# What is Pressure drop: Definition and 160 Discussions

Pressure drop is defined as the difference in total pressure between two points of a fluid carrying network. A pressure drop occurs when frictional forces, caused by the resistance to flow, act on a fluid as it flows through the tube. Pressure drop increases proportionally to the frictional shear forces within the piping network.
There are a number of factors that impact on the degree to which pressure drop occurs in a piping system, including the following:
The nature of the product being pumped, including its density, heat capacity, temperature, viscosity, and the velocity at which it is moving.
Mechanical components in the piping system, including valves, flow meters, adaptors, and couplings. All of these remove energy from the piping system, contributing to pressure drop.
Changes in the elevation of the piping. If the starting elevation of a pipe is lower than its end elevation, the rise in elevation will cause pressure drop as the fluid moves through the pipe. Conversely, if the starting elevation is higher than the end elevation, there will be a pressure gain as the fluid moves through the pipe.

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1. ### How to maintain flowrate and pressure head in a pump?

Pump is supply fluid to the 35 nozzles through 3 inch pipe and manifold.At nozzle the pressure is 32 m and pressure at pump outlet is 30 m .The flow rate required at nozzles is 500 lpm. Pump can deliver 860 lpm at 24 m head.pump size 100x100 mm 1)how delivary pipe size affects the pressure head...
2. ### Two-Phase Pressure Drop (I need an expert)

Hello everyone, I have been trying to find a relatively accurate pressure drop correlation for horizontal flow of air-oil mixture. I have been testing 7 correlation in my test points however I am still hesitated to select the appropriate one based on the results. System Props: * D_pipe: 17.63...
3. ### B Water surface behavior under pressure change

Hi togehter, this may be an easy one for most, but I'm really struggling with imagining the process. Suppose we have a compressed air vessel that is half filled with water. The pressure in the vessel drops from 10 bar to atmospheric pressure within a few seconds. How does the water surface...
4. ### How to calculate the leak rate based on pressure drop

I am currently working on a project trying to calculate leak rate and fluid loss from pressurised vessels filled with water over a time period of 30 minutes. So far I have used the Boyles Law which assumes that PV/T = constant which gets us P1 * V1 = P2 * V2 and PdV+VdP = 0 I formed this over to...
5. ### Pressure drop through volumes of compressible fluid

Thanks for your response. I'm trying to estimate the pressure in the cavity, i.e. P2. I know the areas, A1 which in practicality is an annulus and A2 which is a 600m pipe with i/d 8mm. I would like to initially understand how to calculate the pressure drop across the annulus. At the moment I'm...
6. ### How to calculate water pressure drop in cooling tower piping system?

When calculating water pressure drop in chilled water pipisystem (closed circuit) we always use Hazen Williams equation as follow:- but in case of calculating water pressure drop in cooling tower piping system (open circuit), shall we modify something in Hazen Williams equation or shall we use...
7. ### Scaling pressure drop to other temperatures

Hi, I have some measurements for pressure drop of Helium at room temperature and I would like to scale it to other temperatures. Taking into account that, i) the flow is turbulent, ii) the pressure drop, ##\Delta p##, happens always in the same piping and iii) there is only variation on the...
8. ### Find the pressure drop and power loss of pipe when elevation changes

Summary:: I can’t get the correct answers, I think I haven’t fully understand the theory behind them The answers are given in the picture
9. ### How to determine the pressure drop in pipe diameter sizing

Hi all, I'm a tinkerer with no formal engineering background, but enjoy read about physics and engineering in general. I'm reading up on fluid flow and I'm a bit grasping at the concepts. As far as I understand it, flow rate, pressure drop and pipe size are all interrelated, where one affects...
10. ### How Do You Calculate Static Pressure Drop in a Laminar Flow Channel?

Hallo. Since I'm new in this field, I hope someone can help me. I have a laminar, steady state, incompressible flow in a channel (a fully developed). Geometry of the channel is on the photo. How should I calculate the drop of static pressure across the channel? Since I have Re, I did calculate...
11. ### Advice on pressure drop calculation

Hello everyone, I would appreciate any help with my task I am struggling to resolve. I need to calculate or simulate pressure drop when got the following parameters: 1. Supply pressure: 45barg. 2. Pipe Length: 80 meters 3. Pipe diameter: OD - 10mm, ID - 8mm. 4. Pipe material: stainless steel...
12. ### When a bird flaps it's wings up, doesn't the pressure drop below?

I am trying to understand how birds fly. If you consider a plane, using it's engine & streamline shape of the wings, it can create a low pressure region above the wings and high pressure region below and this makes it fly and the upward force is proportional to the speed. Birds seem to flap its...

14. ### Pressure drop due to holes in a pipeline?

