Air-cooled condenser, A-frame forced draft
Condenses turbine exhaust steam in A-frame bundles, with fans below pushing the air through them.
Fan-driven A-frame bundles condensing turbine exhaust: the mechanical-draft air-cooled condenser that is the most widely installed dry-cooling system. Each tube row has its own characteristic, so the rows condense at different pressures. A dephlegmator, the second-stage reflux bundles, is modelled when the case gives it a share of the bundles.
Pack: Mechanical draft. In the plans: Pro (as its one pack), Expert, Enterprise and Academic. Plans
The analyses it offers
- RatingThe plant at one condition, solved once.
- DesignFix a target and solve for one dimension.
- Parametric sweepThe rating repeated along one or more axes.
- Performance curvesBack pressure against inlet air, one curve per steam flow (ASME PTC 30.1).
- Acceptance testA test's runs corrected to guarantee conditions, with its uncertainty (ASME PTC 30.1).
- Annual runThe rating once per weather point over a year.
- Transient simulationThe plant after an event.
The transient scenarios
- Fan start from rest
- Fan stop
- Step on one boundary channel
- Step in the ambient temperature
- The ambient temperature following a profile
What it predicts, and what that was compared with
The app's capability statement for this system, as every report prints it.
| Analysis | Predicts | Compared with | Agreement |
|---|---|---|---|
| Steady rating, and the sweep, design and annual runs built on it | Air mass flow rate, heat transfer rate, fan power and steam back pressure of an A-frame condenser unit or bank | Kröger's worked Example 8.1.4 | Air mass flow rate, heat transfer rate and fan power within 0.011%; every loss coefficient to five significant figures |
| Discretised transient | Steam back pressure, heat transfer rate and air mass flow rate through a fan ramp or a load change | Its own steady rating, the state it settles to; no measured start-up or run-down | Settles to the steady rating within 0.1% on the air mass flow rate and the heat transfer rate |
Its limits
Wind on a fan-driven bank is Kröger's Section 9.3 procedure on Duvenhage's CFD tables, held constant beyond 3 m/s at 5.7 m, without any representation of the site. Not modelled for this system: hot-air recirculation between streets, fouling that develops in service and degradation (a stated fouling resistance is carried as given), freezing and freeze protection, hybrid or adiabatic inlet assistance, and the plume. Every correlation is a fit over a declared range; the report lists any excursion at the solved state, and a result outside a declared range is an extrapolation and not a prediction.
The validation cases of this system
- Another modelHe et al. 2013A 112-cell air-cooled condenser under crosswind to 12 m/s: the extrapolation's size
- Another modelHe et al. 2013A 2 × 600 MW air-cooled condenser, windless: the first large-ACC steady comparison
- Worked exampleKröger Example 8.1.4A-frame air-cooled steam condenser
- Worked exampleKröger Examples 8.3.2 and 8.4.2An eighteen-unit air-cooled condenser bank
- Another modelASME PTC 30.1 Appendix A: the reconstructed plant against the vendor's curves
- Measurement, plantASME PTC 30.1 Appendix A: the field test against the reconstructed plant
- Another modelASME PTC 30.1 Appendix K: a 35-cell ACC's fans under a 5 m/s wind
- Another modelYang et al. 2012Two 56-cell air-cooled condensers under wind from five directions: what the direction rule can and cannot carry
- Measurement, rigNCEPU wave-finned flat tube: the air-side fit against its own wind tunnel