Questions tagged [pressure]

Questions pertaining to pressurized systems and their applications, from containment to system losses to using as a benchmark for measurement.

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41 views

Force and Headloss Calculations for Three Stage Condenser

I am looking for some guidance on calculations for a natural condenser project. I am a Computer Engineering student, so this stuff is out of my range. The fundamental question I am trying to answer ...
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2answers
456 views

How to get remove water from a submarine that is submerged

How can water be removed from a submarine that is submerged? If a submarine is opened, while it is submerged, water would get in because of the difference between the pressures. For example, I have ...
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1answer
4k views

Relationship between output mechanical power and max pressure for a pump?

If an air pump needs to able to generate a particular pressure at a particular flow rate. How do we size the electrical motor for this particular scenario? The electric motor would be coupled to the ...
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358 views

Why is there negative static pressure in contour?

I studied a paper about turbine and i seen that there is negative static pressure in contour. Why does this happen? Wave Energy Harvesting Turbine: Performance Enhancement
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1answer
83 views

Alternatives to shimming valve springs

Generally, in a pressure drop control valve that uses a piston and a spring (for example, in jet engines to control fuel flow), there is always potential for error in terms of the height of the spring....
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1answer
206 views

How do I find the impact pressure of cavitation due to implosion of a super critical fluid bubble?

I have solved the Rayleigh-Plesset equation for a time varying bubble of a super critical fluid. I am trying to find if the impact pressure caused by SCF bubbles is lesser as compared to that caused ...
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330 views

Some questions about liquid nitrogen cooling [closed]

I am currently tinkering with a railgun experiment, and I was thinking of using a liquid nitrogen loop to cool the rails down to very low resistance, and inject some nitrogen into the barrel between ...
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1answer
65 views

When beverage can stay-on tabs are lifted do they depressurise the can by lifting the rivet?

I understand that the inside of a carbonated aluminium beverage can is pressurised. When the tab is pulled up,a rivet is lifted. Does this cause the can to depressurise? So then the can can be pierced ...
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2answers
34k views

How does loading and unloading work in an air compressor?

I am looking at an ammonia refrigeration unit and trying to understand how loading and unloading solenoid valves work? and also how to modulate the compressor motor over a period of time.
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544 views

Calculate proper stepper torque to convert clay extruder from compressed air to leadscrew actuator. Is this the correct way?

First time poster here. First of all please excuse my english mistakes but most of all my terminology and ignorance on the subject. Now to the question! A friend of mine asked me if I could help him ...
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1answer
2k views

How strict is the direction of air flow in a single direction pneumatic solenoid valve?

I am currently designing a small pneumatic system that pumps air into an airbag, holds the air in, then releases it to the atmosphere. Each pump in the system actually feeds two sets of airbags and ...
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2answers
952 views

Is a filter burst possible under fuel line pressure?

I have read a few ISO standards for performing the so-called 'burst pressure' test in which a filter or an element of one is tested to failure. I am curious whether such a failure can occur under ...
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Is there and easy way to go from 1000 psi to 45 psi without a complicated pressure regulator

I have a C02 tank that is filled at 1000 psi. it's got a duel pressure regulator that allow you to dial it down to 45 PSI. Is there a simple way to regulate pressure from 1000 psi to 45 ( non ...
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126 views

Trasmitting data from pressure transducer to phone/web server

I am creating a 24 hour blood pressure monitor that is designed to be sleek and comfortable, I have decided on The Honey Well Series NBP AN transducer (see more info here: Basic Board Mount Pressure ...
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1answer
730 views

How does the Italian Percolator work?

