18 votes
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Why was Freon used in spray cans before it was declared a threat to ozone?

Spray cans work by containing a propellant which has a boiling point a small amount below room temperature. When the can is sealed the liquid and vapour reach equilibrium at a relatively modest ...
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10 votes
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Is it possible to increase the heat output of a gas stove by connecting two gas supply canisters to it at the same time, and is it safe to do so?

is it possible to increase the heat output of the burner by connecting two low-pressure supplies in parallel via a T-piece like this one? The primary factor is gas pressure at the tee. If the ...
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9 votes

Is it possible to increase the heat output of a gas stove by connecting two gas supply canisters to it at the same time, and is it safe to do so?

No, connecting two tanks together will not double the flow. The regulators fitted to tanks limit the pressure and flow rate so all you do is double the amount of gas the burner has available ie ...
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5 votes
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Why no hydraulic piston gas compressors?

There are two aspects to this. First is that the main advantage of hydraulics is that is provides a compact means of greatly multiplying force but in compressing gasses you have to a huge amount of ...
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5 votes

What is the maximum possible compression with fuel injection in a gasoline combustion engine?

If you want to turn the engine into a compression-ignition one, I suppose there isn't really a limit other than physical based on strength of materials. Your proposed solution is rather how diesel ...
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  • 4,820
4 votes
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What are the advantages of chemical oxygen generation over compressed tank storage?

One advantage these chemical systems may have over compressed tanks is how well they are suited for intermittent use and long-term storage (as opposed to regular, continuous operation). The US FAA ...
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  • 3,211
4 votes

What are the advantages of chemical oxygen generation over compressed tank storage?

From personal experience of refuge systems, oxygen generating systems are preferred over medical oxygen gas tanks because of space requirements, portability and the ease of relocation. When emergency ...
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  • 9,527
4 votes

Replace Hydrogen in an air cylinder

Structurally the pressure is independent from the nature of the gas. So, it shouldn't matter if its $N_2$ or $O_2$. Special care should be taken with corrosive gases, but usually that means the ...
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3 votes
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Do pressurised cans still pose a risk to bursting in normal conditions, but after being exposed to heat?

Assume that high temperature causes no chemical reactions in the contents or between the contents and the can. High temperature will increase the pressure in the can. Assume the can is fully ...
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3 votes
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volume comparison of compressed air and gas duster

According to to the SDS found here the product contains tetrafluoroethane as an ingredient. I looked around and found other similar products with the same ingredient. For sake of simplicity lets say ...
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  • 593
3 votes
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How to determine the choke point in a compressed gas system?

How do I explain the fact that the flow chokes only at the nozzle? To explain why the flow only chokes at a single point, it is important to remember that for a system at steady state, there can only ...
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3 votes

What is the maximum possible compression with fuel injection in a gasoline combustion engine?

Calculate the temperature of the air in the cylinder after compression - if that exceeds the self-ignition temperature of the fuel injected then that is a problem.
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2 votes
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Will helium gas lift more weight in air when it is spread over large volume compared to equal weight heavily compressed small volume?

As a reality check lets consider industrial gas tanks as the specifications are easily available. A BOC size D hydrogen tank has a gross weight of 57kg and contains 23kg of hydrogen at 230bar. At ...
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2 votes
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Device (electronic valve?) for controlling O2/Nitrogen levels in sealed chamber

It sounds like you might be looking at a similar setup to purge gas for arc welding. Here you would typically a regulator which screws into the valve fitting of the gas bottle which provides coarse ...
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2 votes
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Is it standard practice to use a pressure relief valve as a pressure regulator?

Sort of. Certainly things like pressure cookers and turbochargers use blow off vales as a routine way to regulate pressure. Generally this is to make sure that internal pressure doesn't exceed ...
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2 votes

Why no hydraulic piston gas compressors?

The elephant in the room is that while gasses are compressible, hydraulic oil is only negligibly so. This difference has two major effects: Firstly, the output volume flow is limited by the intake ...
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  • 241
2 votes

Calculating mass of gas in container

Isolated System An isolated system allows no mass or heat flow. The equation for an ideal gas is $$ p V = n R T$$ where $p$ is pressure, $V$ is volume, $n$ is number of moles, $R$ is the gas law ...
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2 votes

Time-rate of change of P and T in a pressurized rigid volume with a hole in it

Thanks for a nicely presented first question. First you need a model for the equation of state for the tank. Given the initial conditions, develop formulas that yield static pressure, temperature, ...
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  • 3,590
2 votes

What is the purpose of combustor in a gas turbine

The turbine blades are what turns the compressor blades in the first place. They do this by extracting work from the hot gas shooting out of the combustors at high speed, and feeding it forward on a ...
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2 votes

Is it possible to increase the heat output of a gas stove by connecting two gas supply canisters to it at the same time, and is it safe to do so?

No. The regulator itself will see to that. It's around 30 millibars - 3/100 0f a Bar. The pressure inside a gas cylinder is around 10 Bars - 3,000 times that of what gets into your stove! It wouldn't ...
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  • 209
2 votes

Constant Pressure Variable Volume Tanks

Rolling diaphragms are nothing new. The shaft connected to the rolling diaphragm projects through the housing (unlike the image shows). You generally pressurize the fluid through the shaft. Creating a ...
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  • 486
1 vote

Recommended books for process engineering?

First get the newest edition of Perry's Chemical Engineers' Handbook a.k.a The Chemical Engineer's Bible which covers at the very least the basics of pretty much everything you need. Then look at ...
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  • 229
1 vote

What is the purpose of combustor in a gas turbine

The best way to approach this question is through basic thermodynamics. Suppose you have a compressor and a turbine but no combustion in between. Then we can define processes in this machine as ...
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  • 136
1 vote

Should pressure vessel head be thicker than wall

So if the vessel is rectangular , I assume a flat heads, essentially no different than a side. So the size of sides and heads would determine the necessary thickness. In traditional cylindrical ...
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  • 5,894
1 vote

Relation between Inlet and Outlet mass flow rate for a turbocharger?

The mass flow across a turbocharger is constant: If X kilogrammes of air go in then X kilogrammes of air come out. However if the pressure is twice the inlet pressure then the output volume is ...
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1 vote

Real life example of motor/piston involving an isoterm process?

We assume isothermal as having to include all the heat gains and losses to the gas during the cycle would be too onerous and add little to the accuracy of the result.
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  • 14.1k
1 vote
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Ideal gas law, theory vs reality

Have a look at the following: https://industry.airliquide.us/volume-compressed-gas-cylinder Based on this, if you assume a gas cylinder of 47 litres (standard size) at 200 bar fill pressure, you have:...
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  • 1,806
1 vote

Cheapest way to measure gas flow (mass)?

By knowing the volume flow rate of a gas , you can also find the mass passing through a cross section area for certain thermodynamic conditions.
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1 vote

Is it standard practice to use a pressure relief valve as a pressure regulator?

Id say a regulator is more optimised for attaining a given setpoint with precision and lack of chatter, whereas a relief valve is more concerned with reliability and less with finesse. But you are ...
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1 vote

Lpg cylinder to compressed air tank

According to one of many resources regarding pressure in propane tanks, a tank with 20 pounds of gas at 70°F has a pressure of 145 psi, at 90°F would have 180 psi, at 105°F would have 235 psi, and ...
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