How the evaporator works and why

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Language: en

00:00:04.250
[Music]
00:00:06.509 00:00:06.519 in the last video we talked about the
00:00:10.570 00:00:10.580 expansion device here now this one's
00:00:13.209 00:00:13.219 about the evaporator that's this part
00:00:15.970 00:00:15.980 right here be some sort of coil the
00:00:19.689 00:00:19.699 transfers heat this is a compressor
00:00:22.480 00:00:22.490 that's the suction side of the
00:00:24.070 00:00:24.080 compressor that's a suck side once the
00:00:26.950 00:00:26.960 refrigerant passes through the expansion
00:00:30.220 00:00:30.230 device which is a restriction it's
00:00:33.040 00:00:33.050 temperature and pressure are both lured
00:00:36.100 00:00:36.110 the pressure is lowered because of the
00:00:38.950 00:00:38.960 restriction of the expansion device once
00:00:43.720 00:00:43.730 that pressure is lowered the refrigerant
00:00:46.630 00:00:46.640 inside here will boil at a lower
00:00:50.530 00:00:50.540 temperature than the surrounding air of
00:00:54.970 00:00:54.980 the evaporator know we're using an air
00:00:57.520 00:00:57.530 evaporator we could use water or brine
00:01:00.490 00:01:00.500 and all sorts of things but generally
00:01:02.890 00:01:02.900 it's going to be an evaporator that's
00:01:05.439 00:01:05.449 exposed to air the effect of the
00:01:08.319 00:01:08.329 evaporator is the reason we do
00:01:11.230 00:01:11.240 refrigeration at all just to get stuff
00:01:13.419 00:01:13.429 cold so this is boiling at a temperature
00:01:17.950 00:01:17.960 below the air passing across the coil so
00:01:21.969 00:01:21.979 it's going to boil and as it comes out
00:01:24.370 00:01:24.380 of this expansion device that's a warm
00:01:28.330 00:01:28.340 high pressure liquid as it comes through
00:01:31.649 00:01:31.659 it immediately has to reduce the
00:01:35.219 00:01:35.229 temperature of the liquid to whatever
00:01:39.429 00:01:39.439 temperature it's boiling at part of the
00:01:42.480 00:01:42.490 evaporation takes place just to reduce
00:01:45.160 00:01:45.170 the temperature of that liquid as it
00:01:48.069 00:01:48.079 comes soon let's say the liquid comes
00:01:49.629 00:01:49.639 through at 100 degrees and I'm boiling
00:01:54.039 00:01:54.049 at 40 here in the back well it's that
00:01:58.569 00:01:58.579 sensible he has to be taken off of that
00:02:01.090 00:02:01.100 liquid refrigerant and so that's the
00:02:03.160 00:02:03.170 first short section here it reduces that
00:02:07.599 00:02:07.609 sensible heat off the liquid and gets it
00:02:12.580 00:02:12.590 down to
00:02:13.699 00:02:13.709 the boiling point actually that can be
00:02:15.979 00:02:15.989 up to 25% of the load is just removing
00:02:20.630 00:02:20.640 that sensible heat so that's the first
00:02:24.979 00:02:24.989 thing it does as it starts boiling then
00:02:29.569 00:02:29.579 it starts taking heat out of the air
00:02:32.509 00:02:32.519 passing across the quarter now
00:02:36.289 00:02:36.299 throughout this whole thing this is just
00:02:38.660 00:02:38.670 a bubbling mess there's no bubbles
00:02:40.819 00:02:40.829 coming up there it's all it'll sit there
00:02:42.949 00:02:42.959 absorbing heat now here's where the
00:02:45.970 00:02:45.980 expansion device has so much affect on
00:02:48.710 00:02:48.720 this thing we do not want this entire
00:02:52.069 00:02:52.079 coil filled with boiling liquid
00:02:55.970 00:02:55.980 refrigerant the reason being we don't
00:02:59.300 00:02:59.310 want to dump the liquid into this
00:03:02.059 00:03:02.069 compressive compressors our gas pumps
00:03:05.170 00:03:05.180 they will pump gases they don't do so
00:03:09.830 00:03:09.840 good pumping liquid there can be lots of
00:03:12.589 00:03:12.599 damage and so on like that
00:03:14.509 00:03:14.519 so we want all of this refrigerant to
00:03:18.740 00:03:18.750 boil off before it gets to that
00:03:21.680 00:03:21.690 compressor if the expansion device is
00:03:24.409 00:03:24.419 doing its job then by the time we get
00:03:27.770 00:03:27.780 somewhere around in here we're gonna run
00:03:32.240 00:03:32.250 out of liquid it's going to be
00:03:35.509 00:03:35.519 completely boiled off if it is
00:03:39.110 00:03:39.120 completely boiled off at this point then
00:03:41.360 00:03:41.370 just a pure gas comes back to the
00:03:45.020 00:03:45.030 compressor that is normal operation for
00:03:47.659 00:03:47.669 these things you can have all sorts of
00:03:49.670 00:03:49.680 things happen work that doesn't work out
00:03:52.699 00:03:52.709 and there's liquid coming back you know
00:03:56.360 00:03:56.370 when you block the evaporator coil with
00:03:58.789 00:03:58.799 a plug filter or something like that
00:04:00.020 00:04:00.030 that can change it refrigerant charge if
00:04:04.399 00:04:04.409 the charge is too low then instead of
00:04:06.890 00:04:06.900 boiling off here it boils off
00:04:08.710 00:04:08.720 down here someplace and you don't get
00:04:12.420 00:04:12.430 very much effective cooling so this
00:04:16.150 00:04:16.160 thing working properly could feed the
00:04:18.599 00:04:18.609 proper amount of refrigerant into this
00:04:21.160 00:04:21.170 coil so that we run out of a liquid
00:04:25.570 00:04:25.580 about this point and the gas does what's
00:04:29.170 00:04:29.180 called superheat that means it warms up
00:04:33.370 00:04:33.380 from the tower the saturated temperature
00:04:37.270 00:04:37.280 pressure that was happening here in the
00:04:39.970 00:04:39.980 middle of the coil and then it runs back
00:04:42.730 00:04:42.740 to the compressor and cycles around
00:04:44.380 00:04:44.390 again fairly simple you can see and
00:04:48.910 00:04:48.920 we'll talk more about these later all
00:04:51.100 00:04:51.110 the things that could affect this you
00:04:54.460 00:04:54.470 know refrigerant charge could affect how
00:04:58.000 00:04:58.010 much refrigerant gets in here head
00:05:01.300 00:05:01.310 pressure could affect it blocking
00:05:03.570 00:05:03.580 blockage of filters coils being plugged
00:05:07.300 00:05:07.310 not enough airflow all those things can
00:05:09.550 00:05:09.560 affect the way this floor okay the next
00:05:11.440 00:05:11.450 thing we're going to go into is a
00:05:12.760 00:05:12.770 compressor now the compressor is gonna
00:05:14.710 00:05:14.720 be one of the most complicated parts of
00:05:18.790 00:05:18.800 this refrigeration system it's also the
00:05:21.280 00:05:21.290 most expensive light rail so we will
00:05:25.360 00:05:25.370 continue on with the compressive not
00:05:28.450 00:05:28.460 saying I'm not going to have more on
00:05:29.950 00:05:29.960 about there got plenty more on that
00:05:31.860 00:05:31.870 that's it for this one
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