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Dry cooling, tube to tower

DraftSolver is an online application for the thermal and draft performance of dry-cooling systems. A case describes one plant, every analysis runs on that case, and every result names the equations that produced it.

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How a case is worked

The app's workspace follows the case in four steps, the same for every system and every analysis. Below the plant's figures, a rating's results list what to know about the result, where the losses are and the equations that produced it, each linked to its Handbook page. The screens are the app's own, on the A-frame condenser of Kröger's Example 8.1.4, one of the worked examples the app ships.

The system and the analysis. A case is saved as one file and opened again with its setup and its run settings.

DraftSolver's workspace with the analysis menu open, listing Rating, Design, Parametric sweep, Performance curves, Acceptance test and Annual run, each with a one-line description.
Figure 1. The case. The analysis is chosen beside the system, and every one of the seven runs on the same setup. From DraftSolver 0.1.0.

The plant node by node: the tower shell or the cells and fans, the finned tube, the bundles, the fluid, the ambient and the models. Each node shows whether its fields are valid before anything runs.

The Cells and fans node of an A-frame air-cooled condenser's setup: the fan and the counts of fans, rows and units on the left; a 3-D drawing of the A-frame cell and the fan's static pressure and shaft power against volume flow rate on the right, with the setup nodes listed in the left rail.
Figure 1. The setup of the A-frame condenser of Kröger's Example 8.1.4, one of the worked examples the app ships: one node of inputs, each validated as it is typed, beside the plant drawn from them and the fan's own curves. From DraftSolver 0.1.0.

The analysis's own settings: a sweep's axes, a design target, a test's data, a year's weather, a transient's scenario.

The Run step of a parametric sweep, with an axis of ambient temperature from 0 to 40 °C in steps of 5 °C, the option to give every point its uncertainty band, and the plant beside it.
Figure 1. A run's own settings: a parametric sweep of the ambient temperature from 0 to 40 °C in nine points, each with its uncertainty band. From DraftSolver 0.1.0.

The plant's figures, the findings graded by how much they matter, the equations that produced the result, and the datasheet.

The results of a rating of an A-frame air-cooled condenser, Kröger's Example 8.1.4: heat transfer rate 19.63 MW, steam condensed 8.316 kg/s, back pressure 19.93 kPa, air mass flow 604.5 kg/s, followed by the findings on the result and a table of the example's published values beside the computed ones, within tolerance.
Figure 1. A rating's results: the plant's figures, then what to know about the result, graded by how much it matters, and on a worked example the published values beside the computed ones. From DraftSolver 0.1.0.

The nine systems

Air-cooled condensers

Dry coolers

Air-cooled heat exchangers

Natural-draft towers

The seven analyses

Each analysis is listed with the app's own description of it and the systems that offer it.

  • Rating

    The plant at one condition, solved once.

    Every system.

  • Design

    Fix a target and solve for one dimension.

    Every system.

  • Parametric sweep

    The rating repeated along one or more axes.

    Every system.

  • Performance curves

    Back pressure against inlet air, one curve per steam flow (ASME PTC 30.1).

    Air-cooled condenser, A-frame forced draft; Air-cooled condenser, A-frame induced draft.

  • Acceptance test

    A test's runs corrected to guarantee conditions, with its uncertainty (ASME PTC 30.1).

    Air-cooled condenser, A-frame forced draft; Air-cooled condenser, A-frame induced draft.

  • Annual run

    The rating once per weather point over a year.

    Every system.

  • Transient simulation

    The plant after an event.

    Every system.

From the rating to CFD of the same plant

The rated plant ported to OpenFOAM as it is; the user chooses the mesh resolution, the turbulence model and the discretisation order, sees the mesh and its statistics before the solve, and reads the solution back beside the rating.

CFD in DraftSolver

The uncertainty band

A rating's band re-solves the plant with each correlation it depends on at the 95% bound of that correlation's stated accuracy, and lists what each contributes. A correlation that states no accuracy is named as such and is not counted as exact. The band is in every plan; the Monte Carlo, which draws every correlation at once, is in Expert, Enterprise and Academic.

Case files

One JSON document describes a complete analysis: the setup with every selector inline, and a run block that names its analysis. The worked examples are case files with their expected values attached.

An API for scripts

Everything the interface does goes through this API. A script sends a personal API token with each request. Tokens are made, listed and revoked by the user, and expire within a year.

In the browser

The app runs at app.adiabat.co.za in a current browser, and nothing is installed. CFD runs are queued for Adiabat's compute service.