01Confirm the flow and pressure basis
State whether flow is mass flow, actual volumetric flow or standard volumetric flow, and identify the reference temperature and pressure for standard flow. Compressed-air density changes with pressure and temperature, so values on different bases cannot be used interchangeably.
Provide minimum, normal and maximum operating pressure, inlet and target outlet temperature, and whether operation is continuous or intermittent. Include dew point, oil carryover or moisture details if they affect the equipment.
02Estimate duty and check pressure drop
For sensible heating, start with P = ṁ × cp × ΔT, then account for casing and piping losses and startup requirements. Use properties at the actual pressure and temperature; the preliminary estimate should be reviewed by the heater designer.
The heater flow path adds pressure drop. Include the allowable pressure drop in the specification and check it against compressor capacity, downstream valves and piping resistance.
03Review element materials and surface temperature
The sheath material must suit moisture, oil mist, cleaning residues and maximum operating temperature. Outlet air temperature is not the same as element surface temperature; verify heat flux, flow distribution, local stagnation and control accuracy.
If the air contains flammable substances or the equipment is in a classified area, review the construction, temperature limits and approvals against the area classification and applicable regulations. The generic term “air heater” does not establish suitability.
04Specify operating interlocks and measurement
- Use a suitable flow or differential-pressure signal to prove airflow
- Provide outlet temperature control and assess an independent high limit
- Include fan, compressor or valve status in the operating sequence
- Define safe response to shutdown, low flow and sensor failure
Set the detailed logic from the equipment instructions, risk assessment and project requirements. Record inlet conditions, pressure, flow, current and inlet/outlet temperatures during commissioning.