00:00:00.350 --> 00:00:01.570 - [Instructor] In this video, we're going 00:00:01.570 --> 00:00:04.400 to look at the plate heat exchanger. 00:00:04.400 --> 00:00:06.670 By the end of the video you will know all of the plate 00:00:06.670 --> 00:00:08.910 heat exchanger's main components, 00:00:08.910 --> 00:00:12.480 how it works and some of the advantages and disadvantages 00:00:12.480 --> 00:00:15.870 associated with this type of exchanger compared to other 00:00:15.870 --> 00:00:19.902 types of heat exchanger such as the shell and tube type. 00:00:19.902 --> 00:00:24.240 Plate heat exchangers consist of relatively few parts, 00:00:24.240 --> 00:00:26.610 because plate heat exchangers are used for transferring 00:00:26.610 --> 00:00:30.160 heat, they require inlets and outlets where the flowing 00:00:30.160 --> 00:00:34.960 mediums or fluids, can enter and leave the heat exchanger. 00:00:34.960 --> 00:00:38.630 A fluid may be a liquid, or a gas, as fluids are often 00:00:38.630 --> 00:00:41.080 assumed to be liquid only, we will use the term 00:00:41.080 --> 00:00:43.363 flowing medium to avoid confusion. 00:00:44.800 --> 00:00:46.920 Gaskets and plates are used to separate the 00:00:46.920 --> 00:00:49.323 flowing mediums and prevent them mixing. 00:00:50.500 --> 00:00:54.110 The gaskets are adhered to one side of each plate only. 00:00:54.110 --> 00:00:57.070 The plates hang upon a carry bar and are pressed together 00:00:57.070 --> 00:00:59.400 using clamping bolts. 00:00:59.400 --> 00:01:01.300 When the plates are compressed together, 00:01:01.300 --> 00:01:03.253 they form a plate stack. 00:01:04.240 --> 00:01:07.220 A guide bar ensures the plates are aligned correctly, 00:01:07.220 --> 00:01:09.543 when the plate stack is opened or closed. 00:01:10.720 --> 00:01:13.250 The final components of interest are two covers 00:01:13.250 --> 00:01:15.530 at opposite ends of the plate stack. 00:01:15.530 --> 00:01:19.060 One cover is movable whilst the other is fixed. 00:01:19.060 --> 00:01:22.540 The movable cover and fixed cover are also sometimes 00:01:22.540 --> 00:01:26.370 referred to as the frame plates and pressure plates. 00:01:26.370 --> 00:01:29.060 Note that the inlets and outlets are mounted 00:01:29.060 --> 00:01:30.933 to the fixed cover only. 00:01:32.990 --> 00:01:35.010 Now we know about the plate heat exchanger's main 00:01:35.010 --> 00:01:37.286 components, let's have a look at how it works 00:01:37.286 --> 00:01:39.623 and some of its design features. 00:01:40.550 --> 00:01:43.270 For demonstration purposes, we will assume that we have 00:01:43.270 --> 00:01:46.170 two flowing mediums and that one is cold 00:01:46.170 --> 00:01:47.960 and the other is hot. 00:01:47.960 --> 00:01:50.890 The hot medium needs to be cooled by the cold medium. 00:01:50.890 --> 00:01:53.950 And this will occur in the plate heat exchanger. 00:01:53.950 --> 00:01:55.920 The hot medium enters the heat exchanger through 00:01:55.920 --> 00:01:57.890 the hot medium inlet. 00:01:57.890 --> 00:02:00.474 Gaskets direct the hot medium as it flows through 00:02:00.474 --> 00:02:02.600 the heat exchanger. 00:02:02.600 --> 00:02:05.940 Each plate has an alternating gasket pattern. 00:02:05.940 --> 00:02:08.300 The hot medium flows into the space between the pair 00:02:08.300 --> 00:02:11.210 of plates, but does not flow in the space between 00:02:11.210 --> 00:02:14.990 the next pair of plates, because the gaskets prevent this. 00:02:14.990 --> 00:02:18.220 The process continues so that each second set of plates 00:02:18.220 --> 00:02:20.143 is filled with the hot flowing medium. 