Thermal Discontinuity Research Articles

Assessment of Current High-Temperature Design Methodology Based on Structural Failure Tests

A mature design methodology, consisting of inelastic analysis methods provided in U.S. Department of Energy guidelines and failure criteria contained in ASME Code Case N-47, exists in the United States for high-temperature reactor components. The objective of this paper is to assess the adequacy of that overall methodology by comparing predicted inelastic deformations and lifetimes with observed results from structural failure tests and from an actual service failure. Comparisons are presented for three structural cases: 1) nozzle-to-spherical shell specimens, emphasizing stresses at structural discontinuities; 2) welded structures, emphasizing metallurgical discontinuities; and 3) thermally loaded cylinders and pipes, emphasizing thermal discontinuities. The comparisons between predicted and measured inelastic responses are generally reasonable; quantities are sometimes overpredicted somewhat and sometimes underpredicted. However, even seemingly small discrepancies in predicted stresses and strains can have a significant effect on life, which is thus not always as closely predicted. For a few cases, the lifetimes are substantially overpredicted, which raises questions regarding the methodology and/or the adequacy of the current design margins.

Delimitation of a cryptic Eocene tectono-thermal domain in the Eastern Cordillera of the Bolivian Andes through K–Ar dating and 40 Ar– 39 Ar step-heating

New K–Ar ages and 40 Ar– 39 Ar age spectra for samples from granitoid rocks and meta-sediments of the Cordillera Real, Bolivia, reveal a complex mid-Tertiary tectono-thermal history for this segment of the Central Andean eastern cordillera. Previous radiometric dating of the Cordillera Real intrusions defined two, areally-distinct, plutonic domains: in the N, Upper Triassic–Lower Jurassic; in the S, Upper Oligocene–Lower Miocene. Our new K–Ar ages, many from deformed intrusions, fall between these two episodes. For the variably foliated Zongo massif, there is a marked discordance between biotite and muscovite K–Ar dates, each decreasing consistently from SW to NE across this 8 km wide plutonic centre. The age gradients are developed within the foliated and unfoliated facies of the Zongo intrusions, but do not continue NE into the Palaeozoic meta-sedimentary rocks, for which K–Ar dates are erratic. 40 Ar– 39 Ar step-heating analyses of muscovites and most biotites from granitoid rocks reveal that the oldest and youngest micas yield plateaux (210 and 39 Ma), whereas those with intermediate ages exhibit disturbed spectra. A plateau date for a biotite from the NE margin of the Zongo massif shows that final cooling through c. 300 °C occurred in the Late Eocene. The new data reveal that a marked thermal discontinuity existed 39 Ma ago at the NE contact of the Zongo intrusion. Additional discordant dates for the Yani and Illampu intrusions, to the NW, indicate that the discontinuity was of regional scale. There is no direct relationship between this tectono-thermal event, which affected at least 2000 km 2 , and the Upper Palaeozoic foliation of several of the plutons involved, and thus it is cryptic on outcrop and microscopic scales. We propose that the thermal discontinuity resulted from Late Eocene crustal shortening, SW-verging thrust faulting, and attendant cordilleran uplift at the inner (eastern) boundary of the Andean orogen, coincident with the Incaic deformation defined in Peru.

Ontogenetic and diel vertical migration of a planktonic echinoid larva, Dendraster excentricus (Eschscholtz): Occurrence, causes, and probable consequences

