How Shell and Tube Heat Exchanger Works

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Language: en

00:00:00.199
shell and tube the most basic and the
00:00:03.800 00:00:03.810 most common type of heat exchanger
00:00:05.110 00:00:05.120 construction is the shell and tube this
00:00:08.299 00:00:08.309 type of heat exchanger consists of a set
00:00:10.490 00:00:10.500 of tubes in a container called a shell
00:00:12.650 00:00:12.660 the fluid flowing inside the tubes is
00:00:15.379 00:00:15.389 called the tube side fluid and the fluid
00:00:17.689 00:00:17.699 flowing on the outside of the tubes is
00:00:20.300 00:00:20.310 the shell side fluid at the end of the
00:00:23.060 00:00:23.070 tubes the tube side fluid is separated
00:00:25.370 00:00:25.380 from the shell side fluid by the tube
00:00:27.560 00:00:27.570 sheets he tubes a rolled and press
00:00:30.620 00:00:30.630 fitted or welded into the tube sheet to
00:00:33.410 00:00:33.420 provide a leak tight seal
00:00:35.799 00:00:35.809 so the shell and tube type heat
00:00:38.150 00:00:38.160 exchanger is essentially a series of
00:00:39.860 00:00:39.870 pipes that will pass through a heat
00:00:44.000 00:00:44.010 exchanger and will have one medium
00:00:45.979 00:00:45.989 flowing through the pipes and one medium
00:00:48.529 00:00:48.539 flowing on the outside of the pipes and
00:00:51.110 00:00:51.120 we're going to have a look at an example
00:00:52.189 00:00:52.199 in a moment in systems where the two
00:00:56.750 00:00:56.760 fluids are vastly different pressures
00:00:59.389 00:00:59.399 the higher pressure fluid is typically
00:01:01.459 00:01:01.469 directly through the tubes and the lower
00:01:03.709 00:01:03.719 pressure fluid is circulated on the
00:01:06.020 00:01:06.030 shell side this is due to economy
00:01:08.539 00:01:08.549 because the heat exchanger tubes can be
00:01:10.429 00:01:10.439 made to withstand higher pressures than
00:01:12.679 00:01:12.689 the shell of the heat exchanger for a
00:01:14.750 00:01:14.760 much lower cost the support plates shown
00:01:17.990 00:01:18.000 below act as baffles to direct the flow
00:01:21.109 00:01:21.119 of fluid within the shell back and forth
00:01:23.480 00:01:23.490 across the tubes so what we mean here is
00:01:27.140 00:01:27.150 when we are pumping a fluid or a medium
00:01:30.679 00:01:30.689 through heat exchanger the medium our
00:01:33.499 00:01:33.509 higher pressure is going to go through
00:01:35.690 00:01:35.700 the tubes sometimes if you have two
00:01:39.109 00:01:39.119 mediums such as oil and water where the
00:01:41.990 00:01:42.000 water is cooling down the oil it may be
00:01:44.660 00:01:44.670 very important that the oil does not
00:01:47.120 00:01:47.130 leak out into the water this is
00:01:50.030 00:01:50.040 especially true if we're using something
00:01:51.590 00:01:51.600 like river water or lake water to cool
00:01:54.050 00:01:54.060 down the oil we don't want oil leaking
00:01:57.020 00:01:57.030 out through the tubes and going back
00:01:59.810 00:01:59.820 into the river or the lake or even the
00:02:01.850 00:02:01.860 ocean so what we'll do we'll have what
00:02:04.700 00:02:04.710 they call a double walled tube and we
00:02:07.580 00:02:07.590 will have a tube that has two walls and
00:02:11.029 00:02:11.039 if oil was to leak out of the
00:02:13.550 00:02:13.560 in a wall of the tube it will go into
00:02:16.100 00:02:16.110 the middle between the outer and the
00:02:17.900 00:02:17.910 inner wall and it will set off a leak
00:02:20.240 00:02:20.250 alarm so that way we know that one of
00:02:22.370 00:02:22.380 the tubes is leaking and we have an
00:02:23.930 00:02:23.940 alarm but it doesn't leak out directly
00:02:26.360 00:02:26.370 into the shell and into the water
00:02:29.140 00:02:29.150 let's just load up a model here so I can
00:02:31.640 00:02:31.650 show you in more detail how the heat
00:02:33.770 00:02:33.780 exchanger works okay so here we have a
00:02:39.470 00:02:39.480 standard shell and tube heat exchanger
