines. The results are presented of thermal conductivity measurements on fines samples returned by the Apollo 15 mission from the Hadley-Apennine region of the moon. Data are presented as a function of both density and temperature with typical lunar values being used for these parameters.

Cremers, C. J.↗
NASA NTRS1974

Thermal conductivity of Apollo 16 lunar fines

The vacuum thermal conductivity of the Apollo 16 fines is presented as a function of temperature for the approximate range of diurnal temperatures on the moon. The density used is 1500 kg/cu m, which is approximately the density of the core-tube samples returned from the landing site. The thermal diffusivity was calculated from the conductivity, density, and specific heat and is also presented.

Cremers, C. J.↗
NASA NTRS1973

Thermophysical properties of Apollo 12 fines.

The vacuum thermal conductivity of the Apollo 12 fines is presented as a function of temperature for densities of 1300, 1640 and 1970 kg/cu m. It is found to vary from about .001 W/m-K at 100 K to about .003 W/m-K at 400 K. The conductivity of the fines is found to be close to that of terrestrial basalt both under vacuum and at higher pressures. The thermal diffusivity is calculated from conductivity and specific heat data. Average values of the thermal conductivity, thermal diffusivity and thermal parameter are also presented.

Cremers, C. J.↗
NASA NTRS1973

Low temperature thermophysical properties of lunar soil

The thermal conductivity and thermal diffusivity of lunar fines samples from the Apollo 11 and Apollo 12 missions, determined at low temperatures as a function of temperature and various densities, are reviewed. It is shown that the thermal conductivity of lunar soil is nearly the same as that of terrestrial basaltic rock under the same temperature and pressure conditions.

Cremers, C. J.↗
NASA NTRS1973

Thermal conductivity and diffusivity of Apollo 15 fines at low density

The thermal conductivity of the Apollo 15 fines, sample 15031,38, was measured under vacuum conditions as a function of temperature. Measurements were made for a sample density of 1300 kg/cu m. The conductivity was found to vary from about .00057 W per m per K at 95 K to about .00136 W per m per K at 406 K. The data are compared with the correlation using a cubic temperature dependence and also with data from samples gathered during prior Apollo missions. The thermal diffusivity is obtained for the sample by calculation using the given density and measured thermal conductivity along with specific heats from the literature.

Cremers, C. J.↗
NASA NTRS1972

Thermal characteristics of the lunar surface layer.

The thermophysical properties of the fines from the Apollo 12 landing site have been determined as a function of their relevant parameters. These properties include the thermal conductivity, thermal diffusivity, directional reflectance and emittance. The density used was the same as that observed from the returned core-tube samples and so should be close to the true density of the surface layer at the Apollo 12 site. The measured properties are used to calculate the diurnal temperature variation of the moon's surface as well as for several depths below the surface. The maximum surface of 389 K is obtained at lunar noon while the minimum temperature of 86.1 K is obtained at sunrise. It is shown that the most significant effects on temperature, as compared with previous calculations, are caused by using the directional reflectance which controls the amount of solar energy absorption during the day in place of a constant hemispherical reflectance. The results are compared with previous analyses and remote measurements.

Cremers, C. J.↗
NASA NTRS1972

Thermal conductivity of Apollo 12 fines at intermediate density.

The thermal conductivity of an Apollo 12 fines sample (12001,19) was measured under vacuum conditions over a temperature range of 200 to 400 K for a density of 1640 kg/cu m. It was found to vary from approximately .0012 to about .0026 W/m-K. A least-squares curve was found to represent the data satisfactorily.

Cremers, C. J.↗
NASA NTRS1972

Thermal conductivity of Apollo 14 fines.

The thermal conductivity of the Apollo 14 fines, sample 14163,133, was measured under vacuum conditions as a function of temperature. Measurements were made for densities of 1100 and 1300 kg/cu m. A least-squares curve of the form k = A + B(T-cubed) is fitted to each data set in accordance with elementary theory. Comparisons are made with previously published data for terrestrial basalt and Apollo 11 and 12 samples.

Cremers, C. J.↗
NASA NTRS1971

Lunar surface temperatures from Apollo 12.

The diurnal variation of temperatures in the lunar surface layer is calculated using the measured properties of the Apollo 12 samples. The results are compared with similar calculations made using data from the Apollo 11 samples and with previous infrared temperature measurements. Comparisons are also made with prior calculations which used assumed properties. These are based on an effective value of the thermal parameter (gamma) of 1034 which is obtained from integrated average values of the specific heat and thermal conductivity of the Apollo 12 fines.

Cremers, C. J.↗
NASA NTRS1971

A thermal conductivity cell for small powdered samples.

A thermal conductivity cell is described for making measurements of the thermal conductivity and thermal diffusivity of small samples of powdered dielectric materials. The principle used is that of the line heat source. A novel way is described for applying this method so that much smaller samples than normal may be tested. This size requirement is necessary for investigations involving limited samples as does the Lunar Science Program. The method is checked by measuring the conductivity of standard samples and comparing the results with those found in the literature.

Cremers, C. J.↗
NASA NTRS1971

Vacuum handling system for powdered samples.

A sample system for handling powdered material under vacuum conditions is described. The system features linear motion of up to 0.25 m and the means for complete isolation of the sample and sample system from external apparatus. The system was designed for the measurement of thermophysical properties of lunar material from Apollo missions under thoroughest possible prevention of contamination.

Birkebak, R. C.↗