FRIC_PLATE_MARTINV
This function computes the Darcy friction factor for single-phase flow in chevron-style plate heat exchangers using the VDI Heat Atlas variant of Martin’s formulation. It uses the same overall structure as the Martin model but with revised coefficients to predict somewhat higher friction in many operating ranges.
The formulation is written in terms of reciprocal square root friction factor:
\frac{1}{\sqrt{f}} = \frac{\cos\phi}{\sqrt{b(\phi) + f_0/\cos\phi}} + \frac{1-\cos\phi}{\sqrt{3.8f_1}}
with f_0 and f_1 defined piecewise by Reynolds number and \phi as the chevron angle. This is used to characterize hydraulic resistance and pressure-drop behavior in plate channels.
Excel Usage
=FRIC_PLATE_MARTINV(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_MARTINV(20000, 45)Expected output:
0.781589
Example 2: Laminar Reynolds number range
Inputs:
| Re | chevron_angle |
|---|---|
| 1000 | 30 |
Excel formula:
=FRIC_PLATE_MARTINV(1000, 30)Expected output:
0.456322
Example 3: Turbulent Reynolds number range
Inputs:
| Re | chevron_angle |
|---|---|
| 5000 | 60 |
Excel formula:
=FRIC_PLATE_MARTINV(5000, 60)Expected output:
1.83215
Example 4: Very low Reynolds number
Inputs:
| Re | chevron_angle |
|---|---|
| 200 | 15 |
Excel formula:
=FRIC_PLATE_MARTINV(200, 15)Expected output:
0.501844
Python Code
Show Code
from ht.conv_plate import friction_plate_Martin_VDI as ht_friction_plate_Martin_VDI
def fric_plate_martinV(Re, chevron_angle):
"""
Calculate Darcy friction factor for chevron plate exchangers (VDI Heat Atlas variant).
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_VDI(Re=Re, chevron_angle=chevron_angle)
return float(result)
except Exception as e:
return f"Error: {str(e)}"