This morning, as with every morning, I had my coffee. However, today it was burnt, because I slightly overfilled the water. I use an Italian Percolator on a gas top. Normally, you put it on to boil, ...
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345 views

Latent heat of fusion of water near triple point

When a thermally isolated vessel of liquid water is depressurized to vacuum, part of water will evaporate, remainder will freeze - total heat being split between latent heat of ice and enthalpy of ...
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1answer
95 views

Pressure Differential Analysis

In these units: cm³.20μ/m².24hr.atm - (definition) cubic centimeters for a 20 micron film thickness per square meter per 24 hours under a pressure difference of 1 atm. My question is what does the "...
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1answer
110 views

Pressure-Flowrate relation at Nozzle

If I need to get a pressure of 6 bar at the exit of a nozzle for cleaning purpose, how can I determine the following (assuming nozzle outlet dia to be 5 mm): The pump capacity to provide such a ...
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0answers
44 views

How to convert permeation units to molecules/second?

How do I convert $\dfrac{\text{cm}^3\cdot\text{mm}}{\text{m}^2 \cdot \text{day} \cdot \text{atm}}$ for permeation of gas through EVOH to molecules of gas permeating per second as a function of ...
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204 views

Relationship between Pressure and volume with Air

So the below question might sound like a homework question but in reality it is an oversimplified explanation of what I'm trying to measure. Let's say we have a perfect machine that pushes out 600cfm ...
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1answer
81 views

Understanding Permeation Units

I have encountered a type of unit that I cannot understand. The unit describes the rate of permeation through a substance:(cm^3 . mm)/m^2 . d . atm Could someone please explain how to interpret ...
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3answers
3k views

Method of Calculating pressure of failure in a cylindrical container?

Is there a formula or method to calculate the pressure of failure of a cylindrical container of known material, thickness, and size?
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3answers
249 views

Measuring the level of inflation of an airbag

I want to make an inflatable seat that is electronically controlled. I am specifically looking to be able to estimate the level of inflation of an airbag using small electronic sensors. The airbag is ...
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2answers
1k views

Do bottles leaking due to air pressure in an airplane cargo hold?

Is it possible for essential oils to leak from sealed bottles that are being transported by airplane in the cargo hold?
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875 views

Estimating Maximum Speed for a Pneumatic Cylinder

I am designing an machine that is going to use a pneumatic cylinder to accelerate a projectile. I have a tentative cylinder specified, and am working on the control and supply side. I have verified ...
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0answers
85 views

Contact pressure - screw pretension

I'd like to calculate the max contact pressure in the below assembly, just before contact loss between the beam and the wall. The beam is clamped to the wall with a pretensioned screw, and sustaining ...
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1answer
118 views

failure point of flat panel under pressure

Generally, how would I go about finding the maximum distributed pressure which a flat rectangular panel of material, say glass or acrylic, can withstand given thickness, length, and width? For ...
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1answer
866 views

How do gas flow regulators avoid choking?

According to compressible flow theory, a downstream pressure of 0.528 times upstream pressure is sufficient to choke a flow device. So, how do industrial grade pressure regulators throttle a wide ...
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4answers
567 views

Small bubbles on a pump discharge

I am setting up an experimental station for which I am using a small gear pump to pump water. I have noticed that on the discharge port of the pump, a short row of bubbles comes out at high flows and ...
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4answers
13k views

Water pump at top floor or bottom?

Which position of the water pump in the below diagram provide maximum water output to the overhead tank? Each floor is 12 feet in height. I already have the pump (Centrifugal Regenerative Self ...
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1answer
260 views

Pipe-network pressure - mass flow relation

I have a question regarding a pipe-network: Pressure A > B diameters of the outside pipes are bigger than the pipe with the massflow m2,m3 The brown rectangle ...
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1answer
1k views

Chamber Wall Thickness for Liquid Fuel Rocket

In, How to Design, Build, and Test Small Liquid-Fuel Rocket Engines, by Krzycki, page 18 has the following equation: $$t_w = \dfrac{PD}{16000}$$ Assuming the following: Pressure ($P$) in combustion ...
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1answer
242 views

Fluid dynamics: valve and pressure drop

I have a question regarding valves: Let's assume a district heating system where you want to control the mass flow in a sub-station with a valve. Is (in normal cases) the diameter of the valve (fully ...
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3answers
14k views

How to calculate the velocity of gas in a pipe?

