Plate Heat Exchanger, How it works – working principle hvac industrial engineering phx heat transfer

Plate Heat Exchanger, How it works – working principle hvac industrial engineering phx heat transfer


Hey there guys, Paul here from theengineeringmindset.com. In this video we’re
gonna be looking at the plate heat exchangers and
they’re often referred to as PHE’s, PHX’s, or sometimes just HX or HEX. Now, plate heat exchangers
are very common, they are used extensively in building services and manufacturing. The reason they are popular is because they are very compact,
they’re very efficient, they’re easy to service, they need very low maintenance as well. Their purpose is to
transfer thermal energy from one fluid in one system to another without the two fluids mixing together. For example, in building
services you might want to transfer heat from a primary
loop connected to a boiler over to a separate secondary loop or maybe in a district heating network. Or in manufacturing you
may want to cool down some oil and use water to cool
that down but obviously you don’t want to mix the
oil and the water together. Now, we have pulled one of
the heat exchangers apart. We’re gonna have a look at
some of main components here. So we’ve got the end plates
here or the front and back cover and these are made from usually a mild steel and they’re very strong, they’re there to hold everything together. Then we’ve got the nuts, these
attach obviously and tighten up onto the tightening bolts. The tightening bolts, they
fit in some grooves in there and they’ll run
the entire length of the heat exchanger and the bolts
are tightened on these and that will compress all the plates
together and squeeze the gaskets against the plates to make the heat exchanger completely
waterproof or leak proof. And then wedged in between
there we’ve got the plates where the heat transfer
occurs and we’ve also got the gaskets which sit in between the plates and that’s
what gives it the seal. Larger heat exchangers will
also have this supporting bar at the top and the bottom
and you can see here that the case and the
plates, they just slide along there and there’s various
ways that they can come off, either they twist these
ones, they’d be too big to twist off but there’s a
section removed at the back where these would just drop
out but the smaller ones, these would just slide in and out. And you can see a real plate heat exchanger plate there on the screen. Now, these are typically made from steel or titanium and you can
see they’ve got this pattern grooved into them
or stamped into them. These patterns are gonna
strengthen the plates, obviously they’re incredibly
thin and they’re also gonna increase the heat
transfer surface area as well as creating a very
turbulent flow inside them so it’s not smooth, all
the water has to row across these and come out very
rough and turbulent. Now between the plates
we’ve got the gaskets here, just this rubber gasket
and that is attached to the face of the plate
and the purpose of the gasket is to ensure a tight
fit and to prevent leaks. The gasket also allows or prevents the flow of fluid into the sheet. You can see here, so this
section here we’ve got the rubber seal coming across
and double seal on this one so that no fluid in this
can leak out or flow in, as well as this side, whereas
here there is no gasket there so the fluid if it entered
here could flow down and come down and enter into this one here because there isn’t anything there. Same as this one, the fluid
can only come out of here and travel up and then into this
section here, into that hole. Now, you’ll probably notice
that the tightening bolts they’re actually, they extend
far past the heat exchanger. That’s for a few reasons,
one is obviously to be able to fit all these plates
and et cetera on during the installation or during
maintenance but also this gives you the ability to extend the plate heat exchanger in
future so this one here is actually from a district
heating network and at the moment the building’s only
half complete and they’re expecting to double the building size. So they’ve allowed extra bolt
lengths to be added and that means that the plates
can be added and this heat exchanger can grow with the demand. Now, there’s a couple of ways that the plate heat exchanger can be piped up. This is the most common
version and the version that we’re gonna be looking at today. That is where the inlets
and outlets are all on the front plate so
the fluids will enter, flow through their channels
and then make their way back to the front plate. The other version is where the fluids, one of the fluids enters
through the front plate and it passes through there and
then makes it way and it will then exit through the
back plate as well as one of the fluids will
enter there as well. Now, this version here, the
first version is the most common version and that
is because you don’t need to alter the pipework if
you need to extend the plate heat exchanger in the future, whereas, with the second
version here all the pipework that’s connected would have
