Shell Surface Temperature Research Articles

Study on solidification and heat transfer of billet shell in a new-structure high-speed continuous casting mold

In this work, a three-dimensional finite element model of a newly structured high-speed continuous casting mold was established to study the heat transfer and solidification process of the billet shell. A complete billet shell, from the meniscus to the secondary cooling zone, was obtained through flame cutting. Using both simulations and test verification, detailed analyses were conducted on the temperature field distribution, thickness variation law, and cooling rate law of the billet shell within the mold, revealing its solidification behavior. Additionally, the effects of casting speed, molten steel superheat, and mold taper on the solidification behavior of the billet shell were discussed. Results showed that the simulation data were basically consistent with the test verification results. Within 200 mm from the meniscus, the heat dissipation accounted for three-quarters of the mold's total heat dissipation. The cooling rate at the corners of the billet shell was slightly higher than that at the sides. Between 200 mm and 400 mm from the meniscus, air gaps caused the temperature at the corners of the billet shell to rise. Afterwards, the whole billet shell eventually reached a similar the heat dissipation rates. The thickness of the billet shell increased exponentially within 110 mm from the curved meniscus, and from 110 mm to the exit of the mold, the thickness increased linearly but slowly. The effect of molten steel superheat within a range of 10 °C on billet shell solidification was relatively minor. Increasing the casting speed reduced the billet shell thickness and raised the billet shell surface temperature. However, increasing the taper of the mold had the opposite effect. Both adjustments shifted the gap formation position backward.

Economic and heating efficiency analysis of double-shell downhole electric heater for tar-rich coal in-situ conversion

Downhole electric heater studied in this paper is used for tar-rich coal in-situ conversion, and the closed double-shell structure is proposed to improve the performance and economy of heater. In this paper, four downhole electric heaters were experimentally studied, and the single-shell heater was used as the control. According to the experimental results, it can be seen that the mass flow rate has a great impact on the total cost, and the parallel double-shell downhole electric heater has the highest total cost. In addition, the larger the helical pitch or the heater shell diameter, the lower the heater shell surface temperature, and thermal radiant is the main way of heater shell to lose heat, which is accounts for 78.91%–92.91%. Moreover, from the perspective of heat transfer quality, heater with closed double-shell structure is more efficient than the single-shell heater, and the energy utilization efficiency of heater with closed double-shell structure achieves 97.38%–99.59%. Finally, taking the comprehensive cost of in-situ exploitation of tar-rich coal into account, the small outer shell diameter is an optimal choice for the heater with closed double-shell structure.

Combined Study on Mold Taper and Corner Radius in Bloom Continuous Casting by FEM Simulation and Trial Experiment

A plane stress model was developed to study the coupled effect of mold taper and corner radius on the thermal–mechanical behavior of a 250 mm × 280 mm continuously cast bloom for a given special steel. Good agreement was obtained in both shell thickness and the off-corner cracking location from modeling and trial experiment. The results show that increasing mold taper results in the obvious decrease of surface temperature near the corner, while enlarging mold corner radius makes the shell surface temperature at the corner region more even with the mold taper between 0 and 1.5% m−1. It is also found that both the mold corner radius and taper are the key factors influencing the shell crack sensitivity but with different mechanism. For the internal crack, the mold taper takes more dominant effect for its corner radius between 0–10 mm, as the hoop strain at the solidification front decreases with increasing mold taper. For the surface crack, more sensitivity is noticed to the mold corner radius. Increasing mold corner radius leads to the increase of the surface hoop strain in the corner region, almost regardless of mold taper. The proper mold taper and corner radius for the present bloom casting should be 1.0–1.5% m−1 and 15–25 mm respectively.

Relevance of body size and shell colouration for thermal absorption and heat loss in white garden snails, Theba pisana (Helicidae), from Northern France

The internal temperature of land snails depends on environmental factors, such as exposure to electromagnetic radiation and airflow as well as biotic factors including shell size, shell colouration and thickness or the resting position of the snail. In controlled field experiments, we quantified heating by thermal absorption of light and airflow-induced heat loss in the white garden snail, Theba pisana, from Normandy, France. Heating experiments revealed a significant positive relation of the internal body temperature with illumination period, shell temperature and air temperature at different times of day. The size of the snails was negatively related with both of the given illumination times: smaller animals heated up stronger than larger ones. The temperature at the surface of the shell significantly depended on the illumination period and the time of day. An AIC-based quality assessment of multiple linear modelling showed that, for explaining both shell surface and internal temperature of the soft body, several factors, i.e., exposure time, daytime, shell size and colouration contributed to the best models, respectively. Similarly, heat loss of the soft body after and during exposure of the snails to sunlight by a constant airflow depended on the initial body temperature, shell size, colouration and ambient air temperature. Our study revealed also the importance of both shell size and colouration for the loss of body temperature under natural conditions: small and banded animals that had heated up to temperatures above 30°C cooled down faster than large and un-banded ones.

