UniSim Fired Process Heater Modeler | HTRI

The Challenge

Fired heaters are often used as hot oil heaters, catalyst regenerators, cracking furnaces, reactor charge heaters, as well as for primary distillation of crude oil, and steam reformers. To identify their best operating conditions to meet the ever changing market needs, as well as minimize the operational risks, has become an on-going demand for production processes involving fired heaters.

The Solution: UniSim Fired Process Heater Modeler

Honeywell’s UniSim Fired Process Heater Modeler is a standalone simulation product within the UniSim Design Suite. It provides designers and operators an effective and reliable means for modeling, design checking, thermal rating, and troubleshooting the operations of gas or oil-fired process heaters.


UniSim Fired Process Heater Modeler enables users to identify optimized design for heater configurations and optimized operating conditions to ensure the safety, reliability and efficiency of the overall production. Its comprehensive and reliable calculations, accompanied by well integrated firebox and convection section processes and an extensive selection of graphical representations have made it easy for users to gain insight and better understanding of the fired heaters they design or operate.


UniSim Fired Process Heater Modeler has two calculation modes:

Fixed (Performance Simulation Mode) – Used for simulation or design checking. With user-specified firebox and convection section geometry, information about the fuel, combustion air, and process fluid, the program will calculate the heat transfer, temperature and pressure drop distributions in the heater, as well as the stream outlet conditions.

Calculate (Burner Rate Mode) – A thermal rating option used for calculating the burner fuel flowrate required to achieve a user-specified heat load on the firebox process stream.

Wide Range of Applications

The program supports a variety of fired heater configurations and applications, including:

  • A cylindrical or cabin firebox with either vertical or horizontal tubes;
  • A convection section with up to 9 banks of horizontal, plain or extended surface, each with tubes having different diameters, layouts, and types (plain, finned, or studded), carrying the same or different process fluids (process streams);
  • Up to 9 process streams flowing either co- or counter to the gas stream;
  • A selection of fuels, including a standard set of commonly used fuels and user-defined fuels;
  • An open or re-circulating flue gas exhaust system
  • A comprehensive UniSim Thermo package which contains data for over 1000 compounds and a range of methods for determining vapour-liquid equilibrium and mixture properties.

UniSim Fired Process Heater Modeler brings equipment designers, process engineers, and plant operators the flexibility and user-friendly tools which make their effort in tackling the complexity of such systems more effective.

User-Friendly Input and Output Functionalities

Users are guided through the data input process which is displayed through a hierarchy tree and very easy to follow. Graphic representations based on user-specified configurations further enhance the modeling experience of UniSim Fired Process Heater Modeler users.

The calculation results are presented in both text and graphical formats. Users can choose to view specific information of interest, or the full results output which provides comprehensive information on the exchanger geometry, the process conditions, the physical properties, and other parameters determined during the calculation. The built-in graphical feature enhances users’ experience in visual interpretation of the output information.

UniSim® is a registered trademark of Honeywell International Inc.