I was wondering how I can calculate the velocity of gas through a pipe. The gas, assuming ideal behavior, in a pipe (cylinder) of volume of 222.4 L has a pressure of 1.95 atmospheres and a density of ...
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54 views

How to design a fan that can be used to convert concentrated air to power [closed]

I am trying to design mechanism that is sort of like a wind turbine (uses wind as "fuel") but has a fan size that is in a pelton turbine. I was wondering if there is any math/equation that I can use ...
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1answer
690 views

How do temperature and pressure influence the rate of evaporation of water in a closed vessel?

I am trying to solve a fairly simple question but I'm kind of stuck on the technicalities: Imagine that water is evaporating into initially dry air in the closed vessel shown schematically in Fig....
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1answer
6k views

Working out pressure drop from leak rate

I am trying to work out the acceptable pressure drop/increase on a leak test rig for a given leak rate. A simplified version of the test rig looks like this: The gas (air) supply is at 1 bar above ...
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2answers
227k views

How to calculate flow rate of water through a pipe?

If a water pipe is 15 mm diameter and the water pressure is 3 bar, assuming the pipe is open ended, is it possible to calculate the flow rate or water velocity in the pipe? Most of the calculations I ...
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1answer
65 views

Resistive force sensor: some basic questions about its functionality

I want to know what the circular force sensor outputs when it is connected to the breadboard (with resistor). Does it output force measured in grams? When I slightly touch the sensor with a finger, ...
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1answer
4k views

Basic difference between “compress” and “pressurise”

We call air which is pressurised as "compressed air". But we don't call pressurised liquid as compressed. I know that liquids are incompressible. So, why particular word "compressed" is the created, ...
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1answer
86 views

Calculate pneumatic cylinder dimensions from work done

I have a project for which I need a pneumatic cylinder to impart an impact force in such a way that work-done/energy is 4.5 Joules, and the input pressure is 10 bar. How can I solve this so that I ...
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3answers
630 views

At How Many RPMs Would Aluminum HDD Platters Shatter?

I'm using hard drive platters to create a Tesla Turbine. I'd like to get as much efficiency out of it as possible. That being said, for safety concerns, I'd need to know a generic range at which they'...
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1answer
635 views

Are all pressure-volume processes polytropic?

I was searching for information about pressure-volume processes when I read, in a heat engineering book, "The process is polytropic with $PV^n = \text{constant}$." How can I know that a real life ...
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3answers
98 views

Calibrating and measuring pressure in Megapascals using a pressure transducer

I have two columns of water at different (but constant) temperatures. If I calibrate a pressure transducer using the first column at differing heights, when I measure the second column how do I ...
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2answers
6k views

How metal fittings seal connection without rubber gaskets?

I am well familiar with the concept of gasket. From my non-mechanical engineer perspective, I can understand how a standard rubber gasket works in various plumbing ...
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2answers
387 views

Turning an engine over with engine compression

When you compress a bicycle pump and seal the opening, the pump will automatically return to it's initial position when you release it. I suppose this is how air suspension works as well? if you have ...
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1answer
728 views

Calculating the Fraction of Steam in a Mixture

I have a stream ($10,000$ $m^3/d$) of inert gas and steam. The temperature of the stream is $195$ $^oC$, and the absolute pressure is $1455$ $kPa$. I am trying to find the amount of steam that can ...
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2answers
120 views

How to supply hydrogen to a fuel cell at a pressure lower than the atmospheric pressure?

I have purchased a fuel cell, and the supply pressure must not exceed 0.55 bar. My question is how can I supply the hydrogen at this pressure given that it is below atmospheric pressure.
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166 views

Determining compatibility of pressure gauge with sulphur hexaflouride (SF6)

I have a type of pressure gauge (material in contact with medium: 1.4542 (17-4 PH / 630)²) that I would like to use for sulphur hexaflouride (SF6) at room temperature and pressures of typically 6 bar. ...
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2answers
117 views

Does negative pressure inside the barrel affect low-powered railguns?

Just something I was wondering about when I've seen this on reddit today. Unlike in firearms where the pressure propels the projectile, in a railgun, wouldn't the pressure ahead/behind of the ...

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