A study of the thermal conductivity of granular silica materials for VIPs at different levels of gaseous pressure and external loads

Karami, Peyman; Afriyie, Ebenezer Twumasi; Norberg, Peter; Gudmundsson, Kjartan

doi:10.1016/j.enbuild.2014.09.038

Cited by 17 publications

(5 citation statements)

References 59 publications

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“…In Fig. A1, the new analytical model results for m = 10 and 15 are also compared to a FEM simulation with COMSOL Multiphysics® for the TPS 19 heat conduction problem ( Fig. 1(e, f)) using sensor with finite-width and zero thickness at z = 0 plane in a large sample domain.…”

Section: Traditional Theory: Infinitesimal Ring Widthmentioning

confidence: 99%

“…[16][17][18] For such sample materials, it has been shown that the k measured by the hot disk TPS method with a standard commercial sensor with polyimide (Kapton) as the insulation layer can be 20%-50% higher than the results from the steady-state methods. 18,19 For aerogel samples, there is also a report on the discrepancy in the k result obtained with TPS measurements using different types of sensors insulated with mica and polyimide, where the former type showed a result 54% higher than the later for the same sample. 20 Error in the TPS measurement [20][21][22][23][24][25][26][27][28][29][30][31] comes from two sources: (1) uncertainty in the experimental data and the selection of time interval for analysis, and (2) deviation of the original idealized analytical heat transfer model 3,32 from the practical measurement scenario.…”

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confidence: 99%

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Analysis and improvement of the hot disk transient plane source method for low thermal conductivity materials

Zheng

Kaur

Dames

et al. 2020

International Journal of Heat and Mass Transfer

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The hot disk transient plane source (TPS) method is a widely used standard technique (ISO 22007-2) for the characterization of thermal properties of materials, especially the thermal conductivity, k. Despite its well-established reliability for a wide variety of common materials, the hot disk TPS method is also known to suffer from a substantial systematic errors when applied to low-k thermal insulation materials, because of the discrepancies between the idealized model used for data analysis and the actual heat transfer process. Here, we present a combined numerical and experimental study on the influence of the geometry of hot disk sensor on measured value of lowk materials. We demonstrate that the error is strongly affected by the finite thickness and thermal mass of the sensor's insulation layer was well as the corresponding increase of the effective heater size beyond the radius of the embedded metal heater itself. We also numerically investigate the dependence of the error on the sample thermal properties, confirming that the errors are worse in low-k samples. A simple correction function is also provided, which converts the apparent (erroneous) result from a standard hot disk TPS measurement to a more accurate value. A standard polyimide sensor was also optimized using both wet and dry etching to provide more accurate measurement directly. Experimentally corrected value of k for Airloy® x56 aerogel and a

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Section: Traditional Theory: Infinitesimal Ring Widthmentioning

confidence: 99%

mentioning

confidence: 99%

Analysis and improvement of the hot disk transient plane source method for low thermal conductivity materials

Zheng

Kaur

Dames

et al. 2020

International Journal of Heat and Mass Transfer

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“…However, in each case the increase in thickness in the stage III was much less than the decrease in the stage I. As the structures of pores and HCMs were collapsed due to the compression force of vacuum in the stage I, the thickness of the VIPs were not fully recovered to the original value, upon the breakage of vacuum in the stage III [35,36]. Fig.…”

Section: Compression (ω) and Rebound Ratio (η)mentioning

confidence: 86%

Fabrication and characterization of low-cost and green vacuum insulation panels with fumed silica/rice husk ash hybrid core material

Saeed

Pan

et al. 2016

Materials & Design

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“…To ensure the thermal insulation performance of the VIP over a long time, it is very important to maintain the stability of the vacuum degree in the VIP. As shown in Figure 3, the sensitivity of different core materials to pressure is different, resulting in great differences in their thermal insulation performance under different vacuum degrees [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Impacts Investigation of Gas Barrier on Effective Thermal Conductivity and Service Life of Vacuum Insulation Panel

Shi,

Yang,

Chen

et al. 2023

Preprint

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Vacuum Insulation Panels (VIPs) are highly efficient thermal insulation materials with extremely low thermal conductivity based on the vacuum principle. With the sealing properties of the gas barrier envelopes, long service life of the VIP is obtained. The mechanism and influence factors of gas and water vapor permeability were mathematically analyzed to explore the influence of gas barrier envelopes on the thermal performance of VIPs. Three typical gas barriers were studied and the selection of the gas barrier and other aspects of optimization were involved. The relationships among temperature, humidity, solubility coefficient, diffusion coefficient, and permeability were concluded, which shows that temperature has a much greater effect on the permeability of the gas barrier relative to humidity. The numerical analysis and influencing factors of VIPs’ service life were also exemplified with three different types of gas barrier envelopes. The experimental results show that depending on the environment, the temperature has a major impact on the effective thermal conductivity and service life of VIP. The research was significant in the selection of gas barriers, the optimization of the performance, and the development of vacuum insulation material༎

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A study of the thermal conductivity of granular silica materials for VIPs at different levels of gaseous pressure and external loads

Cited by 17 publications

References 59 publications

Analysis and improvement of the hot disk transient plane source method for low thermal conductivity materials

Analysis and improvement of the hot disk transient plane source method for low thermal conductivity materials

Fabrication and characterization of low-cost and green vacuum insulation panels with fumed silica/rice husk ash hybrid core material

Impacts Investigation of Gas Barrier on Effective Thermal Conductivity and Service Life of Vacuum Insulation Panel

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