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Resistance Equivalent Length

Reference data and engineering information about resistance equivalent length for electrical applications.

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Overview

Engineering reference data for Resistance Equivalent Length in electrical engineering.

Key Formulas

Ohm's Law

V=IRV = IR

Voltage = Current × Resistance.

Power

P=VI=I2R=V2/RP = VI = I^2R = V^2/R

Electrical power.

Energy

E=PtE = Pt

Energy = Power × Time.

Variables

Symbol Description Unit
VV Voltage V
II Current A
RR Resistance Ω
PP Power W

Equivalent Length Concept

The equivalent length method simplifies pressure drop calculations by converting minor losses from fittings and valves into an equivalent length of straight pipe that would produce the same major head loss. This allows engineers to combine all losses into a single pipe length value.

The fundamental relationship is: Leq=K×DfL_{eq} = K \times \frac{D}{f}

Where:

  • LeqL_{eq} = Equivalent length (ft or m)
  • KK = Loss coefficient for the specific fitting
  • DD = Internal pipe diameter
  • ff = Darcy friction factor

Common Fittings Reference

The following fittings are commonly characterized using equivalent length values:

Bends:

  • Elbows - regular 90°, long radius 90°, regular 45°
  • Return bends - regular and long radius

Connections:

  • Tees - line flow and branch flow

Flow Control:

  • Valves - globe, gate, angle, and swing check

Protection Devices:

  • Strainers (especially in hot water piping systems)

Fitting Data Tables

The equivalent length varies significantly with pipe size and fitting type. The following tables provide standardized values for common industrial applications.

Interactive Charts

References