ΔPdynamic=C⋅(ρ⋅V22)=C⋅Pvcap delta cap P sub d y n a m i c end-sub equals cap C center dot open paren the fraction with numerator rho center dot cap V squared and denominator 2 end-fraction close paren equals cap C center dot cap P sub v Pvcap P sub v is the velocity pressure of the air stream. The
Friction loss occurs due to fluid shear stress against the interior duct walls. It is commonly calculated using the to find the friction factor ( ), which is then applied to the Darcy-Weisbach Equation :
pv=0.5×ρ×V2(SI Units)p sub v equals 0.5 cross rho cross cap V squared space (SI Units) : Air density : Air velocity The ASHRAE database contains thousands of these Cocap C sub o ashrae duct fitting database excel
=INDEX(C_Range, Match_Low) + ((Target_X - INDEX(X_Range, Match_Low)) / (INDEX(X_Range, Match_High) - INDEX(X_Range, Match_Low))) * (INDEX(C_Range, Match_High) - INDEX(C_Range, Match_Low)) Use code with caution. Automating Calculations with VBA and Power Query
value based on dimensional ratios (e.g., area ratios, branch-to-main ratios, and diverging/converging angles). 3. The Math Engine ΔPdynamic=C⋅(ρ⋅V22)=C⋅Pvcap delta cap P sub d y n
ΔP=Co×Pvcap delta cap P equals cap C sub o cross cap P sub v ΔPcap delta cap P is the total pressure loss, Cocap C sub o is the loss coefficient, and Pvcap P sub v is the velocity pressure ( in IP). Alternatives & Third-Party Tools
-factor varies dynamically based on geometric ratios (e.g., aspect ratio, radius ratio) and flow ratios (e.g., flow rate fractions in branches vs. mains). Automating Calculations with VBA and Power Query value
The ASHRAE Duct Fitting Database is the foundation for accurate HVAC pressure loss calculations. While the official DFDB app and cloud service offer a streamlined experience, the demand for an persists because Excel provides a level of openness, flexibility, and integration that standalone applications cannot match.
Manually writing complex mathematical formulas for hundreds of rows can slow down your spreadsheet. You can use native Excel automation tools to manage data scaling more efficiently. Power Query for Data Cleanliness