4K-GM Cryocooler Performance and Thermal Conductivity of HoxEr1-xN

2013 ◽  
Vol 1492 ◽  
pp. 53-58
Author(s):  
Takanori Nakano ◽  
Yusuke Hirayama ◽  
Takushi Izawa ◽  
Takashi Nakagawa ◽  
Yasushi Fujimoto ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Stainless Steel ◽  
Electrical Resistivity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Three Samples ◽  
Regenerator Material

ABSTRACTHoxEr1-xN (x=0.25, 0.5, 0.75) samples were synthesized by nitriding of HoxEr1-x alloy bars and their thermal conductivity κ were measured. The measured κ values were comparable to those of stainless steel and Er3Ni. Ho0.5Er0.5N showed the highest κ of the present three samples. The thermal diffusivity calculated from the κ and the specific heat indicates that Ho0.5Er0.5N is a very promising regenerator material for the cryocoolers. The electrical resistivity ρ was also measured as a function of temperature.

Thermal Characterization of Carbon-Carbon Composites

2011 ◽  
Author(s):  
Messiha Saad ◽  
Darryl Baker ◽  
Rhys Reaves
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Critical Role ◽  
Carbon Composite ◽  
Flash Method ◽  
Carbon Composites ◽  
Energy Storage Devices ◽  
Graphitized Carbon

Thermal properties of materials such as specific heat, thermal diffusivity, and thermal conductivity are very important in the engineering design process and analysis of aerospace vehicles as well as space systems. These properties are also important in power generation, transportation, and energy storage devices including fuel cells and solar cells. Thermal conductivity plays a critical role in the performance of materials in high temperature applications. Thermal conductivity is the property that determines the working temperature levels of the material, and it is an important parameter in problems involving heat transfer and thermal structures. The objective of this research is to develop thermal properties data base for carbon-carbon and graphitized carbon-carbon composite materials. The carbon-carbon composites tested were produced by the Resin Transfer Molding (RTM) process using T300 2-D carbon fabric and Primaset PT-30 cyanate ester. The graphitized carbon-carbon composite was heat treated to 2500°C. The flash method was used to measure the thermal diffusivity of the materials; this method is based on America Society for Testing and Materials, ASTM E1461 standard. In addition, the differential scanning calorimeter was used in accordance with the ASTM E1269 standard to determine the specific heat. The thermal conductivity was determined using the measured values of their thermal diffusivity, specific heat, and the density of the materials.

Experimental Study on Thermal Properties of Hollow Sphere Structures

2021 ◽  
Vol 407 ◽  
pp. 185-191
Author(s):  
Josef Tomas ◽  
Andreas Öchsner ◽  
Markus Merkel
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Hollow Sphere ◽  
Plane Source ◽  
Source Method ◽  
Transient Plane Source ◽  
Transient Plane Source Method

Experimental analyses are performed to determine thermal conductivity, thermal diffusivity and volumetric specific heat with transient plane source method on hollow sphere structures. Single-sided testing is used on different samples and different surfaces. Results dependency on the surface is observed.

scholarly journals Comparative study of thermal transport in Zea mays straw and Zea mays heartwood (cork) boards

2010 ◽  
Vol 14 (1) ◽  
pp. 31-38 ◽  
Author(s):  
Sunday Etuk ◽  
Louis Akpabio ◽  
Ita Akpan
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Zea Mays ◽  
Thermal Diffusivity ◽  
Comparative Study ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Thermal Transport ◽  
Insulation Material ◽  
Thermal Absorptivity

Thermal conductivity values at the temperature of 301-303K have been measured for Zea mays straw board as well as Zea mays heartwood (cork) board. Comparative study of the thermal conductivity values of the boards reveal that Zea mays heartwood board has a lower thermal conductivity value to that of the straw board. The study also shows that the straw board is denser than the heartwood board. Specific heat capacity value is less in value for the heartwood board than the straw board. These parameters also affect the thermal diffusivity as well as thermal absorptivity values for the two types of boards. The result favours the two boards as thermal insulators for thermal envelop but with heartwood board as a preferred insulation material than the straw board.

