scholarly journals Hydrogen-bond memory and water-skin supersolidity resolving the Mpemba paradox

2014 ◽  
Vol 16 (42) ◽  
pp. 22995-23002 ◽  
Author(s):  
Xi Zhang ◽  
Yongli Huang ◽  
Zengsheng Ma ◽  
Yichun Zhou ◽  
Ji Zhou ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Thermal Diffusivity ◽  
System P ◽  
High Thermal Diffusivity ◽  
Anomalous Relaxation

O:H–O bond anomalous relaxation and the skin high thermal-diffusivity cool hotter water faster than usual in the non-adiabatic ambient system.

scholarly journals High Thermal Diffusivity in Thermally Treated Filamentous Virus-Based Assemblies with a Smectic Liquid Crystalline Orientation

Viruses ◽  
2018 ◽  
Vol 10 (11) ◽  
pp. 608 ◽  
Author(s):  
Toshiki Sawada ◽  
Yuta Murata ◽  
Hironori Marubayashi ◽  
Shuichi Nojima ◽  
Junko Morikawa ◽  
...  
Keyword(s):  
Thermal Diffusivity ◽  
Liquid Crystalline ◽  
Mean Free Path ◽  
Heat Conducting ◽  
Covalent Bonds ◽  
Crystalline Orientation ◽  
Conductive Materials ◽  
Polymeric Chains ◽  
High Thermal Diffusivity ◽  
M13 Phage

Polymers are generally considered thermal insulators because the amorphous arrangement of the polymeric chains reduces the mean free path of heat-conducting phonons. Recent studies reveal that individual chains of polymers with oriented structures could have high thermal conductivity, because such stretched polymeric chains effectively conduct phonons through polymeric covalent bonds. Previously, we have found that the liquid crystalline assembly composed of one of the filamentous viruses, M13 bacteriophages (M13 phages), shows high thermal diffusivity even though the assembly is based on non-covalent bonds. Despite such potential applicability of biopolymeric assemblies as thermal conductive materials, stability against heating has rarely been investigated. Herein, we demonstrate the maintenance of high thermal diffusivity in smectic liquid crystalline-oriented M13 phage-based assemblies after high temperature (150 °C) treatment. The liquid crystalline orientation of the M13 phage assemblies plays an important role in the stability against heating processes. Our results provide insight into the future use of biomolecular assemblies for reliable thermal conductive materials.

scholarly journals Investigation on the Tensile Strength of the Friction Stir Welded similar joint of Al/Al alloy using high thermal diffusivity backing plate material.

2018 ◽  
Vol 8 (2) ◽  
Author(s):  
Akshansh Mishra ◽  
Abhishek Kumar Sharma ◽  
Hardik Kapoor ◽  
Jaspreet Singh ◽  
Krishna Kumar
Keyword(s):  
Tensile Strength ◽  
Thermal Diffusivity ◽  
Welding Process ◽  
Soft Materials ◽  
Work Piece ◽  
Al Alloy ◽  
Plate Material ◽  
Friction Stir ◽  
Backing Plate ◽  
High Thermal Diffusivity

Friction Stir Welding process is a novel green solid state joining process for soft materials such as aluminium alloys. The weld quality is governed by the proper selection of parameters such as forge force rotational speed of the tool, welding speed, backing plate material etc. Thermal boundary condition at the bottom of the work piece plays an important role for obtaining the sound joint. The backing plate material governs these thermal conditions. In this case study, high thermal diffusivity backing plate material which consisted of AA2099 was used for joining of the plates of Structural Aluminium alloy. It was observed that the tensile strength was improved.

Validation and Development of DNS Database for Low Prandtl Numbers in Rod Bundle

2019 ◽  
Author(s):  
Jonathan K. Lai ◽  
Elia Merzari ◽  
Yassin A. Hassan ◽  
Aleksandr Obabko
Keyword(s):  
Heat Transfer ◽  
Thermal Diffusivity ◽  
Prandtl Number ◽  
Liquid Metals ◽  
Heat Transfer Characteristics ◽  
Reynolds Analogy ◽  
Transfer Characteristics ◽  
Rod Bundle ◽  
High Thermal Diffusivity ◽  
Prandtl Numbers

Abstract Difficulty in capturing heat transfer characteristics for liquid metals is commonplace because of their low molecular Prandtl number (Pr). Since these fluids have very high thermal diffusivity, the Reynolds analogy is not valid and creates modeling difficulties when assuming a turbulent Prandtl number (Prt) of near unity. Baseline problems have used direct numerical simulations (DNS) for the channel flow and backward facing step to aid in developing a correlation for Prt. More complex physics need to be considered, however, since correlation accuracy is limited. A tight lattice square rod bundle has been chosen for DNS benchmarking because of its presence of flow oscillations and coherent structures even with a relatively simple geometry. Calculations of the Kolmogorov length and time scales have been made to ensure that the spatial-temporal discretization is sufficient for DNS. In order to validate the results, Hooper and Wood’s 1984 experiment has been modeled with a pitch-to-diameter (P/D) ratio of 1.107. The present work aims at validating first- and second-order statistics for the velocity field, and then analyzing the heat transfer behavior at different molecular Pr. The effects of low Pr flow are presented to demonstrate how the normalized mean and fluctuating heat transfer characteristics vary with different thermal diffusivity. Progress and future work toward creating a full DNS database for liquid metals are discussed.

