00:00:00.199 shell and tube the most basic and the 00:00:03.80000:00:03.810 most common type of heat exchanger 00:00:05.11000:00:05.120 construction is the shell and tube this 00:00:08.29900:00:08.309 type of heat exchanger consists of a set 00:00:10.49000:00:10.500 of tubes in a container called a shell 00:00:12.65000:00:12.660 the fluid flowing inside the tubes is 00:00:15.37900:00:15.389 called the tube side fluid and the fluid 00:00:17.68900:00:17.699 flowing on the outside of the tubes is 00:00:20.30000:00:20.310 the shell side fluid at the end of the 00:00:23.06000:00:23.070 tubes the tube side fluid is separated 00:00:25.37000:00:25.380 from the shell side fluid by the tube 00:00:27.56000:00:27.570 sheets he tubes a rolled and press 00:00:30.62000:00:30.630 fitted or welded into the tube sheet to 00:00:33.41000:00:33.420 provide a leak tight seal 00:00:35.79900:00:35.809 so the shell and tube type heat 00:00:38.15000:00:38.160 exchanger is essentially a series of 00:00:39.86000:00:39.870 pipes that will pass through a heat 00:00:44.00000:00:44.010 exchanger and will have one medium 00:00:45.97900:00:45.989 flowing through the pipes and one medium 00:00:48.52900:00:48.539 flowing on the outside of the pipes and 00:00:51.11000:00:51.120 we're going to have a look at an example 00:00:52.18900:00:52.199 in a moment in systems where the two 00:00:56.75000:00:56.760 fluids are vastly different pressures 00:00:59.38900:00:59.399 the higher pressure fluid is typically 00:01:01.45900:01:01.469 directly through the tubes and the lower 00:01:03.70900:01:03.719 pressure fluid is circulated on the 00:01:06.02000:01:06.030 shell side this is due to economy 00:01:08.53900:01:08.549 because the heat exchanger tubes can be 00:01:10.42900:01:10.439 made to withstand higher pressures than 00:01:12.67900:01:12.689 the shell of the heat exchanger for a 00:01:14.75000:01:14.760 much lower cost the support plates shown 00:01:17.99000:01:18.000 below act as baffles to direct the flow 00:01:21.10900:01:21.119 of fluid within the shell back and forth 00:01:23.48000:01:23.490 across the tubes so what we mean here is 00:01:27.14000:01:27.150 when we are pumping a fluid or a medium 00:01:30.67900:01:30.689 through heat exchanger the medium our 00:01:33.49900:01:33.509 higher pressure is going to go through 00:01:35.69000:01:35.700 the tubes sometimes if you have two 00:01:39.10900:01:39.119 mediums such as oil and water where the 00:01:41.99000:01:42.000 water is cooling down the oil it may be 00:01:44.66000:01:44.670 very important that the oil does not 00:01:47.12000:01:47.130 leak out into the water this is 00:01:50.03000:01:50.040 especially true if we're using something 00:01:51.59000:01:51.600 like river water or lake water to cool 00:01:54.05000:01:54.060 down the oil we don't want oil leaking 00:01:57.02000:01:57.030 out through the tubes and going back 00:01:59.81000:01:59.820 into the river or the lake or even the 00:02:01.85000:02:01.860 ocean so what we'll do we'll have what 00:02:04.70000:02:04.710 they call a double walled tube and we 00:02:07.58000:02:07.590 will have a tube that has two walls and 00:02:11.02900:02:11.039 if oil was to leak out of the 00:02:13.55000:02:13.560 in a wall of the tube it will go into 00:02:16.10000:02:16.110 the middle between the outer and the 00:02:17.90000:02:17.910 inner wall and it will set off a leak 00:02:20.24000:02:20.250 alarm so that way we know that one of 00:02:22.37000:02:22.380 the tubes is leaking and we have an 00:02:23.93000:02:23.940 alarm but it doesn't leak out directly 00:02:26.36000:02:26.370 into the shell and into the water 00:02:29.14000:02:29.150 let's just load up a model here so I can 00:02:31.64000:02:31.650 show you in more detail how the heat 00:02:33.77000:02:33.780 exchanger works okay so here we have a 00:02:39.47000:02:39.480 standard shell and tube heat exchanger 00:02:42.32000:02:42.330 I'll just do a little spin we