Heat Capacity in Two-Phase Regions and Heat of Phase Transformations of Certain Zr-Nb Binary Alloys

Atomic Energy ◽  
2005 ◽  
Vol 99 (1) ◽  
pp. 451-463 ◽  
Author(s):  
S. G. Popov ◽  
V. N. Proselkov
Keyword(s):  
Heat Capacity ◽  
Phase Transformations ◽  
Binary Alloys ◽  
Two Phase

THE MECHANISM OF RAISING AND QUANTIFICATION OF SPECIFIC HEAT FLUX AT BOILING OF NANOFLUIDS IN FREE CONVECTION CONDITIONS

2017 ◽  
pp. 25-34
Author(s):  
V.N. Moraru
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Capacity ◽  
Specific Heat ◽  
Chemical Properties ◽  
Heating Surface ◽  
Physical Models ◽  
Superheated Liquid ◽  
Two Phase ◽  
Boiling Process

The results of our work and a number of foreign studies indicate that the sharp increase in the heat transfer parameters (specific heat flux q and heat transfer coefficient _) at the boiling of nanofluids as compared to the base liquid (water) is due not only and not so much to the increase of the thermal conductivity of the nanofluids, but an intensification of the boiling process caused by a change in the state of the heating surface, its topological and chemical properties (porosity, roughness, wettability). The latter leads to a change in the internal characteristics of the boiling process and the average temperature of the superheated liquid layer. This circumstance makes it possible, on the basis of physical models of the liquids boiling and taking into account the parameters of the surface state (temperature, pressure) and properties of the coolant (the density and heat capacity of the liquid, the specific heat of vaporization and the heat capacity of the vapor), and also the internal characteristics of the boiling of liquids, to calculate the value of specific heat flux q. In this paper, the difference in the mechanisms of heat transfer during the boiling of single-phase (water) and two-phase nanofluids has been studied and a quantitative estimate of the q values for the boiling of the nanofluid is carried out based on the internal characteristics of the boiling process. The satisfactory agreement of the calculated values with the experimental data is a confirmation that the key factor in the growth of the heat transfer intensity at the boiling of nanofluids is indeed a change in the nature and microrelief of the heating surface. Bibl. 20, Fig. 9, Tab. 2.

Heat capacities and enthalpies of fusion and transformation for solvates of some salts with dimethyl sulfoxide and dimethylformamide

1988 ◽  
Vol 53 (12) ◽  
pp. 3072-3079
Author(s):  
Mojmír Skokánek ◽  
Ivo Sláma
Keyword(s):  
Heat Capacity ◽  
Phase Transformation ◽  
Phase Transformations ◽  
Dimethyl Sulfoxide ◽  
Liquidus Temperature ◽  
Molar Heat Capacity ◽  
Solid Phase ◽  
Zinc Nitrate ◽  
Heat Capacities ◽  
Liquid Phases

Molar heat capacities and molar enthalpies of fusion of the solvates Zn(NO3)2 . 2·24 DMSO, Zn(NO3)2 . 8·11 DMSO, Zn(NO3)2 . 6 DMSO, NaNO3 . 2·85 DMSO, and AgNO3 . DMF, where DMSO is dimethyl sulfoxide and DMF is dimethylformamide, have been determined over the temperature range 240 to 400 K. Endothermic peaks found for the zinc nitrate solvates below the liquidus temperature have been ascribed to solid phase transformations. The molar enthalpies of the solid phase transformations are close to 5 kJ mol-1 for all zinc nitrate solvates investigated. The dependence of the molar heat capacity on the temperature outside the phase transformation region can be described by a linear equation for both the solid and liquid phases.

Influence of thermal treatment of Ti-45Nb alloy in ultrafine-grained states on its structural parameters and heat capacity

2021 ◽  
pp. 84-91
Author(s):  
E.V. Legostaeva ◽  
◽  
M.A. Khimich ◽  
Yu.P. Sharkeev ◽  
A.Yu. Eroshenko ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Heat Capacity ◽  
Phase Transitions ◽  
Structural Parameters ◽  
Structural Phase ◽  
Coherent Scattering ◽  
Normal Stresses ◽  
Two Phase ◽  
Ω Phase ◽  
Ultrafine Grained

The effect of heat treatment of the Ti-45Nb alloy in the UFG state on its structural parameters (lattice parameters, volumetric phase ratio, sizes of coherent scattering regions, residual normal stresses) and their relationship with heat capacity have been studied. It has been established that the different character of the temperature dependence of the heat capacity for the Ti-45Nb alloy in the UFG and CC states is associated with the structural-phase features of the alloy in the UFG state: the two-phase structure of a-grains and b-grains, dispersion-hardened by the ω-phase, and phase transitions in the temperature range 400-600 °С.

