Fired Heater Duty Screening

Use this skill for public, educational fired-heater screening. It estimates the process duty, the fired duty, the fuel-gas rate, and the average radiant-section heat flux using open energy-balance relations so an agent can scope a fired-heater study and check the radiant flux against a public guideline before detailed thermal design.

When to Use

• When a user asks roughly what fired duty and fuel rate a heater needs.
• When an agent needs a quick radiant-flux check to scope a fired-heater study.
• When examples must run without confidential heater designs, vendor data, or company specs.

Inputs

• mass_flow: process mass flow in kg/s.
• specific_heat: process-fluid specific heat in kJ/(kg K).
• inlet_temperature: process inlet temperature in kelvin.
• outlet_temperature: process outlet temperature in kelvin.
• thermal_efficiency: heater thermal efficiency, default 0.85.
• fuel_heating_value: fuel lower heating value in MJ/kg, default 46.0.
• radiant_area: radiant-section tube surface area in m2.
• allowable_radiant_flux: allowable average radiant flux in kW/m2, default 37.0.

Outputs

• process_duty_kw: process absorbed duty Q.
• fired_duty_kw: fired duty from the efficiency.
• fuel_rate_kg_s: fuel-gas mass rate.
• average_radiant_flux_kw_m2: process duty divided by radiant area.
• flux_ratio: ratio of average radiant flux to the allowable flux.
• fired_heater_warning: ok, watch, or high-flux.
• assumptions: public assumptions used by the placeholder model.

Engineering Method

The Python class FiredHeaterDutyModel uses open energy-balance relations only:

• the process duty uses Q = mass_flow * specific_heat * (T_out - T_in).
• the fired duty uses Q_fired = Q / thermal_efficiency.
• the fuel rate uses fuel = Q_fired / fuel_heating_value.
• the average radiant flux uses Q / radiant_area and is compared to a public guideline.

This is educational and screening-only logic. It uses a constant specific heat, treats all process duty as absorbed in the radiant section for the flux estimate, and does not model convection-section split, tube-wall temperature, flame and bridgewall temperature, draft, or emissions. Typical public average radiant fluxes are about 30 to 37 kW/m2. It is not a replacement for validated fired-heater design (for example API 560) and a qualified review.

Python Usage Pattern

from fired_heater_duty_screening import FiredHeaterDutyModel

model = FiredHeaterDutyModel()
result = model.evaluate(
    mass_flow=15.0,
    specific_heat=2.4,
    inlet_temperature=473.15,
    outlet_temperature=623.15,
    radiant_area=200.0,
)

print(result.fired_heater_warning)
print(result.fired_duty_kw)
print(result.average_radiant_flux_kw_m2)

Related NeqSim Functionality

For validated fired-heater calculations, redirect to existing NeqSim classes:

• neqsim.process.equipment.heatexchanger.FiredHeater — fired-heater equipment model with duty and efficiency.
• neqsim.process.equipment.heatexchanger.Heater — generic process heater with duty calculation.
• neqsim.process.equipment.powergeneration.HRSG — heat-recovery steam generator for waste-heat duty.

This skill is a public energy-balance triage layer that decides when to invoke those validated heater classes.

Validation Checklist

• Mass flow, specific heat, and temperatures are positive and T_out > T_in.
• Radiant area and efficiency are positive and in range.
• Tests cover a duty calculation, a high-flux case, and invalid input.
• Results are described as educational screening indicators.
• Real design is redirected to validated methods, API 560, NeqSim, and qualified review.

Common Mistakes

Limitations

• No proprietary heater designs, vendor data, or company specs are included.
• No convection-section split, tube-wall, draft, or emissions modeling is performed.
• A constant specific heat is assumed over the full duty range.

References

• NeqSim repository: https://github.com/equinor/neqsim
• NeqSim Skills Guide: https://github.com/equinor/neqsim/blob/master/docs/integration/skills_guide.md