Boil-out Load Calculator
This free calculator estimates the boil-out load for a submerged coil warming a vessel’s liquid ammonia pool over time — for oil boil-out, hot-gas defrost, or pre-pump-down warm-up. Enter coil geometry, vessel size, flow conditions, and a target bath temperature; it returns cycle time and a boil-off rate estimate — on screen, free, with no account required.
It runs as the Boil-out tab of the Coil Suite, one of the four calculators in the ColdCalcs dashboard, alongside Subcooler and Heat Recovery. Results are a preliminary sizing pass only, not a certified design.
Who it's for
Refrigeration engineers and ammonia system designers planning an oil boil-out or hot-gas warm-up cycle, who need a fast preliminary cycle-time estimate 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. It is a transient estimate built on the same steady-state correlations used elsewhere in the Coil Suite, evaluated in steps as bath temperature rises — not a full transient simulation. 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). |
| Coil-side fluid and mode | Input | — | Warm liquid or hot gas ammonia. |
| Starting and target bath temperature | Input | °F | Beginning and desired ending pool temperature. |
| Cycle time to target | Output | hr | Estimated time to reach the target bath temperature. |
| Boil-to-empty rate | Output | lb/hr | [ELI-REVIEW: vapor boil-off rate estimate at the evaluated bath condition.] |
| Tube-side velocity | Output | ft/s | [ELI-REVIEW: checked against a mode-specific IIAR Bulletin 109-referenced acceptance window.] |
| Pressure drop | Output | psi | Coil-side pressure drop, with a pass/marginal threshold. |
Frequently asked questions
What is boil-out load?
[ELI-REVIEW: Boil-out load is the transient heating duty delivered by a submerged coil to warm a vessel's liquid ammonia pool over time — used for oil boil-out, hot-gas defrost, or pre-pump-down warm-up — as distinct from the steady-state duty a subcooler or heat-recovery coil delivers.]
What does this calculator return?
[ELI-REVIEW: Cycle time to reach a target bath temperature, plus a boil-to-empty rate estimate, for a submerged coil carrying warm liquid or hot gas ammonia.] Results display on screen for free, with no account required.
Does it distinguish oil boil-out from hot-gas defrost?
[ELI-REVIEW: Yes — the calculator supports both a warm-liquid mode and a hot-gas mode, each with its own tube-side velocity acceptance window.] Select the mode that matches your operation before reading the pass/warn/fail checks.
What correlations does it use?
[ELI-REVIEW: The same tube-side forced-convection (Dittus-Boelter, with a helical-flow enhancement factor) and shell-side natural-convection (Churchill-Chu, 1975) correlations used across the Coil Suite, evaluated as the bath temperature rises through the cycle.]
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.