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Physical characteristics.
2.5 kg /Sqm per mm. Of thickness.
-
Hardness: the hardness of glass is 6.5
Mohs, nearly the same as quartz.
-
Elasticity: young’s modulus (e) = 7 x
10ov 10 PASCAL’s.
-
Poisson’s ratio:
s
= 0.2
-
Bending resistance: about 400 Dan /
Sqcm.
-
Compression resistance: 10,000 Dan
/Sqcm.
Different type of glass.
·
Clear glass.
Architectural clear glass is almost
invariably of the soda-lime-silica type with small amounts of magnesium,
aluminum, iron and other elements.
·
Body tinted glass.
Is produced by small additions to
the melt of metal oxides, which do not materially affect the basic
properties except for the solar energy transmission- and hence the color.
·
Rolled Glass.
A-
Patterned glass
or figured is formed by a reversal of pattern on the roller (the other
roller being nominally flat) so that a repetitive design is impressed in
to the glass surface.
B-
Wired glass is made by
the rolling process .a steel wire mesh is sandwiched between separate
ribbons of glass.
C-
Polished wired
glass is now the only product, which is still subjected to a grinding and
polishing secondary process to remove surface irregularities, produced by
the rollers.
·
Surface coatings.
A-
On line coatings modifications is made while the
glass is hot and still in
The annealing
lehr. They may still be considered as basic products and
Size and
tolerance constraints are similar to those for clear float glass.
Surface coatings,
either for solar control purposes or for reduced
Emissivity is
called pyrolitic coating because they are generally applied
To the hot glass
during its passage through the annealing lehr. That
Coating has
the advantages of hardness and durability.
B-
Low emissive coatings. Energy conservation
products use low emissivity (or low e) coatings produced off line and on
line. These reduce emissivity from a value of 0.9 for uncoated glass to
less than 0.1
Definition of energy terms
Absorption :
the percentage of energy incident on
the glazing not directly transmitted or reflected (% absorption = 100% -
direct transmission - % reflected.
U – value :
a
measure of the heat gain or loss through glass due to
the difference between indoor and out door temperature the lower u-value
the better the insulation properties.
R
–
value :
a
measure of the resistance of the glazing to the heat flow it is determined
by dividing the u value into 1. The higher R– value the better the
insulation.
Shading
coefficient (SC) :
a
measure of heat gain through glass from solar radiation specifically, the
shading coefficient is the ratio between the solar heat gain for
particular type of glass and that of double – strength clear glass. Lower
shading coefficient means lower solar heat gain. And it can be divided
into short and long wave shading coefficient.
Short wave (SC.) = direct solar transmission x 1.16.
Long wave ( SC.) = shading coefficient – short wave (SC.).
Relative heat gain (RHG) :
the total heat gain through
for a specific set of conditions. This value considers indoor/outdoor air
temperature differences and the effect of solar radiation.
UV
transmittance :
the percentage of energy in the ultraviolet spectrum, from 300 to 380
nanometers, that is directly transmitted through the glass.
Visible light transmittance
:
the percentage of light in the visible spectrum, from 380 to 780
nanometers, that is transmitted through the glass.
Solar energy transmittance :
the
percentage of energy in the solar spectrum, ultraviolet, visible and near
infrared energy 300 to 4000 nanometers. That is directly transmitted
through the glass.
Solar Conversion:
·
Direct solar trans.= solar energy transmittance.
·Total solar trans.= shading coefficient (S.C.) x .086.
·
Indirect solar trans.= total solar trans.- direct solar trans.
·Absorption = 1 – direct solar trans. – solar reflectance.
Units Of measure.
U_Value : BTU /hr.ft2.F x 5.6745 =
W/m2K
BTU
/hr.ft2.F x 4.883 = kcal / hr. m2. C
Relative heat gain : BTU/hr. ft2 x 3.1525
= W / m2
BTU/hr. ft2 x 2.713
= kcal / hr. m2
RHG =(SCX200 Btu/(hr)(ft2))+(Summer
U Value x14)=Btu/Hr/ft2
Technical Specification
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