Influence of Mesocarp Fibre Inclusion on Thermal Properties of Foamed Concrete

2021 ◽  
Vol 87 (1) ◽  
pp. 1-11
Author(s):  
Siti Shahirah Suhaili ◽  
Md Azree Othuman Mydin ◽  
Hanizam Awang
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Properties ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Specific Heat Capacity ◽  
Volume Fraction ◽  
Thermal Constant ◽  
Volume Fractions ◽  
Foamed Concrete

The addition of mesocarp fibre as a bio-composite material in foamed concrete can be well used in building components to provide energy efficiency in the buildings if the fibre could also offer excellent thermal properties to the foamed concrete. It has practical significance as making it a suitable material for building that can reduce heat gain through the envelope into the building thus improved the internal thermal comfort. Hence, the aim of the present study is to investigate the influence of different volume fractions of mesocarp fibre on thermal properties of foamed concrete. The mesocarp fibre was prepared with 10, 20, 30, 40, 50 and 60% by volume fraction and then incorporated into the 600, 1200 and 1800 kg/m3 density of foamed concrete with constant cement-sand ratio of 1:1.5 and water-cement ratio of 0.45. Hot disk thermal constant analyser was used to attain the thermal conductivity, thermal diffusivity and specific heat capacity of foamed concrete of various volume fractions and densities. From the experimental results, it had shown that addition of mesocarp fibre of 10-40% by volume fraction resulting in low thermal conductivity and specific heat capacity and high the thermal diffusivity of foamed concrete with 600 and 1800 kg/m3 density compared to the control mix while the optimum amount of mesocarp fibre only limit up to 30% by volume fraction for 1200 kg/m3 density compared to control mix. The results demonstrated a very high correlation between thermal conductivity, thermal diffusivity and specific heat capacity which R2 value more than 90%.

Effect of timeliness on the thermal properties of paraffin-based Al2O3 nanofluids

2019 ◽  
Vol 33 (05) ◽  
pp. 1950051
Author(s):  
Yangyang Wu ◽  
Baichao Wang ◽  
Dong Li ◽  
Changyu Liu
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Specific Heat ◽  
Volume Concentration ◽  
Volume Fraction ◽  
Thermal Conversion ◽  
Volumetric Heat Capacity ◽  
Energy Storage Material ◽  
Over Time

Paraffin is an excellent photo-thermal conversion phase change energy storage material, and extensively used in the thermal storage field at the medium-low temperature. However, the low thermal conductivity of paraffin restricts its application in practice. Adding nanoparticles into paraffin is one of the effective methods to improve its thermal conductivity. Nevertheless, the thermal diffusivity, specific heat and volumetric heat capacity of paraffin as well as timeliness were affected after the addition of nanoparticles. In this paper, the influences of volume fraction of Al2O3 nanoparticle and timeliness on these thermal parameters of paraffin were investigated. The results show that the thermal conductivity of paraffin-based Al2O3 nanofluids increases first and then decreases with time, and the maximum thermal conductivity is 0.34 W/[Formula: see text] for volume fraction 1% on third day. The higher volume concentration, the lower specific heat and volumetric heat capacity, all present downtrend over time, until stable in the range of 0.3 MJ/[Formula: see text] and 0.4 MJ/[Formula: see text]. The average enhancement rate of specific heat and volumetric heat capacity are concentrates on −6% to 9%, −10% to 0%, respectively. While increasing the volume concentration, the thermal diffusivity has no obvious regularity, and presents undulatory property over time.

Thermal conductivity, electrical resistivity and specific heat of high- T c Ni 1.4 Pb 0.6 Sr 2 Ca 2 Cu 3 O x superconductor

1989 ◽  
Vol 162-164 ◽  
pp. 512-513 ◽  
Author(s):  
Katsunori Mori ◽  
Masahiro Sasakawa ◽  
Takao Igarashi ◽  
Yosikazu Isikawa ◽  
Kiyoo Sato ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Electrical Resistivity ◽  
Specific Heat

Experimental Characterization of the Thermal Diffusivity of Paraffin Phase Change Material Embedded With Herringbone Style Graphite Nanofibers

2012 ◽  
Author(s):  
Ronald J. Warzoha ◽  
Anthony Rao ◽  
Rebecca Weigand ◽  
Amy S. Fleischer
Keyword(s):  
Thermal Conductivity ◽  
Energy Storage ◽  
Thermal Diffusivity ◽  
Phase Change ◽  
Specific Heat ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Melt Temperature ◽  
Graphite Nanofibers

Phase change materials (PCMs) are promising candidates for thermal energy storage due to their intrinsically high values of latent heat. However, PCMs are unable to effectively utilize all of their energy storage capacities due to their poor thermophysical properties. In this study, the effect of graphite nanofibers (diameter = 2 to 1000 nm, length = 100μm) on the bulk thermal properties of paraffin PCM (Tmelt = 56 °C) is investigated. Material properties including effective thermal conductivity, specific heat, latent heat, melt temperature and thermal diffusivity are measured using a Differential Scanning Calorimeter (DSC) and comparative reference bar apparatus. Results suggest that the addition of nanostructures not only increases thermal conductivity by up to 180%, but also reduces the specific heat capacity and density of nano-enhanced paraffin, leading to improved thermal diffusivity and thus greater utilization of its latent heat for transient thermal energy storage.

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