What is emissivity and how can black coating affect it?
Almost all objects emit electromagnetic radiation, which comes in the form of thermal and infrared radiation. Usually, when an object is hot, it emits thermal radiation. However, the heat is not visible to the human eye unless it becomes hotter to the melting level. That’s why hot lava emits its own light.
If you want to measure the temperature of a hot surface, you use an infrared camera. It helps you see how hot or cold a surface is. If you measure the amount of thermal radiation a surface emits, this is where the term emissivity and emissivity black body comes into being.
What is emissivity?
Emissivity is the term used to describe the ratio of radiation an object emits or absorbs to a black body when placed under the same conditions. In other words, the emissivity of an object refers to the amount of infrared energy an object will emit at a particular temperature. Scientists usually rely on thermal cameras to detect the presence of heat and get an accurate measurement of the temperature.
A simple way to explain this phenomenon is by using three cups. Put hot water in one of the cups, ambient water in the other, and cold water in the third one. When you view the images using an infrared camera, you will notice that the cup with hot water appears brighter than the rest. The one with ambient (or room temperature) will have the same color as the surrounding. The cup with cold water will have a darker shade on it compared to the one with ambient water.
Different surfaces when it comes to emissivity
Different surfaces have different types of emissivity levels. An object can have an emissivity of between zero and one. Black bodies or perfect emitters typically have a higher emissivity, which should be close to one. These types of surfaces are excellent absorbers and emitters.
On the other hand, surfaces with low emissivity will emit low radiation. Instead, they reflect the heat to the surroundings. A good example is shiny metal. When you are measuring the temperature of a shiny surface using an infrared camera, you will not get an accurate measurement as when you do so with high emissivity material.
That’s why you require attaching a black body or coating to the shiny surface. An excellent example of a black coating is black electrical tape. Once you stick it to the polished surface, it will appear brighter when you view it with an infrared camera. Additionally, you will also get an accurate temperature reading as when you use a thermometer.
Uses of black coating
Typically, they are helpful in most industries. When you need to measure the radiation on a shiny surface, these black coatings will help you test and calibrate the temperature without contact or a thermometer. They are helpful in heating, thermal imaging, security, and testing applications.