00:02:21.270 --> 00:02:24.390 At the same time the cold medium enters the heat exchanger 00:02:24.390 --> 00:02:27.500 through the cold medium inlet, but this time, 00:02:27.500 --> 00:02:29.860 the gaskets are positioned to allow the cold medium 00:02:29.860 --> 00:02:33.833 to flow into the space where no hot medium is present. 00:02:34.870 --> 00:02:37.119 We now have a heat exchanger that is filled with both 00:02:37.119 --> 00:02:40.500 hot and cold flowing mediums. 00:02:40.500 --> 00:02:43.370 Each medium flows out of its associated outlet, 00:02:43.370 --> 00:02:45.540 and the process is continuous. 00:02:45.540 --> 00:02:48.290 Notice that the two flowing medium are always adjacent 00:02:48.290 --> 00:02:50.899 to each other throughout 00:02:50.899 --> 00:02:54.192 The flowing mediums thus have a hot cold, hot cold 00:02:54.192 --> 00:02:58.390 flow pattern as they flow through the heat exchanger. 00:02:58.390 --> 00:03:00.740 They are completely separated from each other, 00:03:00.740 --> 00:03:04.210 by the gaskets and plates and they do not mix. 00:03:04.210 --> 00:03:06.850 Due to the close proximity of the flowing mediums, 00:03:06.850 --> 00:03:09.120 heat is exchanged between them. 00:03:09.120 --> 00:03:11.390 The hot medium heats up the plates, and the plate 00:03:11.390 --> 00:03:14.480 passes some of this heat to the cold flowing medium. 00:03:14.480 --> 00:03:17.150 Thus the hot medium temperature decreases 00:03:17.150 --> 00:03:20.223 whilst the cold medium temperature increases. 00:03:21.480 --> 00:03:23.801 But what makes plate heat exchangers so efficient 00:03:23.801 --> 00:03:26.400 compared to other types of heat exchanger, 00:03:26.400 --> 00:03:28.350 such as the shell and tube type? 00:03:28.350 --> 00:03:29.230 Let's look into some 00:03:29.230 --> 00:03:32.410 of the plate heat exchanger's design features. 00:03:32.410 --> 00:03:33.500 The plates themselves are 00:03:33.500 --> 00:03:36.610 the main reason plate heat exchangers are so efficient. 00:03:36.610 --> 00:03:39.344 This plate may appear simple but it is actually full 00:03:39.344 --> 00:03:42.740 of interesting engineering design features. 00:03:42.740 --> 00:03:45.690 For example, when the plates are compressed together 00:03:45.690 --> 00:03:48.630 to form a plate stack, the gap between each other plates 00:03:48.630 --> 00:03:51.568 is very small, which ensure good thermal contact 00:03:51.568 --> 00:03:54.220 between the two flowing mediums. 00:03:54.220 --> 00:03:58.020 The gap between the plates is also known as clearance. 00:03:58.020 --> 00:04:01.550 Plates are thin and have a large contact surface area, 00:04:01.550 --> 00:04:04.900 which gives each plate a high heat transfer rate. 00:04:04.900 --> 00:04:06.910 Plates are manufactured from a material, 00:04:06.910 --> 00:04:10.330 with high thermal conductivity, which further increases 00:04:10.330 --> 00:04:11.663 the heat transfer rate. 00:04:12.770 --> 00:04:16.210 Corrugations on the plate surfaces prevent laminar flow 00:04:16.210 --> 00:04:19.370 and prevent turbulent flow which increases the heat 00:04:19.370 --> 00:04:22.430 transfer rate whilst also reducing the likelihood 00:04:22.430 --> 00:04:25.453 of deposits accumulating upon the plate's surfaces. 