00:02:42.320 00:02:42.330 I'll just do a little spin we can see
00:02:46.220 00:02:46.230 there's two pipes on the top and two
00:02:48.530 00:02:48.540 pipes on the bottom we've got a stand
00:02:51.590 00:02:51.600 and that is for installing the heat
00:02:54.470 00:02:54.480 exchanger do a spin around this side we
00:02:59.240 00:02:59.250 can see the nuts and bolts on the end
00:03:01.729 00:03:01.739 here we will undo those to open up the
00:03:04.670 00:03:04.680 end cover and get inside the heat
00:03:06.410 00:03:06.420 exchanger or do an inspection or
00:03:08.210 00:03:08.220 maintenance just take a cross-section
00:03:13.960 00:03:13.970 okay so we've got a cross-section now as
00:03:16.190 00:03:16.200 a heat exchanger we can see here a tube
00:03:20.330 00:03:20.340 side fluid out tube side fluid in when
00:03:25.460 00:03:25.470 we say tube side we mean the medium that
00:03:27.860 00:03:27.870 is flowing through the tubes the
00:03:30.740 00:03:30.750 opposite of tube side is shell side will
00:03:33.979 00:03:33.989 have shell side fluid in and shell side
00:03:36.740 00:03:36.750 fluid out that is this lower section
00:03:40.069 00:03:40.079 here or the lower pipe I just get to an
00:03:43.759 00:03:43.769 overview so we can follow the flow
00:03:45.949 00:03:45.959 through the heat exchanger
00:03:48.410 00:03:48.420 okay so we have got a cold fluid flowing
00:03:52.940 00:03:52.950 in from the bottom it is then flowing
00:03:56.510 00:03:56.520 along through the heat exchanger through
00:04:00.320 00:04:00.330 these tubes it is doing a u-turn this is
00:04:04.340 00:04:04.350 actually called a u-turn shell and tube
00:04:06.110 00:04:06.120 type heat exchanger u-turn here and then
00:04:09.140 00:04:09.150 it is flowing back that way and it is
00:04:12.080 00:04:12.090 coming out of the top let me just spin
00:04:16.220 00:04:16.230 around this side we can see the entrance
00:04:19.039 00:04:19.049 points and we can see there are the
00:04:22.700 00:04:22.710 tubes and the tubes are going off into
00:04:24.170 00:04:24.180 the distance so the fluid is going to be
00:04:26.120 00:04:26.130 flowing directly into these tubes
00:04:33.390 00:04:33.400 we can also see a plate which is used
00:04:35.430 00:04:35.440 for separating the fluid as it flows in
00:04:39.300 00:04:39.310 from the bottom and then out of the top
00:04:41.719 00:04:41.729 so if we're is to move this plate or
00:04:44.550 00:04:44.560 take it out we would actually just have
00:04:46.469 00:04:46.479 a fluid that flows in from the bottom
00:04:47.850 00:04:47.860 and directly out the top it's going to
00:04:49.650 00:04:49.660 choose the path of least resistance
00:04:52.400 00:04:52.410 but because the place there it's coming
00:04:54.960 00:04:54.970 in and flowing through the bottom tubes
00:04:57.090 00:04:57.100 and we'll just follow it along along
00:05:00.300 00:05:00.310 these tubes and we can see here this is
00:05:03.870 00:05:03.880 where it suddenly turns around it's
00:05:06.180 00:05:06.190 coming while traveling to the right on
00:05:08.610 00:05:08.620 the lower section around the tubes
00:05:10.800 00:05:10.810 around this u-turn and back the other
00:05:13.320 00:05:13.330 way and it's going to keep going all the
00:05:16.080 00:05:16.090 way until it comes out of the top again
00:05:19.080 00:05:19.090 or the top section of the heat exchanger
00:05:21.320 00:05:21.330 what's actually happened is it's gone in
00:05:23.850 00:05:23.860 the bottom out of the top and it has
00:05:25.790 00:05:25.800 absorbed some of that heat and it's then
00:05:30.930 00:05:30.940 going to take away that heat and
00:05:32.719 00:05:32.729 distribute it somewhere else perhaps to
00:05:35.430 00:05:35.440 ambient air or perhaps it would just go
00:05:37.230 00:05:37.240 back to a reservoir sometimes they'll
00:05:39.629 00:05:39.639 even use some of the warmer fluid for a
00:05:41.879 00:05:41.889 later stage in the process it's a good
