/ News & Press / Video / Absorption Chiller, How it works - working principle hvac

Absorption Chiller, How it works - working principle hvac

WEBVTT
Kind: captions
Language: en

00:00:05.954 --> 00:00:06.787
Hey there guys.
00:00:06.787 --> 00:00:08.300
Paul here from TheEngineeringMindset.com.
00:00:08.300 --> 00:00:09.750
In this video we're gonna be looking at
00:00:09.750 --> 00:00:12.060
The Basics of Absorption Chillers
00:00:12.060 --> 00:00:14.210
and learning how they work.
00:00:14.210 --> 00:00:17.610
Now an absorption chiller is
different to other chillers
00:00:17.610 --> 00:00:19.890
because it doesn't have a compressor.
00:00:19.890 --> 00:00:23.480
Instead it uses heat to generate cooling.
00:00:23.480 --> 00:00:25.720
Now that might seem a little
confusing, but don't worry.
00:00:25.720 --> 00:00:27.920
By the end of this video
you'll understand why
00:00:27.920 --> 00:00:29.950
and how that works.
00:00:29.950 --> 00:00:32.750
Another interesting point to
note about absorption chillers
00:00:32.750 --> 00:00:35.520
is that they don't use
conventional refrigerants
00:00:35.520 --> 00:00:38.933
such as R134 A or R22,
00:00:39.880 --> 00:00:43.140
instead they use water as a refrigerant.
00:00:43.140 --> 00:00:45.860
And this water is mixed
with either ammonia
00:00:45.860 --> 00:00:47.650
or lithium bromide.
00:00:47.650 --> 00:00:50.180
Lithium bromide is the more common version
00:00:50.180 --> 00:00:52.540
and that's because it's
safer and nontoxic.
00:00:52.540 --> 00:00:55.930
So we're gonna be
looking at how the water,
00:00:55.930 --> 00:00:59.400
lithium bromide type chillers
will work in this video.
00:00:59.400 --> 00:01:01.890
But essentially they are very similar.
00:01:01.890 --> 00:01:03.860
Now if this is a subject
that interests you,
00:01:03.860 --> 00:01:07.610
then I highly encourage you
to check out our other videos
00:01:07.610 --> 00:01:08.870
and we've got other videos explaining
00:01:08.870 --> 00:01:10.460
how water-cooled chillers work
00:01:12.250 --> 00:01:13.973
as well as air-cooled chillers.
00:01:17.660 --> 00:01:20.120
So do check out some of these videos.
00:01:20.120 --> 00:01:22.020
So just before we go
in and start to look at
00:01:22.020 --> 00:01:25.620
how the inside of an
absorption chiller works,
00:01:25.620 --> 00:01:29.640
I need you to want to understand
free important concept
00:01:29.640 --> 00:01:32.803
for the basic operation of how
these types of chillers work.
00:01:33.730 --> 00:01:36.200
The first point is that
when we boil water,
00:01:36.200 --> 00:01:39.370
it changes states from liquid to vapor.
00:01:39.370 --> 00:01:41.420
Now the water boils at
different temperatures
00:01:41.420 --> 00:01:42.950
under different pressures.
00:01:42.950 --> 00:01:44.560
If you increase the pressure
00:01:44.560 --> 00:01:47.340
then the water boils at
much higher temperatures,
00:01:47.340 --> 00:01:48.800
and if you decrease the pressure
00:01:48.800 --> 00:01:51.800
then water boils at
much lower temperatures.
00:01:51.800 --> 00:01:53.940
For example, we're used the water boiling
00:01:53.940 --> 00:01:57.250
at around 100 degrees Celsius,
212 degrees Fahrenheit,
00:01:57.250 --> 00:02:00.380
and that's because we're
at atmospheric pressure,
00:02:00.380 --> 00:02:04.440
which is around 101kPa or 14.7psi.
00:02:04.440 --> 00:02:05.850
But that is only because all the weight
00:02:05.850 --> 00:02:07.730
of the atmosphere above us,
00:02:07.730 --> 00:02:10.640
all the weight of the
air which is above us.
