| Question |
Can Solar Products heaters be tuned to
the appropriate wavelength? |
| Answer |
All infrared heaters have
the ability to be tuned. The wavelength is inversely proportional to the temperature.
That is to say, as the temperature goes up - the wavelength goes down.
Electric heaters have an infinite ability to be adjusted within the temperature limits
of the heater. This allows for more flexibility in matching the output of the heater
to the product requirements. Gas heaters have less turndown capability. Generally
speaking, gas heaters can go from 100% down to 70%. Below that point the heaters
will shut off.
Many people believe that the goal is to match the output wavelength of the heater
to the absorption of the product. This is a good point to start, but it is not always
the case. For most applications, either short, medium, or long wavelength heaters
can be applied. Generally speaking short wave will heat, cure, or dry the product
in the shortest amount of time. Medium wave will take slightly longer. Long wave
will require the most time to heat, cure, or dry the product. There are factors that
come into play that make the above statement incorrect. An example would be when
heating white plastic sheet, as in a thermoforming application. Short wave infrared
is color sensitive. Meaning that black colors will quickly absorb short wave infrared,
but white colors will reflect a much larger amount of the energy. Therefore, when
heating a white sheet of plastic, the medium wave can actually heat the sheet faster
than the short wave emitter. Testing is the only way to truly determine the results.
All of the heaters in the market do not output energy at a single wavelength. In
fact, the energy is spread across multiple wavelengths, but usually has a peak wavelength
that relates to the temperature of the emitter (25% of the energy is at a shorter
wavelength than the peak and 75% of the energy is at a longer wavelength than the
peak). Many factors will come into play when making the decision on which wavelength
emitter is appropriate. Some of those considerations are: initial cost of the system,
operating cost, available space, process speed, and maintenance costs - just to name
a few.
The reason why Solar products panel heaters are often chosen relates to the high
radiant efficiency (typically 80%) of the heaters, the long life (25,000 hrs), the
durability, the flexibility in available sizes, the temperature uniformity, and the
price is right. |
| Question |
Does infrared heat penetrate a sheet of
plastic? |
| Answer |
Infrared heat does penetrate
the sheet within limits. It has been stated that infrared energy will penetrate the
sheet up to .015 inches. Past that point the sheet is heated via conduction. The
real penetration amount will depend on a lot of variables, such as: heater output
energy, wavelength, sheet type, sheet characteristics, and sheet color.
Heating cycle times are dependant upon that conduction into the sheet and the amount
of power that the sheet can absorb before the surface begins to overheat and possibly
burn. When comparing ABS vs HDPE we find that ABS will burn at a much lower temperature
than will HDPE. For this reason the heater temperature for ABS applications does
not typically exceed 800 F. When heating a sheet of HDPE, the temperature of the
heaters can be raised 300-400F without damage to the sheet surface. This increased
temperature allows more energy to be absorbed by the sheet. HDPE is a crystalline
material which requires more energy to heat the sheet than would be required for
an amorphous material such as ABS. So, being able to turn up the heat with HDPE is
a good thing because it reduces the heating cycle time. Even with more power, the
HDPE typically takes 1 second per mil to heat the sheet and ABS can be heated at
.5 seconds per mil. The heating rate for ABS is accomplished with a lower heater
temperature (therefore, a lower energy output). Those are general rates of heat transfer.
The heat transfer will be faster as the sheet thickness goes down and the heat transfer
will be longer as the sheet thickness goes up. It is stated that the heating cycle
times are proportional to the square of the sheet thickness. |
| Question |
What sizes are available for Solar Products
heaters? |
| Answer |
It depends on the type of
heater that is required. Our most common heater is the F-Series heater due to the
high radiant efficiency (typically 80%) of the heaters, the long life (25,000 hrs),
the durability, the flexibility in available sizes, the temperature uniformity, and
the price is right. These heaters come in standard sizes of 6" and 12"
widths and 6" increments in length up to 60" for the 6" wide heater
and up to 84" for the 12" wide heater. Because Solar Products is a custom
manufacturer of heaters the length and width can be customized to your exact requirements
within good engineering limits. The heater width can range from 3" to 30"
and the heater length can range from 6" up to 84". We prefer to not build
a heater that is 30" x 84". This heater is large and will not hold up over
time.
The G and M-Series of glass and metal face heaters have more limits on the length
and width. Glass face heaters do not typically exceed 36" in length and metal
face heaters can go up 48" in length.
The Q-Series are restricted even more in size. There is a limit in how large the
quartz can be manufactured. These heaters are commonly smaller, such as 6" x
12" and 12" x 12". The heaters have been manufactured in sizes up
to 15" x 16".
The size limits for all of the above mentioned heaters will vary depending on the
application. These sizes are given as general guidelines. |
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