What happens when you mix different pressures?

[@alelaera13]

What a nice video. It explains perfectly what happens in those systems and makes lots of examples. I think this is one of those problems that just are tricky but in reality they're really simple, as you made it look at the end

[@ELHAOUARIAbdelhalim]

I think the problem has deviated from the original question, which is: what is the result pressure in the combined pipe considering its end closed? So the system is isolated from any external effects. Can you answer this question please?

[@alelaera13]

@@ELHAOUARIAbdelhalim If there are no valves, nothing is preventing the pressurized tanks from depressurisation. so it's safe to assume that both of them have a tank on their pipeline. the whole segment afterwards, up until the closed (in this case) pipe, is full with air at a certain pressure. what is that pressure? it's the same exact problem as before, just that now that pressure is not automatically 1 bar since it does not go in the atmosphere but could be anything depending on how you filled this pipe. If you only filled it with air from the top tank, it would be the top pressure. if you filled it with atmospheric air, it would be still 1 bar. if you vacuumed it, would less.

[@Chinguenguenza]

If you take the original problem as stated (similar lines, no valves), then the outlet pressure is 15 bar (minus pressure losses) and there is no flow from source B. If fact, some or all the flow from source A would go into B. The key here is to distinguish between Rating an existing system versus Designing a new one. If I can add valves wherever I want to, I am designing. If I need to calculate pressures for a fixed system, I am Rating.

[@leocurious9919]

This is what I really don't get in this problem. If you want to stay "inside the box" of this odd though-experiment, then A is simply going to back-flow into B as well as exit on the open end. After all, there is no pressure drop in the pipes and the source ALWAYS provides 15 bar, those 15 bar are there all the way until the exit. B can only be at 15 bar too without any additional devices in-between.

[@Jonas_Aa]

@@leocurious9919that's what I thought to. Although I thought a little less than 15 bar since you will drop some pressure with the flow going to the 10 bar side.

[@leocurious9919]

@@Jonas_Aa Just like a source that always provides 15 bar, I would assume that there is no pressure loss. The diameter etc. is not given, so it could really be anything from 0 to 15 bar. It could be a capillary tube for all I know.

[@shotcrete3473]

@@leocurious9919 The pipes are actually carbon nanotubes.

[@allangibson8494]

Actually weirdness happens - I worked on a 30 bar pure nitrogen system where we detected a leak because atmospheric oxygen was contaminating the nitrogen - yes, one atmosphere air was leaking back into a 31 bar nitrogen system… And tightening the leaking tube fitting eliminated the ppm level contamination.

[@nicolaskoutsouvelis608]

To think how many students (and engineers alike) have never truly understood this concept. Extremely clear and entertaining explanation. If only more lecturers had your gift of unwrapping a problem and coaxing out the answer in such a logical and comprehensible form.

[@ProcesswithPat]

Do you remember asking this? Boyle's law, Charles' Law, coleslaw - that was the answer...

[@nicolaskoutsouvelis608]

@@ProcesswithPat I do remember the moment fairly clearly. But I think that "joke" was erased from my memory haha. Maybe I was too stressed at the time to appreciate cabbage based humour

[@scarfbandit177]

@@ProcesswithPat ah, cole's law

[@eduardoramos8317]

​@@ProcesswithPat2

[@jackmclane1826]

It is the same in electrical engineering. The impedance of a line determines the voltage at a given current flow... I love it when seemingly independent fields of engineering go hand in hand. Just as how Navier Stokes and Maxwell equations have a lot of symmetries.

[@philipoakley5498]

And Reynolds ;-) Though we've yet to see that properly in electrical engineering!

[@jackmclane1826]

@@philipoakley5498 I'm not that deep in electrical engineering. I'm more the mechanical guy that has kept an interest for the electronics... rare in my branch, but helps a lot.