The ontogenetic and diel vertical distributions of the planktonic larvae of Dendraster excentricus (Eschscholtz) were examined (1) in the field, (2) in a 2500-1 floating enclosure, and (3) in a 1500−1 outdoor aquarium. In the field, both early (four-armed) and advanced (competent) stage plutei were found predominantly less than 6 m deep. In the enclosure and aquarium, all pluteus stages were distributed similarly at a given time of day, though competent plutei were not included in these experiments. The plutei underwent diel vertical migration in both the enclosure and aquarium, rising towards the surface at night and descending during daytime. Laboratory experiments were conducted to determine (1) how plutei orient vertically, (2) what larval features might regulate ontogenetic depth distribution, and (3) what environmental features cause the diel migration. All pluteus stages oriented vertically and were geonegative because an asymmetrical distribution of body mass, presumably due to the developing larval skeleton, causes plutei to swim and sink anterior-upwards. Forward swimming thus results in geonegative movement. Eight-armed larvae and newly metamorphosed juveniles were also found to have lower specific gravities than younger plutei, probably resulting from an accumulation of lipid reserves prior to metamorphosis. This decrease in specific gravity may account for the shallow distribution of advanced stage plutei observed in the plankton. Experiments to examine causes of the diel vertical migration excluded temperature, thermal discontinuities, and visible light, but showed that ultraviolet light under 315 nm inhibits swimming of all pluteus stages, but not of pre-pluteus stages, and results in daytime sinking of plutei. Ecological consequences of the lack of ontogenetic migration are unknown, though D. excentricus plutei probably are recruited from surface waters into both intertidal and subtidal adult habitats. The diel vertical migration apparently removes plutei from harmful levels of ultraviolet light; when confined in shallow water and exposed to simulated solar ultraviolet light regimes, plutei were killed or their development was retarded.

Imaging with optically generated thermal waves

By absorption of modulated optical power, a thermal wave is generated that interacts with thermal discontinuities. Imaging with scanned local thermal-wave probing is suited for non-contacting and non-destructive inspection of thermal structures in solids.

40Ar/ 39Ar incremental-release ages of biotite from a progressively remetamorphosed Archean basement terrane in southwestern Labrador

Gneisses within an Archean basement terrane adjacent to the southwestern portion of the Labrador Trough were variably retrograded during a regional metamorphism of Grenville age (ca. 1000 Ma). Biotites from non-retrograded segments of the gneiss terrane record 40Ar/ 39Ar plateau and isochron ages which date times of cooling following an episode of the Kenoran orogeny (2376–2391 Ma). A suite of gneiss samples displaying varying degrees of retrograde alteration was collected across the Grenville metamorphic gradient. Biotites in these samples show no petrographic evidence of retrograde alteration, however they do record internally discordant 40Ar/ 39Ar age spectra. Although the extent of internal discordance is variable, the overall character of the release patterns is similar with younger apparent ages recorded in intermediate-temperature gas fractions. The total-gas dates range from 2257±27 Ma (northwest) to 1751±23 Ma (southeast), suggesting that variable quantities of radiogenic argon were lost from the Archean biotites during Grenville metamorphism. The “saddle-shaped” nature of the discordant spectra indicates that argon loss was not accomplished through single-stage, volume diffusion processes. Biotites in portions of the gneiss terrane which were completely recrystallized during Grenville metamorphism are petrographically and texturally distinct. A representative of this phase records a 40Ar/ 39Ar plateau age of 2674±28 Ma. This date is markedly inconsistent with regional constraints on the timing of Grenville metamorphism, and indicates the presence of extraneous argon components. Both the extraneous and radiogenic argon components must have been liberated in constant proportions during experimental heating because the argon isotopic data yield a well-defined 40Ar/ 36Ar vs. 39Ar/ 36Ar isochron corresponding to an age (2658±23 Ma) similar to that defined by the plateau portion of the spectrum. The 40Ar/ 39Ar biotite dates suggest that the effects of Grenville metamorphism extent 15–20 km northward into the Superior Province. The limit of this overprint is approximately coincident with the northernmost development of Grenville age thrust faults in the Archean terrane. Therefore, it is proposed that the northern margin of the Grenville Province in southwestern Labrador should be located along the northernmost Grenville thrust fault because this represents both a structural and a thermal discontinuity.

Ocean features observed from manned spacecraft that influence acoustics in the upper ocean

Ocean fronts, eddies, and internal waves have been observed, photographed, and imaged by synthetic aperture radar during the first four orbital missions of the space shuttle, Columbia. Supporting data show that the visual features correspond to thermal discontinuities, have significant vertical extensions, act as barriers to underwater acoustics, and can be detected by synthetic aperture radar regardless of sky conditions or time of day. Although one thinks of these sea‐surface manifestations as having a certain ubiquity, presently available information seems to show that they are concentrated both generically and geographically. This concept is to be addressed from Columbia and Challenger during 1983.

