Linear Voltage regulator becomes very Hot when connected to Nichrome wire heater
I'm using a 12v linear voltage regulator (L7812CV) as a power adopter which is connected to a rectifier bridge providing 19v.


In this circuit the linear regulator is acting as a resistor with a resistance set so that 12v is dropped across your heater and 7v dropped across your regulator.  Since the same current flows through both and the voltages are almost equal, your regulator is dissipating nearly as much heat as your heating element.  

A better design would be to run the nichrome wire off of 19v (perhaps by putting a little more of it in series) so that you don't need the regulator or to get a switching regulator so that you don't have to dissipate all that heat.