Numerical analysis of the influence of carbon content on the initial shell of continuous casting slab

ABSTRACTA numerical model for calculation of temperature and thermal stress in initial steel shell in plate and grooved slab continuous casting moulds was established to predict the influence of steel carbon content on the temperature and stress fields. The calculated results show that the temperature non-uniformity and surface stress of the initial shell increase as the steel temperature decreases. Among the steel grades with carbon contents of 0.06, 0.17, 0.45 and 0.80 wt-%, the initial shell surface stress of steel with 0.17 wt-% (peritectic steel) is the highest. In the grooved mould the temperature non-uniformity and surface stress of the initial shell are significantly lower than those in the plate mould. At 1.7 s after initial shell formation, the non-uniformity of shell surface temperature and stress in the grooved mould are four to nine times and three to nine times, respectively, lower than those in the plate mould.

Analysis of the Thermal Contraction of Wide‐Thick Continuously Cast Slab and the Weighted Average Method to Design a Roll Gap

A three‐dimensional (3D) thermo‐mechanical coupling model is established to describe the uneven solidification and thermal contraction behavior during the process of continuous casting of wide‐thick slabs. To improve the accuracy of the simulated results, the thermal and mechanical material properties are calculated with the weighted average phase fraction method, and the boundary conditions is derived from the actual measured water flux distribution. The predicted heat transfer results are verified with the measured shell thickness and surface temperature. With this model, the non‐uniform heat transfer and thermal contraction behavior under different casting conditions are investigated. Finally, a weighted average method to design the roll gap is proposed and implemented into practical production. The results from the plant after the roll gap optimization indicate that the internal quality of the wide‐thick slab is dramatically improved and that the casting operation is more stable.

CFD modeling of moisture accumulation in the insulation layers of an aircraft

Modern commercial airplanes operate in an extreme atmospheric environment, where they can easily acquire a large amount of moisture within the porous insulation layers. The accumulated moisture may increase the aircraft’s weight, induce corrosion, and degrade thermal and sound insulation performance. This investigation proposes a numerical model to predict moisture and heat transfer within porous insulation blankets. To capture natural convection flows of gases within the porous material, the volumetric-based Navier–Stokes equations were solved. The moisture in three phases was considered and the phase change rates between any two phases were predicted. The latent heat of absorption or release during phase changes is balanced with the heat conduction in the mixture and the heat convection of the gaseous substances. To validate the model, the moisture gain in a reduced-scale aircraft mockup was measured by placing the mockup inside an altitude psychrometric chamber. Then the validated model was applied to predict the moisture accumulation in a rectangular insulation block from a Boeing 777 airplane. The results reveal that the flight altitude and cabin humidity are the two key parameters determining the moisture accumulation rates. A high outer shell surface temperature is helpful for reducing moisture gain in the insulation blankets.

Generalized constructal optimization for solidification heat transfer process of slab continuous casting based on heat loss rate

Based on constructal theory, generalized constructal optimization of a solidification heat transfer process of slab continuous casting is carried out by taking a complex function as optimization objective. The complex function is composed of the functions of the heat loss rate and surface temperature gradient of the slab subjected to the constraints of shell thickness, surface temperature and liquid core length of the slab. For the specified total water flow rate, the “optimal construct” of the water distribution in the secondary cooling zone is obtained. Comparing the optimal results with the initial ones, it is shown that the complex function, the functions of the heat loss rate and the surface temperature gradient after optimization are decreased by 35.04%, 2.14% and 59.48%, respectively. Therefore, the scheme of the “optimal construct” of the water distribution reduces the heat loss rate and surface temperature gradient of the slab simultaneously, that is, improves its energy retention and quality simultaneously. The optimization results obtained in this paper can provide some guidelines for parameter designs and dynamic operations of the solidification heat transfer process of slab continuous casting.