[@philipoakley5498]

@@jackmclane1826 for fluid flows you can get sidewall effects and turbulent flow so there are some differences between plumbing flows and electrical flows. Electric just depends on potential (pressure) difference. It's all about how the flow 'valves' are constrained adjusted;-)

[@vojtechsmetana5261]

@@philipoakley5498 But you also get eddy currents that have a similar effect to turbulent flows in fluids. They can pretty much push the flow of current more to the inside of the conductor, see 'skin effect' for more info. This can pretty much work as an additional impedance/resistance, creating voltage loss across the wire, just like you can get pressure loss from transfering fluids over ditances. Although I'm not saying the two are the same. It's interesting to see that similiar effects arise in both cases.

[@philipoakley5498]

@@vojtechsmetana5261 Do watch out for some of these analogies, as they fall prey to the fallacy of pushing analogies too far. Things like skin effect have a strong frequency effect. And electrical flow has to be circular, which isn't the case in fluid design. You also don't consider EMC effects with fluids, so caution where caution is due. ;-)

[@robertbradfield8656]

I’ve seen similar problems in electrical systems. It’s very easy to get trolled if you don’t consider the full context or spot what’s yet to be defined. Great video, thanks Pat!

[@gtweak7]

Is it valid to reason about systems like the one described above that unless you know "the load," you cannot know the behavior of the whole system? As in electrical engineering, you don't speak of current until there's a force pushing it (i.e. voltage difference), and even adding a seemingly minor element affects the characteristics of the whole system.

[@rasmussverdrup7479]

I always find it amazing that intuitive understanding of pressures is such a bad guide to reality. Great video!

[@ProcesswithPat]

Similarly, temperature is a construct...

[@JoJoDo]

I actually think there's a bigger point that I notice some people oversee. You nicely demonstrate that anything that happens downstream has a big effect on what's upstream, which is also the case with external flow. And that is what I think people sometimes forget/don't know.

[@shawn.builds]

This is such a well paced video, something I’ve thought about a lot.

[@TheVincent0268]

I also graduated in chemical/process engineering and I am delighted to find a channel dedicated to this subject. Unfortunately, my career took another turn.

[@tiziano7m958]

The result of the video is clear, but I notice it's completely independent from the mixing problem. I can establish pressure on the outlet, for 1, 2, 3 o more tubes converging ok. But this does not tell much about the 2 flows of the example interact which each other. What is the flow from B and from A to outlet? I can't motivate Flow-B being outgoing (positive), even with a "simple valve" (a one-way valve I mean). I think Flow-B could only be ingoing (negative) without a valve, or zero with a valve. The reason is obvious: pA>pB. Using pressure regulator valves to equalize pressure is a solution to a different problem, not what I would like to understand. I hope a complete explanation comes out :p Anyway good job, I really appreciated your approach to the problem.

[@matsonnerby]

Sometimes it’s easier to change a flow problem, to an equivalent electrical problem. If you think about preassure as voltage, pipes and valves as resistors, it might be easier to see how to solve this problem, or actually that it can’t be solved without additional information.

[@rajatdogra96]

0:25 my answer 12.5

[@chrisayers7625]

Excellence presentation. Everyone has the basic understanding that things flow from a higher pressure to a lower pressure (not trying to be sarcastic here). The actual downstream pressure needs to be defined. And yes, depending upon the operating pressure, A will flow more than B, unless a valve is introduced (which will create a pressure drop). Fun problem.

[@robertcarnazzo6382]

This was well presented to help understand the solution to the problem stated.

[@ianbelletti6241]

The problem is that the more restricting the mixing pipe is and the following equipment the more likely source A is going to flow into source B. That is why back flow preventers often get installed.

[@mikefochtman7164]

Also important that the piping after the junction has the combined flow of the two. So in a proper mixing situation, more pressure drop per meter in that piping than upstream.

