Air can be heated with open-coil heaters, tubular heaters, strip heaters and quartz heaters. The choice of one over the other depends mainly on volume, pressure and air velocity. To increase heater life, use a phase-angle fired or zero-cross fired ( SCR ) power control.
Air heaters work by radiating heat into the passing air/fluid. Unfiltered air may contain dirt, grease and water which will reduce heater life, especially for open coil air heaters. Important is an air flow over the air heating element for some time even after the heater is turned off. Use a time delay relay for this. If the temperature sensor is far downstream from the air heating element, place an over-temperature sensor close to the air heater itself. We recommend the use of a flow switch in the airstream to avoid any overheating of the system in case airflow is insufficient.
To calculate the approximate power requirement in kW: multiply the standard cubic feet per minute (scfm) by the temperature difference and divide by 3000. [kW = (SCFM x Delta T)/3000](example: to heat 100 scfm 100 degF you'll need 3.3 kW)
Other important factors to consider:
Open coil air heaters work best below air velocities of 80 FPM. Higher air velocities could cause the coils to touch each other and short out. Because of the low mass and fast response time of these heaters, use a phase angle SCR instead of a zero cross fired SCR with voltage limiting. We do stock different open-coil air heaters.
Tubular and Strip Heaters:
Tubular air heaters and strip heater in various shapes are used to generate hot air. They're often used for comfort heater (HVAC) and ovens. If the process temperature is less than 500 deg F, finned tubular- or strip heaters could be used. For high temperature process air heating of up to 1200 deg F, a tubular air heater element without fins would be the choice.
Quartz and Ceramic Air Heater:
Quartz & Ceramic air heaters work up to 1500 degF, 10 PSI max inlet pressure, and various SCFH). We do stock a variety of quartz air heaters in our facility in Pico Rivera (Los Angeles).
They're commonly used in:
Contact an engineer for more information.