00:02:10.640 --> 00:02:12.520
If we went higher up into the atmosphere,
00:02:12.520 --> 00:02:14.380
say to the top of Mount Everest
00:02:14.380 --> 00:02:17.320
where the atmosphere is much thinner,
00:02:17.320 --> 00:02:19.780
then we would see water would boil
00:02:19.780 --> 00:02:24.440
at around 70 degrees Celsius,
158 degrees Fahrenheit.
00:02:24.440 --> 00:02:26.530
And that's because the
atmospheric pressure
00:02:26.530 --> 00:02:30.650
is around 34kPa/ 4.9psi.
00:02:30.650 --> 00:02:32.410
And that is because there is less air
00:02:32.410 --> 00:02:36.010
or atmosphere weighing down on the water.
00:02:36.010 --> 00:02:38.660
So when the absorption
chiller in the evaporator
00:02:38.660 --> 00:02:40.170
and the absorber chamber,
00:02:40.170 --> 00:02:42.790
we're gonna have a chamber pressure,
00:02:42.790 --> 00:02:46.070
a very, very low pressure
in there almost near vacuum.
00:02:46.070 --> 00:02:49.680
So we're gonna have a low
pressure of about North 0.84kPa
00:02:49.680 --> 00:02:52.083
or which is about 0.12psia.
00:02:53.380 --> 00:02:56.020
And at that pressure the water will boil
00:02:56.020 --> 00:03:00.810
around 4.5 degrees Celsius
or 40 degrees Farenhight.
00:03:00.810 --> 00:03:02.780
Now if you pass the steam over
00:03:03.990 --> 00:03:05.860
a pipe containing cold water,
00:03:05.860 --> 00:03:09.120
then the steam will
transfer its thermal energy
00:03:09.120 --> 00:03:11.520
over into that pipe and
it will then condense
00:03:11.520 --> 00:03:15.430
and the steam will then turn
into a liquid water again.
00:03:15.430 --> 00:03:17.360
So throughout the absorption chiller,
00:03:17.360 --> 00:03:19.380
we are gonna be boiling the water
00:03:19.380 --> 00:03:22.720
to create it into a steam and
then also be condensing it,
00:03:22.720 --> 00:03:24.610
turning it back into a liquid.
00:03:24.610 --> 00:03:28.110
And you'll see why that
is in just the moment.
00:03:28.110 --> 00:03:29.610
The second thing to understand
00:03:29.610 --> 00:03:33.890
is that lithium bromide is
a salt just in a liquid form
00:03:33.890 --> 00:03:37.970
and salt is attracted to water moisture.
00:03:37.970 --> 00:03:40.390
It literally pulls these
particles of moisture
00:03:40.390 --> 00:03:43.900
out of the air and is attracted
to it almost magnetically.
00:03:43.900 --> 00:03:48.720
So if we spray lithium bromide
onto the some water vapor,
00:03:48.720 --> 00:03:52.063
then the two will be attracted
together and will join.
00:03:53.460 --> 00:03:56.090
The third point to
remember is that when water
00:03:56.090 --> 00:03:58.480
and lithium bromide are mixed together,
00:03:58.480 --> 00:04:01.370
you can separate them
again just by adding heat.
00:04:01.370 --> 00:04:03.800
So as you apply heat to this,
00:04:03.800 --> 00:04:07.220
the two will separate where
the lithium bromide particles
00:04:07.220 --> 00:04:10.240
will become heavier and
so they will can condense
00:04:10.240 --> 00:04:15.240
and come towards the bottom
of the tank or the reservoir
00:04:15.460 --> 00:04:18.160
and all the water vapor will boil off
00:04:18.160 --> 00:04:22.350
and head upwards to become
steam or water vapor.
00:04:22.350 --> 00:04:25.133
So you can separate the two
just by applying some heat.
00:04:26.620 --> 00:04:28.900
Okay, so now that we know the very basics
00:04:28.900 --> 00:04:30.440
of what's happening inside,
00:04:30.440 --> 00:04:32.670
let's look at the main
components of there.
00:04:32.670 --> 00:04:36.410
So in the top chamber we'll
always have the condenser
00:04:36.410 --> 00:04:37.830
and the generator.
00:04:37.830 --> 00:04:39.700
In the lower half of the chiller,
00:04:39.700 --> 00:04:42.650
we'll always have the
evaporator and the absorber,
00:04:42.650 --> 00:04:45.310
and then on the side down, down below,
00:04:45.310 --> 00:04:48.200
near the bottom, we'll
also have a heat exchanger.