[@ianbelletti6241]

@@mikefochtman7164 true, but you can't guarantee that blockages won't happen. You need to have back flow preventers any time that you bring two different chemical lines together. You also forgot to mention the angle of entry into the larger pipe being important as well. Ideally you want both lines to meet at a Y instead of a T to insure that the flow is toward the mixing line and not toward each other.

[@goiterlanternbase]

1:45 Depends on the volume of the outgoing pipe. Make it to small and you have backflow in the 10 Bar pipe😜

[@waynejohnstone3685]

Interesting - I do underground process water systems in mining and deal with this constantly. These are generally closed systems (no atmospheric dumps unless we’re filling reservoirs etc and even then we’d use orifice plates with PRV or sustaining)so we deal with frictional losses as back pressure in miles of pipe, a lot of it horizontal. Joining two streams isn’t really ideal underground, the higher pressure from one would just push back against the other until the pressure drop was big enough to cause mixing. We do force this sometimes using sustaining valves though. Anyway, great video and great explanation on how the entire system needs to be understood.

[@weibrot6683]

Ok i completely misunderstood the assignment, but i also only looked at the thumbnail and title before thinking about it, i thought we needed to keep the flowrate and diameter or the pipe the same, so i thought we need to install a compressor at the end of both streams before they mix and compress them down in order to keep the flowrate and pipe diameter the same, because more stuff in the same volume at the same speed = higher pressure than before, i thought we would simply need to add up the different pressures

[@ersinaydin2618]

Having 10 bar in the line A, and 5 bar in the line B, wont you have reverse flow from A to b as well (from higher pressure medium to lower pressure medium)? Or we are assuming that the mixing point geometry is not allowing such flow or something.

[@abc957ok]

Hi, how about let's say during design, I have 2 pumps for mixing. One bigger pump A (200m3/hr) is designed to generally operate at 10 barg, while the other smaller pump B (50m3/hr) is at 6 barg. However, I need the outlet to be at 10 barg (more than 200m3/hr), would the pump B be able to provide the additional flow? For example, to achieve 10 barg, the flow is smaller in the pump curve.

[@bipl8989]

This is not a correct explanation. Upstream pressure also has effects that need to be considered equal in importance to downstream pressure. You cannot simply consider downstream pressures alone. Pressure drop that creates flow must be described by upstream pressure, downstream pressure and the corresponding flow rate. 3 variables. If you know any 2 of them, you can calculate the unknown third value. You have set downstream pressure and assumed some flow rates and pressure drops in pipe and equipment, then somehow determined that the upstream pressures of 10 and 15 bars are enough to make that flow happen. That is not necessarily true and must be verified by adding the pressure drops between up and downstream points, checking that the flow rates in all pipes still balance at the connection point. You have only done half the problem and ignored the rest. Now you must verify that whatever flow rates you have assumed in pipe A and B are indeed what you had assumed they were when you cane up with their pressure drops. See the Hardy Cross method for by hand calculation to understand the iterations involved in determining pipe flow and pressure drops in multiple pipes. In your 15 & 10bar example, what keeps the 15 bar flow simply from entering the 10 bar pipe? It is only that downstream pressure is lower than both 10 and 15bars.

[@boby115]

My thoughts exactly. This is why we use regulators and orifice sizing in the regulators (not to mention the correct pipe sizing). Downstream pressure should be referred to as the working pressure (The required pressure for the load. There also could be a variable load that the regulator would compensate for and keep the working pressure constant & a lock up pressure if the flow stops).

[@TomasSab3D]

Guess... You get to control the flow, by selecting the output pressure... and have to attach the 10bar at a point in the pipe - where the pressure has already dropped below 10... they can't be connected in "parallel".

[@JakubS]

I assume that adding pressures works similarly to adding resistance in electricity, so I think it'd follow the inverse of a sum of inverses. 1/10+1/15=1/x 15/150+10/150=1/x 25/150=1/x 1/6=1/x therefore x=6 bar

[@d3j4v00]

I’m happy to learn that I was correct to become confused when you drew a T connection but were saying “combined streams.” My gut reaction was “how they are they being combined?”

