BOILING

Overview

The BOILING function calculates the Boiling number (Bg), a dimensionless number used in two-phase heat transfer calculations. The Boiling number characterizes the relationship between the heat flux applied to a surface and the mass flux of fluid flowing through a channel during convective boiling.

This implementation uses the fluids library, an open-source Python package for fluid dynamics and heat transfer engineering calculations. For more details, see the fluids.core documentation.

The Boiling number represents the ratio of mass of liquid evaporated per unit area of heat transfer surface to the mass flow rate of fluid per unit flow cross-sectional area. It is defined as:

Bg = \frac{q}{G \cdot \Delta H_{vap}}

where q is the heat flux (W/m²), G is the two-phase mass flux (kg/m²/s), and \Delta H_{vap} is the heat of vaporization (J/kg).

The Boiling number was first introduced by Davidson et al. in their 1943 study on heat transmission through boiler tubing at high pressures. Although often represented by the symbol Bo in literature, the symbol Bg is preferred to avoid confusion with the Bond number. For further reading, see Boiling Number in Thermopedia and the textbook Convective Boiling and Condensation by Collier and Thome.

The Boiling number is particularly important in predicting heat transfer coefficients in flow boiling applications, including refrigeration systems, power plant boilers, and chemical process equipment where phase change occurs under flowing conditions.

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

Excel Usage

=BOILING(G, q, Hvap)

• G (float, required): Two-phase mass flux in kg/m²/s
• q (float, required): Heat flux in W/m²
• Hvap (float, required): Heat of vaporization in J/kg

Returns (float): Boiling number (float), or error message string.

Examples

Example 1: Demo case 1

Inputs:

G	q	Hvap
300	3000	800000

Excel formula:

=BOILING(300, 3000, 800000)

Expected output:

0.0000125

Example 2: Demo case 2

Inputs:

G	q	Hvap
500	3000	800000

Excel formula:

=BOILING(500, 3000, 800000)

Expected output:

0.0000075

Example 3: Demo case 3

Inputs:

G	q	Hvap
300	6000	800000

Excel formula:

=BOILING(300, 6000, 800000)

Expected output:

0.000025

Example 4: Demo case 4

Inputs:

G	q	Hvap
300	3000	400000

Excel formula:

=BOILING(300, 3000, 400000)

Expected output:

0.000025

Python Code

import micropip
await micropip.install(["fluids"])
from fluids.core import Boiling as fluids_boiling

def boiling(G, q, Hvap):
    """
    Calculate the Boiling number (Bg), a dimensionless number for boiling heat transfer.

    See: https://fluids.readthedocs.io/fluids.core.html

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

    Args:
        G (float): Two-phase mass flux in kg/m²/s
        q (float): Heat flux in W/m²
        Hvap (float): Heat of vaporization in J/kg

    Returns:
        float: Boiling number (float), or error message string.
    """
    try:
        G = float(G)
        q = float(q)
        Hvap = float(Hvap)
    except (TypeError, ValueError):
        return "Error: G, q, and Hvap must be numeric values."

    if G == 0:
        return "Error: G (mass flux) must be nonzero."
    if Hvap == 0:
        return "Error: Hvap (heat of vaporization) must be nonzero."

    try:
        result = fluids_boiling(G, q, Hvap)
    except Exception as e:
        return f"Error: Failed to calculate Boiling number: {str(e)}"

    return result

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