Fitting and valve losses calculator

Local pressure loss with supplied summed loss coefficient.

fluids-minor-losses.napkin / editable

SCENARIO COMPARISON

Compare the numbers.

This source describes an analytical model. Its quantities and checks are the view.

Scenario	lossPa
	1500
	1200

All calculated quantities are listed with the inputs. Switch to Source to inspect the equations.

SCENARIOS / CALCULATED VALUESSAME SOURCE

Change an input to see the consequences.

pressure loss budget1500.00 Pa✓ passes

BASELINE INPUTS

coefficient3 density1000 kg/m^3velocity1 m/s

CALCULATED

loss1500 Pa

Edits change the baseline source.

THE SOURCE

Edits below update the same model.

# Fitting and valve losses
# Scope: Local pressure loss with supplied summed loss coefficient.
# Status: illustrative worked example; engineering review pending.
# Inputs are example values. Checks are editable example requirements, not standards.

coefficient = 3
density = 1000 kg/m^3
velocity = 1 m/s

loss := coefficient*density*velocity^2/2 [Pa]

check pressure loss budget: loss <= 2000 Pa

scenario alternative: coefficient = 2.4

Calculated from your source · not saved

Baseline · Baseline

pressure loss budget1500.00 Pa ✓ passes

alternative · alternative

pressure loss budget1200.00 Pa ✓ passes

Illustrative first-order example. Checks are editable requirements, not design standards. The broader topic may require additional equations, data, and validation.

Formula and units

This example uses the following equations. Input names and units match the editable source above.

loss: loss = coefficient*density*velocity^2/2 [Pa]

Original worked example

These are the baseline values in the downloadable source. Edits above let you test your own values.

Given

coefficient: 3
density: 1000 kg/m^3
velocity: 1 m/s

Calculated

loss: 1500 Pa

Assumptions and limits

Local pressure loss with supplied summed loss coefficient.

The requirement checks use the limits written in this example. Passing a check does not establish that the model covers every load, material behavior, or operating condition in a real design.

Download this .napkin example ↓

Take it further with your agent

Napkin keeps the inputs, equations, checks and assumptions together in one study. Your agent sets it up; you change the numbers.

Try with Claude ↗

codex 'Use Napkin (https://napkin.engineering/mcp, or the local Napkin plugin) to build a study: Fitting and valve losses. Inputs: loss coefficients; velocity; density. Outputs: minor pressure drop; equivalent length. Model scope: Single-phase flow unless explicitly configured otherwise. Read napkin_capabilities and the current snapshot. Ask me for the values that matter, label assumptions with units, author .napkin source, validate it and apply it with napkin_source using the current revision, then open the study. Add checks for the limits I supply. Keep unsupported analyses explicit.'

Claude needs the Napkin connector; Codex needs the Napkin plugin. Set up your agent ↗

The broader study

The topic brief below describes the broader scope. The worked example above states the particular calculation it implements.

Inputs: loss coefficients, velocity, density
Outputs: minor pressure drop, equivalent length
Modes: calculate, compare, sweep
Drawing: Flow network and pressure plot

EXECUTABLE WORKED EXAMPLE · FIRST-ORDER MODEL · CHECK THE SCOPE & ASSUMPTIONS