[@ChemEngWeekly]

Really good, clear video Pat! Fair to say it was informative and concise- great job, keep it up 👏 👍

[@ProcesswithPat]

I really appreciate it!

[@ChemEngWeekly]

No worries, fully deserved!

[@alanfate09]

I have a question, let's say A is 10,000,000 bar, B is 1 bar and mixing tube is 0 bar. Would the fluid from A get into B?

[@ProcesswithPat]

You may find the answer in the follow-up I did on reverse flow: Reverse Flow kzbin.info/www/bejne/pKLNcmWVn62Nns0 Give me a shout if this doesn’t help.

[@hetrodoxly1203]

This isn't a question, the higher pressure will always dominate, if you put regulators in line that's a different question, if the end of the system is open to atmosphere you can use a Ventura type valve that will allow different pressures or substances to mix.

[@dontuno]

A problem that baffled me on many occasions, and particularly when those two different pressures were fed into a mixing valve. Even more so when one had a constant cv/kvs value within the valve. Curiously, the mixing valve always achieved the desired result.

[@arshadkhan7488]

what would happen if you do not install control valves to balance the pressure? would the 15 bar line flow slightly into the 10bar stream while the majority would flow into the outlet stream?

[@ProcesswithPat]

I did a video in reverse flow using the exact same setup. Check it out!

[@clytle374]

Good explanation. As an electronics/maintenance person it really describes a conversation I had with a chemical engineer. I was not successful in my attempts to explain it

[@WritersDigest-b8f]

4:10? Why would the ocean water flow back into the pipe if the pressure

[@CxC_Maths]

Good vibes learn a lot. Side question what the name of that art piece in the background??

[@FirstnameLastname-fn6ik]

Nice video! Hypothetical question: If I had a stream of water at 10 bar colliding with a stream of water at 15 bar and there was a single pipe making a T with the intersection point of the two streams (so basically your drawing), would water from the 10 bar stream be able to mix with the 15 bar stream, or would the 15 bar stream just shut out the 10 bar and exit via the single pipe?

[@ProcesswithPat]

It hypothetically possible. The only time the 15 bar stream would flow back into the 10 bar stream is if it was easier for it to do that rather than for both streams to simply flow out of the combined pipe. This would mean that either: 1. the "outlet" (combined, T-piece) actually discharges into a pressure between 10 and 15 bar, say a pressurised tank (but that's weird because why then did we form our analysis from the point of view of the 10 and 15); or 2. The capacity from the 15 bar stream is so high that it is able to put enough flow through the combined pipe such that the pressure drop in that pipe becomes greater than 10 bar, making it possible to send some of the 15 bar stream into the 10 bar stream.

[@wo-olf]

​@@ProcesswithPatif it behaves anything like electric current then there will always be a flow from higher level to lower level in a parallel system. More will flow in the route of less resistance but there will be a tiny flow in the higher resistance route proportional to the resistance. Current cannot choose to not take the route of more resistance completely as long as the voltage is high enough to overcome the resistance. Speaking in fluid dynamics I'd say the 15 bar stream will split up in a certain manner, one part flowing "out" and one flowing in the direction of the 10 bar source.

[@SoulofaPond]

You still give the same value even after I failed year 2.2. Remain sublime

[@trevcam6892]

This is why it's very difficult to get the bathwater temperature you want when the hot water and the cold water pressures are very different.

[@michaelgarrow3239]

Um,,, the 15 bar would contaminate the 10 bar line with a +5 bar pressure. Duh!

