A Heat-Transfer Analysis of the Solidification of a Binary Eutectic System

1967 ◽  
Vol 89 (3) ◽  
pp. 230-233 ◽  
Author(s):  
R. H. Tien ◽  
G. E. Geiger
Keyword(s):  
Heat Transfer ◽  
Error Function ◽  
Pure Metal ◽  
Point Of View ◽  
Heat Transfer Analysis ◽  
Graphical Form ◽  
Eutectic System ◽  
Function Solution ◽  
Infinite Region ◽  
Binary Eutectic

The solidification of a binary system differs from a pure metal in that the latent heat effect no longer occurs at the melting point but rather in a freezing zone between the liquidus and solidus temperatures. Such solidification is analyzed from a heat-transfer point of view. The system considered occupies a semi-infinite region, is initially at the liquidus temperature, and at all subsequent times the surface temperature is considered constant; the fraction solid is assumed to be linear with distance within the freezing zone between the solidus and liquidus. The heat released during solidification is treated as a discontinuous heat generation. This corresponds to the nonequilibrium freezing of a eutectic system. The temperature distribution and thickness of each region are calculated as a function of time using the error function solution and the heat-balance integral; the results are given in graphical form.

The Unidimensional Solidification of a Binary Eutectic System With a Time-Dependent Surface Temperature

1968 ◽  
Vol 90 (1) ◽  
pp. 27-31 ◽  
Author(s):  
R. H. Tien ◽  
G. E. Geiger
Keyword(s):  
Temperature Distribution ◽  
Surface Temperature ◽  
Alloy System ◽  
Heat Transfer Analysis ◽  
Graphical Form ◽  
Eutectic System ◽  
Cu Alloy ◽  
Infinite Region ◽  
Binary Eutectic ◽  
Fraction Distribution

The realistic boundary condition of the surface temperature varying with time is used in the heat transfer analysis of the solidification of a binary eutectic alloy system. The system occupies a semi-infinite region and consists of a solid zone, a freezing zone, and a liquid zone. The heat released in the freezing zone is treated as a discontinuous heat generation. The solid-fraction distribution in the freezing zone, given as a function of temperature, is solved simultaneously with the temperature distribution, which is given as a function of distance within the freezing zone. Using the “heat balance integral” technique, the method for the solution of the temperature distribution and the thickness of each region is given. As an example, the results are shown in graphical form for an Al-5 percent Cu alloy.

Optimization of Radiating Fin Arrays With Respect to Weight

1976 ◽  
Vol 98 (4) ◽  
pp. 643-648 ◽  
Author(s):  
N. M. Schnurr ◽  
A. B. Shapiro ◽  
M. A. Townsend
Keyword(s):  
Heat Transfer ◽  
Minimum Weight ◽  
Heat Transfer Analysis ◽  
Graphical Form ◽  
Cylinder Surface ◽  
Optimization Approach ◽  
Space Applications ◽  
Rate Base ◽  
Triangular Profile ◽  
Weight Design

A nonlinear optimization approach is used to determine the minimum weight design for radiating fin arrays used in space applications. Straight and circular fins of rectangular and triangular profile are considered for emissivities in the range of 0.8 to 1.0. The heat transfer analysis includes fin to fin and fin to base radiative interactions. The results, presented in graphical form, give the optimum geometries for the profiles considered in terms of dimensionless parameters. Thus, for specified values of heat transfer rate, base cylinder surface temperature and thermal properties of the fin material, these curves may be used to design minimum weight fin arrays. Two numerical examples are given.

Insights on Heat Transfer at the Top of Steam Chambers in SAGD

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Helen Pinto ◽  
Xin Wang ◽  
Ian D. Gates
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Oil Sands ◽  
Error Function ◽  
Material Balance ◽  
Heat Transfer Analysis ◽  
Steam Chamber ◽  
Steam Assisted Gravity Drainage ◽  
Critical Issues ◽  
Gas Volume

Steam-assisted gravity drainage (SAGD) is the method of choice for producing oil from oil sands reservoirs. In this method, steam is injected into the formation and the oil, upon heating, is mobilized and driven under gravity to a production well. The accumulation of steam within the reservoir is referred to as the steam chamber. One of the critical issues confronting SAGD operators is the thermal efficiency, measured by the steam-to-oil ratio, of their operations since it directly ties to process costs. Using thermocouple profiles from observation wells on three SAGD fields in Alberta, we use error function fits to estimate the thermal conductivity of the shale above the oil formation (found to be from 0.33 to 3.81 W/mK), heat flux at the top of the steam chamber, vertical height of the steam/gas zone above the steam chamber, and accumulated gas volume present. A gas material balance is then derived to estimate the volume of gas that might be generated through in situ chemical processes. The results of the heat transfer analysis performed on the thermocouple data reveal that the gas co-injection during SAGD operations studied did not directly affect the heat transfer rate at the top of the steam chamber since the gas volume added was small. The results also show that a sufficiently large accumulation of gas at the top of the chamber lowers the heat flux at the edge of the chamber.

scholarly journals Enhanced heat transfer in H2O inspired by Al2O3 and γAl2O3 nanomaterials and effective nanofluid models

