Direct Fired Heater
A direct fired heater, is an equipment used to provide heat for a process or can serve as reactor which provides heats of reaction. The reference standard for this type of fire heater is API 560.
Indirect Fired Heater
Indirect fire heater is an equipment to heat a gas by using a medium that is usually oil or water. For safety reasons if you want to not heat your main fluid directly you will heat it by a medium such as water or oil. But this mater shall be considered that medium temperature can’t be so high and it should not be near it’s vapor temperature. The applicable standard for this package is API spec 12K.