Observations on the surface water characteristics in the western Irish Sea: July 1977

Distributions of physical, chemical and biological characteristics observed in the frontal region of the western Irish Sea during July 1977 are presented. High chlorophyll concentrations and phytoplankton cell numbers were associated with the lateral thermal discontinuity. The characteristics of the stratified and mixed waters varied along the length of the front, such that the changes recorded across each frontal transect were unique. The qualitative composition of the diatom population on either side of the front, however, was distinctive. Observations, concentrated on one transect, showed that the diatom population at the front was a mixture of the populations on either side, and that the high phytoplankton standing crop there was predominantly stimulated by nutrient complementation.

The Mathematical Theory of Frontogenesis

For over one hundred years it has been known that atmospheric depressions have cold frontal regions in which typically the temperature falls rapidly, the wind changes, and precipitation occurs. Sixty years ago Norwegian meteorologists shaped their polar front model in which depressions were considered to grow on a preexisting sloping thermal discontinuity; as the depressions grew it was considered that they distorted the discontinuity into a cold front and also a warm front. The dynamical view changed thirty years ago with the discovery by Charney (1947) and Eady (1949) that realistic depression structures may be obtained as the normal modes of the baroclinic instability of a smooth rather than discontinuous thermal contrast. Fronts then had to be viewed as being formed in a growing nonlinear baroclinic wave, though this secondary role in no way diminished their importance in practical meteorology. The theoretical interest shifted towards the mechanism for generating fronts, namely frontogenesis. When upper air data became available in the 1950s it was apparent that strong frontal regions occurred in the upper troposphere as well as near the surface. Many studies (e.g. Reed & Danielsen 1959) suggested strongly that these upper air fronts are associated with the descent of a tongue of stratospheric air into the troposphere. The existence of fronts in the ocean has been known for many years and when vertical sections were obtained (e.g. Voorhis & Hersey 1964 and Katz 1969) they suggested many structural similarities with atmospheric fronts. Further, the experimental work of Fultz (1952) and Faller ( 1956) has shown that fronts can be reproduced in laboratory experiments using differentially heated rotating water. Thus we conclude that details of latent·heat release and other diabatic heating, and of the boundary layer

Depth and velocity of the laser-melted front from an analytical solution of the heat conduction equation

Analytical solutions for the penetration of the melting front are found by solving the motion equation of the fusion interface, obtained by the conduction heat equation for the liquid region, and by the energy conservation at the fusion front. The problem of temperature dependence of the thermal properties of the material is resolved by introducing new temperature scales; moreover, the discontinuity in the value of the thermal conductivity at the fusion interface is taken into account. Solutions are obtained both for constant and Gaussian light beams, and also for the case of constant thermal properties, while introducing the thermal conductivity discontinuity at the fusion interface. Numerical results for the specific case of Si are presented both for constant and variable thermal parameters, which compare favorably with the results obtained by computer programs.