to be removed and remade to fit depending on how far
you extend your heat exchanger. So it’s not really so practical, that is why this one is far more common. And you can just see in
all these examples here that is exactly what’s happening. So the flow return are happening
on the front plate there. So how does it work? Well, we’ve already seen
that if you remove some of the seal then the fluid
can flow through there. So if we stack a number of plates together then you’ll see it forms this channel, this pipe like feature flowing
through all the plates. And then we can add the
front and back plates onto there and we get these channels where the water or the fluid, whatever
you’ve got can then flow through certain plates and it can’t flow through other plates. And let’s just see an example of how this would work practically. So if we opened up the
heat exchanger again, now you can see here that
the gaskets are oriented differently on the alternating plates there for the heat exchange. So this one here you can
see fluid in this pipe would not be able to pass
through or this one and this one it would so it just alternates, vice versa all the way through. And so if we pass one fluid through there you can see it entering
through this top port, passing all the way through,
it can’t pass through this one, there’s a seal there, it
gets to the next plate, oh there’s no seal there so
we can pass through there, can’t go into this hole but you can into this one because there is no seal and so all these will pass through, collect up and make its way back out. Now, the same thing is gonna be happening with the other fluid
we’re passing through. So you can see here we’re
passing hot fluid through. So this one is entering
through the bottom port, coming along, it’s getting to the plates, some of them it can
pass through so it will, others it cannot leave that
pipe so it will not and then it will just pass through all the way until it creates that loop and exits. So if we mix these two fluids
together what’s gonna happen is the cold fluid is going to enter, pass through and then on
the other side of the plate is the hot fluid so
that is gonna take some of that heat away so the cold fluid will warm up and that will leave as a much warmer fluid and the hot fluid that comes in is going to cool down
because it’s going to give up some of its heat into
the cold stream and then that will leave as a much more cooler fluid. So if we just look at
a very basic example of how this is working,
let’s just say we’ve got a few plates here and
we’ve got a cold channel, hot channel and another cold channel. Now, if we let the hot
fluid enter into the channel there and as that
happens heat is then going to conduct through into the plate
because they are touching, so that heat will then pass
through and warm up this plate. And if we then pass
the cold fluid into the cold channels and some of
the heat in those plates which have been heated up,
it will start to cool down because some of the thermal energy is transferring over into the cold fluid. That’s through conduction. And as that happens the cold
fluid begins to warm up and obviously the hot fluid is
going to start to cool down. So then the heat exchanger
starts to equal up and equalize out and that means that the
cold fluid is going to enter, is gonna exit warm and the hot
fluid is going to exit cool. And that temperature
grading is going to then vary through the heat exchanger,
through the plates and also through the fluids which
is conducting the heat. So when you combine all of this together that is how you get the heat transfer occur in the
plate heat exchanger. You can also notice that
these fluids are flowing in counter flow and that
is the best configuration for the most effectiveness
because the log mean temperature difference, the
LMTD is at the greatest. We’ll have a look at what
that means in another video. This video is just for you to understand how it’s working and why it works. I’ll just give you a real world example of a heat exchanger here as well. So this is a German heat
exchanger as you can see right down here but you can
see this heat exchanger here provides 1500 kilowatts of
thermal energy and has a transmission area of 29.3
meters squared with a flow rate of 42,000, or
almost 43,000 liters per hour. It would also handle up to 100 bar on each side of the plates. So you can see these things
are very powerful and they’re very efficient and they’re
very compact in how they work. Now, if you do have one
of these in your buildings please also remember to
insulate as it’s much more energy efficient,
keep the plastic threads, plastic sheets on the threads to protect them from damage otherwise you won’t be able to get these nuts off very easily. Okay, that’s it for this video, thank you very much for watching. I hope you enjoyed it and it helped you. Please don’t forget to like, subscribe and share and if you have any comments leave them in
the comments section below. I’ll try to get back to
you as soon as possible. Once again, thank you
very much for watching.

