Xfh
Xfh simulates the behavior of fired heaters. This component calculates the radiant section performance of box and cylindrical heaters along with the performance of any convection section present. Xfh also designs process heater tubes and performs combustion calculations.
Process Specifications
Xfh handles the following process conditions:
- combustion
- vapor, liquid, or solid fuels
- vapor fuel components selected from internal data bank
- fuel flow specification directly or by desired heat release
- oxidant flow specification directly or by percent excess
- process fluids
- sensible liquid, sensible vapor, or boiling fluids
- properties specified directly or calculated from internal data bank
- inlet conditions at specified temperature or alternately for two-phase fluids using weight fraction vapor
- process outlet temperatures specified directly or calculated by energy balance
- radiant inlet or outlet process pressure
Geometry Specifications
Xfh accommodates the following geometries:
- radiant section
- cylindrical or cabin/box heater
- dimensions of radiant section and flue gas opening
- radiant tube geometry and radiant tube layout
- flexible specification of process flow through radiant coil
- radiant wall loss characteristics
- burner count, location, and geometry
- stack section
- multiple convection bundles
- automatic pass layout of convection bundles
- complete control over convection tube geometry
- stack geometry using pre-defined stack elements (e.g., straight duct sections)
Calculation Modes
Xfh performs several types of calculations:
- simulation of the radiant section of cylindrical and box heaters
Box heater calculations are based on a 3D analysis using the Hottel zoning method for radiant heat transfer to the tubes and a superposition method for multiple burners using simplified jet theory for flue gas flow. Simulations of box heaters include industrial box-type furnaces, nearly rectilinear steam boilers, and auxiliary equipment. The cylindrical heater option, which uses a rigorous algorithm similar to box heater calculations, simulates cylindrical upshot heaters. Both the box and cylindrical radiant flux calculations are linked to rigorous process-side calculations that provide local and overall values for tubeside heat transfer and pressure drop. - simulation of the convection section of fired heaters
Xfh calculates heat duty, flue gas and metal temperatures, and draft profiles for convection banks on a row-by-row basis. Stack fittings and sizes can be specified; Xfh uses API 560 methods to perform stack draft calculations. - evaluation of heater tubes based on the API 530 procedure
Xfh calculates tube metal design thickness and past/future tube damage based on specified operating conditions, heat transfer coefficients inside heater tubes, and radial temperature profiles across the tube from the bulk to the metal skin. - calculation of combustion products, mass balance, and overall heater energy balance
Xfh can simulate combustion of any fuel gas, fuel oil, liquid fuel, and/or solid fuel with any amount of excess air or oxygen. The oxidant can be air or any oxygen-bearing gas stream such as turbine exhaust.
Special Features
- Scaled graphical representation of geometry input for convenient validation
- Plotting capabilities to examine local process and radiant results graphically
- Graphical tool to lay out convection bundles and firebox tubes
- Single-zone radiant option allows quick calculations with a minimum of input
- “No tubes” option to model cases where tube geometry can not be handled via normal input
- Internal databases for gaseous fuel and process fluid components, facilitating calculations of all required properties from composition of fluid