How should inline heater design be specified for industrial heating elements?

To specify an inline heater, first establish the actual duty: calculate the required thermal power from medium specific heat, flow rate and inlet-to-outlet temperature rise, allow margin for startup, then fix the control scheme and sensor type. Next check watt density against tube diameter and velocity, since low velocity or a small bore raises local heat flux and can burn the element, especially with viscous or fouling media. The housing sets both flow path and pressure boundary, so verify port size and connection standard, design pressure, wetted material corrosion resistance, ingress protection, mounting orientation and service clearance, and place the sensor where it reads true outlet temperature without dead zones. Acceptance should record measured current, insulation resistance, temperature response and pressure drop against the approved drawing revision; whenever medium or flow changes, re-rate watt density instead of reusing old data.