Kefa Thermal Properties

 

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 0,01h to 10h. 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 (Dc). Various tests show that this factor varies somewhat with the coat thickness. See table below. Heat transfer resistance on the inside (Rsi) and heat transfer resistance on the outside (Rse) are included in the Dc factor.

Coat thickness

0,5 mm

1.0 mm

1.5 mm

2.0 mm

Dc factor

92

88

84

80

The heat conductivity (lKEFA) 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* Dc

     l

R = Heat resistance; m2K/W

d = Coat thickness; m

Dc = Dimension correction factor

l = Heat conductivity; W/m*K

 

 

Calculation of the Emergency Homes

 

R= d20* Dc20 + d*  + d40* Dc40

         lKEFA          lSteel    lKEFA

 

R = 0.0005*92 + 0.00047 + 0.001*80 = 1.35 + 0.0002 + 2.35 = 3.70 m2K/W

            0.034          20             0.034

 

R13 equals 3.5 m2K/W   

R = 3.70 m2K/W equals R13.7

 

Conclusion

The suggested KEFA solution is somewhat higher than R13.

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