can see 00:02:46.22000:02:46.230 there's two pipes on the top and two 00:02:48.53000:02:48.540 pipes on the bottom we've got a stand 00:02:51.59000:02:51.600 and that is for installing the heat 00:02:54.47000:02:54.480 exchanger do a spin around this side we 00:02:59.24000:02:59.250 can see the nuts and bolts on the end 00:03:01.72900:03:01.739 here we will undo those to open up the 00:03:04.67000:03:04.680 end cover and get inside the heat 00:03:06.41000:03:06.420 exchanger or do an inspection or 00:03:08.21000:03:08.220 maintenance just take a cross-section 00:03:13.96000:03:13.970 okay so we've got a cross-section now as 00:03:16.19000:03:16.200 a heat exchanger we can see here a tube 00:03:20.33000:03:20.340 side fluid out tube side fluid in when 00:03:25.46000:03:25.470 we say tube side we mean the medium that 00:03:27.86000:03:27.870 is flowing through the tubes the 00:03:30.74000:03:30.750 opposite of tube side is shell side will 00:03:33.97900:03:33.989 have shell side fluid in and shell side 00:03:36.74000:03:36.750 fluid out that is this lower section 00:03:40.06900:03:40.079 here or the lower pipe I just get to an 00:03:43.75900:03:43.769 overview so we can follow the flow 00:03:45.94900:03:45.959 through the heat exchanger 00:03:48.41000:03:48.420 okay so we have got a cold fluid flowing 00:03:52.94000:03:52.950 in from the bottom it is then flowing 00:03:56.51000:03:56.520 along through the heat exchanger through 00:04:00.32000:04:00.330 these tubes it is doing a u-turn this is 00:04:04.34000:04:04.350 actually called a u-turn shell and tube 00:04:06.11000:04:06.120 type heat exchanger u-turn here and then 00:04:09.14000:04:09.150 it is flowing back that way and it is 00:04:12.08000:04:12.090 coming out of the top let me just spin 00:04:16.22000:04:16.230 around this side we can see the entrance 00:04:19.03900:04:19.049 points and we can see there are the 00:04:22.70000:04:22.710 tubes and the tubes are going off into 00:04:24.17000:04:24.180 the distance so the fluid is going to be 00:04:26.12000:04:26.130 flowing directly into these tubes 00:04:33.39000:04:33.400 we can also see a plate which is used 00:04:35.43000:04:35.440 for separating the fluid as it flows in 00:04:39.30000:04:39.310 from the bottom and then out of the top 00:04:41.71900:04:41.729 so if we're is to move this plate or 00:04:44.55000:04:44.560 take it out we would actually just have 00:04:46.46900:04:46.479 a fluid that flows in from the bottom 00:04:47.85000:04:47.860 and directly out the top it's going to 00:04:49.65000:04:49.660 choose the path of least resistance 00:04:52.40000:04:52.410 but because the place there it's coming 00:04:54.96000:04:54.970 in and flowing through the bottom tubes 00:04:57.09000:04:57.100 and we'll just follow it along along 00:05:00.30000:05:00.310 these tubes and we can see here this is 00:05:03.87000:05:03.880 where it suddenly turns around it's 00:05:06.18000:05:06.190 coming while traveling to the right on 00:05:08.61000:05:08.620 the lower section around the tubes 00:05:10.80000:05:10.810 around this u-turn and back the other 00:05:13.32000:05:13.330 way and it's going to keep going all the 00:05:16.08000:05:16.090 way until it comes out of the top again 00:05:19.08000:05:19.090 or the top section of the heat exchanger 00:05:21.32000:05:21.330 what's actually happened is it's gone in 00:05:23.85000:05:23.860 the bottom out of the top and it has 00:05:25.79000:05:25.800 absorbed some of that heat and it's then 00:05:30.93000:05:30.940 going to take away that heat and 00:05:32.71900:05:32.729 distribute it somewhere else perhaps to 00:05:35.43000:05:35.440 ambient air or perhaps it would just go 00:05:37.23000:05:37.240 back to a reservoir sometimes they'll 00:05:39.62900:05:39.639 even use some of the warmer fluid for a 00:05:41.87900:05:41.889 later stage in the process it's a good 00:05:44.82000:05:44.830 way to recycle the heat rather than just 