00:04:48.200 --> 00:04:49.380
The heat exchanger is just there
00:04:49.380 --> 00:04:52.140
to improve the efficiency of the system.
00:04:52.140 --> 00:04:57.030
So it will transfer heat that's
coming from the generator,
00:04:57.030 --> 00:04:59.220
into the liquid, which is
coming from the absorber.
00:04:59.220 --> 00:05:01.370
And we'll see that in just a moment.
00:05:01.370 --> 00:05:05.930
So first of all, a mixture
of around 60% lithium bromide
00:05:05.930 --> 00:05:09.730
and 40% water is pumped from the absorber
00:05:09.730 --> 00:05:11.330
through the heat exchanger
00:05:11.330 --> 00:05:14.400
and then rises up and pours
into the generator tank
00:05:14.400 --> 00:05:16.380
at the top of the chiller.
00:05:16.380 --> 00:05:19.730
Now this line is often referred
to as the weak solution line
00:05:21.400 --> 00:05:23.070
and that is because the lithium bromide
00:05:23.070 --> 00:05:25.863
is mixed with the water,
so it's a weak solution.
00:05:26.960 --> 00:05:29.350
The generator then fills
up with this mixture
00:05:29.350 --> 00:05:33.250
of lithium bromide and
water creating a reservoir.
00:05:33.250 --> 00:05:35.320
Next heat is added to the reservoir
00:05:36.320 --> 00:05:38.630
containing the lithium bromide and water.
00:05:38.630 --> 00:05:40.930
And this will begin the separation process
00:05:40.930 --> 00:05:42.310
that we saw earlier.
00:05:42.310 --> 00:05:44.950
And this heat is using
the form of waste heat
00:05:44.950 --> 00:05:47.980
and will typically come from a hot water
00:05:47.980 --> 00:05:51.210
or steam that's being pushed
around a heat exchanger
00:05:51.210 --> 00:05:54.510
of tubes inside the generator.
00:05:54.510 --> 00:05:55.770
The heat from this hot water
00:05:55.770 --> 00:05:58.680
or steam causes lithium bromide and water
00:05:58.680 --> 00:06:02.517
to separate all the water
particles will start to boil off
00:06:02.517 --> 00:06:04.450
and will fill the condenser
00:06:04.450 --> 00:06:06.773
with a hot water vapor or steam.
00:06:08.140 --> 00:06:10.460
Then the heavy lithium bromide particles
00:06:10.460 --> 00:06:14.263
will sink to the bottom and
form a concentrated liquid.
00:06:15.100 --> 00:06:17.780
This hot liquid flows
down to the heat exchanger
00:06:17.780 --> 00:06:22.780
where it transfers its heat
into the weak solution line
00:06:23.270 --> 00:06:25.080
running in counterflow.
00:06:25.080 --> 00:06:27.350
Once the concentrated
lithium bromide liquid
00:06:27.350 --> 00:06:30.490
has cooled down, it makes
its way to the absorber
00:06:30.490 --> 00:06:32.370
where it is sprayed onto the chamber
00:06:32.370 --> 00:06:34.220
and will mix with the water
00:06:34.220 --> 00:06:36.700
before again being pumped to the generator
00:06:36.700 --> 00:06:37.890
to repeat the loop,
00:06:37.890 --> 00:06:40.240
but we will look at
this part in more detail
00:06:40.240 --> 00:06:41.090
in just a minute.
00:06:42.320 --> 00:06:44.760
Next we want to condense
the hot water vapor
00:06:44.760 --> 00:06:47.740
in the condenser to bring
it back to a liquid.
00:06:47.740 --> 00:06:50.990
So we pass water in a sealed
pipe through the condenser
00:06:50.990 --> 00:06:54.000
and circulate it around
to the cooling tower
00:06:54.000 --> 00:06:55.900
where it will be able
to reject all the heat
00:06:55.900 --> 00:06:56.933
that it collects.
00:06:58.100 --> 00:07:00.330
The temperature of the cooling tower water
00:07:00.330 --> 00:07:03.200
is enough to cause the hot water vapor
00:07:03.200 --> 00:07:06.810
to condense into a liquid
as it comes into contact
00:07:06.810 --> 00:07:08.690
with the surface of the pipe.
