What is Suction: Definition and 61 Discussions

Suction is the colloquial term to describe the air pressure differential between areas.
Removing air from a space results in a pressure differential. Suction pressure is therefore limited by external air pressure. Even a perfect vacuum cannot suck with more pressure than is available in the surrounding environment. Suctions can form on the sea, for example, when a ship founders.
When the pressure in one part of a system is reduced relative to another, the fluid in the higher pressure region will exert a force relative to the region of lowered pressure. Pressure reduction may be static, as in a piston and cylinder arrangement, or dynamic, as in the case of a vacuum cleaner when air flow results in a reduced pressure region.
When animals breathe, the diaphragm and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the chest cavity decreases the pressure inside, creating an imbalance with the ambient air pressure, resulting in suction.

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  1. A

    Calculate Load carrying capacity of vertically mounted suction cup

    I'm looking for means of calculating load carrying capacity of a vertically mounted suction cup. Suction Cup effective diameter = 90mm Mounted on a vertical glass surface Pressure inside the suction cup = 0.75bar Pressure difference = 0.25bar Weight is suspended from a rod attached in the centre...
  2. J

    Is a Venturi Suction the Solution for Low Pressure in a Centrifugal Pump System?

    Good day I am trying to use a venturi across a centrifugal pump. The pressure at suction side is about 2 bar and the discharge pressure about 6 to 7 bar. This pump supply drippers and the delivery is about 180 cub/h. I need to inject entrainment air into the suction side and try to use a...
  3. kunalvanjare

    Venturi injector suction not adequate

    Hey guys, we've been tasked with providing solutions for reducing coolant consumption by our client using automation. One of those is a system to reclaim the coolant dripped off of the chips from a Chip Trolley in a CNC Machine. Around 15-20 Litres of coolant+water emulsion is wasted everyday...
  4. mbeard9

    Calculating the Suction Generated by a Shop-Vac

    I am working on a design project where a shop-vac vacuum will be used to gather kevlar fibers in place for a cut to be made. Currently, the vacuum has a 1.25" diameter attachment. I have created a 0.25" diameter attachment that completes the task perfectly. However, I cannot figure out how to...
  5. tinakaran26

    Direct steam injection into cooling water line at pump suction

    Currently there is an operation scenario at one of our plant which directly injecting steam into cooling water line at pump suction in order to generate hot water at 60 deg C for circulation, by doing this its generate vapor at pump suction and lead to cavitation which ultimately damage pump and...
  6. B

    I Need advice on vacuum / suction experiment

    Summary: Vacuum pump help I need advice on what type of vacuum pump would create max negative pressure in a very small area ( a space no larger than your pinky finger I guess) ? Maybe some kinda high suction low cfm pump? I don't know enough about vacuum pumps to know which type to...
  7. F

    How does high humidity affect suction pressure & discharge pressure?

    In Chapter 40 (titled Typical Operating Conditions) of my textbook Refrigeration and Air-Conditioning Technology, the authors list several different objectives for readers at the beginning of the chapter. One of the stated objectives is for the reader to be able to describe how humidity affects...
  8. S

    Relationship Between Suction Force & Suction Distance

    Hi All, We all have experiences of using vacuum cleaner to clean carpet, floor, etc. and might probably have noticed a super intuitive phenomenon that as you move your vacuum cleaner suction hose closer to the floor, the suction force increases which helps you pull some of large trash off the...
  9. W

    HVAC Understanding the movement of a fluid in a vertical pipe

    The actual problem I am trying to understand is the suction requirement to move #2 home heating fuel from the outdoor tank to the pump of the burner located in my cellar. But first i just want to understand the movement of fluid in a vertical pipe without worrying about viscosity or...
  10. K

    Misc. Generating as much suction with as little weight as possible

    Hello all, as my final project to attain my bachelors, I have tasked myself with designing some sort of device to collect insects from the canopy of soybean plants that can be suspended under a UAS (quad copter/drone). What I am trying to do is essentially build some sort suction device. The...
  11. kyphysics

    Why Doesn't My Air Purifier Have a Suction Feeling at the Intake?

    Hey, everyone I just bought an air purifier yesterday (the Honeywell 50250 model) and have a question about whether or not it's normal what is happening when I turn it on. I followed the instructions exactly in terms of assembly (it was really only putting on the pre-filter - no other assembly...
  12. teunKeusters

    Maximum suction force in a suction cup

    Sorry if I didn't post this at the right place. Hi all, I have a problem that I am not able to solve. I hope you guys can help me! I am creating a suction cup to grab and lift an object with a flexible surface made of out silicone The suction cup is also made out of some sort of flexible...
  13. A

    Determine the pressure gradient for suction

    Hello, Im designing a product which will pump components as vacuum cleaner does. I have 2 questions: Im trying to calculate the pressure different in order to pump those metal component with : M=0.2 kg , dimensions (mm) cylinder with diameter 5.5 mm length 600mm . the formula for pressure...
  14. physea

    I Suction Cavitation in Pumps: Causes and Frequency

    Hello! Do ALL the pumps create suction cavitation (ie bubbles of vacuum inside the water)? Or it is a rare phenomenon? And does it increase with pump speed? thanks!
  15. S

