scholarly journals Methodical selection of thermal conductivity models for porous silica-based media with variation of gas type and pressure

2022 ◽  
Vol 187 ◽  
pp. 122519
Author(s):  
Sebastian Sonnick ◽  
Lars Erlbeck ◽  
Manuel Meier ◽  
Hermann Nirschl ◽  
Matthias Rädle
Keyword(s):  
Thermal Conductivity ◽  
Porous Silica ◽  
Selection Of ◽  
Conductivity Models

Research on Heat Transfer Characteristics of Nano-Porous Silica Aerogel Material and its Application on Mars Surface Mission

2014 ◽  
Vol 924 ◽  
pp. 329-335 ◽  
Author(s):  
Cong Hang Li ◽  
Shi Chen Jiang ◽  
Zheng Ping Yao ◽  
Song Sheng ◽  
Xin Jian Jiang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Silica Aerogel ◽  
Thermal Environment ◽  
Porous Silica ◽  
Heat Transfer Model ◽  
Heat Radiation ◽  
Transfer Model ◽  
Ambient Conditions ◽  
Coupled Heat Transfer

Based on the nanoporous network structure features of silica aerogel, the gas-solid coupled heat transfer model of silica aerogel is analyzed, and the calculation formulas of the gas-solid coupled, the gas thermal conductivity and the heat radiation within the aerogel are derived. The thermal conductivity of pure silica aerogel is calculated according to the derived heat transfer model and is also experimentally measured. Moreover, measurements on the thermal conductivities of silica aerogel composites with different densities at ambient conditions are performed. And finally, a novel design of silica aerogel based integrated structure and thermal insulation used for withstanding the harsh thermal environment on the Martin surface is presented.

scholarly journals Efficient Stabilization of Mono and Hybrid Nanofluids

Energies ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3793
Author(s):  
Sylwia Wciślik
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
New Technologies ◽  
Industrial Processes ◽  
Challenging Tasks ◽  
Future Challenges ◽  
Hybrid Nanofluids ◽  
Very High ◽  
Base Liquid ◽  
Conductivity Models

Currently; the transfer of new technologies makes it necessary to also control heat transfer in different industrial processes—both in practical and research—applications. Not so long ago water and ethylene glycol were the most frequently used media in heat transfer. However, due to their relatively low thermal conductivity, they cannot provide the fast and effective heat transfer necessary in modern equipment. To improve the heat transfer rate different additives to the base liquid are sought, e.g., nanoadditives that create mono and hybrid nanofluids with very high thermal conductivity. The number of scientific studies and publications concerning hybrid nanofluids is growing, although they still represent a small percentage of all papers on nanofluids (in 2013 it was only 0.6%, and in 2017—ca. 3%). The most important point of this paper is to discuss different ways of stabilizing nanofluids, which seems to be one of the most challenging tasks in nanofluid treatment. Other future challenges concerning mono and hybrid nanofluids are also thoroughly discussed. Moreover, a quality assessment of nanofluid preparation is also presented. Thermal conductivity models are specified as well and new representative mono and hybrid nanofluids are proposed.

Use of Fuel Assembly/Backfill Gas Effective Thermal Conductivity Models to Predict Basket and Fuel Cladding Temperatures Within a Rail Package During Normal Transport

2006 ◽  
Author(s):  
Miles Greiner ◽  
Kishore Kumar Gangadharan ◽  
Mithun Gudipati
Keyword(s):  
Thermal Conductivity ◽  
Fuel Assembly ◽  
Effective Thermal Conductivity ◽  
Wall Temperature ◽  
Experimental Studies ◽  
Temperature Profiles ◽  
Fuel Cladding ◽  
Dimensional Finite Element ◽  
Normal Transport ◽  
Conductivity Models

Two-dimensional finite element thermal simulations of a generic rail package designed to transport twenty-one spent PWR assemblies were performed for normal transport conditions. Effective thermal conductivity models were employed within the fuel assembly/backfill gas region. Those conductivity models were developed by other investigators assuming the basket wall temperature is uniform. They are typically used to predict the maximum fuel cladding temperature near the package center. The cladding temperature must not exceed specified limits during normal transport. This condition limits the number and heat generation rate of fuel assembles that can transported. The current work shows the support basket wall temperatures in the periphery of the package are highly non-uniform. Moreover the thermal resistance of those regions significantly affects the maximum fuel clad temperature near the package center. This brings the validity of the fuel/backfill gas thermal conductivity models into question. The non-uniform basket wall temperature profiles quantified in this work will be used in future numerical and experimental studies to develop new thermal models of the fuel assembly/backfill gas regions. This will be an iterative process, since the assembly/backfill model affects the predicted basket wall temperature profiles.

A review and evaluation of 39 thermal conductivity models for frozen soils

Geoderma ◽  
2021 ◽  
Vol 382 ◽  
pp. 114694
Author(s):  
Hailong He ◽  
Gerald N. Flerchinger ◽  
Yuki Kojima ◽  
Miles Dyck ◽  
Jialong Lv
Keyword(s):  
Thermal Conductivity ◽  
Frozen Soils ◽  
Conductivity Models

Effects of polysiloxane on thermal conductivity and compressive strength of porous silica ceramics

2019 ◽  
Vol 45 (17) ◽  
pp. 21270-21277 ◽  
Author(s):  
Shalini Rajpoot ◽  
Rohit Malik ◽  
Young-Wook Kim
Keyword(s):  
Thermal Conductivity ◽  
Compressive Strength ◽  
Porous Silica

A Parameter for Selection of Nano-Dispersoids in Nanofluids for Thermal Applications

2012 ◽  
Vol 736 ◽  
pp. 223-228
Author(s):  
M.M. Ghosh ◽  
S. Ghosh ◽  
S.K. Pabi
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Elastic Modulus ◽  
Heat Source ◽  
Ethylene Glycol ◽  
Preliminary Identification ◽  
Water Based ◽  
Selection Of ◽  
Poissons Ratio

A model reported by the present investigators has earlier shown that the extent of heat pick up by a nanoparticle during its collision with the heat source in a given nanofluid would depend on the thermal conductivity (kp, unit W/m.K), density (ρ, unit kg/m3), elastic modulus (E, unit GPa) and Poissons ratio (μ) of the nanoparticle and heat source. Considering the expression for collision period and thermal conductivity of nanoparticle, a factor χ =kp(ρ/E)0.4 is proposed here and examined for the preliminary identification of the potential of a dispersoid in enhancing the thermal conductivity of a nanofluid. The χ-factor for Ag, Cu, CuO, Al2O3 and SiO2 are 2960, 2247, 116, 14.1 and 5.5, respectively. The higher χ-factor of CuO compared to that of Al2O3 can explain why water and ethylene glycol (EG) based CuO-nanofluid is reported to show higher enhancement in the thermal conductivity, when compared to similar Al2O3-nanofluid. The χ for SiO2 is much smaller than that for Ag, which also corroborates well with the marginal enhancement in thermal conductivity of water based nanofluid containing SiO2 nanoparticles. Therefore, a high value of χ of the nanodispersoid can serve as a parameter for the design of nanofluids for heat transfer applications.

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