00:07:08.690 --> 00:07:11.630
So it will rain down and
collect in the collection tray
00:07:11.630 --> 00:07:13.083
just below, just here.
00:07:15.000 --> 00:07:16.480
Once it collects in the tray,
00:07:16.480 --> 00:07:19.110
it will start to flow
down to the evaporator
00:07:19.110 --> 00:07:21.450
and will be sprayed into the chamber.
00:07:21.450 --> 00:07:23.520
The amount of water that can flow
00:07:23.520 --> 00:07:27.430
is restricted by a small
orifice in this pipe.
00:07:27.430 --> 00:07:29.660
Now the evaporator, as
we mentioned earlier,
00:07:29.660 --> 00:07:31.050
is a very low pressure.
00:07:31.050 --> 00:07:33.870
It's almost near a vacuum condition.
00:07:33.870 --> 00:07:35.920
Now this sudden change in pressure
00:07:35.920 --> 00:07:39.160
will cause that water that's
entering to suddenly flash
00:07:39.160 --> 00:07:41.920
and drop in temperature into a cold water
00:07:41.920 --> 00:07:44.250
of around just four degrees Celsius,
00:07:44.250 --> 00:07:45.743
maybe 40 degrees Fahrenheit.
00:07:47.240 --> 00:07:50.080
The chilled water loop then
runs into the evaporator
00:07:50.080 --> 00:07:52.530
bringing all the unwanted
heat from the building,
00:07:52.530 --> 00:07:55.130
which was collected from the AHUs
00:07:55.130 --> 00:07:57.180
and the fan coil units, et cetera.
00:07:57.180 --> 00:07:59.270
So this cold condensed water
00:07:59.270 --> 00:08:01.770
will spray over the chilled water tubes
00:08:01.770 --> 00:08:03.530
and cover the surface of the tube
00:08:03.530 --> 00:08:05.623
with a thin film of cold water.
00:08:06.930 --> 00:08:08.480
The chilled water will enter
00:08:08.480 --> 00:08:11.960
at around 12 degrees Celsius,
54 degrees Fahrenheit
00:08:11.960 --> 00:08:14.278
and this will transfer it's thermal energy
00:08:14.278 --> 00:08:16.240
its heat all the unwanted
heat from the building.
00:08:16.240 --> 00:08:18.870
It will transfer that
through the tube wall
00:08:18.870 --> 00:08:21.670
and into the low temperature water film
00:08:21.670 --> 00:08:23.760
which was sprayed across the outside
00:08:23.760 --> 00:08:25.830
of the chilled water tubes.
00:08:25.830 --> 00:08:27.630
Remember the two waters never mix.
00:08:27.630 --> 00:08:29.470
They're always kept separate
00:08:29.470 --> 00:08:32.690
and they are separated by the pipe wall.
00:08:32.690 --> 00:08:34.940
As this heat transfers into the water
00:08:34.940 --> 00:08:36.680
on the outside of the tubes
00:08:36.680 --> 00:08:39.400
this outer water will
evaporate into a steam
00:08:39.400 --> 00:08:43.270
or water vapor due to the
low pressure of the chamber.
00:08:43.270 --> 00:08:45.400
As it evaporates, it carries away
00:08:45.400 --> 00:08:47.760
all the unwanted heat with it.
00:08:47.760 --> 00:08:50.750
And remember earlier we
did learn how water boils
00:08:50.750 --> 00:08:53.143
at lower temperatures under low pressure,
00:08:54.000 --> 00:08:56.470
so the chilled water
circuit has now given up
00:08:56.470 --> 00:08:59.550
all the unwanted heat and by
the time it leaves the chiller,
00:08:59.550 --> 00:09:02.140
it should be around seven degrees Celsius,
00:09:02.140 --> 00:09:04.540
which is approximately
45 degrees Fahrenheit
00:09:04.540 --> 00:09:06.410
and this water is now ready to be pumped
00:09:06.410 --> 00:09:08.640
around the building again
to collect more heat
00:09:08.640 --> 00:09:11.073
and bring it back to
the absorption chiller.
