Filters

Overview

Filtration is the process of separating suspended particles from a fluid (liquid or gas) by passing it through a permeable medium. In engineering systems, filters, screens, and strainers are essential for protecting sensitive equipment (pumps, compressors, nozzles) from debris and for ensuring product purity.

The primary engineering concern with filters is the pressure drop (\Delta P) they induce. As fluid passes through the media, energy is lost to viscous friction and turbulence. This pressure loss typically follows a quadratic relationship with velocity for turbulent flow (Darcy’s law applies for laminar flow in deep beds).

\Delta P = K \cdot \frac{1}{2} \rho v^2

where K is the resistance coefficient, which depends heavily on the solidity (or conversely, the open area ratio) of the filter element.

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Python Libraries

These functions rely on the fluids library, which provides loss coefficients (K) and discharge coefficients for diverse filter and screen geometries. The library implements rigorous models from authoritative sources like Idelchik and Miller, ensuring engineering-grade accuracy.

Screen and Fitting Loss Models

The functions in this category provide loss coefficients (K) for various filtration geometries, primarily based on the extensive experimental data from Idelchik’s Handbook of Hydraulic Resistance:

• SQ_EDGE_SCREEN: Calculates resistance for square-edged screens (punched plates).
• RND_EDGE_SCREEN: Calculates resistance for round-wire screens (woven mesh).
• RND_EDGE_GRILL: Calculates resistance for grills with rounded edges.

Native Excel Capabilities

Excel has no built-in functions for calculating screen or filter pressure drops. Engineers typically use simple quadratic head loss formulas but must manually find and enter the loss coefficient K. These coefficients: - Vary significantly with open area ratio - Depend on the edge geometry (sharp vs. rounded) - Are often only found in specialized engineering handbooks (Idelchik, Crane)

The Python functions provided here provide immediate access to these validated models, eliminating the need for manual lookup and implementing the correct dependencies on solidity and flow conditions.

Tools

Tool	Description
RND_EDGE_GRILL	Calculate the loss coefficient for a rounded edge grill or perforated plate.
RND_EDGE_MESH	Calculate the loss coefficient for a round edged open net or screen mesh.
RND_EDGE_SCREEN	Calculate the loss coefficient for a round edged wire screen or bar screen.
SQ_EDGE_GRILL	Calculate the loss coefficient for a square edged grill or perforated plate.
SQ_EDGE_SCREEN	Calculate the loss coefficient for a square edged wire screen, bar screen, or perforated plate.