00:05:44.820 00:05:44.830 way to recycle the heat rather than just
00:05:47.279 00:05:47.289 waste it because essentially when you're
00:05:49.589 00:05:49.599 removing the heat that is a efficiency
00:05:53.129 00:05:53.139 or an energy loss so if you can use it
00:05:55.920 00:05:55.930 earlier or later in the process again
00:05:57.960 00:05:57.970 you're recovering some of that energy
00:05:59.670 00:05:59.680 and your increase in the process
00:06:02.430 00:06:02.440 efficiency so have a look at the fluid
00:06:05.700 00:06:05.710 comes in at the top the shell side fluid
00:06:08.159 00:06:08.169 in in at the top now it does not unlike
00:06:12.719 00:06:12.729 the tubular flow which flows relatively
00:06:14.939 00:06:14.949 direct the fluid that is flowing in on
00:06:18.629 00:06:18.639 the shell side is going to flow around a
00:06:21.210 00:06:21.220 series of baffle plates it's going to
00:06:23.909 00:06:23.919 come around here and be forced to turn
00:06:25.500 00:06:25.510 it's going to turn again it's going to
00:06:27.629 00:06:27.639 turn again and it's going to keep doing
00:06:30.060 00:06:30.070 that all the way along and then it is
00:06:33.089 00:06:33.099 going to exit at the bottom of the heat
00:06:37.320 00:06:37.330 exchanger I have to say
00:06:40.790 00:06:40.800 be slightly better if this discharged
00:06:43.159 00:06:43.169 port from the heat exchanger was more to
00:06:44.869 00:06:44.879 the right in order that he could throw
00:06:46.700 00:06:46.710 through the heat exchanger and down on
00:06:48.740 00:06:48.750 the right hand side rather than here but
00:06:51.080 00:06:51.090 that is how the heat exchanger has been
00:06:52.670 00:06:52.680 built in 3d here the reason for this
00:06:56.839 00:06:56.849 Criss crossing pattern this is actually
00:06:59.270 00:06:59.280 called cross flow is because we want to
00:07:02.029 00:07:02.039 maximize the heat transfer between the
00:07:04.879 00:07:04.889 two flowing fluids and we do this by
00:07:08.149 00:07:08.159 having a cross flow pattern
00:07:10.580 00:07:10.590 there's no point the fluid entering in
00:07:12.980 00:07:12.990 the top flowing directly here and then
00:07:14.990 00:07:15.000 dropping out at the bottom because if we
00:07:17.629 00:07:17.639 do like that we've had very little
00:07:19.640 00:07:19.650 turbulent flow and there's not going to
00:07:22.189 00:07:22.199 be as much heat transfer between the two
00:07:24.890 00:07:24.900 mediums compared to when we do this
00:07:26.899 00:07:26.909 cross flow pattern and although you
00:07:30.200 00:07:30.210 can't actually see it inside these tubes
00:07:32.990 00:07:33.000 there is normally a thin piece of copper
00:07:36.619 00:07:36.629 or plastic and it will slide into each
00:07:40.640 00:07:40.650 and every one of these tubes now this
00:07:43.850 00:07:43.860 thin piece of copper or perhaps plastic
00:07:46.879 00:07:46.889 or other form of metal it depends on the
00:07:48.680 00:07:48.690 system that you're actually using it for
00:07:50.089 00:07:50.099 is similar to a very thin strip a flat
00:07:55.189 00:07:55.199 bar a thin flat bar of copper for
00:07:58.219 00:07:58.229 example and the idea is that as the
00:08:00.860 00:08:00.870 fluid is flowing through the tubes it
00:08:02.779 00:08:02.789 does not get to flow in a straight
00:08:05.269 00:08:05.279 laminar direction it is going to come
00:08:08.209 00:08:08.219 into contact with this thin perforated
00:08:11.869 00:08:11.879 copper bar and then it is going to be
00:08:14.330 00:08:14.340 forced to flow over and under the copper
00:08:17.390 00:08:17.400 bar in other words it's going to have a
00:08:19.159 00:08:19.169 very very turbulent path through the
00:08:22.790 00:08:22.800 tubes and this is what we want we want
00:08:25.100 00:08:25.110 turbulent flow because this is going to
00:08:27.890 00:08:27.900 increase our heat transfer the other
00:08:30.290 00:08:30.300 benefit with turbulent flow is simply
00:08:32.209 00:08:32.219 that if we have suspended bodies within