    Pump has a suction lift of more than 10.3 m

    As I was going through a course on Hydraulics, there was a brief explanation about how the atmospheric pressure can only support a water column of 10.3 m.A few more points that are prerequisite to the discussion are as follows 1)A fluid cannot be pulled;it has to be pushed. 2)A centrifugal...
  16. T

    Suction side and discharge side pump pressure

    Consider a closed system (central heating). Before the pump is started the static pressure is 2.0 bars. Say the system head loss is 0.6 bars. When the pump starts, will the suction side pressure and the discharge pressure each read half the total head loss (1.7 and 2.3 bars)? Or will the head...
  17. S

    Calculating suction area around the intake of a jet engine

    I am looking to calculate the area around the engine where, if an object enters this area, it would be "ingested" by the engine (subsonic flight). In other words, I am looking to draw the shape around the engine, where the air within that shape is disturbed air (being ingested by the engine)...
  18. W

    How Does Specific Gravity Impact NPSH in Centrifugal Pumps?

    Head psa(suction surface pressure) = 2.31xP/specific gravity This is one of the factors to calc NPSH. Shows how much head is pushing liquid through the pump. What does the specific gravity have to do with surface pressure of a liquid before it goes into the pump? Isn't it just involving the...
  19. B

    B Suction Through Small & Large Pipes

    Hi, I am wondering if suction power from a vacuum for example that has a set amount of power, is increased or decreased depending on the size of pipe. Does a large pipe decease/ increase the suction power, or does a small pipe decease/ increase the suction power? Is there a link to the size in...
  20. K

    Vacuum created or suction created when we use peristaltic pump

    Hi All, How to find vacuum created or suction created when we use peristaltic pump?
  21. M

    Can a gravity fed pump effectively draw fluid from a tank at a higher elevation?

    Hello, I have a general problem. I have a tank sitting at elevation of 63 feet. With 24 inch pipe to 1400 feet away from the facility. The facility is sitting at 59 feet. To get to our vertical can pumps suction we need to run the pipe up 7 feet for 150 feet of 12 inch pipe and then drop down...
  22. R

    I Simple suction air filter: items and preventing implosion

    I want to make a simple air filter(for dust and air pollution) but was a bit confused about some stuff. Basically I've decided to use an exhaust fan to create a vacuum in a sealed box and the air to come in through the filters. Box fans aren't available here, so that can't be used. I want to...
  23. DrFreeman

    Calculating CO2 expansion time and generated suction

    I need help with figuring out how to devise an equation that I'm going to plug into an algorithm for my software. These are the components: CO2 cartridge pressure regulator output should be around 200 psi. Tank #1 has a volume of 800 mL, pressure is around 15 psi. There are no valves between...
  24. A

    Multi-Suction Point Pipe Flow

    If I a pump with a main suction header and 4 smaller branch connections of difference sizes. Let's say for this example we have (2) 3", (1) 1", and (1) 2". Also let's say our pump is requiring 20 gal/min. The flow rate of each branch would be proportional to the area of the pipe correct? flow =...
  25. T

    I How Can Boundary Layer Suction Reduce Flow Separation in Pipe Expansion?

    I have a question about the following scenario involving a flow separation issue in a pipe expansion The angle of the expansion is 30* - doubling the diameter from 1D to 2D We can consider this flow fully developed with a Reynolds of 5000+ Associated with this expansion is a head loss...
  26. L

    I Aspiration Power: Needle Tip Effect

    Does it affect my aspiration power if I use a needle (beveled tip) Vs. straight tip Having a bevel increases the cross sectional area of the cylinder
  27. Sarah00

    Medicine & Physics -- Question about chest tube suction techniques

    Homework Statement Hi, I'm a junior doctor. It's been so long since I had physics! I've question about tube that's placed in chest cavity to drain air/fluid/etc. The second bottle, is under-water seal bottle. I know that its purpose is to prevent air moving TO the patient. but how? The "trap...
  28. P

    Radial Suction Fan Design & Equations

    Hi, I've been considering the design of a fan that sucks air radially and blows axially to resolve a technical problem of a machine. I've looked around for the equations governing the air particles and the angle of the radial blades (angle between a flat blade and a radial line) of the fans, but...
  29. N

    Increasing water pressure without increasing pump output

    I am curious as to whether a nozzle at the end of a pipe that is completely submerged in water and has a pressurized flow being pumped through it in a closed condition can increase the amount of flow and pressure of the water in a pipe fixed to the exit side of that nozzle if the nozzle uses the...
  30. Mr Davis 97

    Force diagram of a suction cup

    I am a little confused about how to construct a force diagram for a suction cup, like a plunger, as it is stuck to a wall. First, I know that the cup is not accelerating, so the gravitational force pulling down on the cup has to be met with an equal but opposite force vector pointing up...
  31. P

    Non-steady suction induced by Venturi Injector

    This is not really homework but an engineering problem nonetheless. 1. I have a venturi injector sucking in liquid (by all means and purposes identical to water) and injecting into a pressurized water line. A straight tube is inserted into the container of liquid (below the liquid surface) and...
  32. B

