SPIRAL

Overview

Calculate the loss coefficient (K) for a spiral coil pipe section.

Excel Usage

=SPIRAL(Di, rmax, rmin, pitch, fd)

• Di (float, required): Inside diameter of pipe [m]
• rmax (float, required): Radius of spiral at extremity [m]
• rmin (float, required): Radius of spiral at end near center [m]
• pitch (float, required): Distance between two subsequent coil centers [m]
• fd (float, required): Darcy friction factor [-]

Returns (float): Loss coefficient K for the spiral [-]

Examples

Example 1: Basic spiral coil

Inputs:

Di	rmax	rmin	pitch	fd
0.01	0.1	0.02	0.01	0.0185

Excel formula:

=SPIRAL(0.01, 0.1, 0.02, 0.01, 0.0185)

Expected output:

Result
7.9509

Example 2: Wide radius range spiral

Inputs:

Di	rmax	rmin	pitch	fd
0.015	0.2	0.05	0.015	0.02

Excel formula:

=SPIRAL(0.015, 0.2, 0.05, 0.015, 0.02)

Expected output:

Result
13.4557

Example 3: Tight pitch spiral

Inputs:

Di	rmax	rmin	pitch	fd
0.01	0.1	0.02	0.005	0.0185

Excel formula:

=SPIRAL(0.01, 0.1, 0.02, 0.005, 0.0185)

Expected output:

Result
15.8408

Example 4: Small spiral

Inputs:

Di	rmax	rmin	pitch	fd
0.008	0.08	0.02	0.01	0.022

Excel formula:

=SPIRAL(0.008, 0.08, 0.02, 0.01, 0.022)

Expected output:

Result
7.0637

Python Code

import micropip
await micropip.install(["fluids"])
from fluids.fittings import spiral as fluids_spiral

def spiral(Di, rmax, rmin, pitch, fd):
    """
    Calculate the loss coefficient (K) for a spiral coil pipe section.

    See: https://fluids.readthedocs.io/fluids.fittings.html#fluids.fittings.spiral

    This example function is provided as-is without any representation of accuracy.

    Args:
        Di (float): Inside diameter of pipe [m]
        rmax (float): Radius of spiral at extremity [m]
        rmin (float): Radius of spiral at end near center [m]
        pitch (float): Distance between two subsequent coil centers [m]
        fd (float): Darcy friction factor [-]

    Returns:
        float: Loss coefficient K for the spiral [-]
    """
    try:
        Di = float(Di)
        rmax = float(rmax)
        rmin = float(rmin)
        pitch = float(pitch)
        fd = float(fd)
    except (ValueError, TypeError):
        return "Error: All parameters must be numbers."

    if Di <= 0:
        return "Error: Di must be positive."
    if rmax <= 0 or rmin <= 0:
        return "Error: Rmax and rmin must be positive."
    if rmax <= rmin:
        return "Error: Rmax must be greater than rmin."
    if pitch <= 0:
        return "Error: Pitch must be positive."
    if fd <= 0:
        return "Error: Fd must be positive."

    try:
        result = fluids_spiral(Di=Di, rmax=rmax, rmin=rmin, pitch=pitch, fd=fd)
        return float(result)
    except Exception as e:
        return f"Error: {str(e)}"

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