FP_MARTIN
Computes Darcy friction factor for single-phase flow in chevron plate heat exchangers using the Martin (1999) correlation. The model combines Reynolds number with chevron angle to represent the added hydraulic resistance created by corrugated plate geometry.
The correlation uses a piecewise definition of internal terms for laminar and turbulent conditions and then combines them into a single expression for the exchanger friction factor. This makes it suitable for sizing and pressure-drop estimation in compact plate exchanger channels.
Excel Usage
=FP_MARTIN(Re, chevron_angle)Re(float, required): Reynolds number with respect to the hydraulic diameter of the channels, [-]chevron_angle(float, required): Angle of the plate corrugations with respect to the vertical axis [degrees]
Returns (float): Darcy friction factor for chevron plate heat exchanger flow [-]
Example 1: Laminar flow with low chevron angle
Inputs:
| Re | chevron_angle |
|---|---|
| 500 | 30 |
Excel formula:
=FP_MARTIN(500, 30)Expected output:
0.549801
Example 2: Laminar flow with high chevron angle
Inputs:
| Re | chevron_angle |
|---|---|
| 1000 | 60 |
Excel formula:
=FP_MARTIN(1000, 60)Expected output:
2.05016
Example 3: Turbulent flow with moderate chevron angle
Inputs:
| Re | chevron_angle |
|---|---|
| 5000 | 45 |
Excel formula:
=FP_MARTIN(5000, 45)Expected output:
0.834656
Example 4: Turbulent flow with high Reynolds number
Inputs:
| Re | chevron_angle |
|---|---|
| 20000 | 45 |
Excel formula:
=FP_MARTIN(20000, 45)Expected output:
0.781892
Python Code
Show Code
from fluids.friction import friction_plate_Martin_1999 as fluids_fp_martin
def fp_martin(Re, chevron_angle):
"""
Calculate Darcy friction factor for single-phase flow in Chevron-style plate heat exchangers using Martin (1999) correlation.
See: https://fluids.readthedocs.io/fluids.friction.html#fluids.friction.friction_plate_Martin_1999
This example function is provided as-is without any representation of accuracy.
Args:
Re (float): Reynolds number with respect to the hydraulic diameter of the channels, [-]
chevron_angle (float): Angle of the plate corrugations with respect to the vertical axis [degrees]
Returns:
float: Darcy friction factor for chevron plate heat exchanger flow [-]
"""
try:
Re = float(Re)
chevron_angle = float(chevron_angle)
if Re <= 0:
return "Error: Reynolds number must be positive."
if chevron_angle < 0 or chevron_angle > 90:
return "Error: Chevron angle must be between 0 and 90 degrees."
result = fluids_fp_martin(Re=Re, chevron_angle=chevron_angle)
if result != result:
return "Error: Result is NaN."
if result == float('inf') or result == float('-inf'):
return "Error: Result is not finite."
return float(result)
except Exception as e:
return f"Error: {str(e)}"