The steady-State corrosion kinetics of two-phase binary alloys forming the most-stable oxide

1996 ◽  
Vol 46 (5-6) ◽  
pp. 383-398 ◽  
Author(s):  
F. Gesmundo ◽  
P. Castello ◽  
F. Viani
Keyword(s):  
Steady State ◽  
Binary Alloys ◽  
Two Phase ◽  
Stable Oxide ◽  
Corrosion Kinetics ◽  
Kinetics Of

Nanocomposites Based on Hyperbranched Polymers and Montmorillonite

2011 ◽  
Vol 108 ◽  
pp. 91-94 ◽  
Author(s):  
Shao Jian He ◽  
Jun Lin
Keyword(s):  
Heat Capacity ◽  
Glass Transition ◽  
Full Range ◽  
Hyperbranched Polymers ◽  
Xrd Analysis ◽  
Rigid Amorphous Fraction ◽  
Two Phase ◽  
Heat Capacity Jump ◽  
Silicate Layers ◽  
Rigid Amorphous

Nanocomposites based on hyperbranched polymers and sodium montmorillonite were prepared over the full range of compositions. The XRD analysis showed the full exfoliation of silicate layers at lower silicate content (up to 9.1 wt%). With the further increase of silicate loading, an intercalated structure was developed with a constant d-spacing due to the unique structure of hyperbranched polymers. The heat capacity jump at the glass transition of the nanocomposites was found to deviate from the two-phase model prediction, indicating the formation of a rigid amorphous fraction. The glass transition temperature and heat capacity jump behaviors suggested that the molecular mobility of hyperbranched polymers were restricted by the introduction of silicate layers. The mechanical properties of the nanocomposites were also investigated.

High-Temperature Materials Based on Quaternary Ir-Nb-Ni-Al Alloys

2000 ◽  
Vol 646 ◽  
Author(s):  
X. Yu ◽  
Y. Yamabe-Mitarai ◽  
Y. Ro ◽  
S. Nakaza ◽  
H. Harada
Keyword(s):  
Coherent Structures ◽  
Binary Alloys ◽  
Lattice Misfit ◽  
Al Alloys ◽  
Quaternary Alloys ◽  
Rich Region ◽  
Two Phase ◽  
High Temperature Materials ◽  
Novel Method ◽  
Potential Use

ABSTRACTA novel method to develop new quaternary alloys with an fcc/L12 coherent structure is proposed. This paper reviews the development of quaternary Ir-Nb-Ni-Al alloys. The microstructure, lattice misfit, and compressive 0.2% flow stress of 15 kinds of alloys were investigated systematically. Two kinds of coherent structures, fcc/L12-Ir3Nb and fcc/ L12-Ni3Al, were observed in most alloys. Two two-phase structures, fcc+L12-Ir3Nb and fcc+L12-Ni3Al, were observed in Ir-rich and Ni-rich regions, respectively. The lattice misfits of quaternary Ir-Nb-Ni-Al alloys were higher than those of Ni- or Ir-base binary alloys. The compressive 0.2% flow stresses of quaternary alloys increased dramatically compared with those of Ni-base superalloys. The quaternary alloys located in the Ir-rich region were not only had higher strength but also better ductility than Ir-base binary alloys. The potential use of quaternary alloys is discussed.

An experimental study of reflected liquefaction shock waves with near-critical downstream states in a test fluid of large molar heat capacity

1994 ◽  
Vol 277 ◽  
pp. 163-196 ◽  
Author(s):  
Seyfettin C. Gülen ◽  
Philip A. Thompson ◽  
Hung-Jai Cho
Keyword(s):  
Shock Wave ◽  
Heat Capacity ◽  
Phase Change ◽  
Molar Heat Capacity ◽  
Continuous Process ◽  
Nucleation And Growth ◽  
Test Fluid ◽  
Average Lifetime ◽  
Wave System ◽  
Two Phase

Near-critical states have been achieved downstream of a liquefaction shock wave, which is a shock reflected from the endwall of a shock tube. Photographs of the shocked test fluid (iso-octane) reveal a rich variety of phase-change phenomena. In addition to the existence of two-phase toroidal rings which have been previously reported, two-phase structures with a striking resemblance to dandelions and orange slices have been frequently observed. A model coupling the flow and nucleation dynamics is introduced to study the two-wave system of shock-induced condensation and the liquefaction shock wave in fluids of large molar heat capacity. In analogy to the one-dimensional Zeldovich–von Neumann–Döring (ZND) model of detonation waves, the leading part of the liquefaction shock wave is a gasdynamic pressure discontinuity (Δ ≈ 0.1 μm, τ ≈ 1 ns) which supersaturates the test fluid, and the phase transition takes place in the condensation relaxation zone (Δ ≈ 1–103 μm, τ ≈ 0.1–100 μs) via dropwise condensation. At weak to moderate shock strengths, the average lifetime of the metastable state, τ ∞ 1/J, is long such that the reaction zone is spatially decoupled from the forerunner shock wave, and J is the homogeneous nucleation rate. With increasing shock strength, a transition in the phase-change mechanism from nucleation and growth to spinodal decomposition is anticipated based on statistical mechanical arguments. In particular, within a complete liquefaction shock the metastable region is entirely bypassed, and the vapour decomposes inside the unstable region. This mechanism of unmixing in which nucleation and growth become one continuous process provides a consistent framework within which the observed irregularities can be explained.

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