00:04:27.490 --> 00:04:29.910 The corrugations also serve to stiffen the plate's 00:04:29.910 --> 00:04:32.990 structure, which allows a thinner plate to be used 00:04:32.990 --> 00:04:35.240 compared to a plate that has no corrugations. 00:04:36.320 --> 00:04:39.120 Note, that plate corrugations are sometimes referred to 00:04:39.120 --> 00:04:40.993 as having a herringbone pattern. 00:04:42.750 --> 00:04:45.850 So although the plates look simple, a lot of engineering 00:04:45.850 --> 00:04:47.523 was applied to their design. 00:04:48.640 --> 00:04:50.640 But the plates are not the only part of 00:04:50.640 --> 00:04:54.100 the plate heat exchanger with extensive design features. 00:04:54.100 --> 00:04:56.470 Take the gaskets for example. 00:04:56.470 --> 00:04:59.178 The gaskets are able to maintain a seal between the plates 00:04:59.178 --> 00:05:02.990 even when the system pressure and temperature varies. 00:05:02.990 --> 00:05:06.410 Holes in each gasket known as telltales are used 00:05:06.410 --> 00:05:08.760 to identify leaking gaskets. 00:05:08.760 --> 00:05:11.837 This feature allows operators to change the affected plates 00:05:11.837 --> 00:05:15.690 before the leaking medium leaks through the next gasket 00:05:15.690 --> 00:05:17.793 and contaminates the other flowing medium. 00:05:18.690 --> 00:05:21.498 Because the gaskets guide flow through the heat exchanger, 00:05:21.498 --> 00:05:25.180 it is essential that they be installed in the correct order. 00:05:25.180 --> 00:05:28.055 For this reason, gaskets are often fitted with markings 00:05:28.055 --> 00:05:30.230 so that operators can check each plate 00:05:30.230 --> 00:05:31.940 is installed in the correct order 00:05:31.940 --> 00:05:34.200 throughout the entire plate stack. 00:05:34.200 --> 00:05:36.430 Another way to check the order of the plates, 00:05:36.430 --> 00:05:39.310 is to spray paint a diagonal line from the top left 00:05:39.310 --> 00:05:42.093 to bottom right of the entire plate stack. 00:05:44.510 --> 00:05:47.010 Although we have only shown two gasket designs 00:05:47.010 --> 00:05:50.350 so far in this video, there are actually three. 00:05:50.350 --> 00:05:52.690 Gaskets alternate throughout the heat exchanger 00:05:52.690 --> 00:05:55.160 except for the first and the last plates within 00:05:55.160 --> 00:05:57.110 the plate stack which press against 00:05:57.110 --> 00:05:59.640 the fixed, and movable covers. 00:05:59.640 --> 00:06:01.260 Plates that press against the fixed 00:06:01.260 --> 00:06:02.840 and moveable covers are known 00:06:03.727 --> 00:06:05.220 as start and end plates. 00:06:05.220 --> 00:06:08.290 Because of their position within the plate stack, 00:06:08.290 --> 00:06:10.410 the purpose of the start and end plates is 00:06:10.410 --> 00:06:13.180 to prevent flow into the space between the fixed cover 00:06:13.180 --> 00:06:16.760 and start plates and to prevent flow into the space 00:06:16.760 --> 00:06:19.470 between the movable cover and end plate 00:06:20.523 --> 00:06:21.430 and this way the covers are not 00:06:21.430 --> 00:06:24.660 actively used to exchange heat. 00:06:24.660 --> 00:06:26.990 This makes sense, because each of the covers 00:06:26.990 --> 00:06:28.380 is quite thick. 00:06:28.380 --> 00:06:31.530 There are no corrugations, and they're poorly designed 00:06:31.530 --> 00:06:32.913 to exchange heat. 00:06:34.500 --> 00:06:36.900 There are several ways to vary the cooling capacity 00:06:36.900 --> 00:06:38.530 of a heat exchanger. 