[@misharialshahrani5188]

Thanks. Please do more videos. This video was very helpful 👍🏻

[@kestans]

once I made a water gun using 10liter canister, drilled a hole in bottom and inserted car windshield motor and water is sprayed via silicon tube. But then I installed additional same size windshield motor and but also now each motor had an aquarium one way valve and connected to silicon tube via T connector - to my surprise running two motors did not increase the water flow of the water gun :D

[@allangibson8494]

Because windscreen wiper pumps are positive displacement pumps and water is mostly incompressible (380bar pressure produces a 2% compression on water - Titan oops pressure). Compressible fluids and centrifugal pumps give different results (but pump sizing is important too).

[@frankezendam5409]

What about the flow of both products? You might want to control the flow because you might need mol of product A and less mol of product B.

[@panoskb9405]

I love your videos. I am gonna watch all of them deeply. And then I will come to you with questions! Congratulations that you like deep understanding! :D

[@ProcesswithPat]

That's really kind. And you're welcome to come with questions. Will be happy to give it a crack it it's something I am capable of doing.

[@panoskb9405]

@@ProcesswithPat thanks! I will come soon with my questions. Btw, very nice topics would be overpressure scenarios and PSVs. I am pretty sure you will give an amazing insight to these topics as well. ☺️

[@BB2Hale]

Thank you, I appreciate you posting these videos. I’m currently a field power engineer in the oil and gas sector. Can you suggest a layout program where I can drop in fittings and pipe that will automatically do the flow calculations for me? I’m trying to re design a glycol heating system, but with my own money so price is an issue. Thank you.

[@Paul-wn8zo]

I m facing a problem that I don t understand and the thing is that i am facing 2 inlets at different pressures and pipe sized and I am guessing why the fluid at the highest pressure will not block the fluid at the lowest pressure because fluid pass from high pressure to low pressure. In ur case you installed valves and made the pressure at each inlet the same so you would know your outlet pressure. What if we don t have these valves what would happen? will the 2 flows mix up and go to the outlet or if the pressure in one inlet is higher than the other one will it block it or go throw it even? Thx :)

[@ProcesswithPat]

I have a video that’s a follow-on from this one on reverse flow. Go check it out and see if it helps. About the valves - they are in the example but even if they weren’t it wouldn’t matter. Valves cause pressure drop. So does piping. The flows of each stream regulate themselves so that the pressure drops of each stream are such, that the streams combine at the same pressure.

[@Paul-wn8zo]

@@ProcesswithPat thank you sooooo soooooooooooooooooooooooooooooo much :)

[@ProcesswithPat]

You bet!

[@saiftherockstar2]

What if its two streams of saturated water at different temperatures

[@vaibhavpatil6488]

Have to be honest, basically it was a wrong problem and Bernoulie's is correct way to solve it, which he tried to disregard. But failed to do so because without knowing discharge or conduit dimensions we won't design shit.

[@medotedo8410]

I like your video but I did not get the point why you subtract same amount from both streams? and how t make them equal at the mixing point? also what did you mean by drop in pressure 5 bar in the reactor that when the inlet is 5 bar the outlet will be 0 bar ?! how come !

[@freefreepalestine360]

At what altitude the vacuum of space starts sucking?

[@ThatJay283]

i have electronics knlowlege, and tried to solve this by comparing it with the water analogy of electricity. so pressure = voltage, and volume of liquid moved = current. the analogy is far from perfect, but i still came to the conclusion that there is not enough information. so yeah i tried to solve this using ohms laws lol

[@dimong2392]

It seems like true.

[@tiisetso]

Delighted to see this!

[@alimahdi821]

Thank you Pat very interesting.

[@crashandrise]

It's a delight to see you speak again. Guess I'm gonna be a chemical engineer now

[@brofenix]

Hmm~ interesting, I guessed wrong thinking the pressures would average. That makes sense though that the pressure downstream of the mixing point is dependent on the backpressure downstream.

[@MechGZ]

Very interesting video. @3.16 states that pressure will be 0 gauge at the point of leaving to the atmosphere. So, in that condition what about pressure at Points A and B. Is it also 0 gauge (plus friction loss in the pipe )?. I am just confused about how upstream pressure will be maintained when an outlet is open to atmospheric ?.

