Brewing Packaging, Bright-Tank Cellaring & Draught Dispense, ASBC Zahm-Nagel Carbonation
Beer Carbonation Volumes CO2 (Zahm-Nagel) & Line Formula
Calculate ASBC Equilibrium Dissolved Carbonation (Volumes CO2 and g/L), Draught Choker Restriction Line Length (ft), and Beer Style Carbonation Band from Gauge Pressure & Temp.
Hold bright-tank CO2 regulator pressure fixed at 12.5 psi when glycol chilling warms from 38°F to 54°F and beer loses 25% of its carbonation!
Gases dissolve *exothermically* in cold liquids (**Henry’s Law with Van’t Hoff exponential temperature decay**): bright-tank cellarmen and draught technicians measure **Beer Carbonation in `Volumes of CO_2`** (`1.0` Volume = `1` L of `STP` `CO_2` gas per `1` L of beer = **`1.96` g/L** mass concentration!) via the **ASBC / Zahm & Nagel Empirical Henry’s Correlation** across Gauge Head Pressure `P_g` (`psig`, `+ 14.696` psia atmospheric) and Liquid Temperature `T_F` (`°F`): **`V_{CO2} = (P_g + 14.696) * (0.01821 + 0.090115 * EXP(-(T_F - 32) / 43.11)) - 0.003342`**! Simultaneously, serving foam-free draught pints requires **Balancing Applied Keg Pressure `P_g`** against **Static Vertical Tower Lift `0.5 * H_{lift}`** (`psi` across `H_{lift}` ft) plus `~1.0` psi faucet dynamic head using **`3/16"` ID Vinyl Choker Restriction Tubing (`R_{line} ~= 2.2` psi/ft): `L_{choker} = (P_g - 0.5 * H_{lift} - 1.0) / R_{line}`** (`ft`)!
Verify on a `38.0°F` (`3.3°C`) Bright Tank / Walk-In Cooler Keg—Equilibrium_Head_Pressure `P_g` = 12.5 psig (B2), Beer_Temperature `T_F` = 38.0°F (B3), Vertical_Tap_Tower_Lift `H_{lift}` = 6.0 ft (B4), and `3/16"`_Choker_Resistance `R_{line}` = 2.20 psi/ft (B5): Dissolved Carbonation equals **`2.62` Volumes `CO_2`** (E2) = **`5.14` g/L** (E3), Balanced `3/16"` Choker Line Length equals `3.86` ft (E4), hitting `"STANDARD LAGER / ALE (2.3-2.8 vol)"` right in the crisp sweet spot (E5)!
| ASBC Zahm-Nagel Carbonation & Draught KPI (Pg=12.5 psig, Lift=6 ft, Choker=2.2 psi/ft) | Formula | Verified Output |
|---|---|---|
| Dissolved Carbonation (Volumes CO2) | (Pg + 14.696)*(0.01821 + 0.090115*EXP(-(TF-32)/43.11)) - 0.003342 | 2.62 vol @ 38°F (1.96 vol FLAT @ 54°F!) |
| Dissolved CO2 Mass Conc (g/L) | Volumes_CO2 * 1.96 (STP CO2 Density) | 5.14 g/L (3.85 g/L @ 54°F) |
| Balanced Choker Line Length (ft) | (Gauge_psi - 0.5*Lift_ft - 1.0) / Resist_psi_ft | 3.86 ft of 3/16" ID choker |
| BJCP / ASBC Carbonation Band | >= 2.30 Volumes Standard American/Euro Spec | STANDARD LAGER / ALE (2.3-2.8 vol) |
ASBC / Zahm-Nagel Henry’s Law Solubility & Draught Hydrostatic-Friction Balance Formula
Validate `Gauge_Pressure P_g` in `[4, 45]` psig, `Beer_Temp T_F` in `[30, 75]`°F, `Vertical_Lift` in `[-10, 40]` ft with positive choker drop `P_g - 0.5 * H_{lift} - 1.0 > 0.5` psi, and `Choker_Resistance` in `[0.2, 5.0]` psi/ft right on `E2` (checking `ISTEXT(E2)` on `E3..E4` so `E5` text stays decoupled)!
=LET(pg_p, B2, tf_d, B3, hl_f, B4, rl_p, B5, vc_o, (pg_p + 14.696) * (0.01821 + 0.090115 * EXP(-(tf_d - 32) / 43.11)) - 0.003342, IF(OR(pg_p < 4, pg_p > 45, tf_d < 30, tf_d > 75, hl_f < -10, hl_f > 40, (pg_p - 0.5 * hl_f - 1) <= 0.5, rl_p < 0.2, rl_p > 5), "Invalid Carbonation Input", IF(vc_o >= 2.3, "STANDARD LAGER / ALE (2.3-2.8 vol)", "FLAT / CASK LEVEL (<2.3 vol)")))Warm 54°F Walk-In Cooler at Unchanged 12.5 psig Regulator Flat-Beer Check (Set B3 = 54°F)
Let a walk-in cooler warm to `B3 = 54.0°F` (`12.2°C`) while leaving the `CO_2` regulator at `12.5` psig: `CO_2` breaks out of solution into the headspace (causing wild faucet foam on the first pours!) until equilibrium Carbonation E2 falls `-25.2%` to **`1.96` Volumes (`3.85` g/L in E3)**—flagging `"FLAT / CASK LEVEL (<2.3 vol)"` in E5 (holding `2.62` vol at `54°F` would have required `~21` psig!)!
=IF(ISTEXT(E2), E2, LET(vc_o, (B2 + 14.696) * (0.01821 + 0.090115 * EXP(-(B3 - 32) / 43.11)) - 0.003342, ROUND(vc_o * 1.96, 2)))Try the example
Use the original values or change them to test your understanding.