A Study of a Thermal Discontinuity in Well Test Analysis

Summary The presence of zones of different temperatures in nonisothermal reservoirs may resemble permeability boundaries during well testing. This investigation employed numerical modeling to examine such effects in drawdown, buildup, and injection well tests. The results indicate that nonisothermal influence can be detected and accounted for by tests of sufficient duration with suitably placed observation wells. Introduction A challenge to the interpretation of well test results from nonisothermal reservoirs is the effect on the pressure response due to fluid and rock temperature-dependent properties. Since zones of different temperatures in the reservoir may resemble permeability boundaries, care in interpretation of results is required. This study is an examination of these temperature effects on well test data where the producing well is completed in the center of a circular hot zone surrounded by a concentric cooler water region. The investigation was carried out with the intent of comparing the results of such tests with the classical Theis solution and discovering ways in which temperature differences can be accounted for in well test data analysis.Only recently have there been discussions of nonisothermal well testing in the literature. An analytical study by Tsang and Tsang motivated this study by giving semilog results to be expected from cold-water injection into a hot reservoir. By assuming a specific form for the variation of the permeability/viscosity ratio (k/mu) across the transition zone (from cold to hot water), they were able to derive solutions that follow the classic Theis curve for each region. From early- and later-time data, reservoir transmissivity (kh/mu) and storativity (phi ch) can be determined so that compressibility (c), reservoir permeability (k), porosity (phi), and thickness (h) can be evaluated. Their results prompted this numerical investigation of viscosity effects where production, buildup, and partial-penetration well tests are considered. Background The standard methods of well test data analysis in isothermal reservoirs have been documented thoroughly by Earlougher. The problems of well testing in geothermal reservoirs have been discussed by only a few authors in the past decade. Recently, Narasimhan and Witherspoon have reviewed the problems in carrying out and analyzing well tests in these systems. They mention that the conventional concept of transmissivity should be replaced by absolute permeability (k) or the product kh. In another recent study of reinjection at the East Mesa geothermal area, pressure distributions based on viscosity ratios of 1:1.9 between hot and cold water were described. The semilog plots show a distinctive change in slope at the cold front. The approach used, however, was a series of steady-state runs with the cold front at varying distances from the production well and with energy and mass transport equations decoupled. Rice used computer models to describe drawdown and buildup tests in single- and two-phase reservoirs under isothermal conditions. Earlier, Chappelear and Volek Modeled the injection of a hot liquid into a porous medium using temperature-dependent viscosity. They assumed that specific heat and density were independent of temperature, and they calculated temperature (not pressure) distributions within the reservoir, caprock, and bedrock. JPT P. 1095^

Effect of Temperature on the Synthesis and Secretion of α-Amylase in Barley Aleurone Layers

The effect of temperature on alpha-amylase synthesis and secretion from barley (c.v. Himalaya) half-seeds and aleurone layers is reported. Barley half-seeds incubated at 15 C in gibberellic acid (GA) concentrations of 0.5 and 5 micromolar for 16 hours do not release alpha-amylase. Similarly, isolated aleurone layers of barley do not release alpha-amylase when incubated for 2 or 4 hours at temperatures of 15 C or below following 12 hours incubation at 25 C at GA concentrations from 50 nanomolar to 50 micromolar. There is an interaction between temperature and GA concentration for the process of alpha-amylase release from aleurone layers; thus, with increasing GA concentration, there is an increase in the Q(10) of this process. A thermal gradient bar was used to resolve the temperature at which the rate of alpha-amylase release changes; thermal discontinuity was observed between 19 and 21 C. The time course of the response of aleurone tissue to temperature was determined using a continuous monitoring apparatus. Results show that the effect of low temperature is detectable within minutes, whereas recovery from exposure to low temperature is also rapid. Although temperature has a marked effect on the amount of alpha-amylase released from isolated aleurone layers, it does not significantly affect the accumulation of alpha-amylase within the tissue. At all GA concentrations above 0.5 nanomolar, the level of extractable alpha-amylase is unaffected by temperatures between 10 and 28 C. It is concluded that the effect of temperature on alpha-amylase production from barley aleurone layers is primarily on the process of enzyme secretion.

Effect of fatty acids on physical properties of microsomes from isolated perfused rat liver

