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

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Kind: captions
Language: en

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Hey there guys, Paul here from
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theengineeringmindset.com.
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In this video we're
gonna be looking at the
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plate heat exchangers and
they're often referred to as
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PHE's, PHX's, or sometimes just HX or HEX.
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Now, plate heat exchangers
are very common,
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they are used extensively in
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building services and manufacturing.
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The reason they are popular is because
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they are very compact,
they're very efficient,
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they're easy to service,
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they need very low maintenance as well.
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Their purpose is to
transfer thermal energy
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from one fluid in one system to another
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without the two fluids mixing together.
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For example, in building
services you might want
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to transfer heat from a primary
loop connected to a boiler
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over to a separate secondary loop
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or maybe in a district heating network.
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Or in manufacturing you
may want to cool down some
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oil and use water to cool
that down but obviously
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you don't want to mix the
oil and the water together.
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Now, we have pulled one of
the heat exchangers apart.
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We're gonna have a look at
some of main components here.
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So we've got the end plates
here or the front and back cover
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and these are made from usually
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a mild steel and they're very strong,
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they're there to hold everything together.
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Then we've got the nuts, these
attach obviously and tighten
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up onto the tightening bolts.
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The tightening bolts, they
fit in some grooves in
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there and they'll run
the entire length of the
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heat exchanger and the bolts
are tightened on these and that
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will compress all the plates
together and squeeze the
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gaskets against the plates to make the
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heat exchanger completely
waterproof or leak proof.
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And then wedged in between
there we've got the plates
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where the heat transfer
occurs and we've also
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got the gaskets which sit in between
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the plates and that's
what gives it the seal.
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Larger heat exchangers will
also have this supporting bar
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at the top and the bottom
and you can see here
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that the case and the
plates, they just slide along
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there and there's various
ways that they can come off,
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either they twist these
ones, they'd be too big to
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twist off but there's a
section removed at the back
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where these would just drop
out but the smaller ones,
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these would just slide in and out.
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And you can see a real plate heat
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exchanger plate there on the screen.
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Now, these are typically made from steel
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or titanium and you can
see they've got this
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pattern grooved into them
or stamped into them.
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These patterns are gonna
strengthen the plates,
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obviously they're incredibly
thin and they're also
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gonna increase the heat
transfer surface area
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as well as creating a very
turbulent flow inside them
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so it's not smooth, all
the water has to row across
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these and come out very
rough and turbulent.
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Now between the plates
we've got the gaskets here,
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just this rubber gasket
and that is attached
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to the face of the plate
and the purpose of the
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gasket is to ensure a tight
fit and to prevent leaks.
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The gasket also allows or prevents
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the flow of fluid into the sheet.
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You can see here, so this
section here we've got the
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rubber seal coming across
and double seal on this one
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so that no fluid in this
can leak out or flow in,
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as well as this side, whereas
here there is no gasket there
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so the fluid if it entered
here could flow down and come
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down and enter into this one here
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because there isn't anything there.
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Same as this one, the fluid
can only come out of here and
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travel up and then into this
section here, into that hole.
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Now, you'll probably notice
that the tightening bolts
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they're actually, they extend
far past the heat exchanger.
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That's for a few reasons,
one is obviously to be able
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to fit all these plates
and et cetera on during
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the installation or during
maintenance but also
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this gives you the ability to extend the
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plate heat exchanger in
future so this one here
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is actually from a district
heating network and at the
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moment the building's only
half complete and they're
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expecting to double the building size.
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So they've allowed extra bolt
lengths to be added and that
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means that the plates
can be added and this
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heat exchanger can grow with the demand.
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Now, there's a couple of ways that the
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plate heat exchanger can be piped up.
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This is the most common
version and the version
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that we're gonna be looking at today.
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That is where the inlets
and outlets are all
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on the front plate so
the fluids will enter,
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flow through their channels
and then make their
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way back to the front plate.
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The other version is where the fluids,
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one of the fluids enters
through the front plate and it
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passes through there and
then makes it way and it will
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then exit through the
back plate as well as
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one of the fluids will
enter there as well.
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Now, this version here, the
first version is the most
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common version and that
is because you don't need
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to alter the pipework if
you need to extend the
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plate heat exchanger in the future,
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whereas, with the second
version here all the pipework
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that's connected would have
to be removed and remade
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to fit depending on how far
you extend your heat exchanger.
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So it's not really so practical,
