Rate, simulate, and design air coolers and economizers

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Xace® is an incremental program that rates, simulates, and designs crossflow heat exchangers, such as air coolers and heat recovery bundles. The heat transfer and pressure drop correlations are continually improved as a result of our ongoing research.

As a module in Xchanger Suite®, Xace lets you quickly transfer applicable case data to other components like Xist® or Xhpe®.


  • Models virtually any bundle arrangement.
  • 3D incrementation calculates localized profiles for heat transfer, pressure drop, and flow regimes.
  • Detailed output reports provide overall and localized results.
  • Extensive visualization tools show exactly how the exchanger is performing.
  • Integrated physical property system eliminates requirement for additional property generation software. Xchanger Suite includes VMGThermo™, an extensive and rigorous fluid physical property generator from Virtual Materials Group, Inc.
  • Includes built-in interface to most process simulators and mechanical design software.
  • Can be embedded as a unit operation in any process simulator supporting CAPE-OPEN.
  • Both input and output can be displayed in multiple unit sets, including user-defined sets. Dynamic display of values in all unit sets. 
  • Integration with Exchanger Optimizer™ provides embedded costing features, which include fabrication, installation, and operational estimates for design cases.
Xace Geometry
Bundle layout tool allowing complete customization of bundle.

Geometry Specifications

  • Forced and induced draft, A-frame, and no fan configurations
  • Horizontal, vertical, and inclined tubes
  • Up to nine different tube geometries per bundle
  • High-finned, low-finned, continuous-finned, stud-finned, and plain tubes
  • Twisted tape inserts and internal microfin tubes
  • Staggered and inline arrangements with any combination of transverse and longitudinal pitch
  • Up to 99 tuberows per bundle
  • Automatic or user-specified bundle layouts
  • Single bundle, multiple bays, bundles in parallel, and multiple bundles/services options
  • Split-pass headers with up to 24 tubepasses in each tuberow
Xace Calculation
3D plot displaying local air flows for natural draft unit.

Calculation Features

  • Rigorous heat transfer and pressure drop calculations using a 3D incrementation scheme that divides the exchanger into a large number of zones
  • Flexible process input allowing specification of known process information (temperature, weight fraction vapor, and/or flow rate) with the program calculating missing information based on energy balance
  • Three modes: rating (known duty and geometry), simulation (unknown duty and known geometry), and design (known duty and unknown geometry)
  • Forced- and natural-draft calculations
  • Option to switch on/off effects of gray gas radiation 
  • Airside flow and temperature maldistribution models
  • Integrated vendor-supplied fan selection software
  • HTRI research-based methods or ESCOA methods for high-finned tubes

Design Tools

  • Automatic optimization of tuberows, bundle width, tubepasses, and airside face velocity
  • Grid design option to vary geometry over user-specified ranges and step sizes
  • Design constraints to prevent selection of undesirable designs
Xace Outputs
Display of multiple output views for single unit.


  • Extensive set of spreadsheet-style output reports can be printed or exported to Microsoft® Excel®
  • Summary reports with overall results in one or two pages
  • Detailed reports for local profiles of all important parameters (temperature, pressure, heat transfer coefficients, heat flux, etc.)
  • Standard API 661/ISO 13706 style specification sheet
  • 2D and 3D scaled drawings provide visual confirmation of exchanger geometry, allowing for quick identification of performance issues
  • Bundle layout drawing illustrates exact tube placement, including tubepass and tube type
  • User-defined graphs for easy accessibility