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Chiller flow rate measurement and calculation, chilled and condenser water
WEBVTT Kind: captions Language: en
00:00:03.650 hey there guys pulled here from the 00:00:05.86900:00:05.879 engineering mindset calm in this video 00:00:07.97000:00:07.980 we're going to be looking at how to 00:00:09.29000:00:09.300 measure the water flow rate through a 00:00:11.39000:00:11.400 chiller now this is useful to analyze 00:00:13.78900:00:13.799 the performance of a chiller and ensure 00:00:15.77000:00:15.780 it is meeting the design specifications 00:00:18.08000:00:18.090 in our previous video we looked at how 00:00:20.02900:00:20.039 to calculate the cooling capacity of a 00:00:22.07000:00:22.080 chiller and for this you would need to 00:00:23.75000:00:23.760 know the flow rate of water through the 00:00:25.64000:00:25.650 chiller there's a link on the screen now 00:00:27.43900:00:27.449 if you want to see that or see the video 00:00:29.33000:00:29.340 description below so to measure the flow 00:00:31.31000:00:31.320 rate we need to locate an orifice plate 00:00:33.35000:00:33.360 in the system these will look something 00:00:35.38900:00:35.399 like this 00:00:36.04900:00:36.059 although the flange face won't be 00:00:37.67000:00:37.680 visible when connected to the pipe but 00:00:39.86000:00:39.870 you can spot these because they have the 00:00:41.45000:00:41.460 two pipe sticking out of them on the 00:00:43.76000:00:43.770 engineering schematic drawing you should 00:00:45.70900:00:45.719 see them look something like this and 00:00:47.47900:00:47.489 we'll here of course do check the 00:00:49.88000:00:49.890 drawing legend to make sure we also need 00:00:52.18900:00:52.199 a tool to measure the flow rate with so 00:00:54.22900:00:54.239 for this we need a special manometer 00:00:55.93900:00:55.949 which can suit the pressure difference 00:00:57.61900:00:57.629 of the system you can buy compact 00:00:59.99000:01:00.000 digital versions which are easier to 00:01:01.81900:01:01.829 transport and more precise however I'm 00:01:04.34000:01:04.350 going to use an older mercury based poly 00:01:06.77000:01:06.780 meter to measure the flow rate simply 00:01:08.78000:01:08.790 because that's all I had available at 00:01:10.58000:01:10.590 the time now if you're going to buy a 00:01:12.35000:01:12.360 manometer then I recommend spending that 00:01:14.35900:01:14.369 little extra to get the digital version 00:01:16.52000:01:16.530 or leave some links below as well so 00:01:18.53000:01:18.540 this is a simplified version of the 00:01:20.30000:01:20.310 actual chilled and condenser water 00:01:22.07000:01:22.080 schematic of the building as you can see 00:01:24.77000:01:24.780 it has free chillers and free cooling 00:01:26.63000:01:26.640 towers and this feeds the ahu is in both 00:01:29.06000:01:29.070 the east and the west side of the 00:01:30.98000:01:30.990 building now I've only animated the flow 00:01:33.44000:01:33.450 path of the chilled water for this 00:01:35.24000:01:35.250 example as that's what we're measuring 00:01:36.83000:01:36.840 although the procedure will be the same 00:01:39.14000:01:39.150 if you wanted to measure the condenser 00:01:41.03000:01:41.040 water just to note that not all for each 00:01:43.58000:01:43.590 others do need to run this would only 00:01:45.71000:01:45.720 occur at maximum demand you can see on 00:01:48.26000:01:48.270 the left of the East and the west wing 00:01:49.94000:01:49.950 split off from a main header and the 00:01:52.03900:01:52.049 return water joins into another header 00:01:54.49900:01:54.509 before returning back to the chillers 00:01:56.45000:01:56.460 this separates the primary and the 00:01:58.67000:01:58.680 secondary circuits now we've already 00:02:00.62000:02:00.630 covered this in another video and the 00:02:02.53900:02:02.549 link is on the screen now for that if 00:02:04.45900:02:04.469 you need to learn that as well now also 00:02:06.98000:02:06.990 notice that only one of the two pumps is 00:02:09.44000:02:09.450 running in each pump set this is because 00:02:12.14000:02:12.150 they are using 00:02:13.07000:02:13.080 duty and standby configuration where a 00:02:15.68000:02:15.690 pump is made the leader and will run 00:02:18.20000:02:18.210 while the other pump acts as a backup 00:02:20.33000:02:20.340 just in case the leader pump fails and 00:02:22.94000:02:22.950 these roles are reversed they be so 00:02:24.59000:02:24.600 often just to keep the run out or 00:02:26.36000:02:26.370 similar and this will usually reverse 00:02:28.43000:02:28.440 every week or so so let's look