    Suction Pressure at different orifices

    Hello engineers, I am struggling with this seemingly simple problem and I was hoping to get some directions. Please look at the attached figure. I have a small chamber with a tube (radius=3mm) that is connected to a vacuum pump. The pump operates at -600 mmHg. The chamber is filled with air at...
  33. halfgt2

    Pump Head & Suction (leaky closed system) PF Newbie

    Hi physicists! I am scratching my head to remember the most basic laws of fluid flow while I try to irrigate things from a barrel. Not exactly rocket science, I know ;-) But very exciting for me ... The situation is simply a pump (cheap submersible one) put into a barrel (sitting on the...
  34. Dennis C

    Pump NPSHA (net positive suction head) question

    Simple (I hope) pump question. With the pump not even running, would like to know what my static NPSHa is if I had a flooded pump suction with 10 feet suction head of water and a vacuum of 27" Hg above the water? Basically it is the hotwell from a condensing turbine exhaust after the steam...
  35. A

    Suction velocity of different vacuum heads

    I've been trying calculate the capacity of one of our dust collection systems. It features four vacuum slots lined up (27 inches by 1 inch each) shown as #3 on the diagram attached. Using a manometer, I took pressure measurements at points #1 and #2. Both were around 1.1 inwc, which...
  36. M

    Suction force and pressure difference

    I am doing a study to see whether suction force can act as a mechanism to compress air. Let's say I have a normal syringe, which consist of the small cylindrical tip at the top of syringes where you attach the needle. Then there is the larger middle barrel for the liquid, medication, etc. Lastly...
  37. M

    Electroplating Fume Suction System Design

    I've recently been put in- charge of reviving a Fume Suction System installed at the electroplating section of factory. After my stint in the army my engineering skills leave a lot to be desired, even though i am a Mechanical Engineer (by education not profession) so it is my request to PFers to...
  38. R

    Suction caused by an air jet acting on a plate, why?

    Homework Statement We set up in a lab a vertical pointing air jet giving a constant output and gradually increased the height of the plate above the jet whilst measuring the force upon it as imparted by the jet using a Newton-metre. At a big distance the air jet was imparting an upthrust on...
  39. S

    Am I understanding the concept of suction correctly?

    My understanding of suction is that it is a phenomenon describing the flow of fluid from a (relatively) high pressure volume into a (relatively) low pressure volume. This makes sense to me, as I grasp that air pressure is a measurement that describes a large number of molecules, each with its...
  40. S

    Max Mass Supported by 5.6-Diameter Suction Cup

    Homework Statement How massive an object can be supported by a 5.6 -diameter suction cup mounted on a vertical wall, if the coefficient of friction between cup and wall is 0.65? Assume normal atmospheric pressure. Homework Equations - The Attempt at a Solution I calculated the maximum...
  41. L

    How can I calculate the pressure drop for a vacuum system?

    Hey guys, I am currently trying to figure out how to build a really small vacuum system and trying to maximize the suction force. I understand that in order to create the vacuum suction force we must have a pressure drop within the chamber so the molecules rush into the low pressure region...
  42. P

    Branched suction pipe foR a pump

  43. L

    How much suction required to lift?

    Hi - am looking for some data points on how much suction is required to lift an object at different weights and volumes. Especially interested in any data relative to displacing an object caught in the throat if you are choking. Appreciate any help!
  44. A

    Relationship between soil suction and angle of repose

    I am writing a report for my civil engineering subject. and i have few questions. is there any relationship between angle of repose and total soil suction. is there any relationship between angle of repose and particle size distribution. is there any relationship between angle of repose and...
  45. T

    Relation between impeller diameter and suction pipe length?

    Hi all, I want to know if impeller diameter of a Blower can influence its suction pipe length. If so, then how are they related?
  46. B

    Effect of suction flow rate over flow separation

    Dear all, Take my best wishes. I am facing a problem designing my experimental setup for my research. I want to produce flow separation over a flat plate. Here is my experimental setup: Diffuser angle is 16deg. I need some documentation/text book regarding the effect of suction flow rate...
  47. B

    Calculate Suction Pressure from Walls & Cups

    Hi, I had a question regarding pressure and suction. Say you have 2 walls with a suction cup that is attached to each. Initial volume of the cup is 1m^3, area attached is 1m^2 Initial pressure is 1 atm Both walls have a hole of different sizes with a pipe leading out to atmosphere. 1 pipe...
  48. K

    Solving Tony's 400 Suction Cup Project

    Hi everyone! I am not sure if I am posting in right place, please correct me if needed. I have an interesting project in my mind. And I need some help as I do not know how to implement it. I need 400 suction cups and all of them have to be working independently. Cups are supposed to be...
  49. H

    Placing air suction next to the air flow ventilation of a PC. Good or bad idea?

    This is something that came up at work, as there are four computers running with their air vents placed four to six inches away from the air suction (so that it would suck up the air which was blown out from the air vent fan of a PC.) While this may seem like a good idea on paper (as the suction...