Pressure Drop Calculation for a 3D Resistance

There are three methods for modeling the pressure drop: Device/approach, power law, and loss curve. In each of the methods, Icepak calculates the velocity based on the thermal properties of the surrounding environment.

Device/Approach

, where

• is the user-specified device loss coefficient (for each coordinate direction in 3D)
• is the fluid density
• is the approach velocity
• is the ratio of the area through which the fluid can flow unobstructed to the total planar area of the obstruction

• is the velocity dependence relationship where n = 1 denotes a linear relationship and n = 2 represents a quadratic relationship; pressure drop can be:

  • Linear - for a viscous flow regime (e.g., laminar flow, slow flow, very dense packing), where

    

  • Quadratic - for an inertial flow regime (e.g., turbulent flow), where

    

  • both linear and quadratic, where

    

  Because the resistance to the fluid flow due to a volumetric resistance may be different in each of the three coordinate directions, you must provide the loss coefficient and free area ratio to calculate the pressure drop in each direction.

  Note:

  When using the Device/Approach pressure loss type, enter Loss Coefficient and Free Area Ratio values for Linear and/or Quadratic to specify linear, quadratic, or both. When specifying Linear, you must leave the Quadratic values as zero and vice versa.

Power Law

, where

• is the pressure drop across the 3D resistance
• is the velocity
• and are constants

Pressure Loss Curve

Pressure loss curve is defined as a piecewise-linear profile for the pressure drop as a function of the speed of the fluid through the resistance in the three coordinate directions.