A Study of Porosity Influence on Thermal Diffusivity of Aluminium Foam by Experimental Analysis and Numerical Simulation

2010 ◽  
Vol 297-301 ◽  
pp. 814-819 ◽  
Author(s):  
A. Adamčíková ◽  
B. Taraba ◽  
J. Kováčik
Keyword(s):  
Thermal Conductivity ◽  
Numerical Simulation ◽  
Thermal Diffusivity ◽  
Transfer Task ◽  
Aluminium Foam ◽  
Flash Method ◽  
Inverse Heat Transfer ◽  
High Thermal Diffusivity ◽  
Specific Heat Capacities ◽  
Measured Specific Heat

Aluminium foam is a unique material possessing very high thermal diffusivity due to high thermal conductivity of the cell walls accompanied with rather low overall thermal conductivity, controlled via porosity [1]. There is a presumption of increasing influence at thermal diffusivity of aluminium foam by decreasing porosity, following the presented results (e.g. by using the transient plane source method [2]) and relation between thermal diffusivity and density. Thermal diffusivity of aluminium foam considering various porosity and various compositions of precursors were observed. The Aluminium foam was prepared by the powder metallurgy route, also well known as the ALULIGHT process, and various densities were achieved by changing of parameters (temperature, time) of foaming. The following types of foamable precursors were used: AlMg1Si0.6, AlSi10, as blowing agent was used 0.8 wt. % of TiH2.The thermal diffusivity of particular precursors by the flash method was measured. Specific heat capacities of samples with different density were measured by a calorimeter for various temperatures. The coefficient of thermal conductivity as a function of temperature was calculated by heat transient experiment data and numerical simulation consequently as an inverse heat transfer task. The problem was solved by the finite element method using the engineering-scientific program code ANSYS. The results depend on the thermal diffusivity, on the porosity and the type of precursor. Despite that aluminium foam is considered as a type of composite, thermophysical properties could be calculated upon known volume of aluminium alloy and air in the pores However there is a presumption that this rule cannot be used in case of porous materials. Values obtained by the mentioned methodology shown a significant influence on the porosity and the thermal diffusivity of the aluminium foam.

Revising the exceptionally high thermal diffusivity of spider silk

2014 ◽  
Vol 114 ◽  
pp. 1-3 ◽  
Author(s):  
Raquel Fuente ◽  
Arantza Mendioroz ◽  
Agustín Salazar
Keyword(s):  
Thermal Diffusivity ◽  
Spider Silk ◽  
High Thermal Diffusivity

Proton transfer in a short hydrogen bond caused by solvation shell fluctuations: an ab initio MD and NMR/UV study of an (OHO)− bonded system

2015 ◽  
Vol 17 (6) ◽  
pp. 4634-4644 ◽  
Author(s):  
Svetlana Pylaeva ◽  
Christoph Allolio ◽  
Benjamin Koeppe ◽  
Gleb S. Denisov ◽  
Hans-Heinrich Limbach ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Proton Transfer ◽  
Ab Initio ◽  
Aprotic Solvent ◽  
Solvation Shell ◽  
System P ◽  
Polar Aprotic Solvent ◽  
Short Hydrogen Bond ◽  
Ab Initio Md ◽  
Double Well Potential

The polar aprotic solvent fluctuations in the first solvation shell lead to a double-well potential and proton tautomerism in a low-barrier hydrogen bond.

Development of iron-base composite materials with high thermal conductivity for DEMO

2014 ◽  
Vol 1645 ◽  
Author(s):  
H. Homma ◽  
N. Hashimoto ◽  
S. Ohnuki
Keyword(s):  
Composite Materials ◽  
Thermal Diffusivity ◽  
High Heat ◽  
High Heat Flux ◽  
Plasma Sintering ◽  
The Matrix ◽  
Critical Issues ◽  
High Thermal Diffusivity ◽  
Copper Composite ◽  
Thermal Diffusivities

ABSTRACTOne of the critical issues for development of the nuclear fusion demonstration reactor (DEMO) is the high heat flux on heat-resistant equipments, especially the blanket and divertor. Materials of such equipments require relatively high thermal conductivities. In this study, we developed iron-based composite materials with carbon nanotube (CNT) and copper, which have high thermal diffusivities, by means of Hot Pressing (HP) and Spark Plasma Sintering (SPS).The thermal diffusivity in the iron/CNT composites was not high enough compared with that of pure iron, while iron/copper composite showed a relatively high thermal diffusivity in the joining conditions. One of the reasons not to be improved thermal diffusivity could be non-mono-dispersion of CNT by the formation of carbides in the matrix.

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