A computer-centered spectrofluorimeter was used to examine the physicochemical properties of hepatic microsomes and microsomal lipids obtained from isolated rat livers perfused with medium containing palmitate or oleate. The fatty acid composition and degree of unsaturation of the liver microsomal lipids reflected that the fatty acid present in the perfusate. The absorption corrected fluorescence, relative fluorescence efficiency, polarization, and fluorescence anisotropy of several fluorescent probe molecules were measured to determine if their different microenvironments may be altered by the type of fatty acid infused. The probe molecules β-parinaric acid and 1.6-diphenyl-1,3,5-hexatriene had higher values for each of these parameters when incorporated into microsomes obtained from livers perfused with a medium containing palmitate than with oleate. The same parameters measured for cholesta-5,7,9(11)-trien-3β-ol and N-phenyl-1-naphthylamine were not altered. These differences appeared to be primarily due to alterations in microviscosity of the probe microenvironments since the rotational correlation time of 1,6-diphenyl-1,3,5-hexatriene was 25% lower in the microsomes from livers perfused with oleate as compared to livers perfused with palmitate. Thermal discontinuities in Arrhenius plots were noted in the intact microsomes but not in the isolated microsomal lipids with the fluorescence probe molecule β-parinaric acid. Break points occurred at 10°C and 26°C for microsomes from livers perfused with palmitate and at 12°C and 17°C for microsomes from livers perfused with oleate containing medium. These results suggest that the physicochemical properties of liver microsomes were determined in part by the fatty acid in the perfusate.

Diurnal variation of phytoplankton in Loch Lomond

A study of diurnal variation over a 48 hour period was undertaken in July 1973 to ascertain the extent and timing of some major chemical, physical and biological variables in Loch Lomond. The phytoplankton population was dominated by the diatom Tabellaria fenestrata, with a maximum abundance between 04.00 and 06.00 h in surface waters on both days. A distinct diurnal variation in cell numbers was also recorded. Chlorophyll a values also showed a regular pattern of variation with a single peak between 10.00 and 14.00 h each day. Some chemical changes appeared to be a direct consequence of phytoplankton multiplication. Nitrate-nitrogen showed a decrease in concentration coinciding with the period of cell multiplication, whereas dissolved silica concentrations only fell on the completion of this process. Other common diatoms displayed less distinct patterns of variation although Fragilaria crotonensis attained its maximum abundance in surface waters. Considerable variation was recorded in the number of organisms and chlorophyll a levels at 25 cm intervals in the upper metre of the water column, with large variations in standing-crop and chemical parameters in the space of one hour. Diurnal oscillations in the position of the thermocline were recorded, with the thermal discontinuity being at its greatest depth in the early hours of the morning. The hypolimnion and thermocline regions clearly acted as a source of nutrient supply to the epilimnion. From this investigation it is apparent that for the proper understanding of diurnal variation a 24 hour study alone is insufficient and may give rise to misleading results.

Static Pressure Measurements of Enclosure Fires.

Some enclosure-fire static pressure measurements are presented for both full and scale model rooms and are compared with the present hydraulics-orifice flow model for fire induced flows into and out of enclosures. Results indicate that the vertical pressure differential (enclosure to ambient) follows the expected hydrostatic distribution quite well and accurately reflects the doorway inflow and outflow gas velocities. Measurement of ceiling and floor differential pressure using different numbers of gas burners yields insight into gross plume entrainment and illustrates how the neutral plane and thermal discontinuity vary with upper gas temperature. Correlating upper gas temperature with fire size and enclosure height makes it possible to predict at what heat release rate a given enclosure might become fully involved, i.e., by using the temperature at which the thermal discontinuity approaches the floor. In terms of present fire plume modeling large entrainment coefficients (0.3-0.4) are required in order to reproduce the enclosure flows for both the small and large scale results. A noted deficiency in the plume model appears in the small scale results where the data suggest that the entrainment should exhibit a much stronger dependence on the fuel injection rate than that predicted by the theory.

Age-Related Alterations in Membrane Lipid and Protein Interactions: Arrhenius Studies of Microsomal Glucose-6-Phosphatase

Arrhenius plots of glucose-6-phosphatase (EC 3.1.3.9) activity in liver microsomes from 6-month-old rats (young) showed discontinuities at 39, 30, 20 and 12 degrees C and change in activation energy at 20 degrees C. The enzyme activity in kidney microsomes of young rats showed essentially the same thermal discontinuities. In liver microsomes of 24-month-old rats (old) the enzyme showed discontinuities at 38, 30, 24 and 16 degrees C but not at 12 degrees C and the activation energy changed at 24 degrees C. In kidney microsomes of old rats discontinuities were seen at 38, 31, 22, 16 and 12 degrees C and the activation energy was constant from 0 to 41 degrees C. These results indicate that the interactions of membrane components are altered with age.