at a real 00:02:31.31000:02:31.320 world example first we need to find a 00:02:33.59000:02:33.600 point in the system that we want to know 00:02:35.48000:02:35.490 what the flow rate is for this we'll use 00:02:37.91000:02:37.920 this orifice plate here on the chilled 00:02:39.77000:02:39.780 water flow pipe coming out of the 00:02:41.51000:02:41.520 chiller we can just check on the drawing 00:02:43.91000:02:43.920 legend that this is an orifice plate 00:02:45.62000:02:45.630 which means that we can measure here so 00:02:49.88000:02:49.890 we need to find the evaporator for tudor 00:02:51.80000:02:51.810 number 3 which is this one here and we 00:02:54.68000:02:54.690 follow the pipe work until we find the 00:02:56.44900:02:56.459 orifice plate which was just after the 00:02:58.61000:02:58.620 bypass valve and there it is now these 00:03:02.96000:03:02.970 are likely covered with installations 00:03:04.69900:03:04.709 they might be a little difficult to find 00:03:06.23000:03:06.240 at first but you can identify them by 00:03:08.72000:03:08.730 spotting the two thin choose which stick 00:03:10.61000:03:10.620 out of them now the tubes will be 00:03:12.41000:03:12.420 colored so one tube will be blue which 00:03:14.54000:03:14.550 means this is the low-pressure side and 00:03:16.69900:03:16.709 the other tube will be red which means 00:03:18.22900:03:18.239 this is the high pressure side it will 00:03:20.60000:03:20.610 probably have these little plastic tags 00:03:22.07000:03:22.080 on them as well to help identify them 00:03:23.75000:03:23.760 then open up the manometer and find your 00:03:26.60000:03:26.610 high pressure side which is colored red 00:03:29.68000:03:29.690 ensure that the two top valves to your 00:03:32.09000:03:32.100 high and low pressure side are both 00:03:33.89000:03:33.900 fully closed and that the lower-middle 00:03:36.56000:03:36.570 bypass valve is fully open they connect 00:03:41.81000:03:41.820 the red high-pressure hose to the high 00:03:43.85000:03:43.860 pressure tube of the orifice plate you 00:03:46.40000:03:46.410 might need to change the connection 00:03:47.54000:03:47.550 fitting depending on which valve has 00:03:49.34000:03:49.350 been used 00:03:49.94000:03:49.950 you'll also need to check that the 00:03:51.71000:03:51.720 threads are all clean as these are often 00:03:54.05000:03:54.060 covered with dust and dirt just turn it 00:03:56.93000:03:56.940 hand tight and ensure that it isn't 00:03:58.58000:03:58.590 leaking lastly just double check that 00:04:01.10000:04:01.110 you've connected the correct hose to the 00:04:03.35000:04:03.360 correct side 00:04:04.19000:04:04.200 you should also now check for any 00:04:06.35000:04:06.360 pockets of air within the hose or the 00:04:08.18000:04:08.190 manometer tubing and flush this out 00:04:10.49000:04:10.500 before continuing as any air pockets 00:04:12.38000:04:12.390 will cause inaccuracies with your 00:04:14.09000:04:14.100 measurements 00:04:15.38000:04:15.390 then locate the blue low-pressure hose 00:04:17.90000:04:17.910 and connect this to the blue 00:04:19.55000:04:19.560 low-pressure side of the orifice plate 00:04:23.06000:04:23.070 [Music] 00:04:28.99000:04:29.000 now you'll need to zero the measurement 00:04:31.49000:04:31.500 gauge so just open up the valve on the 00:04:33.50000:04:33.510 high pressure side of the orifice plate 00:04:35.30000:04:35.310 as well as the high pressure valve in 00:04:37.64000:04:37.650 the manometer and after that you can 00:04:39.98000:04:39.990 then check that the bottom of the little 00:04:41.96000:04:41.970 ball within the manometer is level with 00:04:44.48000:04:44.490 the zero mark on the gauge if it's not 00:04:47.27000:04:47.280 level with this then you can just move 00:04:48.92000:04:48.930 the measurement gauge up or down to 00:04:50.72000:04:50.730 align this now once you're happy with 00:04:53.45000:04:53.460 the zero alignment you can then open up 00:04:55.70000:04:55.710 the low-pressure side of the orifice 00:04:57.59000:04:57.600 plate sometimes when you open these 00:04:59.96000:04:59.970 valves up they dribble just a little bit 00:05:01.88000:05:01.890 if this happens they just make the 00:05:03.77000:05:03.780 connection a little bit tighter and it 00:05:05.39000:05:05.400 will stop after that you can then open 00:05:08.06000:05:08.070 up the low pressure valve within the 00:05:09.95000:05:09.960 manometer and once that's fully open you 00:05:12.44000:05:12.450 can then begin to close the bypass valve 00:05:14.77000:05:14.780 when you do this make sure you close the 00:05:17.30000:05:17.310 bypass valve very slowly and what's the 