We have a project that relating with pipeline system and pressure control, the project is actually having goal to knowing how much pressure drop will occurs in pipe line system that in initial condition the pressure inside the pipeline staying at steady or constant in particular psi and at the...
15. ### How to calculate a pressure drop in a branch of a loop ring pipe

Good day I'm trying to calculate the pressure drop in each branch of the following loop ring system I used the following formula to find the pressure drop but i seems that it worked only for the ring, and the branch #2 ( the branch in the middle), the solution given by the professor show...
16. ### Huge pressure drop after changing pipe length (Don't think it's loss)

Hi All, Recently, I have been struggling to seek a solution for a seemingly simple flow question and try to rationalize my thoughts with mechanical engineering knowledge I have acquired from school but none of them can make me feel comfortable about answering the phenomenon I encountered in...
17. ### Pressure drop as volume changes

I am trying to calculate pressure losses. I've attached an image to show what I mean. Starting out tank 1 is 92.8 litres at 155 psi and when the shutoff valve is open the volume goes from 92.8 to 192.8 and so I thought the pressure would drop by the same factor that the volume increased by so...
18. ### How does the pressure drop as a fluid flows through a pipe

Assuming laminar viscous (meaning not frictionless) flow. Here is what I know about fluids flowing: You have a pressure difference between the two ends of the pipe. This causes a net force acting on the left side of the fluid in the pipe. Therefore, this incompressible fluid flows from left to...
19. ### How Does Pressure Affect Dissolved Oxygen in Water Systems?

Hello Everyone, I've been trying to find an answer to this but am not getting anywhere. Any help would be greatly appreciated! I need to be able to calculate (or more likely estimate) the pressure drop I can expect when putting water under pressure if I know there is air in the system. For...
20. ### Pressure drop necessary to have desired gas flow rate

Hello, I'm a chemist and I'm currently working on my PhD on materials science. I'm trying to determine the pressure difference necessary to achieve the desired gas flow inside a chamber. The scheme of the chamber is the following: I have a big chamber which is evacuated to 0.2 bar, and another...
21. ### Adjusting the pressure drop in an injection plate

Hello everybody, I'm designing a gas pressure feed system for a hydrogen peroxide - ethanol rocket engine, and after analyzing the devised injection plate, I noticed it is very sensitive to the propellants' pressure drops and discharge coefficients. Once the plate is manufactured, the only...
22. ### Injector pressure drop in a liquid rocket engine

Hello everybody, I hope you are doing fine. I'm currently designing an injector for a hydrogen peroxide - ethanol engine, and the following formula is confusing me: Q = Cd * A * sqrt( 2 * dP / rho); where Cd is the discharge coefficient, A the total area, dP the pressure drop, and rho the...
23. ### How long will it take for compressed air to reach 29 psi?

A large tank filled with air is compressed to 49 PSI. A valve is open and air escapes through the hole (d = 0.04 ft) to the atmosphere. How long will it take for the compressed air to reach 29 PSI. Assume constant temperature. Not exactly sure how to approach this problem since the flow rate...
24. ### Pressure drop along a pipe with a branch

Hi, I'm trying to determine if a compressed air system has sufficient system to feed a new load The minimum pressure required for existing loads and the current load is 7 bar. In order to determine the pressure at E i did a pressure loss calculation for the following A to B - △P start of pipe...
25. ### Pressure drop across a thick orifice

Greetings, I am trying to understand how to setup/solve for the pressure drop across an orifice L=3.5in The pipe diameter starts at 1in, then abruptly decreases to 0.5in for the length of the orifice, and abruptly transitions to 1in diameter. (See the attached file for an illustration.)...
26. ### Pressure Drop Across a Change in Diameter

Greetings, I have very little experience with fluid dynamics and I was wondering how I can calculate a pressure drop across an abrupt change in diameter of the piping used for water. Any help is appreciated! Thanks!
27. ### Understanding Pressure Drop in Pipes: Causes and Solutions

Hi There, I have constantly come across the fact that as fluid (hydraulic oil say) travels along a pipe you will see a continual drop in pressure the further you travel down the pipe. Am I right in saying that the pressure at any point is simply the result of the resistances (friction with pipe...
28. ### Fluid Mechanics: Choosing a fuel line diameter for a required pressure drop

Homework Statement [/B] Homework Equations - The pressure drop equation. [/B]The Attempt at a Solution
29. ### Pressure Drop in a fire fighting network with loops

Hello Everyone, Can someone please explain to me how I would go about verifying the External Static Pressure of a pump that feeds a pressurized fire fighting network with loops in it. An image of the network is attached. I'm not being able to grasp the concept of pressure drop in a pressurized...
30. A

### Pressure drop over double parallel system

I have a system where pipes run 24l L/min of water @60 degrees through 3 manifolds and those manifolds distribute the water over 8 heat exchangers. Every heat exchanger requires 1 L/min, and has a resistance of about 1.333 KPa per heat exchanger at that flow (2 meter @ 9mm diameter + 2...
31. M

### Pressure drop across a valve in tank

Hey I've gotten some good answers here before, so I'm giving it another try: Recently I attended a building-engineering meeting, and trying to learn something new (or refresh old knowledge in some cases..) I had a hydrodynamic question/case. My firm is engineering a concrete tank for a water...
32. E

### Calculate Pressure Drop through Expansion/Reduction for Gas

Something that routinely comes up as a problem at work is when we size flow projects for piping systems. We calculate pressure drop across a length of fixed diameter for compressible gasses, but we do not calculate pressure changes through an expansion or contraction with gas (for example...
33. ### Water pressure vs pressure drop

Hi guys, I know the difference between these two things but I'm struggling with something that I hope someone could help me with. What dictates the water pressure needed for a "system" to work? I would imagine that if you've calculated your system to have a pressure drop of 1 bar (for...
34. ### Pressure Drop value location

Hello, I am calculating pressure drop through a pipe using CFD, which will be validated with hand calculations and experiments for a project. When I take results from my software, I can either take the pressure at a specific point (assume the centreline of the pipe) or I can take an average...
35. ### Can someone help calculate pressure drop ?

