FRIC_PLATE_MARTIN99
This function computes the Darcy friction factor for single-phase flow in chevron-style plate heat exchangers using the Martin (1999) correlation. The model combines angle-dependent terms with Reynolds-number-dependent sub-correlations for laminar and turbulent regimes.
The correlation is commonly represented in reciprocal square-root form:
\frac{1}{\sqrt{f}} = \frac{\cos\phi}{\sqrt{a(\phi) + f_0/\cos\phi}} + \frac{1-\cos\phi}{\sqrt{3.8f_1}}
where f_0 and f_1 are piecewise functions of Reynolds number and \phi is the chevron angle. This function is useful for estimating pressure-drop-related flow resistance in compact plate heat exchanger channels.
Excel Usage
=FRIC_PLATE_MARTIN99(Re, chevron_angle)Re(float, required): Reynolds number with respect to hydraulic diameter of the channels (-).chevron_angle(float, required): Plate chevron angle relative to flow direction (degrees).
Returns (float): Darcy friction factor, or error message if invalid.
Example 1: Example from documentation
Inputs:
| Re | chevron_angle |
|---|---|
| 20000 | 45 |
Excel formula:
=FRIC_PLATE_MARTIN99(20000, 45)Expected output:
0.781892
Example 2: Laminar Reynolds number range
Inputs:
| Re | chevron_angle |
|---|---|
| 1000 | 30 |
Excel formula:
=FRIC_PLATE_MARTIN99(1000, 30)Expected output:
0.45632
Example 3: Turbulent Reynolds number range
Inputs:
| Re | chevron_angle |
|---|---|
| 5000 | 60 |
Excel formula:
=FRIC_PLATE_MARTIN99(5000, 60)Expected output:
1.83307
Example 4: Very low Reynolds number
Inputs:
| Re | chevron_angle |
|---|---|
| 200 | 15 |
Excel formula:
=FRIC_PLATE_MARTIN99(200, 15)Expected output:
0.501842
Python Code
Show Code
from ht.conv_plate import friction_plate_Martin_1999 as ht_friction_plate_Martin_1999
def fric_plate_martin99(Re, chevron_angle):
"""
Calculate Darcy friction factor for chevron plate exchangers (Martin 1999).
See: https://ht.readthedocs.io/en/latest/ht.conv_plate.html
This example function is provided as-is without any representation of accuracy.
Args:
Re (float): Reynolds number with respect to hydraulic diameter of the channels (-).
chevron_angle (float): Plate chevron angle relative to flow direction (degrees).
Returns:
float: Darcy friction factor, or error message if invalid.
"""
try:
result = ht_friction_plate_Martin_1999(Re=Re, chevron_angle=chevron_angle)
return float(result)
except Exception as e:
return f"Error: {str(e)}"