91 COMMENTS

    ⚠️ Found this video super useful? Buy Paul a coffee to say thanks: ☕

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    Is this type of heat exchanger most suitable to act as an evaporator ( the hot fluid is hot exhaust gas from a combustion engine and the cold liquid is water) for a form of waste heat recovery

    Question.
    Based on your presentation. Your cold side rotates clockwise (right) and your hot side rotates counterclockwise (left). What if, my connection goes like this. My cold side is connected to the right and rotates counterclockwise and hot side connected to the left rotates clockwise with the same type of HEX. Is that affects my cooling efficiency?

    Very good and interesting vid, i have been watching a few of your vids and am really pleased to have found your channel, loads of good info and very good to use to tech fellow work colleagues interested in increasing knowledge . *The real heat exchanger at the end is 10Bar not 100bar.

    I left with a doubt, how does in this case the hot fluid travels vertically against gravity? Does it has to do with the liquid surface tension? Or pressure?

    Done an experiment at uni, realised that transfer efficiency decreased as hot water flow rate was increased . Why is this ?

    The heat exchanger example you use in the end is of a Swedish HX, not a German one. Really good video though, thanks!

    أنا أعمل في شركة المانية ضخمة لتصنيع المبادلات الحرارية بجودة عالية

    What are the chances of leakage in the exchanger and mixing of hot and cold fluids? Where does the leak usually occur? Is it because of gasket failure? How common are such leaks?

    thanks for your videos,how to calculate the friction loss due to the heat exchanger. if we make a comparison can we expect the equivalent length for the heat exchanger in the chilled water network. thanks

    Hi.
    Is it possible to send cold fluid from diffrent port which is indicated on the Heat.Exchenger originally? I mean chang the circuit ( hot & cold fluid). Is there any effects on efficiency??

    Would you please make video on " heat transfer and pressure drop of a four flat tube with different air inlet angles : experimental study "

    Hi Sir, I immensely like your videos, very informative and precise. I would request you to please create a video for heat exchanger performance and efficiency

    Plate Eva 5 Effs: (1st Eff, 2nd Eff-connection box,- 3rd- connection box), with designed capacity of 10 m3 / h, 5 pumps with capacity of 12m3 / h (density: 1). what will be the cause for the unstable output density, output varies greatly from density 1.08 to 1.125

    Hi iv just come across your Chanel, I have subscribed and given thumbs up and will share. your videos and explanations are fantastic and so very helpful I wish you all the success in the world. Thank you keep up the great work 👍

    This video was awesome. Thanks so much. I recently toured a district Heating plant and this helped a ton to watch afterward. One question: at the plant, the water temperatures basically flipped (cold got hot and hot got cold). How did they do this as opposed to the temperatures just meeting in the middle? Do they run the water through multiple exchangers (there was many at this plant). Thanks again and awesome video!

    Funny seeing this randomly browsing YouTube. I am a one mechanic at Sondex, been so for 15 years. I can say, the video is pretty accurate. 👍

    Very good explanation, but if the plates are spherical (not rectangular) with the same area. has the same efficiency? or the length of plates determine the efficiency?

    Can it work for the liquid high vecosity 30000 cp, high temp 95 C? I want to cool down this liquid by cooling water 30C

    As a Danish I can confirm that it is infact a Danish heatexchanger and not a German one.
    But great video, learned alot

    Your channel is the best engineering channel on YouTube I have came across.
    Great content and great video.
    Love u bro !! Great job.

    I have one question, why is the valve being installed between the cold water coming in and out of the exchangers, I often see the valve completely open on the exchangers ??
    With this valve the exchanger loses its purpose ..

    what is the disadvantage of plate lubeoil cooler compared to tube type cooler?

    A. Locating cooling leaks is more difficult
    B. Smaller and lighter
    C. Additional plates can be added in pairs to increase capacity
    D. Higher efficiency

    Please sir answer this. 😊

    Sir I say you are the best explaining. Thank you thank i really like how you explain computer, talking, pictures wow than you please continue teaching

    Thank you thank you sir. You explain very clear & in many ways, schematics, computer, material, how it works, very very broken so yes thank you you a great teacher

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