Solar radiation stress in climbing snails: behavioural and intrinsic features define the Hsp70 level in natural populations of Xeropicta derbentina (Pulmonata)

Ectotherms from sunny and hot environments need to cope with solar radiation. Mediterranean land snails of the superfamily Helicoidea feature a behavioural strategy to escape from solar radiation-induced excessive soil heating by climbing up vertical objects. The height of climbing, and also other parameters like shell colouration pattern, shell orientation, shell size, body mass, actual internal and shell surface temperature, and the interactions between those factors may be expected to modulate proteotoxic effects in snails exposed to solar radiation and, thus, their stress response. Focussing on natural populations of Xeropicta derbentina, we conducted a 'snapshot' field study using the individual Hsp70 level as a proxy for proteotoxic stress. In addition to correlation analyses, an IT-model selection approach based on Akaike's Information Criterion was applied to evaluate a set of models with respect to their explanatory power and to assess the relevance of each of the above-mentioned parameters for individual stress, by model averaging and parameter estimation. The analysis revealed particular importance of the individuals' shell size, height above ground, the shell colouration pattern and the interaction height × orientation. Our study showed that a distinct set of behavioural traits and intrinsic characters define the Hsp70 level and that environmental factors and individual features strongly interact.

Numerical Simulation of Billet Continuous Casting Solidification Based on the Measurement of Shell Thickness and Surface Temperature

In order to more accurate simulation the solidification of billet continuous casting. The measured shell thickness and surface temperature have been used to revise the heat transfer model. The calculated results of the model are in excellent agreement with the experimental ones based on an actual casting machine. The revised model can excellent to simulate the billet solidification process. So it provides the possibility for better simulation the dynamic solidification process and optimizing of the secondary cooling water.

Flow and Thermal Characteristics of Condensing Steam in a Single Horizontal Mini-Channel of a Multiport Cylinder Dryer

In papermaking processes it is well known that the dryer uses the greatest amount of energy and has costly components compared with other devices. These dryers thus offer outstanding opportunities for energy savings and cost reduction. Recently, Argonne National Laboratory developed the concept of a multiport cylinder dryer in which the steam flows through “ports,” or longitudinally oriented mini-channels, which are close to the cylinder–dryer surface. It was reported that the innovative design minimized the condensate layer thickness and increased the dryer shell's surface temperature. However, no systematically obtained experimental data are available. In this study we conducted experiments to investigate the flow and thermal characteristics of condensing steam in a single horizontal mini-channel, which represents a part of a multiport cylinder dryer. Based on the results, the flow pattern through a single horizontal mini-channel is presented. Also, we observed that the condensing heat transfer coefficient in the single horizontal mini-channel was about seven times higher than that of a conventional dryer with spoiler bars. Finally, the effects of the steam mass flux, system pressure, and aspect ratio of the mini-channel on the average condensing heat transfer coefficients as well as the pressure drops are presented.

Thermal preference of the yellow-margined box turtle (Cuora flavomarginata) (Testudines: Geoemydidae) inhabiting a mesic lowland forest, northern Taiwan

AbstractThermal preference of free-living yellow-margined box turtle, Cuora flavomarginata, was studied in a mesic forested habitat using a combination of radiotransmitters and temperature dataloggers attached to individual turtles. Patterns of mean weekly shell surface temperature variation of selected individuals were highly related to seasonal change of environmental temperature, with a peak temperature of 24.5-25.1°C in males and 26.0-27.0°C in females during June and July. Minimum shell surface temperature occurred in late January (4.5-7.6°C). Despite a small sample size, there were significantly intersexual differences in mean weekly shell surface temperature during nesting season. Individual females of C. flavomarginata tended to maintain higher shell surface temperature during nesting season (May-July). This difference was mostly pronounced during the day. There were no obviously intersexual differences prior to and after nesting season. Our results do not support the previous predictions that gravid C. flavomarginata may select higher environmental temperatures prior to nesting season.

Applying of Real-time Heat Transfer and Solidification Model on the Dynamic Control System of Billet Continuous Casting

In this paper, a real-time mathematical heat transfer model for billet continuous casting of low carbon steel has been presented and solved by finite volume method. This model can be used to simulate the casting conditions which vary frequently. As taking the variation of superheat of liquid steel into consideration in the water flow rate distribution, the fluctuation of billet surface temperature has been decreased. Meanwhile the fluctuation of measured temperature has been largely reduced when it is measured with thermal imager. The mathematical model has been validated by measuring shell thickness and surface temperature in industrial caster. The on-line model can monitor surface temperature and shell thickness along the caster machine in the casting process, and it has been applied on the dynamic control system to adjust the operation parameters. The billet defect has been decreased greatly and the quality of billet has been obviously improved.

Modeling the heat flow in spray formed steel shells for tooling applications

This article concerns a metal spraying process for the manufacture of production tooling at reduced time and cost. Critical to the successful operation of this process is control of the sprayed steel shell temperature to eliminate thermal residual stresses and distortion. A computational model of the transient heat flow in steel shells during spray forming has been developed. The critical data for the distribution of convective heat-transfer coefficient distribution over the shell surface and average spray temperature has been obtained from experiments using embedded calorimeters and process monitoring respectively. Shell average temperature and temperature variance have been investigated using the model, and predictions compared well with experimental measurements obtained using infrared thermal imaging. The wire feed rate was identified as the most suitable control parameter for a closed loop control system to regulate shell surface temperature during manufacture.

