Sizing Results
Primary Results
Required Cv--
Kv (metric)--
Valve Authority
--
--
Cavitation Index (sigma)
--
--
Characteristic--
Recommended Valve--
| Step | Formula | Value |
|---|
Valve Selection Table
| Valve Size | Rated Cv | % of Rated at Design | Verdict |
|---|
Method Notes
- Standard: ANSI/ISA-75.01.01-2002 (IEC 60534-2-1 Mod), incompressible flow only
- Cv = N1 * Q * sqrt(SG / dP), where N1 = 1.0 for US units (GPM, psi)
- Choked flow: dP_max = FL^2 * (P1 - FF * Pv), FF = 0.96 - 0.28*sqrt(Pv/Pc)
- Piping geometry factor FP from ISA Section 8.1, iterative method per Eq. 20-27
- Valve authority = dP_valve / (dP_valve + dP_circuit), ASHRAE recommends >= 0.5
- Cavitation index sigma = (P1 - Pv) / dP, compare against valve-specific sigma_i
- Kv = Cv / 1.156 (metric flow coefficient)
- Fluid properties: ASHRAE Fundamentals Ch. 31, Engineering ToolBox / NIST
- FL, Fd values: ISA-75.01.01 Table 2 (typical, consult manufacturer for exact values)
- Glycol vapor pressure approximated with water vapor pressure (conservative)
- Reynolds number: Rev = (N4 * Q) / (nu * Fd * sqrt(Cv)), N4 = 21530 for Cv/GPM/cSt
- Turbulent flow assumed (Rev > 10,000). If below, ISA Section 6.2 non-turbulent sizing recommended.