I am a non technical innovator trying to develop a new product. Can someone help me calculate pressure drop and flowrate across a cylinder packed with uniform spheres of 10mm diameter. I found this online but unable to calculate...
36. ### Pressure and temperature of expanding humid air

As a follow-on to this thread, which in turn followed this closed thread, I'm starting a new thread on a related real-world problem. Say I have a 2-liter plastic soda bottle filled partway with water, and pressurized. It has been sitting inverted (with the opening pointed down, and sealed) for...
37. ### Pressure drop calculation

I have a pump running at 400rpm with 8" inlet and outlet with head 30 ft 500 gpm. Now I am planning to reduce the discharge line to 6" . Assuming the flow rate and speed constant the velocity in the pipe will increase. How do I calculate the change in head?
38. ### The Best Orifice Type for highest pressure drop

I'm an engineering student, one of my task is to search the best orifice type for pressure drop. I have no idea which one would it be since I believe that the beta ratio is the one that would determine the best orifice for pressure drop.
39. ### Need Help Transposing the pressure drop formula

Homework Statement Hi, Iv got to find the minimum diameter of a pipe if the pressure drops in a system is to be limited to 0.3bar. when delivered through a pipe of equivalent length 160m I have to use the formula Pressure Drop = 800lQ^2/Rd^5.31 I believe I have to transpose this to find...
40. ### Pressure drop across a tube section - compressible flow

So, a coworker approached me today with a 'simple problem' to solve, looking to sanity-check a design choice. Much to my dismay, I had no idea how to approach it. Worse, google had no straight-forward answers either, and any formulae I did find seemed circular. This seems too simple to...
41. ### Accounting for Pressure Drop in Propeller Calculations

I'm trying to optimize a system involving one or more propellers / fans driving air through a packed bed for scrubbing (compressed then expanded) and out the other side to achieve propulsive thrust. So there's going to be a pressure drop in the slipstream. I've already set up a system to do the...
42. ### Equations explaining pressure drop across an air filter

Hi all, I'm having a Kaiser compressor producing compressed air for my garage. I've installed a FRL unit at point of use. I understand that the filter medium adsorbs atmospheric dust, moisture and oil particles in compressed air. Gradually the pressure drop across the filter builds up and I need...
43. ### Pressure Drop in a vacuum cleaners

Homework Statement [/B] Q = A / V Bernollis therom → γH = P+γZ+ρ.v2 /2 Air Flow Speed = 0.058 m3/s A = Section Area of the tube = π.r2 r = 19.65 mm ρ =1000 kg/m3 g =9.8 m/s2 P=pressure energy of water = 2.338 Homework Equations Find : V= Fluid Velocity = ? H=Energy Denisty = ? Z= Geodesic...
44. ### Calculate theoretical static pressure drop in moving fluid

Hi folks, I have a pressure sensor working with arduino to measure depth. I want to calculate what I should see as a change in pressure if I move the tube horizontally under the surface of the water, keeping the tube opening parallel to the flow. I have calculated the dynamic pressure but...
45. ### Determine air flow rate from pressure drop and hose diameter

Good evening everyone, I have a pressure meter from where we determined a pressure drop of 5.5 psi (Initial pressure 45.5 psi, final pressure 40 psi). The working fluid is air. The diameter of one of the hoses that is connected to the pressure meter is 1/4". I wasn't able to take a picture of...
46. ### Pressure Drop In Bulb : Application of Graham's Law

Homework Statement The pressure in a bulb dropped from 2000 to 1500 mm of mercury in 50 minutes when the contained oxygen leaked through a small hole. The bulb was then evacuated. A mixture of oxygen and another gas of molecular weight 72 in the molar ratio of 1 : 1 at a total pressure of 6000...
47. ### Pressure drop doesn't depend on pipe material (laminar flow)

why does the pressure drop equation derived for the laminar flow has no parameter to indicate the surface roughness of the material of the pipe,unlike the turbulent flow !
48. ### Pressure drop does not match theory

I've modeled a U-Pipe with laminar flow. The pressure drop from Fluent is about 3 kpa , but by theory it should be about 6 kpa (checked several times and I'm sure) My mesh is very fine and boundary conditions are vel-inlet and pre-outlet and wall. Would you please help me with the problem?
49. ### Pressure drop in fuel assemblies

Hello! I am studying the mentioned topic I am confused in calculating the average value of friction factor in sub channels ... please help ?? thank you in advance
50. ### Pressure drop in rod bundles without spacer grid

Hello! I am studying the mentioned topic I am confused in calculating the average value of friction factor in sub channels ... please help ?? thank you in advance