[@ssu7653]

This question is the same as "how big is a fish?" Answer is as with all these "trick" questions: depends on unknown factors

[@tebatsoreginald9318]

What way to explain this simple problem. Thanks Pat.

[@Nachocosta5]

Really good!

[@kylethompson1379]

Great video. For some people it may be easier to understand this using circuit theory with voltages and currents. It's basically the same deal.

[@BillSaltbush]

Understanding science . . . fascinating! Nicely done.

[@Southghost5997]

Great explanation. One thing to add is that geomtery plays a big role in the way fluids mix and pressure change occurs. For example ejectors and venturis are practical devices for mixing fluids and allowing a low pressure stream to increase in pressure past the mixing point. Whereas two pipes coming to a T can cause backflow unless pressure is reduced in the high pressure stream.

[@Ozzy3333333]

Being in electronics, my first question was what are the load and source impedances, since they were not given I called it a trick question in under 20ms.

[@antman7673]

It is always pressure times volume.

[@davidklempfner826]

You mentioned that water flows from a high pressure location to a low pressure location. A hose connected to a pump that is going down hill would have higher pressure due to head gain at the nozzle compared to at the pump outlet, but the water still flows down hill. Can you explain what's going on in that situation?

[@emilyferreiraplanets]

Was also breaking my head about this at some point

[@aspen_school]

Thank you for addressing very basic but highly confusing problem. 👏

[@thaddeudeladia1014]

Hi i am i bit confuse .. so you have 2 cylinders high pressure and Low pressurecand in middle you have a Pressure regulator .. so when i open the Pressure regulator what will happen if i open the Pressure regulator??? Cna help me what isbthe answer thanks

[@mavairick]

I don't have any knowledge in engineering and spent 2/3 of the video wondering how you "mix" pressure since the 15bar would just push back the 10bar then you complete the scheme with valves and I was lie : "oh yeah, now it makes sense"

[@M3dicayne]

Your answer is in fact partly wrong or at least missing something out. Because you see it as a chemist, who wants to keep a process running, not a mathematician. In fact, combining two different pressures always result in an output pressure potential of the bigger one, with the option of increased flow amount as pressure basically is the flow rate. There are a couple of examples for that: If you have a compressor that produces 8 bars and you use the pistol to let air out, the compressed air shoots in the room with atmospheric pressure. The air is venting with atmospheric pressure however with the amount of air 9 times faster than the idle air inside the room - as the compressor compresses air to 8 bars above atmosphere. Another example is two rivers, the one is smaller, the other a huge river, broad and deep. For the sake of the example, we will ignore changes in the riverbed as angles, disturbances, wheather, etc. They meet each other at a T-junction. The bigger river will flow - no matter what the small river or the output of the T-junction does - everywhere until gravity will finally combines the amount of water of the two rivers, letting the combined stream run out of the T-junction with increased mass (amount of water), but not increased speed (flow rate). Back to your example, you create a lot of turbulances just by using a simple T-junction. Gasses can overcome some of that but still need to flow at a 90° angle, facing a force opposing it (even possible to create a backflow). Simply by changing the T-junction to a Y and increasing the output pipe size, you will reduce backpressure and resistance. Depending on the distance and the size of the pipes, you will still face the problem of generating heat, as particles in motion produce a lot of it; converting kinetic energy to heat.

[@Vo0Do0972]

As a random bloke that just landed on this video, i'm lost at the atmosphere part... only got worse after that. Why does it leave at atmosphere? I turn my hose on, water comes out at high or low pressure. I'm thinking I don't have a certain understanding to help with this. Usually im pretty good with physics but never ever looked at plumbing stuff before. Fells like when i looked at circuits the first time.

