Calculator 1 of 4
System Volume Estimator
Estimate total closed loop system volume from piping inventory and equipment volumes. Use the Pipe Inventory for detailed estimates or Quick Estimate mode for rule-of-thumb results.
Pipe Inventory
| NPS (Nominal) | Schedule | Length (ft) | Qty | Vol (gal) |
|---|
Equipment Volumes
| Equipment Type | Volume Override (gal) | Qty | Total Vol (gal) |
|---|
Results
Pipe Volume: V = (π/4) × (ID/12)² × L × 7.481 where ID is internal diameter in inches, L is length in feet, and 7.481 is gallons/cubic foot.
Pipe IDs used (Schedule 40): ½" = 0.622", ¾" = 0.824", 1" = 1.049", 1¼" = 1.380", 1½" = 1.610", 2" = 2.067", 2½" = 2.469", 3" = 3.068", 4" = 4.026", 6" = 6.065", 8" = 7.981", 10" = 10.020", 12" = 11.938"
Quick Estimate rule-of-thumb: Fan coil: 0.0020 gal/sq ft; Radiator: 0.0030 gal/sq ft; Process coil: 0.0040 gal/sq ft. Add 15% for header/riser allowance.
Calculator 2 of 4
Inhibitor Charge Concentration
Calculate the volume of inhibitor product needed to achieve a target concentration in the closed loop, accounting for current concentration and product active content.
Results
Dilution Water Required
Active inhibitor mass: M_active (lb) = V (gal) × 8.34 (lb/gal) × ΔC (ppm) ÷ 1,000,000
Product volume: V_prod (gal) = M_active ÷ (C_active_fraction × SG × 8.34)
Dilution (C_current > C_target): V_dilute (gal) = V_sys × (C_current − C_target) ÷ C_target
Water density assumed 8.34 lb/gal at 60°F. For high-glycol systems, adjust SG accordingly.
Calculator 3 of 4
Glycol Freeze & Burst Protection
Convert between glycol concentration and freeze protection temperature. Supports both ethylene glycol (EG) and propylene glycol (PG) with ASHRAE lookup-table interpolation.
Results
Data source: ASHRAE 2021 Fundamentals, Chapter 31 (Brines, Coolants and Antifreeze Solutions). Freeze points interpolated linearly between tabulated data points.
EG data points (% v/v → freeze °F): 0→32, 10→26, 20→14, 25→7, 30→−4, 35→−17, 40→−34, 45→−54, 50→−34, 55→−27, 60→−60
PG data points (% v/v → freeze °F): 0→32, 10→28, 20→22, 25→18, 30→12, 35→4, 40→−8, 45→−22, 50→−33
Specific gravity (approx.): EG: SG ≈ 1.0 + 0.0013 × %v/v; PG: SG ≈ 1.0 + 0.0011 × %v/v
Glycol volume needed: V_glycol = V_system × concentration/100
°C = (°F − 32) ÷ 1.8
Calculator 4 of 4
Closed Loop Inhibitor Consumption
Project inhibitor concentration depletion over time using a CSTR dilution model. Accounts for makeup water dilution and optional first-order thermal decay.
Results
Concentration Profile
| Time (months) | Concentration (ppm) | C/C₀ | Status |
|---|
CSTR Dilution Model:
C(t) = C_makeup + (C_sys − C_makeup) × exp(−t/τ − k·t)
where τ = V_sys / V_makeup_rate (years) is the dilution time constant.
Time to minimum (k = 0): t = τ × ln((C_sys − C_makeup) / (C_min − C_makeup))
Time to minimum (k > 0): t = ln((C_sys − C_makeup) / (C_min − C_makeup)) / (1/τ + k)
Re-treatment interval: t_retreat = t_min × 0.80 (20% safety margin)
Reference: Analogous to CSTR material balance used in ASHRAE Guideline 12 and CTI AHU-1 for open systems; adapted for closed-loop dilution.