00:06:38.530 --> 00:06:41.520 One way is to regulate the outlet valves so that the flow 00:06:41.520 --> 00:06:43.810 is increased or decreased. 00:06:43.810 --> 00:06:46.360 This method is useful because no dismantling 00:06:46.360 --> 00:06:48.570 of the heat exchanger occurs. 00:06:48.570 --> 00:06:51.040 Another way is to increase or decrease the number 00:06:51.040 --> 00:06:53.340 of plates in the plate stack. 00:06:53.340 --> 00:06:55.690 Increasing the number of plates in the plate stack 00:06:55.690 --> 00:06:59.000 gives the corresponding increase in cooling capacity. 00:06:59.000 --> 00:07:01.380 Decreasing the number of 00:07:01.380 --> 00:07:05.110 decrease in cooling capacity. 00:07:05.110 --> 00:07:08.460 In short, more plates equals more cooling 00:07:08.460 --> 00:07:11.240 and less plates equals less cooling. 00:07:11.240 --> 00:07:14.090 The final method, a varying of plate heat exchanger's 00:07:14.090 --> 00:07:16.930 cooling capacity is to use a single pass 00:07:16.930 --> 00:07:18.433 or multi pass design. 00:07:19.720 --> 00:07:23.150 Single pass heat exchangers allow the two flowing mediums 00:07:23.150 --> 00:07:26.170 to flow past each other only once. 00:07:26.170 --> 00:07:29.100 Multi pass heat exchangers allow the flowing mediums 00:07:29.100 --> 00:07:32.480 to flow past each other several times. 00:07:32.480 --> 00:07:36.720 Most plate heat exchangers use the single pass design. 00:07:36.720 --> 00:07:39.830 Flow through plate exchanger may be parallel, 00:07:39.830 --> 00:07:42.040 cross, or counter. 00:07:42.040 --> 00:07:44.930 Plate heat exchangers usually use counter flow, 00:07:44.930 --> 00:07:47.180 as this is the most efficient type of flow 00:07:47.180 --> 00:07:48.620 for heat transfer. 00:07:48.620 --> 00:07:51.403 Counter flow is also sometimes known as contraflow. 00:07:52.600 --> 00:07:55.160 Because plate heat exchangers are used for wide ranging 00:07:55.160 --> 00:07:57.800 applications, they must be designed to withstand 00:07:57.800 --> 00:08:00.680 the process conditions in which they operate. 00:08:00.680 --> 00:08:03.920 This may include corrosive and erosive environments. 00:08:03.920 --> 00:08:06.170 It's possible to construct plate heat exchangers 00:08:06.170 --> 00:08:09.310 from various materials, including metals, 00:08:09.310 --> 00:08:11.670 alloys, and plastics. 00:08:11.670 --> 00:08:13.820 Different materials make the plate heat exchanger 00:08:13.820 --> 00:08:16.640 more suitable for different applications. 00:08:16.640 --> 00:08:19.930 For example, if a particular flowing medium reacts 00:08:19.930 --> 00:08:23.270 aggressively when coming into contact with certain metals, 00:08:23.270 --> 00:08:25.910 polymer based materials, such as Teflon, 00:08:25.910 --> 00:08:27.373 may be used instead. 00:08:28.410 --> 00:08:30.650 There are numerous advantages associated with 00:08:30.650 --> 00:08:32.690 plate heat exchangers. 00:08:32.690 --> 00:08:36.080 Plate heat exchangers weigh less, require less space 00:08:36.080 --> 00:08:38.470 and are more efficient compared to other heat exchanger 00:08:38.470 --> 00:08:40.820 designs of the same size. 00:08:40.820 --> 00:08:43.930 Replacing and cleaning of the plates is a simple task, 00:08:43.930 --> 00:08:46.660 because the plate stack can be opened easily, 00:08:46.660 --> 00:08:49.170 and unlike shell and tube heat exchangers, 00:08:49.170 --> 00:08:51.010 plate heat exchangers do not require 00:08:51.010 --> 00:08:53.540 additional space for dismantling. 