The choice of insulation strips
The isotherms of windows are usually observed and measured by thermal imaging cameras or thermometers, but we can also simulate them by software.
The isotherms of thermal-break profiles are denser than those of ordinary profiles. Glass and thermal insulation materials are on the same line, and the isotherm is straighter.
The insulation cavity and the periphery of the glass are places where convection and radiation heat transfer are common. Filling insulation materials in such places, such as styrofoam, PE and PU, can effectively reduce the heat transfer in these areas.
We usually see some insulation strips with different sizes and structures in the market.Theoretically speaking, the insulation effect can be improved by adding more cavity structure to the insulation strip. However, after comparing the experimental data, in some cases, the results are different.
1. All insulation strips are designed as C-shaped insulation strips, as shown in Design 1 in the figure;
2. All insulation strips are designed as internal fin insulation strips, as shown in Design 2 in the figure;
3. All insulation strips are designed as hollow insulation strips, as shown in design 3 in the figure;
We use the 65 series model with 18mm insulation strips to show the influence of cavity design on the thermal insulation profile of small insulation strips.
It can be seen from the simulation results that the Uf values of the three designs have little difference. After changing the C-shaped strip into the inner fin strip, the Uf value increased by 0.08W/m2K, while all the heat insulation strips were changed into the third model of cavity design, and the better heat insulation performance of the profile was not obtained because of the cavity design, but it was the worst of the three.
This is because when the width of the insulation strip is small, the energy transmitted by convection and radiation in the insulation area is very small, so the design of the cavity insulation strip will not produce greater insulation contribution because it can inhibit the energy transmission by convection and radiation, but will bring more energy transmission by conduction.
The following simulation shows the results of filling foam materials in the insulation areas of the above three models.
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In such a small width of the insulation strip, the improvement of the insulation performance of the profile caused by filling foam in the insulation area is very small.
If we increase the width of the insulation strip to 20mm, what will happen?The following is the simulation result of 20mm insulation strip.
The following simulation shows the results of filling and foaming the insulation area of 20mm insulation strip.
Through the comparison of the two groups of tests, we can know that if the width of the insulation strip is small, whether it is foam filling in the insulation area or full cavity insulation strip design, the improvement of the insulation performance of the whole window is not obvious, but it increases the cost of the whole window.
Therefore, it is not recommended to adopt the design of full-cavity heat insulation strip when the profiles with the width of insulation strip of 20mm or less. It is of little significance to change C-shaped strip into internal fin strip and multi-cavity strip, and the cost performance is not high.