# Calculation Methods - Kv (Flow Coefficient)

To utilize this type of flow coefficient you must know a pressure loss at a given flow. This information is often obtained from the fitting manufacturer. FluidFlow utilizes this data and adjusts it to the calculated flow conditions. The pressure loss across a flow coefficient element adjustment is expressed by the equation: For liquids and slurries: ΔP = (ρ Ref/ρ)n-1 (m/mRef)n ΔPRef where: ΔP is the calculated pressure loss (Pa). ρ Ref is the reference density defined in the Input Inspector (kg/m3). ρ is the fluid density at flowing conditions (kg/m3). mRef is the reference flow rate defined in the Input Inspector (kg/s). Note, you can define either mass or volumetric flow units. When volumetric flow units have been defined, FluidFlow will automatically convert to mass flow units based on the reference density defined for ρ Ref. m is the calculated mass flow in the system (kg/s). ΔPRef is the reference pressure loss defined in the Input Inspector (kg/m3). n is the exponent defined in the Input Inspector (usually 2 - normally the pressure loss is a function of flow squared). Note, if you have set the field titled "Use Kv from Database", FluidFlow obtains the required reference conditions/parameters noted above from the database. FluidFlow modifies this formula for gas and two phase flow.