Steady-state Thermal Conditions Research Articles

Thermal Stresses During Quenching of Short Glass Cylinders

The thermal stresses are calculated during quenching of short glass cylinders for materials used in solid‐state laser devices. The stresses are determined numerically, and they are parameterized by the Biot number which characterizes cooling by convection. The solution is compared to the stresses for flat, penny‐shaped and for long, rod‐shaped cylinders. The validity of the steady‐state thermal boundary conditions is discussed.

Two-dimensional condensing vapor flow on parallel flat plates in an enclosure

A vapor flow of pure fluid condensing onto a vertical flat plate in an enclosure was examined in order to develop knowledge of the mechanism of vapor condensation and flowfield characteristics. A specific Pyrex glass thermosyphon-like container filled with a certain amount of pure fluid, with or without noncondensable gas, was heated and the upward vapor flow between a pair of cooled parallel plates installed in the upper portion of the container was investigated by means of temperature and pressure sensors as well as laser holographic interferometry. With a pure fluid only (single-component, two-phase flow) in the container, the entire flowfield of condensation region is uniform in density and temperature. On the other hand, with a pure fluid containing a noncondensable gas (two-component, two-phase flow), a distinct flowfield structure is obtained. Its characteristics are: (1) the flowfield in the vapor/gas mixing region has a clear interfacial layer in the longitudinal or axial direction and a rather thick boundary layer near the cooled plate; (2) the condensing vapor flow has an oscillatory character with a low frequency of around 1 Hz, even in the steady-state flow and thermal conditions; and (3) sharp pressure drop was observed at the initiation of nonequilibriummore » vapor condensation when a large temperature difference existed between the vapor and the cooled plates. 12 references.« less

Thermal effects in radiation processing

The balance of ionizing radiation energy incident on an object being processed is discussed in terms of energy losses, influencing the amount really absorbed. To obtain the amount of heat produced, the absorbed energy is corrected for the change in internal energy of the system and for the heat effect of secondary reactions developing after the initiation. The temperature of a processed object results from the heat evolved and from the specific heat of the material comprising the object. The c p of most materials is usually much lower than that of aqueous systems and therefore temperatures after irradiation are higher. The role of low specific heat in radiation processing at cryogenic conditions is stressed. Adiabatic conditions of accelerator irradiation are contrasted with the steady state thermal conditions prevailing in large gamma sources. Among specific questions discussed in the last part of the paper are: intermediate and final temperature of composite materials, measurement of real thermal effects in situ, neutralization of undesired warming experienced during radiation processing, processing at temperatures other than ambient and administration of very high doses of radiation.

Transient Annealing of Ion-Implanted Silicon Using A Scanning IR Line Source

ABSTRACTRecent interest in finding an efficient method for transient annealing of ion-implanted silicon has led to studies of various rapid annealing schemes such as graphite heaters and high intensity incoherent light sources as alternative methods to laser annealing. In this paper, we describe a recent study of transient annealing of ion-implanted silicon using a scanning IR line source created by a single tungsten filament enclosed in a quartz envelope. Various dopants (B+, P+ and As+) with fluences of 1014 to 1016 ions/cm2 were implanted and annealed under both transient and steady-state thermal conditions. Dopant depth distributions were analyzed using the SIMS technique. Sheet resistance measurements indicated that almost 100% activations of the implanted dopants were achieved. Sensitivities of dopant activation to transient annealing conditions were studied as a function of dopant concentrations, and high-dose As- and B-implanted samples were found to be sensitive to transient thermal cycle, particularly to the peak temperature. Recrystallization was studied with Rutherford backscattering spectroscopy using 2 Mev He+ ions.

Thermal régime of the northern Bay of Biscay continental margin in the vicinity of the D. S. D. P. Sites 400-402

Average heat flow values on land in western Europe are about 2 h.f.u., whereas recently acquired surface-ship measurements and the downhole heat flow determinations at D.S.D.P. Site 402 indicate that the heat flow is only about one-half of this value over the continental slope and rise of the adjacent northern Bay of Biscay margin in the vicinity of the D.S.D.P. Sites 400- 402. Assuming that both the margin and the adjacent continental area are close to steady state thermal conditions, we suggest that the observed heat flow contrast reflects different radioactive crustal contributions to the surface heat flow in the two areas. Under the margin, the crust is thinner and would have a smaller radioactive contribution, the decrease in the contribution being related to the nature of the crustal thinning process under the margin. The heat flow data are compatible with a model of crustal thinning that considers this to be mainly a result of mechanical deformation of the crust through extension.

Numerical method of determining the boundary conditions at the surfaces of a continuous casting from the profile of the solidification front

A stable numerical method of solving the inverse Stefan type of heat-conduction problem is proposed. An applied thermophysical problem is then examined — that of calculating the boundary conditions on the cooled surface of a solidifying continuous circular casting under practically steady-state thermal conditions. The calculated results are compared with experimental data.

Calculation of steady-state thermal conditions of a multi-block evaporator with a steam-jet compressor

Calculation of steady-state thermal conditions of a multi-block evaporator with a steam-jet compressor

Steady-state thermal gradient in the sediments of a meromictic lake

Steady-state thermal conditions have been found in the sediments of a small meromictic lake. The temperature gradient at the center of the lake is constant and has a value of 0.20°C/m during the year. Total heat flow through these sediments is calculated to be 2.8 × 10−6 cal/cm² sec. Approximately half of this flux is attributed to the temperature contrasts between the rim and the central portion of the lake's basin.