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that is why this one is far more common.
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And you can just see in
all these examples here
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that is exactly what's happening.
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So the flow return are happening
on the front plate there.
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So how does it work?
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Well, we've already seen
that if you remove some
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of the seal then the fluid
can flow through there.
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So if we stack a number of plates together
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then you'll see it forms this channel,
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this pipe like feature flowing
through all the plates.
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And then we can add the
front and back plates onto
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there and we get these channels where
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the water or the fluid, whatever
you've got can then flow
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through certain plates and it can't
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flow through other plates.
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And let's just see an example of
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how this would work practically.
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So if we opened up the
heat exchanger again,
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now you can see here that
the gaskets are oriented
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differently on the alternating
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plates there for the heat exchange.
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So this one here you can
see fluid in this pipe
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would not be able to pass
through or this one and this
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one it would so it just alternates,
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vice versa all the way through.
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And so if we pass one fluid through there
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you can see it entering
through this top port,
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passing all the way through,
it can't pass through this one,
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there's a seal there, it
gets to the next plate,
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oh there's no seal there so
we can pass through there,
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can't go into this hole but you can
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into this one because there is no seal and
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so all these will pass through,
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collect up and make its way back out.
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Now, the same thing is gonna be happening
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with the other fluid
we're passing through.
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So you can see here we're
passing hot fluid through.
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So this one is entering
through the bottom port,
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coming along, it's getting to the plates,
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some of them it can
pass through so it will,
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others it cannot leave that
pipe so it will not and then
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it will just pass through all the way
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until it creates that loop and exits.
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So if we mix these two fluids
together what's gonna happen
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is the cold fluid is going to enter,
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pass through and then on
the other side of the plate
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is the hot fluid so
that is gonna take some
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of that heat away so the cold fluid will
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warm up and that will leave as a much
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warmer fluid and the hot fluid that comes
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in is going to cool down
because it's going to
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give up some of its heat into
the cold stream and then that
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will leave as a much more cooler fluid.
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So if we just look at
a very basic example of
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how this is working,
let's just say we've got
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a few plates here and
we've got a cold channel,
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hot channel and another cold channel.
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Now, if we let the hot
fluid enter into the
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channel there and as that
happens heat is then going to
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conduct through into the plate
because they are touching,
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so that heat will then pass
through and warm up this plate.
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And if we then pass
the cold fluid into the
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cold channels and some of
the heat in those plates
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which have been heated up,
it will start to cool down
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because some of the thermal energy
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is transferring over into the cold fluid.
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That's through conduction.
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And as that happens the cold
fluid begins to warm up and
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obviously the hot fluid is
going to start to cool down.
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So then the heat exchanger
starts to equal up and equalize
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out and that means that the
cold fluid is going to enter,
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is gonna exit warm and the hot
fluid is going to exit cool.
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And that temperature
grading is going to then
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vary through the heat exchanger,
through the plates and also
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through the fluids which
is conducting the heat.
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So when you combine all of this together
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that is how you get the heat
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transfer occur in the
plate heat exchanger.
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You can also notice that
these fluids are flowing
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in counter flow and that
is the best configuration
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for the most effectiveness
because the log mean
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temperature difference, the
LMTD is at the greatest.
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We'll have a look at what
that means in another video.
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This video is just for you to understand
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how it's working and why it works.
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I'll just give you a real world example of
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a heat exchanger here as well.
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So this is a German heat
exchanger as you can see
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right down here but you can
see this heat exchanger here
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provides 1500 kilowatts of
thermal energy and has a
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transmission area of 29.3
meters squared with a
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flow rate of 42,000, or
almost 43,000 liters per hour.
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It would also handle up to 100
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bar on each side of the plates.
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So you can see these things
are very powerful and they're
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very efficient and they're
very compact in how they work.
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Now, if you do have one
of these in your buildings
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please also remember to
insulate as it's much
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more energy efficient,
keep the plastic threads,
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plastic sheets on the threads to protect
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them from damage otherwise you won't be
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able to get these nuts off very easily.
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Okay, that's it for this video,
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thank you very much for watching.
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I hope you enjoyed it and it helped you.
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Please don't forget to like,
00:10:05.440 --> 00:10:06.960
subscribe and share and if you have
00:10:06.960 --> 00:10:08.890
any comments leave them in
the comments section below.
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I'll try to get back to
you as soon as possible.
00:10:11.330 --> 00:10:13.553
Once again, thank you
very much for watching.
Office location
Engineering company LOTUS®
Russia, Ekaterinburg, Lunacharskogo street, 240/12

Phone: +7 343 216 77 75

E-mail: info@lotus1.ru

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