00:05:47.27900:05:47.289 waste it because essentially when you're 00:05:49.58900:05:49.599 removing the heat that is a efficiency 00:05:53.12900:05:53.139 or an energy loss so if you can use it 00:05:55.92000:05:55.930 earlier or later in the process again 00:05:57.96000:05:57.970 you're recovering some of that energy 00:05:59.67000:05:59.680 and your increase in the process 00:06:02.43000:06:02.440 efficiency so have a look at the fluid 00:06:05.70000:06:05.710 comes in at the top the shell side fluid 00:06:08.15900:06:08.169 in in at the top now it does not unlike 00:06:12.71900:06:12.729 the tubular flow which flows relatively 00:06:14.93900:06:14.949 direct the fluid that is flowing in on 00:06:18.62900:06:18.639 the shell side is going to flow around a 00:06:21.21000:06:21.220 series of baffle plates it's going to 00:06:23.90900:06:23.919 come around here and be forced to turn 00:06:25.50000:06:25.510 it's going to turn again it's going to 00:06:27.62900:06:27.639 turn again and it's going to keep doing 00:06:30.06000:06:30.070 that all the way along and then it is 00:06:33.08900:06:33.099 going to exit at the bottom of the heat 00:06:37.32000:06:37.330 exchanger I have to say 00:06:40.79000:06:40.800 be slightly better if this discharged 00:06:43.15900:06:43.169 port from the heat exchanger was more to 00:06:44.86900:06:44.879 the right in order that he could throw 00:06:46.70000:06:46.710 through the heat exchanger and down on 00:06:48.74000:06:48.750 the right hand side rather than here but 00:06:51.08000:06:51.090 that is how the heat exchanger has been 00:06:52.67000:06:52.680 built in 3d here the reason for this 00:06:56.83900:06:56.849 Criss crossing pattern this is actually 00:06:59.27000:06:59.280 called cross flow is because we want to 00:07:02.02900:07:02.039 maximize the heat transfer between the 00:07:04.87900:07:04.889 two flowing fluids and we do this by 00:07:08.14900:07:08.159 having a cross flow pattern 00:07:10.58000:07:10.590 there's no point the fluid entering in 00:07:12.98000:07:12.990 the top flowing directly here and then 00:07:14.99000:07:15.000 dropping out at the bottom because if we 00:07:17.62900:07:17.639 do like that we've had very little 00:07:19.64000:07:19.650 turbulent flow and there's not going to 00:07:22.18900:07:22.199 be as much heat transfer between the two 00:07:24.89000:07:24.900 mediums compared to when we do this 00:07:26.89900:07:26.909 cross flow pattern and although you 00:07:30.20000:07:30.210 can't actually see it inside these tubes 00:07:32.99000:07:33.000 there is normally a thin piece of copper 00:07:36.61900:07:36.629 or plastic and it will slide into each 00:07:40.64000:07:40.650 and every one of these tubes now this 00:07:43.85000:07:43.860 thin piece of copper or perhaps plastic 00:07:46.87900:07:46.889 or other form of metal it depends on the 00:07:48.68000:07:48.690 system that you're actually using it for 00:07:50.08900:07:50.099 is similar to a very thin strip a flat 00:07:55.18900:07:55.199 bar a thin flat bar of copper for 00:07:58.21900:07:58.229 example and the idea is that as the 00:08:00.86000:08:00.870 fluid is flowing through the tubes it 00:08:02.77900:08:02.789 does not get to flow in a straight 00:08:05.26900:08:05.279 laminar direction it is going to come 00:08:08.20900:08:08.219 into contact with this thin perforated 00:08:11.86900:08:11.879 copper bar and then it is going to be 00:08:14.33000:08:14.340 forced to flow over and under the copper 00:08:17.39000:08:17.400 bar in other words it's going to have a 00:08:19.15900:08:19.169 very very turbulent path through the 00:08:22.79000:08:22.800 tubes and this is what we want we want 00:08:25.10000:08:25.110 turbulent flow because this is going to 00:08:27.89000:08:27.900 increase our heat transfer the other 00:08:30.29000:08:30.300 benefit with turbulent flow is simply 00:08:32.20900:08:32.219 that if we have suspended bodies within 00:08:36.05000:08:36.060 the