UniSim Cross-Flow Exchanger Modeler | HTRI

The Challenge

Energy recovery is one of the most important aspects in every production facility nowadays, where the high productivity and low production cost are constantly under scrutiny. It has inspired manufacturers to seek for the most convenient and effective way to recover excess energy rejected from their production processes, as high grade energy is too valuable to waste and the recovery of low grade energy can result in large costly exchangers. That’s where cross-flow heat exchangers come in.

The Solution: UniSim Cross-Flow Exchanger Modeler

UniSim Cross-Flow Exchanger Modeler is a member of the Honeywell UniSim Design Suite, used for modeling crossflow (air-cooled and heat recovery) heat exchangers. It provides detailed thermal design, checking or simulation of cross-flow heat exchangers including process air-cooled heat exchangers, economizers, and the convection sections of fired heaters for industrial applications. It can be used standalone by the thermal specialist for exchanger design or as an integrated product with UniSim Design for process simulation.


UniSim Cross-Flow Exchanger Modeler allows users to identify the most appropriate exchangers for their process needs. Supported by decades of industrial driven research work, the technologies behind this product enable users to design new air-cooled heat exchangers; check whether an existing exchanger will satisfy the required process conditions; and examine how an existing exchanger fits into a given process.


UniSim Cross-Flow Exchanger Modeler has three calculation modes:

Design: To determine the optimum configuration of an air-cooled heat exchanger including the number of bundles, bays and fans required in addition to the necessary airflow, for the specified process duty. It can present an envelope of feasible designs; defines overall exchanger length/width, numbers of bays in a unit, number of bundles in per bay, as well as number of fans per bay.

Checking: To calculate whether the given exchanger is large enough to provide the required duty.

Simulation: To determine the heat load, pressure change and certain unknown stream conditions that will occur with a user-specified exchanger, with given stream conditions. This mode can be used to model any cross-flow heat exchanger. In addition to the standard simulation, there are eight other simulation options: Tube-side Outlet Temperature; Tube-side Inlet Temperature; Natural Convection; Tube-side Flowrate; X-side Flowrate (air flow); Tube-side fouling Resistance; X-side Bundle Velocity, and X-side Bundle Pressure Drop.

The stream on the X-side can be:

  • Dry Air: The default setting for an air-cooled heat exchanger using internal physical property.
  • Humid Air: For modeling air-conditioning units, using internal physical property data.
  • Dry Gas: for any cross-flow heat exchanger where the dry gas can be a mixture of gas. User-specified physical properties are required.

Easy-to-Follow Input Views

Users will be lead step-by-step through the data input process following a hierarchy tree. Some of the data are already provided by default and indicated on the input view, but in other cases depending on context and other input values, they are set up when you Run the calculation.

Wide Range of Process Applications

The UniSim Cross-flow Exchanger Modeler can perform heat transfer and pressure drop calculations on single- or two-phase streams, involving sensible heating or cooling, boiling or condensation, or any of their combination, for single component or multi-component systems.

Comprehensive Physical Properties

Physical property data can be imported from process simulators, such as UniSim Design, or generated from the UniSim Thermo package, which contains data for over 1000 compounds and a range of methods for determining vapor-liquid equilibrium and mixture properties. It is comprehensive and flexible to use. Users also have the option of importing physical properties and process data from their own physical property software with preconfigured interface.

Flexible and User-Friendly Output Functionality

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.

Other Important Features

  • The Setting Plan – a scale drawing of the unit, with some basic dimensions showing overall exchanger size, location of nozzles, fans and supports. A scaled drawing of tube layout is also generated for each calculation run.
  • The Word Specification Sheet – allows users to edit and save their design/simulation results into Word format.

UniSim® is a registered trademark of Honeywell International Inc.