00:08:53.540 --> 00:08:56.120 But there are also some disadvantages. 00:08:56.120 --> 00:08:58.630 tend to be more expensive 00:08:58.630 --> 00:09:00.860 than other heat exchanger designs. 00:09:00.860 --> 00:09:03.380 If there is a leaking gasket causing one flowing medium 00:09:03.380 --> 00:09:05.930 to mix with the other, the leaking plate is often 00:09:05.930 --> 00:09:07.830 difficult to locate. 00:09:07.830 --> 00:09:09.810 Replacement of plate gasket in situ 00:09:09.810 --> 00:09:12.180 can difficult or impossible. 00:09:12.180 --> 00:09:14.950 Some plate gaskets must be returned to the manufacturer 00:09:14.950 --> 00:09:18.890 for replacement, which costs both time and money. 00:09:18.890 --> 00:09:20.500 When plates are compressed together to form 00:09:20.500 --> 00:09:24.220 a plate stack, the clearances between the plates is small. 00:09:24.220 --> 00:09:26.320 This increases the likelihood of fouling, 00:09:26.320 --> 00:09:29.870 with the corresponding reduction in the heat transfer rates. 00:09:29.870 --> 00:09:32.610 When reassembling the plate stack, over tightening of 00:09:32.610 --> 00:09:35.340 the clamping bolts can lead to crushing of the plates, 00:09:35.340 --> 00:09:37.970 which will damage the plate corrugations and squeeze 00:09:37.970 --> 00:09:39.500 out the gaskets. 00:09:39.500 --> 00:09:41.420 If the gaskets are squeezed out, 00:09:41.420 --> 00:09:44.190 the plates will no longer seal correctly. 00:09:44.190 --> 00:09:46.810 Plate heat exchangers are not suitable for high pressure 00:09:46.810 --> 00:09:49.380 applications because the gaskets would be expelled 00:09:49.380 --> 00:09:51.060 by the system pressure. 00:09:51.060 --> 00:09:54.340 This situation is referred to as gasket blow out. 00:09:54.340 --> 00:09:57.030 However, it is possible to get around this problem 00:09:57.030 --> 00:09:59.470 by using a gasketless design. 00:09:59.470 --> 00:10:03.380 These designs usually use braised or welded plates. 00:10:03.380 --> 00:10:06.350 Braised and welded plate heat exchangers are more suitable 00:10:06.350 --> 00:10:10.361 for high temperature and higher pressure applications. 00:10:10.361 --> 00:10:11.343 You now know all of the 00:10:11.343 --> 00:10:14.530 plate heat exchanger's main components. 00:10:14.530 --> 00:10:17.690 You know how it works, some of its design features, 00:10:17.690 --> 00:10:20.380 and the advantages and disadvantages associated 00:10:20.380 --> 00:10:22.680 with this type of heat exchanger. 00:10:22.680 --> 00:10:24.807 If you enjoyed this video, then check out 00:10:24.807 --> 00:10:26.910 our heat exchanger video playlist 00:10:26.910 --> 00:10:29.060 in the video description area. 00:10:29.060 --> 00:10:32.100 You'll also find discount price links to our engineering 00:10:32.100 --> 00:10:34.590 video courses, and 3D models 00:10:34.590 --> 00:10:36.740 00:10:36.740 --> 00:10:38.990 If you would like to access hundreds of interactive 00:10:38.990 --> 00:10:42.200 3D models like those seen in this video, then you can do 00:10:42.200 --> 00:10:44.620 so at savree.com. 00:10:44.620 --> 00:10:45.940 Like this video? 00:10:45.940 --> 00:10:47.320 Then please do share it or like it 00:10:47.320 --> 00:10:49.490 on social media or subscribe. 00:10:49.490 --> 00:10:51.880 It really does help us out, and allows us to produce 00:10:51.880 --> 00:10:53.093 more and more content. 00:10:54.800 --> 00:10:56.350 Thanks very much for your time.
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