Could someone please explain why there are 2 types of space heaters-- one that is convective and one that is infrared? Why does the first one not radiate and why does the second one not heat the air?
I know also that a convective heater is built with a spiral wire over a ceramic core that act like a resistor that gets heated. How exactly is infrared heater built?
A human body feels heat while in contact with the air, so it is desirable to heat the air. This is what convectional heaters do - they have a developed surface and relatively low temperature to transmit the heat to the air. The radiation power is proportional to the following temperature difference: $Q \propto (T_{heater} ^4 - T_{air} ^4)$, so it can be small. The heater transfers its heat mainly to the air and the air transfers it to the walls.
The radiating heater has small surface, but much higher temperature so its radiating power is the main heat transfer (it works just like a lamp). The infrared waves get on the skin and heat it. Otherwise they get on the walls and heat thick walls. The radiating heater heats the air too, but due to too high temperature this hot air goes straight up and heats the ceiling, so it is poorly mixes with the room air.
Convective heaters do indeed radiate, but they radiate much less than an infrared heater because they are at a lower temperature. The amount of energy radiated by an object (strictly speaking a black body) is determined by Stefan's Law and varies as $T^4$ so a small increase in temperature makes a big difference.
Air is transparent to infrared radiation, so an infrared heater can't heat the air directly. Instead it heats anything it's radiation hits and that object then heats the air.
Almost all of you might have been told or learned about an infrared heater. It is innovatively manufactured to give heat by means of infrared light. This way of home heating is definitely effective since this is the same method that our great sun heats the entire world.
