*Background*
As a result of the space technology new insulation materials have been developed. These materials
have insulation properties that cannot be explained by the conventional formulas for insulation. Most of these new materials
are based on micro porous ceramic spheres. KEFA HeatProtection is a based on a different kind
of micro porous material and differs from both conventional insulations and the so-called ceramic coatings. **The pores vary in size from 0,01****h**** to 10****h****. This gives the coating a relative
surface which is 20 - 50 000 times the visible surface.**
** **
The heat flow through this insulation
consists of radiation and conduction. Contrary to conventional insulation there is no convection involved. The heat conduction follows
the shortest way through a material. This distance is considerably longer in a micro pore matrix than in e.g. mineral wool. There is always a minor heat
resistance when the heat goes from one material to another. In the micro pore matrix the heat flow constantly goes between
different materials. The micro pore matrix also affects
the heat radiation. The heat radiation flow consists of reflexion, adsorption and radiation. In the micro pore matrix the
amount of reflexion/adsorption/radiation is enormous. It is not practical nor possible to calculate all these transmissions. To make the calculation
understandable and practical the conventional formulas must include a Dimension Correction Factor (D_{c}). Various
tests show that this factor varies somewhat with the coat thickness. See table below. Heat transfer resistance on the inside
(R_{si}) and heat transfer resistance on the outside (R_{se}) are included in the D_{c} factor. Coat
thickness | 0,5 mm | 1.0 mm | 1.5 mm | 2.0 mm | D_{c} factor | 92 | 88 | 84 | 80 |
The heat conductivity (l_{KEFA}) of KEFA HeatProtection without the micro pore matrix has been calculated to 0.034 W/m*K.
With the Dimension Correction
Factor, the R-value of a certain KEFA HeatProtection coat can be calculated using the normal formula: R=__d* D___{c} l R = Heat resistance; m^{2}K/W d = Coat thickness; m D_{c} = Dimension correction factor l = Heat conductivity; W/m*K **Calculation of the Emergency Homes**
R=
__d___{20}* D_{c20} + __d* __ + __d___{40}* D_{c40} l_{KEFA} l_{Steel} l_{KEFA} R = 0.0005*92 + 0.00047 + 0.001*80 = 1.35 + 0.0002 + 2.35 = 3.70 m^{2}K/W 0.034
20 0.034 R13 equals 3.5 m^{2}K/W
R = 3.70 m^{2}K/W equals R13.7 **Conclusion**
The
suggested KEFA solution is somewhat higher than R13. |