00:00Hi friends welcome to our channel concept engineering flux focus on fundamentals we
00:07have started our lecture on module 2 heat exchangers in today's session we will see
00:12shell side flows which are the different flows in shell sides and what are the leakage streams
00:17and how to minimize it so let us start so shell side flow distribution basically shell
00:26side fluid flow through the shell in a five different paths and this path are nomenclature
00:38given as like a stream b stream c stream e stream and f stream so these five streams generally
00:48flows from the shell side however on the tube sides it's only single stream because it's
00:55flowing through inside the tubes only so there is no different flow patterns or flow paths
01:01and out of this there are some streams are leakage streams and some are the main streams some
01:07the other than b stream all other streams are called as leakage stream because this they
01:13are not taking part in heat exchange and they just bypassing the fluid so they called as
01:18the leakage streams so shell side flow distribution the stream a which is basically flows through
01:27the gap between the tube and baffles so you know the in the baffles for any baffles the tubes are
01:35passing
01:35through the baffles and there is a holes between them to pass the tubes so the liquid which is flow
01:41through that gap between the tubes and the baffle opening is called the leakage stream a which is this
01:49is why this is called leakage because this is not taking part in heat exchange that's why it is called
01:53a leakage stream where the steam b which is flows between the tube across the bundle means which is flow
02:02from the main like this between the fluid this is the b stream which is the main stream and this
02:07is the
02:08most important stream which is taking part in the heat exchange so whenever we do the heat exchanger we
02:15should maximize the b stream which is a main cross flow stream c stream basically this is also called
02:25as a leakage stream this passes between the gap between the bundle and the shell so when you know
02:31the tube bundles the complete tube bundle is enclosed in the shell so between the tube
02:38bundle and shell there is a gap so so this stream just passes from the bottom of the shell you
02:44can
02:44say so and which is not touching anywhere into the tube so it is not taking part in heat exchange
02:50and
02:50it just flowing at the bottom of the shell so that's why this is a leakage stream again
02:59next stream is stream e this is also called a leakage stream and this is passes between the baffle and
03:05the shell so you know that baffles are just welded to the shell like this so when the stream is
03:12passes
03:12just down of this or below the baffles from the top or the bottom side this is called a e
03:20stream and
03:21this is also in a leakage stream the next stream is f stream the last stream is f stream this
03:26is also
03:27called a leakage stream this is basically passed through the pass partition lane of the shell side not on
03:32the tube side so this is a leakage stream occurs because the shell fluid is supposed to be completely
03:39separated into the two passes and longitudinal baffles but some fluid managed to leak across the
03:45baffles and short circuiting the desired flow path so as you know on the shell side suppose this is a
03:50f
03:51type of shell it's having a longitudinal baffle so with the stream which is just leak from this section
03:59is called the f stream or you can say if the shell side passes is shown here so if passes
04:07through this
04:07it means this is an leak stream this is a f stream so other than b stream all the streams
04:14called are
04:14leakage stream and needs to be minimize them so we'll see how to minimize them when when you do the
04:19htri or
04:20the heat exchanger design on the edr you will you will come to know which streams are what what are
04:28the percentage of the east stream and then you can you have to change check that how to minimize it
04:34as we understand there are the leakage stream and that stream needs to be minimized
04:38so to minimize it we should know how much percentage it is allowed
04:43so expected percentage of leakage stream so a stream is allowed to be around 5 to 10 percent of the
04:49total
04:49flow flow on the shell side b stream is the main stream so it should be more than 60 to
04:5580 percent
04:56of the your shell side fluid c stream should be minimized to less than 3 percent for the better
05:04thermal design e stream should be minimized to less than 5 percent f stream should be negligible because
05:12it is between the shell side passes so it should be it should be zero or a negligible value
05:19similarly if you are not able to minimize the individual stream like a or s e then combined
05:26a and e together should be less than 15 percent and the total leakage from all these leakage stream a
05:34c e
05:35and f should should not increase more than 30 to 35 percent and as per the best engineering practices
05:42also anything about 35 percent if you find in your thermal design it means your thermal design is not
05:48properly designed and you have to redesign it and now we will see how to minimize each stream
05:55by by doing some actions how to minimize this leakage stream and may bringing bringing it in into the
06:03desirable levels in the next slide
06:06so to minimize the leakage stream so first stream is a stream so we have to tight the tolerance between
06:13the tube od and the baffle id so as you know the this is a baffle and you have opening
06:18for your tubes
06:19so we and the tubes and this is a baffle opening and the tube is the inside like this it's
06:28going through
06:28it it shown here so as per tema guideline if your baffle spacing is less than 36 inch or less
06:38than 915 mm
06:40then your tube od to baffle id gap should be 0.8 mm
06:50and if your baffle spacing is greater than 36 inches or 915 mm then your baffle space
07:01baffle id to the tube od should be 0.4 mm only so gap between your baffle opening and the
07:09tube opening
07:09we are talking about this gap this gap this section should be 0.8 for
