Effective Thermal Conductivity of Closed Cell Insulation: Impact of Gas Diffusion to Long-Term Performance

2021 ◽  
Author(s):  
Daniel Howard ◽  
Som Shrestha ◽  
Diana Hun ◽  
Amit Rai ◽  
Tianli Feng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Gas Diffusion ◽  
Closed Cell ◽  
Long Term Performance ◽  
Term Performance

Temperature dependency of the long-term thermal conductivity of spray polyurethane foam

2021 ◽  
pp. 174425912110454
Author(s):  
Neal Holcroft
Keyword(s):  
Thermal Conductivity ◽  
Polyurethane Foam ◽  
Cellular Structure ◽  
Gas Diffusion ◽  
Temperature Dependent ◽  
Blowing Agent ◽  
Closed Cell ◽  
Wall Assembly ◽  
Cell Foam

The thermal properties of closed-cell foam insulation display a more complex behaviour than other construction materials due to the properties of the blowing agent captured in their cellular structure. Over time, blowing agent diffuses out from and air into the cellular structure resulting in an increase in thermal conductivity, a process that is temperature dependent. Some blowing agents also condense at temperatures within the in-service range of the insulation, resulting in non-linear temperature dependent relationships. Moreover, diffusion of moisture into the cellular structure increases thermal conductivity. Standards exist to quantify the effect of gas diffusion on thermal conductivity, however only at standard laboratory conditions. In this paper a new test procedure is described that includes calculation methods to determine Temperature Dependent Long-Term Thermal Conductivity (LTTC(T)) functions for closed-cell foam insulation using as a test material, a Medium-Density Spray Polyurethane Foam (MDSPF). Tests results are provided to show the validity of the method and to investigate the effects of both conditioning and mean test temperature on change in thermal conductivity. In addition, testing was conducted to produce a moisture dependent thermal conductivity function. The resulting functions were used in hygrothermal simulations to assess the effect of foam aging, in-service temperature and moisture content on the performance of a typical wall assembly incorporating MDSPF located in four Canadian climate zones. Results show that after 1 year, mean thermal conductivity increased 15%–16% and after 5 years 23%–24%, depending on climate zone. Furthermore, the use of the LTTC(T) function to calculate the wall assembly U-value improved accuracy between 3% and 5%.

scholarly journals Study on the temperature dependence of gas permeation and adsorption behavior of the vacuum insulation panel with getter materials

2020 ◽  
Vol 172 ◽  
pp. 21001 ◽  
Author(s):  
Hideya Yamamoto ◽  
Daisuke Ogura
Keyword(s):  
Thermal Conductivity ◽  
Temperature Dependence ◽  
Pressure Sensor ◽  
Glass Wool ◽  
Adsorption Behavior ◽  
Vacuum Insulation ◽  
Long Term Performance ◽  
Term Performance ◽  
Vacuum Insulation Panel

Vacuum insulation panel (VIP) is a high-performance heat insulation material that has contributed to the energy efficiency of refrigerators, vending machines, and cooler boxes. Glass wool or fumed silica covered by a laminated film are the core materials of VIP; by evacuating air inside, it is possible to reduce the gas thermal conductivity to be close to 0 and exhibit high thermal performance. In recent years, the research on long-term performance prediction has been conducted for use in building insulation. Specifically, various getter materials have been developed to improve the long-term performance of glass wool VIP. However, there are no studies that clearly show the adsorption behavior or temperature dependence inside VIP with getter materials. We measured the adsorption temperature dependence of two types of getters using the constant volume method and then observed the adsorption behavior inside VIP using VIP equipped with a micro pressure sensor. Regarding the internal pressure of VIPs equipped with the micro pressure sensor, the pressure fluctuation derived from the adsorbent was confirmed by the temperature change, and it was confirmed that the thermal conductivity changed accordingly. If the internal temperature of VIP increases, gases may be released from the getter. Therefore, in the building environment, it is necessary to select a getter that is suitable for the usage environment and to use an appropriate amount of getter.

The Role of Carbonate Formation on the Long-Term Performance of Gas Diffusion Electrodes for Carbon Dioxide Electrolysis in Alkaline Media

2020 ◽  
Vol MA2020-02 (63) ◽  
pp. 3247-3247
Author(s):  
Emiliana R. Cofell ◽  
Uzoma Nwabara ◽  
Danielle A. Henckel ◽  
Saket Bhargava ◽  
Zachary Park ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Gas Diffusion ◽  
Alkaline Media ◽  
Gas Diffusion Electrodes ◽  
Carbonate Formation ◽  
Long Term Performance ◽  
Term Performance

Long-term performance of carbon gas-diffusion air electrodes in saline electrolyte

1987 ◽  
Vol 17 (3) ◽  
pp. 657-660 ◽  
Author(s):  
S. K. Zečević ◽  
A. R. Despić ◽  
D. M. Dražić ◽  
A. Kaisheva ◽  
S. Gamburzev ◽  
...  
Keyword(s):  
Gas Diffusion ◽  
Long Term Performance ◽  
Term Performance

Fine Particle Mass Monitoring with Low-Cost Sensors: Corrections and Long-Term Performance Evaluation

2019 ◽  
Author(s):  
Carl Malings ◽  
Rebecca Tanzer ◽  
Aliaksei Hauryliuk ◽  
Provat K. Saha ◽  
Allen L. Robinson ◽  
...  
Keyword(s):  
Performance Evaluation ◽  
Fine Particle ◽  
Low Cost ◽  
Particle Mass ◽  
Long Term Performance ◽  
Term Performance

Long-term performance of the Hancock bioprosthetic conduit for aortic root replacement

2008 ◽  
Vol 56 (S 1) ◽  
Author(s):  
CC Badiu ◽  
W Eichinger ◽  
D Ruzicka ◽  
I Hettich ◽  
S Bleiziffer ◽  
...  
Keyword(s):  
Aortic Root ◽  
Aortic Root Replacement ◽  
Long Term Performance ◽  
Term Performance
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