2021 ◽  
Vol 13 (5) ◽  
pp. 168781402110236
Author(s):  
Adnan ◽  
Umar Khan ◽  
Naveed Ahmed ◽  
Syed Tauseef Mohyud-Din
Keyword(s):  
Heat Transfer ◽  
Colloidal Suspension ◽  
Fluid Motion ◽  
Flow Characteristics ◽  
Heat Transfer Analysis ◽  
Flow Parameters ◽  
Thermal Improvement ◽  
Infinite Region ◽  
Layer Region ◽  
Performance Rate

Currently, thermal improvement in the nanofluids over a curved Riga sheet is a topic of interest and attained popularity among the researchers. Therefore, the colloidal suspension of water suspended by [Formula: see text] and [Formula: see text] over a curved Riga surface is modeled for the heat transfer analysis. The nondimensionalization of the model is accomplished via invertible variables. On the basis of dynamic viscosities and thermal conductivities of [Formula: see text] and [Formula: see text] nanoparticles, two nanofluid models developed over a semi-infinite region. Then, the models solved numerically and found graphical results for the flow characteristics, thermophysical properties and local thermal performance rate by altering the pertinent flow parameters. It is examined that the fluid motion rapidly decreases for [Formula: see text] and momentum boundary layer region decreases. The squeezed and curvature parameters lead to reduce in the nanofluid velocity. The temperature of more magnetized enhances significantly. Thermophysical characteristics of the nanofluids enhance for higher volumetric fraction factor. More heat transfer at the Riga surface for higher M and R.

scholarly journals Thermal Scaling of Transient Heat Transfer in a Round Cladded Rod with Modern Dimensional Analysis

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1875
Author(s):  
Botond-Pál Gálfi ◽  
Ioan Száva ◽  
Daniela Șova ◽  
Sorin Vlase
Keyword(s):  
Heat Transfer ◽  
Dimensional Analysis ◽  
Point Of View ◽  
Heat Transfer Analysis ◽  
Necessary Condition ◽  
Experimental Point ◽  
Experimental Measurements ◽  
Circular Section ◽  
Independent Variables ◽  
Model Law

Heat transfer analysis can be studied efficiently with the help of so-called modern dimensional analysis (MDA), which offers a uniform and easy approach, without requiring in-depth knowledge of the phenomenon by only taking into account variables that may have some influence. After a brief presentation of the advantages of this method (MDA), the authors applied it to the study of heat transfer in straight bars of solid circular section, protected but not thermally protected with layers of intumescent paints. Two cases (two sets of independent variables) were considered, which could be easily tracked by experimental measurements. The main advantages of the model law obtained are presented, being characterized by flexibility, accuracy, and simplicity. Additionally, this law and the MDA approach allow us to obtain much more advantageous models from an experimental point of view, with the geometric analogy of the model with the prototype not being a necessary condition. To the best knowledge of the present authors there are no studies reporting the application of the MDA method as it was used in this paper to heat transfer.

scholarly journals STUDII DE TRANSFER DE CĂLDURĂ ÎN MAȘINI ELECTRICE UTILIZATE ÎN CONDIȚII DE FUNCȚIONARE SPECIALE

2021 ◽  
Vol 2020 (1) ◽  
pp. 1-8
Author(s):  
Ioana IONICA ◽  
Mircea MODREANU ◽  
Alexandru-Mihail MOREGA ◽  
Cristian BOBOC
Keyword(s):  
Heat Transfer ◽  
Atomic Oxygen ◽  
Moisture Absorption ◽  
Transfer Problem ◽  
Low Earth Orbit ◽  
Point Of View ◽  
Environmental Stability ◽  
Heat Transfer Analysis ◽  
Space Conditions ◽  
Limited Angle

"This paper aims to analyze the heat transfer of a DC limited angle torque motor, in special conditions, of space. Three-dimensional models will be used and two current values will be considered. As a working hypothesis, several variants will be numerically analyzed in which the boundary conditions will take into account different values of the emissivity of the motor surfaces varying in the range 0.2 ÷ 1. Inside the motor subassemblies the heat transfer will be done by conduction and between the motor and the environment by radiation. Using thermal modeling, it will be possible to determine the time in which the winding temperature reaches the maximum value allowed for the DC limited angle torque motor, in space conditions. The approached motor presents specific technical aspects (constructive and functional) and novelty in the field of torque motors with limited angle. These types of motors are recommended for applications where both volume and weight are critical requirements. The applications of DC-LATM are diverse: in the fields of aerospace, military technique, medical etc. For special applications (eg aerospace) a redundant motor solution is required [7]. The motor is designed for applications that require rotation over a certain angular range, (the working domain of this motor is 45 ÷ 135°). The space industry is a field of maximum interest from a scientific, economic and strategic point of view. Compared to other fields, its growth in recent years is extraordinary, as evidenced by the availability of telecommunications services. The requirements of the motor given by the application in which it is used including the environmental conditions in which the motor operates will determine the input data of the heat transfer problem. There are two categories of requirements that are equally important: general (mechanical, thermal, electrical) and environmental (stability to vacuum and radiation, resistance to AO - atomic oxygen) etc. Also, several aspects must be considered, such as: environmental effects (LEO - Low Earth Orbit or GEO - Geostationary Orbit), constraints applicable to materials (temperature, vacuum, thermal cycles, chemical - corrosion, galvanic compatibility, atomic oxygen , moisture absorption / desorption, fluid compatibility), if materials will degrade over time, the system in which the product will be integrated, interfaces [8]. The heat transfer analysis addressed in this paper establishes the DC-LATM behavior from a thermal point of view in space conditions."

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