00:09:12.140 --> 00:09:14.590
Another loop will recirculate any water
00:09:14.590 --> 00:09:16.970
that missed the tubes and
didn't boil off into steam
00:09:16.970 --> 00:09:20.040
or water vapor and this
will be be pumped back
00:09:20.040 --> 00:09:21.440
to the top of the evaporator
00:09:21.440 --> 00:09:23.250
and sprayed again and again and again
00:09:23.250 --> 00:09:25.563
until all of it evaporates into steam.
00:09:28.190 --> 00:09:30.650
All of this water that's evaporating
00:09:30.650 --> 00:09:33.110
into water vapor and steam will build up
00:09:33.110 --> 00:09:37.160
and collect in around
the evaporator chamber
00:09:37.160 --> 00:09:40.210
and this water vapor or
steam is then attracted
00:09:40.210 --> 00:09:43.310
and pulled towards the strong
lithium bromide solution
00:09:43.310 --> 00:09:47.430
being sprayed in the absorber,
almost like a magnetic force.
00:09:47.430 --> 00:09:49.600
The attraction is so strong
00:09:49.600 --> 00:09:51.910
that water particles flow by themselves
00:09:51.910 --> 00:09:53.340
straight to the absorber
00:09:53.340 --> 00:09:56.400
to be together with the
lithium bromide particles.
00:09:56.400 --> 00:09:58.570
This strong almost magnetic attraction
00:09:58.570 --> 00:09:59.837
between the water particles
00:09:59.837 --> 00:10:01.940
and the lithium bromide particles
00:10:01.940 --> 00:10:04.870
is what causes the vacuum in the chamber.
00:10:04.870 --> 00:10:07.940
The lithium bromide attraction
for the water is so strong,
00:10:07.940 --> 00:10:11.900
they will pull the water
particles inside its own fluids
00:10:11.900 --> 00:10:13.760
and it will all mix together.
00:10:13.760 --> 00:10:17.650
The stronger the concentration
of lithium bromide,
00:10:17.650 --> 00:10:20.793
the stronger the attraction
will be for water particles.
00:10:22.210 --> 00:10:24.040
When the two fluids come in contact,
00:10:24.040 --> 00:10:25.750
they generate a little heat.
00:10:25.750 --> 00:10:27.440
And this as well as the heat collected
00:10:27.440 --> 00:10:30.720
from the chilled water
loop needs to be removed.
00:10:30.720 --> 00:10:33.160
So that is why the
cooling tower water loop
00:10:33.160 --> 00:10:37.840
also passes through here to
take the unwanted heat away
00:10:37.840 --> 00:10:40.060
and the cooling tower
water will also condense
00:10:40.060 --> 00:10:43.150
any of the residual water vapor particles
00:10:43.150 --> 00:10:45.730
or the lithium bromide particles
00:10:45.730 --> 00:10:48.060
and turn it back into a liquid.
00:10:48.060 --> 00:10:49.480
And once this has occurred,
00:10:49.480 --> 00:10:51.530
the mixture of lithium bromide and water
00:10:51.530 --> 00:10:53.700
is collected at the bottom of the tank
00:10:53.700 --> 00:10:55.310
in the bottom of the absorber
00:10:55.310 --> 00:10:57.830
and it is now ready to be
pumped back to the generator
00:10:57.830 --> 00:11:00.180
again to repeat the entire cycle.
00:11:00.180 --> 00:11:01.013
So there you have it.
00:11:01.013 --> 00:11:02.070
That's the basics.
00:11:02.070 --> 00:11:05.073
The basic operation of how
an absorption chiller works.
00:11:06.370 --> 00:11:08.450
And that is the end of this video.
00:11:08.450 --> 00:11:09.340
So thanks for watching.
00:11:09.340 --> 00:11:10.900
I hope this has helped you.
00:11:10.900 --> 00:11:12.850
Please don't forget to
like subscribe and share.
00:11:12.850 --> 00:11:13.830
And if you have any comments,
00:11:13.830 --> 00:11:16.140
leave me in the comment section below.
00:11:16.140 --> 00:11:17.738
Also, don't forget to
check out our website,
00:11:17.738 --> 00:11:19.580
theengineeringmindset.com
00:11:19.580 --> 00:11:21.853
and once again, thanks
very much for watching.

Sales phone