The Eco Heat Blog

Now that we’ve covered the basics of heat transfer and infrared heating, let’s get into the nitty gritty of the science behind infrared radiation.

Lesson #1: Electromagnetic Radiation and Wavelength
Electromagnetic radiation is classified into several types according to the frequency of its wave; these types include (in order of increasing frequency and decreasing wavelength):

• Radio Waves,
• Microwaves,
• Terahertz Radiation,
• Infrared Radiation,
• Visible Light,
• Ultraviolet Radiation,
• X-rays
• Gamma Rays.

A small window of frequencies are sensed by human eyes; this is what we call the visible spectrum, or light.

Because all electromagnetic waves travel at the speed of light, the behaviour of electromagnetic radiation depends on its wavelength. Higher frequencies have shorter wavelengths, and lower frequencies have longer wavelengths. This is depicted by the formula:
v = f x λ (speed = frequency x wavelength)

Light and electromagnetic waves of any frequency will heat surfaces that absorb them.

Lesson #2: Temperature and Wavelength
Every object in the universe that has a temperature gives off electromagnetic radiation. Its electromagnetic waves will peak at a specific wavelength, depending on its source and temperature, and no object gives off all wavelengths equally.

The emitted wave frequency of the thermal radiation is a probability distribution depending only on temperature, and for a genuine black body is described by Planck’s law of radiation. Wien’s law gives the most likely frequency of the emitted radiation, and the Stefan–Boltzmann law describes the heat intensity.

If the object is a black body, the radiation is termed black-body radiation.

The graph on the right uses Planck’s law to determine the different wavelengths at a set temperature (y-axis is Watt / area / wavelength). This graph shows that black bodies give off electromagnetic waves at wavelengths of the electromagnetic spectrum, but not equally at all wavelengths. The peak wavelength is derived from the temperature of the black body using Wien’s displacement law.

Wien’s displacement law states that there is an inverse relationship between the wavelength of the peak emission and the back body’s temperature, i.e. the hotter the object, the shorter the wave length and vice versa.

At room temperature, black bodies emit mostly infrared light, but as the temperature increases past a few hundred degrees Celsius, black bodies start to emit visible wavelengths, from red through orange, yellow and white before ending up at blue, beyond which the emission includes increasing amounts of ultraviolet if it is heated to extreme temperatures.

Lesson #3: Radiation from a human body
The total surface area of an adult is about 2 m², and the mid- and far-infrared emissivity of skin and most clothing is near unity, as it is for most nonmetallic surfaces.

Radiation from a human account for about 2/3 of thermal energy loss in cool, still air.

Humans at normal body temperature radiate chiefly at wavelengths around 10µm (micrometers) at 37.0 °C.

Ever sit, basking in warmth, thinking “gee, I wonder what the science behind this nifty heater is”? Then this post is for you.

Here is a short and sweet explanation of the different ways that heat can be transferred and what makes infrared heaters energy efficient.

Lesson #1: Sources of Heat

Heat can be transferred by means of conduction, convection and radiation.

Heat Conduction:
Conduction is the transfer of energy through matter from particle to particle.

Some examples of heat conduction are:
- Water boiling on a stove
- Ice melting in your mouth

Heat Convection:
Convection is the transfer of heat by the actual movement of the warmed matter, such as air or water.

Some examples of heat convection are:
- The heater in a car that heats air by blowing it over a hot element
- An old-fashioned radiator that heats up the air in a room
- The heated air above a hot stove will rise to the ceiling

Radiation (Infrared):
Radiation is electromagnetic waves that directly transport energy through space.
It does not need a medium like convection or conduction.

Some examples of thermal radiation are:
- Heat from the sun warming your face
- Heat from a light bulb
- Heat felt when standing next to a fire
- Food staying warm under a heat lamp

Lesson #2: Why is Infrared Heating Energy Efficient?
Infrared heaters work by emitting radiant heat, also known as thermal or infrared radiation. This heat comes from electromagnetic waves that travel through the air and are absorbed by objects.  Radiant heat is safe and similar to the heat you feel from the sun on your skin, but does not contain the harmful UVA and UVB rays.

Most traditional heating methods work by raising the ambient air temperature. Infrared heat directly warms people, animals and other objects, thus using energy more efficiently. The energy is not wasted by raising the ambient temperature through convection, but is instead converted into infrared heat that is safe and ideal for absorption by the human body.

The heat generated by an infrared heater is focused and projects a ray of heat over a defined area. This allows the user to target specific areas to be heated and avoids money being spent to heat unnecessary areas. Infrared heaters do not dry out the air, burn any oxygen or produce any gasses or pollutants.

Lesson #3: Black Body Radiation, or How to Make Infrared Heating More Efficient
Eco Heat’s heaters take the energy efficiency of infrared heat up a notch with the use of “black body emitters.” The elements Eco Heat uses are known as black body emitters because they radiate mostly infrared radiation and not visible light.  More energy is saved because electricity is not wasted by creating visible light.

Stay tuned for Infrared U: 102 – we’re going to get nerdy with the science behind infrared heating!