Cut the Iteration Cycle: Cross-App Thermal Linking Now in Fathom & Arrow

Engineering systems that involve both gas and liquid flows often rely on heat exchangers to transfer energy efficiently. Cooling water systems are a prime example: they frequently serve as the backbone for cooling gas piping systems through multiple heat exchangers. Until now, modeling these types of systems in Fathom and Arrow has required significant manual effort, forcing users to iterate between the two applications to achieve balance. With the introduction of the Cross-App Heat Exchanger Thermal Link, this process becomes automated, more accurate, and far less time-consuming.

Why This Feature Matters

Traditionally, engineers modeling a liquid-gas heat exchanger needed to alternate between Fathom (for liquid systems) and Arrow (for gas systems). Each run required manual adjustments of the heat exchanger junction inputs, followed by rerunning simulations until the two sides agreed. Not only was this process tedious and slow, but it also left room for human error – particularly when juggling multiple heat exchangers.

The new Thermal Link solves this problem by creating a direct connection between Fathom and Arrow. The two applications now run simultaneously, exchanging data automatically until a converged solution is reached. This streamlined workflow allows engineers to focus on system optimization instead of repetitive input tweaking.

How the Thermal Link Works

The Cross-App Thermal Link connects heat exchanger junctions in Fathom and Arrow, simulating the thermal interaction where liquid flows through one side and gas flows through the other. Once the link is enabled, the software takes care of the iteration loop:

1. Initialization – Fathom runs its liquid system model with the user-defined heat exchanger inputs.
2. Exchange – The results for the secondary fluid are passed automatically to Arrow.
3. Iteration – Arrow runs the gas system, converges, and returns updated secondary fluid conditions back to Fathom.
4. Convergence – This back-and-forth process continues until the heat balance between the two models converges within the defined tolerance.

By default, the tolerance is 0.1% with a maximum of 20 iterations, though users can adjust these settings as needed. Once convergence is achieved, both models retain the results and can be saved for further analysis.

What once took dozens of manual iterations can now be solved automatically in one integrated run.

Key Requirements and Setup

To use the Thermal Link effectively, there are a few setup requirements:

• Both Fathom and Arrow models must be fully defined and contain a heat exchanger configured with a secondary fluid (Counter-Flow, Cross-Flow, Parallel, or Shell & Tube).
• User-specified values for flow rate, specific heat, and inlet temperature can be entered initially – these will be replaced by data exchanged between the two applications.
• Arrow must be opened and run as Administrator, and only one instance of Arrow can run at a time.
• Enable Run Thermal Links in Analysis Setup > Solution Utilities in both programs. In Fathom, also specify the heat exchanger junctions to be linked.

Once enabled, the familiar Run Model button is replaced with Run Thermal Links, signaling that the two applications are now connected.

Benefits for Engineers

The automation introduced by the Cross-App Thermal Link provides three major benefits:

• Efficiency – Iterations that once took hours can now be completed in a single run, freeing engineers to focus on higher-value tasks.
• Accuracy – By eliminating manual data entry and adjustments, the risk of introducing errors is reduced.
• Productivity – Engineers can model complex liquid-gas systems more confidently, knowing the heat balance is being solved with precision.

For systems with multiple heat exchangers, these gains compound, offering dramatic time savings across an entire project.

A Smarter Way to Model Mixed Systems

This feature represents a significant step forward in integrating liquid and gas system modeling within the Datacor Pipe Flow Modeling ecosystem. By enabling seamless collaboration between Fathom and Arrow, the Cross-App Heat Exchanger Thermal Link ensures that engineers can achieve accurate thermal solutions without the hassle of manual iteration.

For organizations modeling large-scale cooling water and gas piping systems, this advancement will translate into faster project timelines, more reliable results, and ultimately better-performing systems.

The days of juggling spreadsheets and rerunning models by hand are over – Fathom and Arrow now handle the heavy lifting for you.