Ammonia Subcooler Sizing Calculator
This free calculator sizes a submerged helical coil that subcools high-pressure liquid ammonia against a boiling ammonia pool. Enter coil geometry, vessel size, flow rate, and inlet conditions; it returns outlet liquid temperature, duty, and velocity/pressure-drop checks — on screen, free, with no account required.
It runs as the Subcooler tab of the Coil Suite, one of the four calculators in the ColdCalcs dashboard, alongside Boil-out and Heat Recovery. Results are a preliminary sizing pass only, not a certified design.
Who it's for
Refrigeration engineers and ammonia system designers sizing a subcooler coil for an accumulator or intercooler vessel, who need a fast preliminary duty and outlet-temperature number before a full design pass. It is not a substitute for a design package prepared by a qualified engineer.
Limits
This calculator performs a preliminary sizing pass only. [ELI-REVIEW: its shell-side pool-boiling coefficient uses a correlation calibrated to a small set of reference designs over a stated bath-temperature range, not a universal correlation], and it does not verify pipe pressure rating separately. Every result must be independently verified by a qualified engineer against the applicable code edition before it is used for design, fabrication, or construction.
Inputs and outputs
| Parameter | Type | Unit | Notes |
|---|---|---|---|
| Coil pipe size / schedule | Input | NPS | Tube size and wall schedule. |
| Winding count and length | Input | —, ft | Coil construction (single- through six-wound). |
| Liquid flow rate | Input | gpm / lb/hr | High-pressure liquid ammonia flow. |
| Inlet temperature / bath temperature | Input | °F | Warm-liquid inlet and shell-side boiling temperature. |
| Outlet (subcooled) temperature | Output | °F | Or required coil area, in sizing mode. |
| Duty | Output | Btu/hr | Heat rejected from the liquid to the boiling pool. |
| Tube-side velocity | Output | ft/s | [ELI-REVIEW: checked against an IIAR Bulletin 109 practical velocity window.] |
| Heat-flux utilization | Output | % | [ELI-REVIEW: against a fixed practical flux ceiling, not the Zuber critical-heat-flux limit.] |
Frequently asked questions
What does the subcooler calculator compute?
[ELI-REVIEW: For a helical coil submerged in a boiling ammonia pool, it computes outlet liquid temperature for a given coil (or required coil area, in sizing mode) using tube-side forced-convection and shell-side pool/natural-convection correlations.] Results display on screen for free, with no account required.
What is liquid subcooling, in this context?
[ELI-REVIEW: Subcooling is warm high-pressure liquid ammonia flowing through submerged coil tubes while lower-pressure ammonia boils on the shell side, lowering the liquid's temperature below its condensing saturation point before it reaches the expansion device.]
What correlations does it use?
[ELI-REVIEW: Dittus-Boelter tube-side forced convection, a Schmidt (1967) or Kern/Patil helical-flow enhancement factor, an optional Sieder-Tate wall-viscosity correction, and Churchill-Chu (1975) natural convection on the shell side.] These are engineering correlations, not code-mandated formulas.
Does it check velocity and pressure drop limits?
[ELI-REVIEW: Yes — tube-side velocity against an IIAR Bulletin 109 practical window, Reynolds number against Dittus-Boelter validity, and pressure drop and heat-flux-utilization thresholds.] These are on-screen pass/warn/fail checks, not code compliance certifications.
Is it free to use?
Yes. Full on-screen results are free for every user, with no account required. PDF export and saved projects are part of a paid plan; on-screen results never are.
Related
Preliminary sizing for engineering evaluation only. Not for construction. All results must be independently verified by a qualified engineer against the applicable code edition.