07:20for less than 36 inch and 0.4 for less greater than 36 inches or you can say 900 mm
07:29and 915 mm exactly
07:33to minimize the c stream you need to tighten the tolerance between the otl it is outer tube limit
07:39or you can say bundle limit and the shell id so as per tema guideline if your shell id if
07:45your shell id is
07:466 inch then your clearance should be approximately 0.125 inches or you can say 3.1 or 3.2
07:53mm and if your
07:55shell id is 60 inch 60 inch or around 1.5 meter then your clearance should be around 8 mm
08:05so
08:06this is a shell id and there is a tube bundle id so these we are talking about this gap
08:13this gap should be 0.8 for the higher size like 16 inch and for the smaller
08:18exchanger size it should be only around 3.2 mm and for general application default clearance is 3 mm
08:25in common and while larger clearance is 6 mm typically required for heat exchanger within the removal bundle
08:32is facilitated so because this clearance is required for the removal bundle to remove the bundle for the
08:40maintenance so c stream when you see any heat htri data sheet or tube layout on the htri data you
08:47will
08:48find that there is a shell id and actual otl is given so if you see here the otl is
08:5697.32 inches
08:58and then your shell id is 98.32 inches so this this this this gap we are talking so this
09:05gap has to be reduced
09:07so this is your otl and then this is the shell id so this gas gap has to be minimized
09:14to avoid the or to
09:16minimize the leakage c leakage stream so accordingly in htri you can update this and you can reduce the c
09:22stream so next stream is e stream to minimize the e stream you have to tight the tolerance between
09:31the baffle and the shell id so as we know the e stream is between the gap between the baffle
09:36and the shell id it passes so as per tema guideline if your shell id is 6 inch to 17
09:43inches or you can
09:44say 1.6 inches 1.5 152 mm to 432 mm then your clearance should be around 3 mm if
09:54your shell id is
09:55around 18 to 39 inch or you can say half a meter to 1 meter then your the tolerance between
10:03the baffle
10:04and the shell id should be around 5 mm when your shell id is around 40 40 to 54 inches
10:10or you can say
10:111 meter to 1.5 meter then you have a clearance should be 6 mm as per tema guideline and
10:18if your shell id is
10:1950 to 60 inch which is around 1.4 meter to 1.5 meter then your clearance should be 8
10:28mm so so when you
10:31do the designing in the htri or any design you have to to minimize the stream you have to minimize
10:37this
10:37clearance you have to see the clearance and you have to minimize it and other also there are some other
10:43industrial standards which tells that if your shell id is 60 61 to 69 inches which is just higher than
10:51this like 1.5 meter to 1.7 meter then 8 mm is sufficient and if you go further higher
10:58size like
10:5870 to 84 inches then or around 1.7 meter to 2.1 meter shell id the clearance should be
11:0710 mm and for the
11:09highest size like 100 inches your clearance should be 11 mm so in this this guidelines you have to follow
11:16to maintain your clearance and to minimize the e-stream so last leakage stream is your upstream
11:24so upstream is basically to minimize this tolerance you have to for for the longitudinal baffle on the
11:31shell id the most effective way is to continuously weld the longitudinal baffles directly on the shell
11:38wall of the fixed tube arrangement so when you continuously weld it your f-stream will be zero then
11:43as we seen in the given percentage like f-stream should be zero percent if it is a fixed tube
11:48and it is
11:49length longitudinally welded then the your f-stream will be become the zero but wherever you have a
11:54removable tube bundle in that case you cannot weld that longitudinal baffles then if it is a properly
12:01sealed against the partition plate then you can you can minimize or neglect this f-stream or it can be
12:11minimized or negligible value will come the longitudinal baffle must either be continuously welded on the shell
12:16wall or securely bolted with the full length gasket seal welding is usually preferred for the high
12:23pressure and critical services as per tema class r so in this case this f-stream can be minimized so
12:29when you see the htri output you have to see the f-stream if f-stream is very it generally
12:34not high
12:34if there is no passes on the shell side this stream will be zero again so when we see any
12:41thermal data
12:41sheet from htri output on the first page that is output summary you will find the flow fractions
12:48here so in this flow fraction you will find that a stream b stream c stream e stream and f
12:54stream
12:55this is the first check you have to do that whether these fractions are well within the limit or not
13:02so like in this it is well within the limit a is around seven to eight percent b stream is
13:08more
13:08than eighty percent c stream is less than or or at almost around three percent e stream is just
13:15around five percent and f stream is zero so this is the ideal way of giving the flow fraction for
13:24the
13:24shell side fluid so we have to see in the htri output this flow fractions and if you find that
13:31these
13:31are not as per our guideline then you can minimize by giving the the earlier slide we have told that
13:38how to
13:38minimize it you have to reduce the gaps between the baffles you have to reduce the gap between
13:42hotel and other things so in this way you can minimize this stream and you can increase your
13:47mainstream f b stream
13:52so this way we concluded our flow fraction through the shell side
13:59so thank you for watching this video
14:03you can write your question in the comment box i will be happy to answer it you can reach us
14:07on
14:08conceptengineering2020gmail.com link of the our older module 2 the all the lectures are given in the
14:16description also we have completed the module 1 on pressure relief walls there it is also given in the
14:22the description box if you like the video kindly share it with others thank you
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