Published February 24, 2021 © GPL3+

Orifice Plate and Fluid dynamics!

It's a device which allows you to compute the mass flow within a pipe. The implementation with arduino is very easy.

AdvancedFull instructions provided1,080

Things used in this project

Hardware components

NXP MPX5050dp

MAX6675

Arduino UNO

Software apps and online services

Arduino IDE

MICROSOFT EXCEL

Story

WHO AM I? WHY I DID IT?

I'm a mechanical engineer and I developed this project for my degree thesis. Naturally, creating an Orifice Plate from zero is not so easy, because you need to study Technical Physics (in detail Fluid dynamics). But, don't worry, I'll try to explain you how it works and how you can compute the mass flow within a pipe.

All the information are provided by UNI ISO 5167 2003 1 - 2.

I hope this project could help some Engineer or Science lovers. For any questions, don't hesitate to contact me!

WHAT DO YOU NEED TO KNOW?

Physics, Fluid dynamics (Reynold's number, Bernoulli equation), Numerical Analysis.

WHAT DO YOU NEED?

An Orifice Plate (there are different types of it, the model "D and D/2 tappings" is the easiest to build, so I recommend it to you, but if you want to learn more about the other prototypes, check the UNI ISO 5167-1-2 2003)

Arduino UNO

MPX 5050dp

thermocouple MAX 6675

HOW DOES IT WORK?

An orifice plate is a device which allows the user to calculate the axial velocity (and so the mass flow) of a fluid, within a pipe. For example, it is used in power stations, labs or airplanes (Pitot Tubes)!

In this case, I've built the model: "D and D/2 tappings".

One of the most important physics law involved in this process is the "Bernoulli's law".

I'll try to explain how you can adopt it in this particular case:

V. Mitchell e K. Cheesman, «Gas, tubes and flow», Anaesthesia & Intensive Care Medicine.

In an horizontal pipe, we can identify two sides ( in this picture it is identified by 1 and 2). When the pipe section decreases, the axial velocity increases from the section 1 to 2 (so v1<v2). To balance the "Bernoulli's Law", the pressure needs to drop down in section 2 (P2<P1).

Shown below, the equation:

Bernoulli's Law

from this we can obtain this formula:

Massic flow

where:

qm = massic flow

C and 𝜀 = corrective coefficient

A1 = the initial Area of the pipe, before the section reduction

A2 = the reduced Area

P1-P2 = the pressure drop

𝜌 = fluid density

The Pressure drop and density will be found with Arduino, C and qm with numerical analysis and 𝜀 with its formula.

CONSTRUCTION REQUIREMENT (D&D/2 tappings)

From my thesis ( Ref. UNI ISO 5167 2003) :

UNI ISO 5167 2003-1

d = diameter of the orifice

D = diameter of the pipe

𝛽 = d/D

ReD = Reynold's number computed with D.

I chose the following dimension.

For the orifice, I took in consideration three different diameters:12.93 mm, 24 mm, 31 mm.

ALL THE MOST IMPORTANT FORMULAS USED

qm [kg/s] =

w (axial velocity) [m/s]= qm/A1

ReD [adim] =

where 𝜇 is dynamic viscosity

C [adim] =

(Where: L1~1, L'2~0.47, M'2 = 2*L'2/(1-𝛽), A = (19000*𝛽/ReD)^0.8)

and if D<71.12 mm

𝜀 [adim] =

where k is the coefficient of adiabatic expansion.

HOW DO YOU GET THE MEASUREMENT?

Unfortunately, cause to Covid-19, I could not enjoy the laboratories of UniMore, so I used a fan to create the flow.

Before taking the measurement, I built a "U pressure gauge", to calibrate the pressure sensor.

At the end, for different fan's velocity, I've detected different pression drops and I've made a numerical analysis for each one.

NUMERICAL ANALYSIS

The calculation was carried out with excel.

I took in consideratiom different pression values and then I made the numerical analysis for each value.

