Direct-Fired Heaters
A direct-fired heater burns hot gasses but transfers the heat to a process liquid or gas flowing directly through heat exchanging coils. Direct-fired heaters offers flexibility since they can be used in radiant and convection heat exchanges, and can be configured in a wide variety of ways to meet requirements in an industrial or commercial application. The flexibility also allows these furnaces to be used in single or multi-burner operations.
Radiant Heater
A radiant heat transfer is a large collection of coils made up of bare tubes in a loose, serpentine pattern allowing a radiant heat transfer around the tubes. This system has drawbacks in temperature sensitive applications since radiant heat transfer from the bare tubes can be more intense and unevenly distributed around the coil’s surface.
Convection Heater
A convection heater eliminates the uneven distribution of heat found in radiant heat transfer. The convection heater is a combination of bare tubes and tubes with fins arranged in a tight bundle. The bare tubes shield the finned tubes from direct radiant heat.
Radiant-Convection Heater
The most common direct-fired heater combines the intense heat capabilities of the radiant heater with the even heat distribution of the convection heater by using both types of coils in tandem within one system.
In a radiant-convection heater, the heating process begins in the radiant section, designed to yield efficiency in a minimal space..
Flue gas then travels up from the radiant section to the convection system. The tight bundle of bare and finned tubes absorbs the remaining heat in the flue gas, increasing the heater’s efficiency and temperature consistency.
Typical Applications
Direct-fired heating & ventilating systems are used in commercial warehousing, distribution, storage, and exhibition or sports facilities, as well as in most every type and size of industrial manufacturing facility.
Direct-fired heaters typical system applications include:
- Thermal oil heating
- Regeneration gas heating
- Other direct process heating
- Natural gas heating
- In-line liquid heating
- In-line gas heating
- Crude oil heating