Magis Global –


October 16, 2015

Global Warming Potential

Category: General – Tags: , – admin – 8:02 pm

Nevertheless, taking into account the global trend to reduce emissions of CFCs, ozone depleting Earth, this direction is very promising. Table. 1 compares the main VA on effects on global warming. Global Warming Potential (GWP or GWP) – a coefficient which is introduced in the Kyoto Protocol (1997). PGP allows equivalent comparison of the various greenhouse gases in terms of their impact on global warming and / or duration of the atmosphere. Adopted as the standard for carbon dioxide: its GWP is one. Mechanisms responsible for heat transfer in plastic foams, including XPS, are well known. Traditionally it is assumed that the thermal conductivity of XPS panels made up of four components: the thermal conductivity of the solid phase material (polystyrene); thermal conductivity of the gas phase (BA), transfer of radiant energy, heat transfer by convection.

In the case of XPS, where the cell size is small (less than 2 mm), the convection component can be neglected. In the slabs of XPS (as in any foam) heat transfer through the thermal conductivity of the solid phase and by radiation unchanging over time. Only component associated with the thermal conductivity of the gas phase changes with time as a result of diffusion of BA from the cells and counter-diffusion of air (oxygen and nitrogen). The concentration of BA, located in the slab XPS, determined by transport properties of the gas. Table.

Figure 2 shows the key characteristics of the transport of certain gases – permeability and effective diffusion coefficient in polystyrene. The data for this table were obtained as a result of long-term trials, so they better reflect the true diffusion of BA for a very long period time (decades). From Table. 2 shows that HCFC-22 and HFC-152a have a diffusion coefficient two orders of magnitude larger than the "durable" VA is these two gases do not linger long in the cells of XPS.

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