Repeat the last four steps as long as the values converge within a specific tolerance.

ex. P1-P2= 1000 Pa, d=12.93 mm.

(from left to right).

MY RESULTS

d=12.93 mm

d=24 mm

d=31 mm

UNCERTAINTIES OF THE MEASUREMENT OF THE FLOW RATE

If you want to know how to compute the error, I can advice you to read UNI ISO 5167-1 2003. This is the formula:

I'll show you my values of uncertainties.

d=12.93 mm

where "ro" is the density.

MY EXPERIENCE

Here there are some images of the project caught from my thesis : "Progettazione e realizzazione di un misuratore di portata massica su piattaforma hardware open source".

Progettazione e realizzazione di un misuratore di portata massica su piattaforma hardware open source.

from above: d=31mm,d=24mm,d=12.93mm

flow's rectifier created with straws.

realized with Solidworks 2018

THANKSTO MY UNIVERSITY, PROFESSORS AND ASSISTENTS.

Schematics

Code

SENSOR_ORIFICE_PLATE.ino

#include <MemoryFree.h>

#include "max6675.h"

  //variables initialization
float Vs = 5.1;


float T_1=0;

  // START Thermocouple
int thermo1DO = 3;
int thermo1CS = 4;
int thermo1CLK = 2;
MAX6675 ktc1(thermo1CLK, thermo1CS, thermo1DO);

// START MPX5050
int PIN_P1 = A0;        
float Analog_P1 = 0;
float Vout_P1 = 0;
int P_1 = 0;

//SETUP

void setup() { 
  Serial.begin(9600);      // START serial communication

}

  // LOOP
void loop() {

  // read the thermocouple
T_1 = ktc1.readCelsius();


// read the pressure sensor
Analog_P1 = analogRead(PIN_P1);
Vout_P1 = ((Analog_P1 * 0.00369) + 0.04);
P_1 = (Vs * Vout_P1);
delay(1000);


  // print data
 Serial.print("T=");
 Serial.print(T_1);
 Serial.print("C");
 Serial.print("\n");
 Serial.print("P = ");
 Serial.print(P_1,1); 
 Serial.print("Kpa");
Serial.print("\n");
}

Credits

cicchine_ing

0 projects • 3 followers

I'm a mechanical engineer, graduated in Modena (Unimore).

Orifice Plate and Fluid dynamics!

Things used in this project

Hardware components

Software apps and online services

Story

WHO AM I? WHY I DID IT?

WHAT DO YOU NEED TO KNOW?

WHAT DO YOU NEED?

HOW DOES IT WORK?

CONSTRUCTION REQUIREMENT (D&D/2 tappings)

ALL THE MOST IMPORTANT FORMULAS USED

HOW DO YOU GET THE MEASUREMENT?

NUMERICAL ANALYSIS

MY RESULTS

UNCERTAINTIES OF THE MEASUREMENT OF THE FLOW RATE

MY EXPERIENCE

Custom parts and enclosures

DRAWING

Schematics

connections

connections (2)

Code

SENSOR_ORIFICE_PLATE.ino

Credits

cicchine_ing

Comments

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Orifice Plate and Fluid dynamics!

Orifice Plate and Fluid dynamics!

Things used in this project

Hardware components

Software apps and online services

Story

WHO AM I? WHY I DID IT?

WHAT DO YOU NEED TO KNOW?

WHAT DO YOU NEED?

HOW DOES IT WORK?

CONSTRUCTION REQUIREMENT (D&D/2 tappings)

ALL THE MOST IMPORTANT FORMULAS USED

HOW DO YOU GET THE MEASUREMENT?

NUMERICAL ANALYSIS

MY RESULTS

UNCERTAINTIES OF THE MEASUREMENT OF THE FLOW RATE

MY EXPERIENCE

Custom parts and enclosures

DRAWING

Schematics

connections

connections (2)

Code

SENSOR_ORIFICE_PLATE.ino

Credits

cicchine_ing

Comments

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