Multiple thermal discontinuities in glucose-6-phosphatase activity

The temperature dependence of glucose-6-phosphatase ( d-glucose-6-phosphate phosphohydrolase EC 3.1.3.9) was studied in rat liver and kidney microsomal fractions. Arrhenius plots were non-linear and showed four distinct discontinuities in enzyme activity over the temperature range 2–41°C. The discontinuities occurred at approx. 39, 30, 20 and 12°C in the liver and were similar to this in the kidney. Changes in the energy of activation for the enzyme were noted at approx. 20°C in both tissues. The multiple discontinuities in glucose-6-phosphatase activity are viewed as a reflection of complex reorganization and/or change in physical state of the membrane components, primarily lipid.

Nonsymmetric buckling of cylinders with axisymmetric thermal discontinuities.

Two problems are treated: an infinite cylinder heated uniformly over half of its length and a clamped cylinder with an axial thermal gradient near the edge. In both cases the cylinders are free to expand axially. The cylinder heated along half of its length does not buckle at any temperature because the destabilizing effect of the circumferential band of hoop compression near the thermal discontinuity is more than counteracted by the stabilizing effect of the shape change of the cylinder as it is heated. Predicted buckling temperatures of clamped cylinders are strongly dependent on details of the thermal gradient very close to the clamped edge. Agreement with test results is obtained only if prebuckling meridional rotations are included in the stability analysis.

Thermal neutron transport near a moderator discontinuity using the method of weighted residuals: III. Temperature discontinuities in graphite and light water

A detailed analysis is made of the spatial variation of the effective thermal neutron temperature near temperature discontinuities in large volumes of graphite and light water. For graphite comparisons are made with recent measurements by Day. It is seen that it is important that proper consideration be made for the gradient of the epithermal flux. For water a number of predictions are made for both poisoned and unpoisoned systems and some doubt is cast on the feasibility of such measurements for determining the accuracy of different scattering kernels for light water. It is demonstrated, for both graphite and light water, that additional information can be obtained by extracting neutron beams at angles other than perpendicular to the axis of the system.

The Design and Operation of an Acoustic Radar

The history and theory of the acoustic radar are briefly reviewed. It is pointed out that scattering of sound by the atmosphere is produced by temperature and wind fluctuations, but that only temperature variations produce backscatter. Concepts for using the acoustic radar to measure profiles of temperature, wind, and humidity are discussed. A technique for measuring humidity profile using the relationship between attenuation of sound and absolute humidity is described. Design of the acoustic radar components is discussed with particular emphasis given to the problem of the antenna design. Some of the results of eight months of operation of the system are discussed. One case in which the acoustic radar was able to detect the passage of a thermal structure discontinuity not detectable by conventional observational and analysis techniques is described. It is concluded that the analog form of the data has great potential usefulness for continuously monitoring the thermal structure of the lower troposphere. Further measurement of wind and humidity profiles, and perhaps also the temperature profile to heights of a few thousand feet by means of the acoustic radar, seems feasible if the signal-to-noise ratio in the present system can be improved.

Structure of a viscous isoelectron thermal discontinuity in a plasma

The structure of a plane stationary shock wave in a dense high-temperature plasma has several distinguishing features. These features have mainly been described and studied in [1–4] (also see survey [5]). As has been demonstrated in these studies, the structure of a shock wave in a plasma is discontinuous for rather large Mach numbers: within the wave, there is a jump in the ion temperature, density, and velocity of the plasma (the electron temperature remains constant). The importance of radiation in this case reduces to some effect on the conditions for formation of the discontinuity if, of course, the photon mean free path is considerably greater than the particle mean free path. This discontinuity is naturally called a viscous isoelectron thermal discontinuity.