Parallel Flow Heat Exchanger and Counter Flow Heat Exchanger HMT Tutorial- 20, Heat and Mass Transfer, Mechanical Engineering, GATE Video Lecture | Topper Handwritten Notes & Videos for GATE ME

oh hello my dear so in this video you
are going to learn a lot of things and
let me share with you today in this
video I am going to share with you a
couple of tips and tricks and that's why
you can easily solve gate problems right
or maybe numerical problems will ask in
inverse examination so the purpose of
making this video is to help you to
understand while parallel flow and
counter flow for different condition as
well as in simple condition so let us
get started well this is one of the type
of rejection or even say if you want it
wanted to classify heat exchanger then
there are many ways and according to
flow we are having two types of among
three types of heat exchanger one is
parallel flow counter flow and another
one is cross flow but engaged most of
our time quad quotient from parallel
flow and counter flow with some simple
signatur simple little bit extra things
I am going to share with you in this
video only that's why you don't need to
go anywhere else right so what is alpha
we need to know what is parallel flow
and what is counter flow if a
directional flow is different I mean if
the flowing that were what flee or whole
field is flowing the direction is same
that is known as parallel flow if
direction is different just I must say
opposite then it is known as counter
flow I hope you understand but this is
only the basic approach we need to
understand it in that way that's why we
can sort numerical problems related to
this topic
all right so let's go for it
so first of all we have to draw a
parallel flow heat exchanger and the
counter flow is xn here okay and
remember my dear before going to solve
any question any question related to
parallel flow and counter flow heat
exchanger you need to first draw the
diagram without drawing diagram you
cannot solve the problem right away you
need to understand this my idea this is
most important right okay so this is a
case of parallel flow and this is a case
of
counterflow okay got it
now suppose that this one is th one this
one is TS 2 TC 1 and TC do so here it is
easy to and DC 1 th 2 th 1 now what
happened most of the time we get
question related to this that we are
giving you bailout for exchanger we are
giving counterfeit exchanger these dis
that that and find out LM telling find
out L M DV so we know that theta 1 minus
theta 2 natural log beta 1 by theta 2 we
know the formula and theta 1 is
difference between these two difference
between these two theta 2 and theta 1
and respective here only okay let me
share with you how how you can find out
these differences that means theta one
as you can see theta 1 is equal to th 1
minus T C 1 and theta 2 is equal to t h2
minus TC 2 for the case of this these
two formula is only applicable for
parallel flow heat exchanger remember
that and for counter flow it will change
little weight th 1 minus TC 2 and theta
2 is equal to t h2 minus TC 1 so these
formulas by using these formulas we can
easily find out parallel flow occurs
among LM TD for parallel flow heat
exchanger and counter for DES they are
not selective what is that what is that
that is most important that is most of
the time most of our time we cleared
theta 1 is equal to I mean we can get
only get only get for the K single case
only the theta 1 is equal to theta 2 for
the case of counter flow heat exchanger
okay if this happen then how we can find
out LM TD because we're having one thing
here theta 1 minus theta 2 then a lambda
T will become zero if theta 1 is equal
to theta 2 are you getting me okay don't
worry let me give you an example suppose
that we are having a theta one is equal
to 40 degree centigrade and theta 2 is
equal to 40 degree centigrade same
temperature differences then what and
this is only can happen in case of
counter flow heat exchanger remember
that and then what would be the value of
L MTD for this case ll be due to be 40
degree centigrade simple tree and this
quotient and this type of question
already asked in gate I have solve I can
remember the quotient but I'm 0 I have
solved this type of problem already okay
I hope you understand the concept what I
mean to time I wanted to share with you
now
next topic okay let me change the face
yeah we got fresh face right now so this
is important most of the student miss
this part what right now I am going to
share with you that is case there are
two special cases we most of them most
of our student missed because they don't
have they don't study and then go they
don't go to DeWitt in that that's why
the nest is that is two cases are there
one is for steam condenser and another
one is for steam generator steam
condenser and steam generator these two
cases are most important and play most
important role and you know one thing my
dear these two cases having to do
diagrams I mean for steam let's say I'm
going to share with you here parallel
flow and counter flow diagram for steam
condenser and Here I am going to share
with you parallel flow and the counter
flow diagram for steam generator and one
more thing here here what is happening
doesn't matter what type of flow they
are going to give you the answer would
be same for LM TD I mean L M TD
logarithmic mean temperature difference
will be same for value flow as all as
counter flow this is the real beauty of
getting question in this topic okay
I have already proved all these I mean I
have salt so suppose that this is th I
am here also same like exit say and
taken three temperature will increase e
CIE and TCE the parallel flow and in
case of counter plot will happen this
would be like this th i th e TC IE TC e
okay this two are for the case of
condenser only for the case of condenser
okay so here steam temperature is same
steam and here the cold coolant of water
or something else even more time we use
water its temperature is keep on
increasing because of this steam
temperature and one most important thing
that I am just are going to share with
you in case of steam generator in case
of steam generator
it is just like rivers just what you
want to do you need to understand its
basic concept let me share with you this
is for parallel flow and this is for
counter right parallel flow and counter
flow here what will happen in the case
of parallel flow suppose that which is
flue gases suppose that fifteen verses
and th I is entering th is exceed and
here what are you suppose that going on
TC I and TC as you can see this is just
jumping I am just opposite to each other
here we're using water and it says this
is what a steam generator okay and water
is boiling here you can say that water
is boiling it that means the temperature
what it is boiling here into steam and
in that case we are just driving flue
gases in this case I mean we can do this
too in case you can say efficiency also
you can at least that we can use the
waste flue gases to increase efficiency
of this okay I mean we can utilize
utilize waste flue gases here also this
is for parallel flow this is for
parallel flow now let's go for this one
this is for
counterflow right so hero to happen
water is flowing like this TC i TC e and
this would be like this so the what is
the major defense here you can see me
defenses there is that direction here
see the direction is this side right
hand side here the direction is left
hand side I don't know for which side he
was watching this video but for me I
think this is like this right so so so
what is the most important case I have
shared with you that is you have to know
these two cases first because you cannot
see these diagrams all the time in a
most wartime they just be just going to
give you input temperature or exit
temperature you see and they give you
this is the case of steam contention so
work where exactly welcome to make
mistake you will just you don't know
what is the value of input argument both
good values you are not going to know so
that's why you need to know the cases
diagrams for these two cases steam
condenser and steam generator I hope you
understand some crucial concept
regarding heat exchanger for complete
examination point of view or numerical
approach one must say thanks for
watching see you soon in my next video
bye bye