fluid that may stick to the sides of 00:08:38.83900:08:38.849 the tubes they won't be able to stick to 00:08:42.46900:08:42.479 the size of the tubes as easily if they 00:08:45.82900:08:45.839 do stick to the sides of the tubes that 00:08:47.75000:08:47.760 is going to reduce our heat transfer 00:08:49.22000:08:49.230 rate where our heat transfer capacity so 00:08:52.81900:08:52.829 by having this turbulent flow 00:08:54.14000:08:54.150 we're preventing them or reducing the 00:08:56.18000:08:56.190 risk that they're going to be able to 00:08:57.35000:08:57.360 stick it to the size of the tubes and 00:08:59.92000:08:59.930 this will maintain heat transfer 00:09:02.86000:09:02.870 capacity now if you don't know what I'm 00:09:06.05000:09:06.060 talking about when I talk about things 00:09:07.97000:09:07.980 sticking to the size or surfaces of a 00:09:11.24000:09:11.250 heat exchanger go another look at your 00:09:13.94000:09:13.950 kettle now if you boil your kettle a 00:09:16.43000:09:16.440 thousand times using standard tap water 00:09:18.79000:09:18.800 it's very likely you'll notice a thin 00:09:22.31000:09:22.320 white powdery substance building up 00:09:25.97000:09:25.980 within the kettle now this is actually 00:09:28.13000:09:28.140 reducing your heat transfer this white 00:09:31.25000:09:31.260 powdery substance comes from the water 00:09:32.87000:09:32.880 itself the minerals and suspended bodies 00:09:35.66000:09:35.670 within the water and over time it will 00:09:39.56000:09:39.570 stick to the inside metal surfaces of 00:09:42.77000:09:42.780 your kettle and it will reduce the heat 00:09:45.23000:09:45.240 transfer rate and that's exactly what 00:09:47.12000:09:47.130 can also happen in a heat exchanger 00:09:50.11000:09:50.120 another example is a boiler with boilers 00:09:53.66000:09:53.670 they go to great lengths to ensure that 00:09:55.55000:09:55.560 the water quality is as clean as 00:09:58.67000:09:58.680 possible and the reason again is there 00:10:01.49000:10:01.500 any suspended bodies that stick to the 00:10:03.71000:10:03.720 surface of the boiler tubes will reduce 00:10:07.37000:10:07.380 the heat transfer rate and in severe 00:10:09.59000:10:09.600 conditions this can actually cause the 00:10:11.42000:10:11.430 piping to melt so it's very important 00:10:15.08000:10:15.090 that you keep the contact surface areas 00:10:17.36000:10:17.370 within your heat exchanger as clean as 00:10:19.85000:10:19.860 possible so that is a you type shell and 00:10:23.93000:10:23.940 tube heat exchanger if we were to click 00:10:26.51000:10:26.520 here we could actually have a look at 00:10:27.92000:10:27.930 some of the more specific pieces example 00:10:34.07000:10:34.080 let's just have a look at the tubes and 00:10:36.65000:10:36.660 we can see tubes if I do a full version 00:10:41.75000:10:41.760 again you can see all of our tubes there 00:10:44.33000:10:44.340 and the way they are installed can also 00:10:47.24000:10:47.250 highlight the baffles and the baffles 00:10:50.81000:10:50.820 now shown and we'll see our flow comes 00:10:53.78000:10:53.790 in and around the baffles like so so two 00:10:58.43000:10:58.440 baffles so I just highlight them for you 00:11:02.20000:11:02.210 are those pieces here and they'll be 00:11:04.88000:11:04.890 designed to be installed in this pattern 00:11:07.06000:11:07.070 so that 00:11:08.30000:11:08.310 get this cross float if that was all a 00:11:12.26000:11:12.270 bit quick don't worry we are going to go 00:11:14.69000:11:14.700 through this in more detail later in the 00:11:16.67000:11:16.680 course with some different examples I 00:11:18.89000:11:18.900 just think that was a nice introduction 00:11:20.33000:11:20.340 to what a shell-and-tube type heat 00:11:22.76000:11:22.770 exchanger is now let's go on to the next 00:11:25.64000:11:25.650 lesson 00:11:27.56000:11:27.570 [Music]
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