Thermophysical properties melts

Table 1. Dimensionless values of parameters in the Solutal Model for two cases studied here. The systems I and II are representative of the thermophysical properties of the succinonitrile-acetone systems with differing values of the dif-fusivity ratio Rm, temperature gradient G and capillary parameter F. System III corresponds to parameters for a Pb-Sb alloy with equal diffusivities in melt and crystal...

Containerless processing is also of interest in physical metallurgy, as it provides opportunities to study thermophysical properties of high temperature metals and alloys, avoid sample contamination due to contact with container walls, and observe the solidification of materials that have been rapidly cooled from the melt. 

As pointed out in the previous section, melting can often be modeled in terms of simple geometries. Here we analyze the transient conduction problem in a semi-infinite solid. We compare the solutions of this problem, assuming first (a) constant thermophysical properties, then (b) variable thermophysical properties and finally, and (c) a phase transition with constant thermophysical properties in each phase. These solutions, though useful by themselves, also help demonstrate the profound effect of the material properties on the mathematical complexities of the solution. 

Example 5.4 Melting of a Semi-infinite Solid with Constant Thermophysical Properties and a Step Change in Surface Temperature The Stefan-Neumann Problem The previous example investigated the heat conduction problem in a semi-infinite solid with constant and variable thermophysical properties. The present Example analyzes the same conduction problem with a change in phase. 

The preceding examples discuss the heat-conduction problem without melt removal in a semi-infinite solid, using different assumptions in each case regarding the thermophysical properties of the solid. These solutions form useful approximations to problems encountered in everyday engineering practice. A vast collection of analytical solutions on such problems can be found in classic texts on heat transfer in solids (10,11). Table 5.1 lists a few well-known and commonly applied solutions, and Figs. 5.5-5.8 graphically illustrate some of these and other solutions. 

The thermophysical properties, such as glass transition, specific heat, melting point, and the crystallization temperature of virgin polymers are by-and-large available in the literature. However, the thermal conductivity or diffusivity, especially in the molten state, is not readily available, and values reported may differ due to experimental difficulties. The density of the polymer, or more generally, the pressure-volume-temperature (PVT) diagram, is also not readily available and the data are not easily convertible to simple analytical form. Thus, simplification or approximations have to be made to obtain a solution to the problem at hand. 

In Table 6, we can see the average thermophysical properties of kerogenes as compared to the values of the same characteristics of thermoplasts. Thermophysical properties of processed compositions in the area of phase transitions are of prime importance. In Table 6, we can see the avera values of the corresponding thermal co-efficients at 100-150 °C. The data for polymers are cited from [69,70]. Assuming that there are no local thermal tensions in the melt, we can calculate the composition s thermal linear expansion coefficient by the additive equation [69,70] ... 

Let us discuss the influence of changing the complex of thermophysical properties of the mineralorganic-filled-composition melts on the flow character of these media in the field of variable temperatures. This problem was studied in [18, 19, 32]. 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E.W., McLinden, M.O., and Huber, M.L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is Buecker, D., and Wagner, W, A Reference Equation of State forthe Thermodynamic Properties of Ethane for Temperatures from the Melting Line to 675 K and Pressures up to 900 MPa, J. Phys. Chem. Ref. Data, 35(1) 205-206, 2006. The source for viscosity and thermal conductivity is Friend, D.G., Ingham, H., and Ely, J.E, Thermophysical Properties of Ethane, /. Phys. Chem. R. Data, 35(l) 205-266, 2006. 

Converted from tables in Vargaftik, Tables of the Thermophysical Properties of Liquids and Gases, Nauka, Moscow, 1972, and Hemisphere, Washington, 1975. m = melting point. The notation 1.78.-13 signifies 1.78 x 10". ... 

Terpene Mixtures. Recently, U.S. Patent 5,847,246 has described the use of eutectic mixtures of monocycloterpenes for low-temperature applications. " These new environment friendly HTFs have a melting point lower than — 110°C and thermophysical properties comparable to many other HTFs. Because the ingredients of these new HTFs are biobased and obtained from renewable sources, these fluids conserve energy for production as compared with the other synthetic HTFs. With the addition of proper antioxidants and using an inert gas such as N2, these fluids can be used from 100°C to +150°C in a variety of applications. 

Dinsdale, A. T., CALPHAD, 15,317,1991 (melting points, enthalpy of fusion). 2. Touloukian, Y. S., Thermophysical Properties of Matter, Vol. 12, Thermal Expansion, IFI/Plenum, New York, 1975 (coefficient of ex- Technology, Vol. 2, Part 1, Mechanical-Thermal Properties of S 1971 (density). 10. Physical Encyclopedic Dictionary, Vol. 1—5, Encyclopedy Publisl House, Moscow, 1960—66. ... 

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