00:08:36.050 00:08:36.060 the fluid that may stick to the sides of
00:08:38.839 00:08:38.849 the tubes they won't be able to stick to
00:08:42.469 00:08:42.479 the size of the tubes as easily if they
00:08:45.829 00:08:45.839 do stick to the sides of the tubes that
00:08:47.750 00:08:47.760 is going to reduce our heat transfer
00:08:49.220 00:08:49.230 rate where our heat transfer capacity so
00:08:52.819 00:08:52.829 by having this turbulent flow
00:08:54.140 00:08:54.150 we're preventing them or reducing the
00:08:56.180 00:08:56.190 risk that they're going to be able to
00:08:57.350 00:08:57.360 stick it to the size of the tubes and
00:08:59.920 00:08:59.930 this will maintain heat transfer
00:09:02.860 00:09:02.870 capacity now if you don't know what I'm
00:09:06.050 00:09:06.060 talking about when I talk about things
00:09:07.970 00:09:07.980 sticking to the size or surfaces of a
00:09:11.240 00:09:11.250 heat exchanger go another look at your
00:09:13.940 00:09:13.950 kettle now if you boil your kettle a
00:09:16.430 00:09:16.440 thousand times using standard tap water
00:09:18.790 00:09:18.800 it's very likely you'll notice a thin
00:09:22.310 00:09:22.320 white powdery substance building up
00:09:25.970 00:09:25.980 within the kettle now this is actually
00:09:28.130 00:09:28.140 reducing your heat transfer this white
00:09:31.250 00:09:31.260 powdery substance comes from the water
00:09:32.870 00:09:32.880 itself the minerals and suspended bodies
00:09:35.660 00:09:35.670 within the water and over time it will
00:09:39.560 00:09:39.570 stick to the inside metal surfaces of
00:09:42.770 00:09:42.780 your kettle and it will reduce the heat
00:09:45.230 00:09:45.240 transfer rate and that's exactly what
00:09:47.120 00:09:47.130 can also happen in a heat exchanger
00:09:50.110 00:09:50.120 another example is a boiler with boilers
00:09:53.660 00:09:53.670 they go to great lengths to ensure that
00:09:55.550 00:09:55.560 the water quality is as clean as
00:09:58.670 00:09:58.680 possible and the reason again is there
00:10:01.490 00:10:01.500 any suspended bodies that stick to the
00:10:03.710 00:10:03.720 surface of the boiler tubes will reduce
00:10:07.370 00:10:07.380 the heat transfer rate and in severe
00:10:09.590 00:10:09.600 conditions this can actually cause the
00:10:11.420 00:10:11.430 piping to melt so it's very important
00:10:15.080 00:10:15.090 that you keep the contact surface areas
00:10:17.360 00:10:17.370 within your heat exchanger as clean as
00:10:19.850 00:10:19.860 possible so that is a you type shell and
00:10:23.930 00:10:23.940 tube heat exchanger if we were to click
00:10:26.510 00:10:26.520 here we could actually have a look at
00:10:27.920 00:10:27.930 some of the more specific pieces example
00:10:34.070 00:10:34.080 let's just have a look at the tubes and
00:10:36.650 00:10:36.660 we can see tubes if I do a full version
00:10:41.750 00:10:41.760 again you can see all of our tubes there
00:10:44.330 00:10:44.340 and the way they are installed can also
00:10:47.240 00:10:47.250 highlight the baffles and the baffles
00:10:50.810 00:10:50.820 now shown and we'll see our flow comes
00:10:53.780 00:10:53.790 in and around the baffles like so so two
00:10:58.430 00:10:58.440 baffles so I just highlight them for you
00:11:02.200 00:11:02.210 are those pieces here and they'll be
00:11:04.880 00:11:04.890 designed to be installed in this pattern
00:11:07.060 00:11:07.070 so that
00:11:08.300 00:11:08.310 get this cross float if that was all a
00:11:12.260 00:11:12.270 bit quick don't worry we are going to go
00:11:14.690 00:11:14.700 through this in more detail later in the
00:11:16.670 00:11:16.680 course with some different examples I
00:11:18.890 00:11:18.900 just think that was a nice introduction
00:11:20.330 00:11:20.340 to what a shell-and-tube type heat
00:11:22.760 00:11:22.770 exchanger is now let's go on to the next
00:11:25.640 00:11:25.650 lesson
00:11:27.560 00:11:27.570 [Music]
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