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5-4.Proper use of near-infrared heating and far-infrared heating

Proper use of near-infrared heating and far-infrared heating

The temperature radiation is light (in the broad sense) electromagnetic waves emitted when it is heated to a high temperature material.
There is such as laser heating as the optical heating method of non-temperature radiation.

The near-infrared heater, using a halogen lamp generally light of 2000 – 3150 ℃ level is emitted.
Peak wavelength is distributed in the range of about 1μm (0.001mm), a 0.5 – 3μm.
Includes much visible light, dazzling in general.
There are also measures how to reduce the visible light by, for example, colored glass.
Further, if set to 2000 ℃ below the heating element temperature, it is not so much glare.

The adhesive heating.

Since the far-infrared is not transmitted through the object of most of it will be very heated surface of (0.1 – 0.2mm).(By utilizing this characteristic, the glass heating has been widely used.)
In the example that uses far-infrared heater to heat the adhesive Therefore, it is burning surface and in the adhesive close to transparent example, heat is not transmitted until quite internal.
Because it is heated from the inside by osmosis (transmitted), the foam comes out from the inside in the case of near-infrared heater.
Therefore, it has been a must in this near-infrared heater to the adhesive heating.

Infrared Transmittance of the Glass

Confirmation of absorption rate

The printed paper heating.

Upon heating the printed paper, it is heated as a whole in the case of a far infrared heater.
Part of the white paper is not so much part of the heating and photos printed characters is heated strongly in the case of near-infrared heater.
That is the difference between the ease of the absorbed large surface state of the object to be heated (such as color) is the near-infrared, that tend to easy to get uneven heating degree.

The meat heating.

The now better absorb near-infrared and bake meat in the near infrared heater, where it began burnt becomes black,
Circulation that part that is heated more intensive occurs, it will strongly burnt locally.
That browning tends to be uneven in the same material. Browning is attached evenly towards the far-infrared heater.
It is also a disadvantage, but I will also benefit depending on the purpose.
Activated, for example, may be if painted black and only the portion to be heated if it is desired to heat partially.

Start-up time

Normally, it can use about 5 second after the start of energization near-infrared heater, but far-infrared heater can take 30 seconds to a few minutes.
If it does not matter by heating rapidly, who was allowed to temperature rise sharply in a short period of time to give the highest possible energy density will be very well power consumption efficiency.

When the temperature is increased over a long time at low energy density, because the heat radiated from the heated object to reach the target temperature is lost.
It may need power amount is several times at low speed heating and rapid heating.
Since near-infrared heater capable of providing an energy density of several tens of times of far infrared heater, high energy efficiency can be expected in such cases.
It can control or turn off the power if necessary Upon reaching the target temperature, so as to keep the target temperature by lowering the power.

And to heat rapidly giving a large energy density, there may not be suitable depending on the type of the object to be heated.
For example there may be an internal temperature that is not increased sufficiently by burning only the surface in the case of heating the food and thick.
Must be multiplied by the long low energy density in this case.

Heat is easily transmitted to the inside and because it takes a long time to heat inevitably the case of far-infrared heating, energy density is low originally.
Should be controlled to lower the energy density in some cases near-infrared heater.
It seems misconception that such “is heated from within to penetrate the inside of an object” was born in the far-infrared radiation that is not absorbed only at the surface a very small, cause time is took to the heating energy density is low.
In many cases, better results in the near infrared heater is good will appear in the performance of our cases that are exchanged in the far-infrared heater there are many it is determined by experience and experiment.
And since is that it can be seen in a simple experiment, please try it first.

Conversion efficiency radiant energy

Conversion efficiency of radiant energy to the power supply is good is 85% or so in the near infrared heater.
It is pretty bad in the 60-70% about the case of the far-infrared heater.
Ross energy did not become infrared warms the air mainly.
Some people are mistaken visible light emanating from near-infrared heater (lamp) and does not contribute to the heating, but the light energy visible light is absorbed into heat all.

Absorption rate is worse than the far-infrared generally with respect to the object of relatively light-colored wood, paper, cloth, such as a human body near-infrared.
However, consider the difference between the will reduce the conversion efficiency of the heater itself.
Is not limited towards the far-infrared heater is good and efficient, if energy efficient prefer near-infrared (lamp heater) but rather is often necessarily also taken into consideration the loss of time and energy required for the rise of the heater itself.

When heated in that to create a closed space with a highly reflective material further, high overall thermal efficiency can be expected.
To repeat the fact that resorbed Upon the heated object light reflected without being absorbed by the first exposure may also be re-reflected by the walls, which are at the high absorption rate.

η , overall thermal efficiency
S1, area of the wall,
D1 absorption rate
S2. Surface area of the heated object,
D2 absorption rate,

efficiency η ≒ S2 × D2 / (D1 × S1 + D2 × S2) ×(Conversion efficiency of the heater)

Even if not up to a closed space, in the case, such as to cover the object to be heated in a large reflector plate, it becomes close to the situation above, it will be high overall thermal efficiency.

Energy density emitted from the heating element of the heater is low near-infrared heater infrared heater is far higher.
The difference will also be 20-40 times.
Since not never, in principle, on the surface energy density of the heating element more even collected at one point the infrared light-collecting mirror, very high energy density is not given in the far infrared heater.
(Infrared heater is 170w / cm ^ 2 or more lamp heater of a few w / cm ^ 2 degree. Near-infrared)

Radiat intensity and wavelength distribution

Therefore, high-temperature heating and rapid heating, spot heating is difficult in the far-infrared, near-infrared heater is ideally suited for use in such applications.
For energy cost and processing speed is important, in most cases, rapid heating will be required in industrial.
Near-infrared heater is advantageous for industrial heating.

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