[@mlvz6571]

Pat, thanks for this video. Could you do a video of pump head calculation in the situation where on the discharge side, several lines connect to the main discharge line ? For the pressure drops should we consider the total flow rate for the section of the main pipe after connection of the other pipes ? And/or should we consider also the head of the pumps from other lines than connect to the main one ? I realized that everybody knows how to calculate pump head in the easiest scenario (2 tanks, 1 pipe, no other connections) but no one explains how to deal with connections. Have a nice day !

[@darshankumar7419]

Nicely explained,each sentence is well framed.yes it is true pressure mixing is rare and most engineer are confused about it because it is counter intuitive.

[@russellcollins5692]

This is a very badly designed system you have described. If I came across a system designer proposing this as a limitation, instant demotion. I use in this very situation A/B to atmosphere mixed via a venturi or cyclone vortex valve. Look I may have misunderstood the end function, but still there are always solutions, thats the Art off system designer to never end up with a negative, unless that’s what’s called for.

[@mmenjic]

6:22 but this is not the same question and this answer does not have much to do with the original question which seems to be what pressure would be after mixing the 15 bar with 10 bar!!! Yes it does depend on what happens next but you did not tell us that so best assumption is your 15 bar fluid would go into your 10 bar fluid and the reactor. Installing pressure drop valves literally deletes your starting point and now you have 2 streams of 5 bar, they can be 10 bar or 15 bar or 7 million bar before those pressure drop valves it does not matter, those valves are designed to give you 5 bar after them so now you have 2 streams of 5 bar which is not even close to original question. It is like asking what the max speed of your car is, and after someone answers that for example 200 kmh, you say that it is not correct because if you do not have fuel in your tank your car cannot go very fast, which is true but has nothing to do with original question!!!!!!

[@PauloDacosta-s1s]

The video is good but the explanation given between 6 min and 6 min 15 sec is not clear. I would expect that the pressure of both pipes after mixing should be 5 bar and the valves should reduce the pressure of 15 bars to 5 bars and the pipe of 10 bars to 5 bars…. Did I miss something?

[@Xadhoom80]

My initial reaction on title: Don't! i seen what happens when someone thinks adding the pneumatic systems 8 bar to the high pressure 120 bar water line thinking they would get better pressure. They had a lot of work drying out the pneumatic system afterwards. But yeah, in an open system its a different tale.

[@wo-olf]

Real world scenarios show an exit pressure of 0 bar in standard atmosphere is not true. If there was, there wouldn't be any flow whatsoever. If you have an air compressor and pull the trigger there will be air flow around the nozzle and there will be a specific geometry of higher pressure around the nozzle, obviously so the exiting pressure will be somewhere in between system pressure and atmospheric pressure. If you have a vacuum chamber and air it up there will be an "input pressure" as high as atmospheric pressure.

[@TexasEngineer]

The flow from the 15 bar would have a pressure drop from the source and along the pipe to the outlet at a given pressure. If the pressure at the mixing point was higher than 10 bar the flow would back up into the 10 bar system and you would need a check valve. The 15 bar system would want to shut off or limit the 10 bar flow. It is a very bad design and lead to chaos. I was hoping for an actual working model to prove the chaos theory.

[@titaniumsandwedge]

Too complicated. Nobody would put a 10 bar stream into a 15 bar stream or vice versa and hope for good results. The solution is to pipe both streams into the mixing tank and control the pressure at the outlet of the tank. If the tank is a reactor, then both streams need to be flow controlled (FIC) into the reactor.

[@ИванИванов-м6ч1о]

How the fuck something with lower pressure flows into something with higher pressure? If you have one inlet at 15bar and the other at 10 and a reactor, as stated initially, then everything will be at 15 bar and filled with the medium from the inlet with 15bar

[@sebastjansslavitis3898]

I though it gonna be 15 bar.. my idea was that weaker stream not gonna work at all because 15 bar pressure gonna push it in, you know, like a pump, it gonna pressurize it until its 15... yeah I'm not engineer

[@tristanginod9238]

Great video but it's a little bit confusing because with an engineer approach you consider the lost in conduit, but just with this diagram we can just think you are connecting three pressure level with a perfect conduit system, and it doesn't make any sense. As an electrical engineer it's like drawing two different voltages sources in parallel without considering any resistance, which is an heresy.

