Fermenter Glycol Cooling Load
Computes the heat of fermentation, the peak fermenting load.
Example
You enter
- Batch volume (gal) 310
- Original gravity 1.055
- Final gravity 1.012
- Heat of fermentation (Btu per lb extract) 280
- Share released on the peak day (%) 40
- Crash start temperature (deg F) 68
- Crash target temperature (deg F) 34
- Hours allowed for the crash 24
- Tank surface area (sq ft) 143
- Tank shell U-factor (Btu/h-sq ft-deg F) 0.15
- Cellar temperature (deg F) 70
- Glycol temperature rise (deg F) 8
You get
- Extract consumed (lb) 289.783
- Heat of fermentation, whole batch 81,139 Btu from 290 lb of extract
- Rise with the glycol off 32.5 deg F -- the check on the heat figure
- Peak fermentation load 1395.22
- Crash load 4313.64
- Crashing in half the time 7,855 Btu/h (0.65 tons) from one fermenter
- Glycol flow at the crash 1.16 gpm to this tank
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeComputes the heat of fermentation, the peak fermenting load, and the crash-cooling load with ambient gain and glycol flow. The worked 310 gal fermenter peaks at 0.12 tons fermenting and 0.36 tons crashing in 24 hours -- 3.1 times as much. Halving the crash time takes 0.65 tons from one tank: the crash schedule sizes the chiller.
Formula or tableextract = (OG - FG points) x gal / 46; Q = extract x 280 Btu/lb; crash = gal x 8.4 x 0.96 x dT / hours; ambient = A x U x (cellar - beer), at the fermenting beer for the fermentation load and the crashed beer for the crash; gpm = load / (60 x 8.6 x 0.90 x glycol rise).
Source and editionHeat of fermentation about 280 Btu per lb of extract. The chiller manufacturer's capacity at the actual glycol temperature governs.
Free accessPublic heat-balance arithmetic.
What governsEstimate. AHJ and licensed professional govern.
API field namesbatch_volume_gal, original_gravity, final_gravity, heat_of_fermentation_btu_per_lb, peak_day_share_pct, crash_start_temp_f, crash_target_temp_f, crash_hours, tank_surface_sqft, tank_u_factor, cellar_temp_f, glycol_delta_t_f, extract_consumed_lb, fermentation_heat_btu, adiabatic_rise_f, fermentation_load_btuh, crash_load_btuh, fast_crash_load_btuh, glycol_gpm
- Beer heat capacity 8.4 lb/gal x 0.96 Btu/lb-F (ASHRAE Refrigeration Handbook ch. 8 Eq. 8 gives about 0.97 for 3-5% solids; Briggs 2014 prints wort at 4.0 kJ/kg K = 0.955); chiller vendors (American Chillers, Brau Supply) size the crash on water, 8.33 x 1.0, about 3% higher, and quote heat of fermentation per degree Plato per barrel rather than per lb of extractAmerican Chillers; Brau Supply glycol sizing guides
- Beer 8.4 lb/gal at 0.96 Btu/lb-degF (0.90 until 2026-10-03)ASHRAE 1998 Refrigeration Handbook ch. 8 Eq. 8; Briggs of Burton 2014
- Glycol 8.6 lb/gal at 0.90 Btu/lb-degFspec-v1784