00:05:19.90900:05:19.919 little red ball begin to rise as this 00:05:21.92000:05:21.930 can suddenly shoot up very fast if it 00:05:25.07000:05:25.080 does get to higher towards the top then 00:05:26.84000:05:26.850 you should immediately open up the 00:05:28.37000:05:28.380 bypass valve fully to prevent the 00:05:30.65000:05:30.660 mercury from escaping so just leave it a 00:05:32.78000:05:32.790 moment to settle down and once it is 00:05:34.40000:05:34.410 stable you can then take a measurement 00:05:36.43000:05:36.440 now just note that the little ball will 00:05:38.87000:05:38.880 likely move up and down slightly and 00:05:40.94000:05:40.950 that's just due to the pumps and the 00:05:42.20000:05:42.210 turbulent flow within the pipe work once 00:05:44.21000:05:44.220 you're happy that it has settled down 00:05:45.62000:05:45.630 you can then take the reading here you 00:05:47.69000:05:47.700 can see it has a reading of around 6.2 00:05:50.42000:05:50.430 kiloPascals and that's just the pressure 00:05:52.37000:05:52.380 difference between the high and the low 00:05:53.93000:05:53.940 side of the orifice plate so just take a 00:05:56.75000:05:56.760 note of the reading and then you can 00:05:58.58000:05:58.590 begin to disconnect the equipment so to 00:06:01.25000:06:01.260 do this just open up the bypass valve 00:06:02.90000:06:02.910 and close the high and low pressure 00:06:04.88000:06:04.890 valves within the manometer after that 00:06:08.21000:06:08.220 you can then close the high-pressure 00:06:09.77000:06:09.780 valve on the orifice meter and 00:06:11.56000:06:11.570 disconnect the hose then after that do 00:06:14.48000:06:14.490 exactly the same on the low pressure 00:06:15.95000:06:15.960 side of the orifice 00:06:17.79000:06:17.800 so now we can calculate the flow rate to 00:06:20.71000:06:20.720 do this we first need to know what the 00:06:22.24000:06:22.250 KVS value is and this is set by the 00:06:24.55000:06:24.560 manufacturer of the orifice plate 00:06:26.86000:06:26.870 now the kb/s value will vary between 00:06:29.20000:06:29.210 manufacturers as well as the model 00:06:31.03000:06:31.040 numbers and also the size of the orifice 00:06:33.19000:06:33.200 plate to make sure you use the correct 00:06:34.87000:06:34.880 value they will also usually provide a 00:06:37.87000:06:37.880 chart to z' you can just perform a very 00:06:39.64000:06:39.650 quick lookup so let's mark our reading 00:06:42.73000:06:42.740 on the chart which was 6.2 kiloPascals 00:06:45.22000:06:45.230 and we'll just put this on the y-axis 00:06:47.17000:06:47.180 then we can draw a horizontal line 00:06:49.09000:06:49.100 across until it hits that dark kvs line 00:06:51.91000:06:51.920 from there we can then draw another line 00:06:54.37000:06:54.380 down vertically from there straight down 00:06:56.86000:06:56.870 to see what the flow rate is so here you 00:06:59.38000:06:59.390 can see it has a flow rate of around 55 00:07:01.84000:07:01.850 liters per second but if you want a more 00:07:04.45000:07:04.460 precise way than we can perform a 00:07:06.19000:07:06.200 calculation for that we need to use this 00:07:08.50000:07:08.510 formula which is the flow rate Q is 00:07:10.93000:07:10.940 equal to the KBS value multiplied by the 00:07:14.32000:07:14.330 square root of the pressure difference 00:07:16.06000:07:16.070 divided by 36 and we know what our kvs 00:07:20.02000:07:20.030 value is so we can just drop that number 00:07:21.94000:07:21.950 in we also know what the pressure 00:07:24.22000:07:24.230 difference value is - so we can drop 00:07:26.23000:07:26.240 that in also then we just square that 00:07:28.87000:07:28.880 value and multiply it by the KBS value 00:07:31.51000:07:31.520 then we just divide this all by 36 to 00:07:34.99000:07:35.000 get the answer of 54.7 liters per second 00:07:38.50000:07:38.510 and there you have it that is the water 00:07:40.57000:07:40.580 flow rate through your chart okay that's 00:07:43.84000:07:43.850 it for this video thank you very much 00:07:45.43000:07:45.440 for watching I hope this has helped if 00:07:47.05000:07:47.060 it has then please hit the like 00:07:48.46000:07:48.470 subscribe and share button and if you 00:07:50.38000:07:50.390 have any questions leave them in the 00:07:51.67000:07:51.680 comment section below 00:07:53.11000:07:53.120 don't forget to check out our website 00:07:54.46000:07:54.470 the engineering mindset comm are also 00:07:56.59000:07:56.600 available on Facebook Twitter and 00:07:58.66000:07:58.670 Instagram place again for watching 00:08:01.82000:08:01.830
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