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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3answers
217 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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0answers
736 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
77 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
811 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
448 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
11k 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 ...
2
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1answer
241 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
230 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
12k 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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0answers
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
635 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
5k 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 ...
9
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2answers
209k 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
79 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
602 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
536 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
95 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
5k 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
377 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
575 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
118 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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1answer
159 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
115 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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4answers
9k views

How does pressure change with depth in earth?

I've learned in school that pressure in water changes like $$p(h) = \rho g h$$ where $h$ is depth in meters, $\rho$ is density (e.g. 1000 $\frac{\text{kg}}{\text{m}^3}$ for water) and $g$ is ...
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1answer
163 views

Is it possible to store leftover pressure from burning a propellant in a pressure vessel?

Say, in a firearm, after giving off a shot, if the barrel were to be closed off, does there exist a way to store some of it in an external pressure vessel, without requiring a mainly-external source ...
2
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1answer
291 views

Is this pressure vessel feasible?

I am intending to construct a small pressure vessel. It needs to be around 7 centimeters in length and width and around 1-2 centimeters in depth. It must be capable of being pressurised to 300 psi ...
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3answers
2k views

How an airfoil works

I have read on many sites that for lift to occur, the pressure below a wing must be higher than the pressure above it. This happens by somehow moving air faster over the top of the air foil so the ...
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5answers
4k views

Understanding pressure drop and mass average values

While studying some papers, I didn't understand the following sentences: deltP the pressure drop across the turbine, evaluated using the mass average values at ...
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2answers
1k views

Water pressure in a filled sphere

If I were to fully fill a sphere with water without any air trapped inside, how to find the pressure of the water at, say, the center of the sphere?
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1answer
192 views

Pressure sensors with best precision

Measuring pressures have many different applications which require proper encapsulating of the sensors, but at the core there is a limited amount of techniques. To my understanding, the two leading ...
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2answers
6k views

If aircraft are pressurised, why do our ears pop during liftoff and landing?

Something hit me during my last flight: our ears feel that the pressure around us changes quickly during liftoff and landing, they hurt more and more until we make them pop. However, the cabin must ...
8
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1answer
169 views

Water hammer and expansion waves

I was thinking about the relationship between water hammer and expansion waves. Pressure seems to drop across a surge wave travelling at the speed of sound in water hammer (after the fluid has been ...
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2answers
691 views

Pressure drop across column in gas phase: what changes?

If you force high-pressure gas through a packed-bed, the gas pressure drops. However, the ideal gas law states: $$P = \frac{RT}{v}$$ so for an ideal gas, the pressure drop must be associated with a ...
3
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1answer
695 views

Controlling the flow of powder from a container

I was wondering how you would control the flow of powder from a container (with a small cylindrical dispenser at the bottom). The container is filled with powder. As the container drains, less ...
3
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1answer
8k views

Vacuum Pump Power Calculation

This may be a silly question, but I'm not a mechanical engineering. What's the best way to calculate the energy required to reduce the pressure of a gas stream below atmospheric pressure? Obviously ...
2
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2answers
201 views

Can pressure rise due to heat flux in a pipe?

I'm talking about a: smooth circular pipe without any valve at inlet or outlet without pressure losses due to friction subjected to a constant heat flux from outside on the entire pipe ...
6
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1answer
928 views

Calculate elasticity of rubber balloon

I am developing a model for the respiratory system of a neonate (newborn child) for a BME project by using pressure/volume data of the lungs. To model these, I plan to use a rubber balloon. However. ...
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0answers
58 views

How to attach a shell covering to a flat piece with clay as adhesive? [closed]

I have a ceramic nozzle type structure sort of like this: The outer casing is joined with clay material with the inner ceramic nozzle. What we do is, we attach the clay in the casing, put the nozzle ...
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4answers
3k views

Calculating maximum internal pressure from maximum rated external pressure?

Is there a calculation / rule of thumb that can determine a containers rough maximum negative pressure (vacuum) from it's rated internal pressure (assuming a single layer construction so there is no ...
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0answers
499 views

Calculating engine pressure from measureable quantities

How can I calculate the engine pressure in units of Bars by using torque, the cylinder volume, motor efficiency, and the gear reduction ratio? My values are as follows: ...
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3answers
538 views

Would a structurally sound pressure cooker be able to withstand an internal vacuum?

Would the body of a normal round pot shaped pressure cooker (built to cook foods at 15 psi) be able to withstand being evacuated down to high-vacuum pressures? Apparently it has been done before: i.e....
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3answers
1k views

How do I calculate the max flow rate for a pump with no power restrictions?

Let's assume we have a pump and it can draw as much power as it needs. As the pump speeds up, it creates vacuum in the intake. At some point it draws the gas/liquid so fast, the intake pressure is so ...
6
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2answers
1k views

Can I seal the inside of a water well to use it as water reservoir when the well is dry?

We've had unusually dry weather and our well has run so low that we had to call in a water hauling company to refill it a few days ago. The water man told me that even though he dumped in ~ 1000 ...
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2answers
699 views

Why is minimum pressure specified on a PSU water cooling circuit?

I work in consultancy and I am designing a product for a customer. The customer has requested a specific PSU. I have contacted this PSU manufacturer and they request 6 L/min of coolant flow and ...
3
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2answers
487 views

How to verify results from a manometer/venturimeter?

I'm designing a system to determine pressure drops across thin samples while simultaneously measuring velocity (and through multiplying by area, volumetric flowrate). I need a way of determining how ...