[@discoveringthegardenofeden7882]

Not answered in the video? Is the flow from the second stream blocked or not? Does mixing even occur?

[@affanbhaijaan65]

Still confused😅

[@haydengalloway5177]

I think he is wrong. Because A is a higher pressure then B cannot flow at all. So the pressure leaving will be just the pressure of A. Eventually enough A will flow into B that they will equalize and at that point the pressure leaving will just be whatever they equalize at.

[@BeholdTheLight23]

I don't get your solution, you just made the problem into a completely new one with the valves. I'm still sitting here and waiting for the answer: How much the pressure is in the middle section?

[@Hleidude]

The practicality when using two valves (pressure regulating devices) to control a determined outlet pressure from independent pressure supplies is idealistic and will not work to provide mixing with any certainty.

[@guardrailbiter]

This explains why the Ghostbusters did not want to cross streams. They couldn't readily calculate the pressure of the combined flow. 😉

[@benjaminzedrine]

I think this is the problem with the plumbing in my house. Random mess of pipes. Too many bends, too many different kinds of pipes, wrong pressures.

[@sumadoolpeep7171]

thank you! great video and clear! looking forward to more of your videos on the process design!!

[@andrewbradfield5500]

Amazing stuff pat 😆 you will make process engineers out of us yet !

[@muhsinalhameed6408]

What is the meaning of the ( reactor) ? Anyone can help, please. is it a component such as valves, or is it a pressure generator?

[@wildmonkiesJR]

I mean you could have just asked can I make the flow the same pressure and realized bernoulli equation tells you the answer of how to drop the pressure.

[@BogoblinGamer]

10 + 15 = 25, so hopefully it's that

[@takudzwamashamba7453]

im havign exactly this same problem but in a reformer. m,y fuel and air reaacting are mixing at different temperatures and pressures. dealing with the temperature part is simpler, one can use enthalpy balance, but the pressure one is mind boogling. and papers really dont say much about this

[@ProcesswithPat]

I’m glad to hear it was helpful. Yeah this one really messed with my head early in my career and it’s not something that is explained very well, that’s why I thought I’d do it! Good luck with your reformer!

[@Muck-qy2oo]

Could one applay something like Kirchhoffs law to this?

[@gerryb5578]

The 15 bar will flow into the T junction and the 10 bar will be equalised and effectively not flow.

[@sali32123]

Thank you. In youtube videos which are full of s**t, this kind of content is like a bright light in a tunnel.

[@forbaldo1]

when he says valves I think he means regulated and there would have to be anti flowback valves to so much like his problem . he can do the maths but you need to know what things are called to

[@Gimlet42]

Don't cross the streams!

[@KallePihlajasaari]

Lovely video. Another way to design the process and perhaps even a preferred way for safety and management in most cases would be to have the two pipes combine in the reactor vessel then the feed lines have a constant back pressure (as you choose) and are not affected by pressure or feed rate changes in the other reactant. I can think of no compelling reason to combine the two feeds inside the plumbing, a mechanically coupled two gang feed pump would be preferred even if the excuse of saving on a pressurised feed pump was the excuse. Saving on a reactor fitting would be a rare reason to justify the early mixing. Someone on Facebook recommended your video, said you were worth watching. I will keep an eye out for more.

[@scottieb6442]

Vastly depends on the process. Most solid-liquid injection processes for scrubbers can be done in piping to optimize against pluggage and make sure the slurry is homogenized ie soda ash for scrubbing. Lots of applications for static pipeline mixers as well

[@koenth2359]

Just solve the Navier-Stokes equations first and you'll have the full answer😊

[@maxzet368]

wouldn't the higher pressure just push into the 10bar line and the output line?