A Numeric Study of the Dependence of the Surface Temperature of Beta-Layered Regions on Absolute Thickness

Beta-layering of deuterium-tritium (D-T) ice in spherical shell geometries is numerically and analytically considered to investigate the relationship between temperature differences that arise because of inner-surface perturbations and the absolute shell thickness. The calculations use dimensions based on a proposed design of an inertial confinement fusion target for use at the National Ignition Facility. The temperature differences are calculated within D-T ice shells of varying total thicknesses, and the temperature differences calculated in three dimensions are compared both to the one-dimensional results and to the expected limits in three dimensions for long- and short-wavelength surface perturbations. The three-dimensional numeric results agree well with both the long- and short-wavelength limits; the region of crossover from short- to long-wavelength behavior is mapped out. Temperature differences due to surface perturbations are proportional to D-T layer thickness in one-dimensional systems but not in three-dimensional spherical shells. In spherical shells, surface perturbations of long wavelength give rise to temperature perturbations that are approximately proportional to the total shell thickness, while for short-wavelength perturbations, the temperature differences are inversely related to total shell thickness. In contrast to the one-dimensional result, we find that in three dimensions there is not a general relationship between shell thickness and surface temperature differences.

Modeling incubation temperature: the effects of incubator design, embryonic development, and egg size

A simple model to describe the relationship between the temperature of the developing embryo, incubator temperature, embryo heat production, and thermal conductivity of the egg and surrounding air is presented. During early incubation, embryo temperature is slightly lower than incubator temperature because of evaporative cooling. However, from midincubation onwards, metabolic heat production from the embryo raises embryo temperature above incubator temperature. The extent of the rise in embryo temperature depends on thermal conductivity, which, in turn, is mainly influenced by the air speed over the egg. The importance of air speed and restrictions to air flow within artificial incubators is discussed. Exact determinations of optimum incubation temperatures from studies reported in the literature are difficult because only incubator temperatures are reported. Embryo temperatures can differ from incubator temperature because of differences in thermal conductivity between different incubation systems and differences between incubators in their ability to control temperatures uniformly. It is suggested that shell surface temperatures are monitored in experiments to investigate temperature effects to allow consistent comparisons between trials. Monitoring shell temperatures would also make it easier to translate optimum temperatures derived in small experimental incubators to the large commercial incubators used by the poultry industry. The relationship between egg temperature, the metabolism of the developing embryo and egg size is discussed.

Automated Spray Sanitizing of Broiler Hatching Eggs 1. Physical Characteristics of The Egg

This study examines the physical effects of spray sanitizing nest clean broiler hatching eggs with the MS Technologies, Inc. Mini-Master/4000® or by immersion dipping immediately following collection. The measurements taken during sanitizing were air, shell surface, and yolk surface temperatures. Researchers studied eggshell conductance, percentage egg moisture weight loss, and cuticle integrity following sanitizing. Treatments included non-sanitized controls and eggs sanitized by water dipping or automated spray washed with water, or spray washed and sanitized with chemical solutions. The automated spray washing consisted of two stages. In Stage 1, the temperature of the washing solution was 111°F, and in Stage 2 the temperature of the sanitizing solutions was 118°F. Automated spray sanitizing at fast processing speed (16 sec per flat) caused air and shell surface temperatures to rise by 28.4° and 20.3°F, respectively. These temperatures returned rapidly to pre-treatment temperature (83°F). Dipping eggs for 2 min in a sanitizer solution at 111°F resulted in a pattern of air and shell surface temperature increase and recovery similar to eggs sanitized by automation. Automated spray sanitizing caused a reduction in the shell cuticle, but cuticle removal was not severe enough to significantly increase eggshell conductance or percentage egg moisture weight loss.

Thermoregulation in the desert tortoise, Gopherus agassizii

1. 1. Deep body and shell surface temperatures were monitored via radio-telemetry from unrestrained desert tortoises in their natural habitat. 2. 2. The surface of the carapace acts as a buffer against solar radiation, resulting in deep body temperatures up to 10°C below shell surface at the time of the midday retreat to burrows. 3. 3. The burrow of the desert tortoise provides the only ambient temperatures at ground level which are below the lethal range for this species during midday hours. 4. 4. Evening retreat to burrows permits an extension of higher body temperatures into the mid-evening hours. 5. 5. The use of evening burrow retreats lessens in mid-summer. This behavioral change results in lower body temperatures at the onset of morning activity and permits a longer surface activity period in the face of rising ambient temperatures.