Hey there guys Paul here from
TheEngineeringMindset.com. In this video we're going to be learning all about the different
types of chillers available, their applications, as
well as their limitations. Now before we jump in, I
just want to take a moment to thank our partner DanFoss
for sponsoring this video. DanFoss have been creating
solutions for chillers for a long time and
they have a broad range of high quality products
available for all chiller types. In fact, they have up
to 70% of the products you need for your chiller system, including compressors, a/c
drive system protectors, heat exchangers, valves,
electronics and sensors. All of these solutions help
you create better chillers from the inside out. To find out more visit
chillers.danfoss.com. If you're working within
commercial refrigeration, especially chillers or
you're about to start, perhaps you're a student or an apprentice, maybe you're a building
manager or an architect, etc., then you're going to hear
engineers say things like the recep, the turbo
call, the towers, etc.
You might not have any idea
what they're talking about. If so don't worry because by
the end of this video you will. Now we've covered how these chillers work in great detail previously, links are in the video description below and if you're not already a subscriber then hit the subscribe button now and we'll help you become an expert. Just to recap you on your
previous knowledge of chillers, chillers are simply machines
used to generate cold or chilled water, which is
distributed around buildings to provide air conditioning. They are also used in
some industrial processes, but we're going to primarily
focus on the application in air conditioning of
buildings within this video. As you can imagine there
are a lot of different types of chillers and they
are categorized by types, so it's important you
understand what the names mean, the differences between them,
when and where they are used, as well as why. The first way to categorize a chiller is by defining whether
it is a vapor compression or a vapor absorption type chiller. Vapor compression chillers use an electrically driven
mechanical compressor to force a refrigerant around the system.
These are the most
common type of chillers. There are two subcategories
for vapor compression chillers, which are water cooled
or air cooled chillers and we'll look at these both shortly. The other main category of chiller is the vapor absorption type. Instead of using an electrically powered mechanical compressor,
these units use heat to move the refrigerant around the system. Coming back to vapor compression chillers, the two main types we said were
air cooled and water cooled. Now both types of chillers have the same essential components, which are the evaporator, the compressor, the condenser and the expansion valve. When we talk about air or water cooled this simply refers to the way in which the unwanted heat is
ejected from the building via the chillers condenser. The working principle for both air cooled and water cooled chillers
is essentially the same. The compressor pushes a
refrigerant around the inside of the chiller between the condenser, the expansion valve, the evaporator, and back to the compressor. The only difference is that
with an air cooled chiller, fans force air across the
exposed tubes of the condenser, which carries the heat away.
Whereas with a water cooled chiller, this has a sealed condenser
and water is pumped through this condenser
to take the heat away and disperse this through
the cooling tower. A cooling tower we use a
fan to reject the heat also. So where are these
chillers typically used? Large buildings with
cooling loads in excess of around 400 tons or 1,400
kilowatts typically use water cooled chillers and they'll usually be centrifugal type or turbo coil type
compressors within the central plant cooling system. They might also use a separate
smaller air cooled chiller to handle the cooling
loads of critical rooms, such as computer and communication rooms. There might also be an absorption chiller within the central plant system making use of waste heat from
maybe a CHP engine for example but these are mostly used
alongside mechanical chillers.
Medium sized buildings with
cooling loads of around 200 to 400 tons or 700 to 1400 kilowatts will typically use screw compressors or turbo core compressor chillers. Now these chillers can
be either water cooled or air cooled and we'll look at why that would be just shortly. These types of buildings might also use an absorption chiller if
enough high-quality waste heat is available. Smaller buildings with
cooling loads of around 200 tons or less or 700 kilowatts will typically use scroll compressors or even turbo call compressors and these are mostly going
to be air cooled design.
Again we'll look at why
that would be just shortly. They might also use a
completely different system such as a VRF unit but this
really depends on the size of the building and the cooling load. If you have a building
with a medium to large cooling load then it's
recommended that you do not use only one oversized chiller to handle the entire cooling load. This is not efficient and if it fails you will have no cooling capability left. Instead you should use multiple
chillers in parallel of different sizes to meet
the changing seasonal load at optimal performance
redundancy built in. For example you have a
building with a cooling load of 2,200 tons then you
should use combinations such as two 1,200 ton chillers or two 900 and a 500 ton chiller or 1,000 ton and two 700
ton chillers etc., etc.
The options are almost limitless. You also need to consider the
criticality of the building and the redundancy required, which is known as the N plus number. Where the N is the number
of chillers you need and the plus 1, plus 2 or plus 3, etc. is the number of backup chillers you need to be able to continue to
meet a cooling capacity in the event of a failure. So that if any chiller fails you always have a backup
ready to come online and take over to handle the cooling load. You might need to use chillers
with multiple compressors that can work independently
from one another so that if one compressor fails then the chiller can still
remain partly operational.
Unfortunately many building
owners want the cheapest upfront option but this is a bad idea because for a little extra
they could have bought a more efficient chiller which
will be cheaper to operate especially as chillers last around 15 to maybe 25 plus years in operation. So it would have paid
for itself multiple times and would have resulted in
reduced environmental emissions. So how do you decide between
choosing an air cooled or water cooled chiller? Well this really depends
on a lot of factors so let's have a look at the
pros and cons for both of them. Now some of the pros for
using water cooled chillers is that water cooled chillers
are typically more efficient especially for larger cooling loads.
They use the evaporation of
water to dissipate the heat which is obviously going
to be less energy intensive than blowing air across a hot surface like air cooled chillers do. Water also has a higher
heat capacity than air so it's inherently easier
to remove the heat. Water cooled chillers can
also handle larger loads for their floor space that they
consume within the building. And water cooled chillers
generally last longer because they are held within the building so they're going to
deteriorate much slower. So some of the cons to
using water cooled chillers is that these type of
chillers use cooling towers and for this you need
access to a constant supply of clean water.
If the chiller is therefore
going to be installed in an area of water
restriction or conservation then you won't be able to
use this type of chiller. Water cooled chillers are
located within the building and they are very large machines so depending on the
compressor technology used they can create a lot
of noise and vibration inside the building, which is why they are usually
located in the basement. Water cooled chillers
do cost more to install and also to maintain. Water cooled chillers take
up space within the building, they need more mechanical
plant rooms, more risers, more pumps, more cooling towers and water treatment facilities. This space therefore can't then be used for business purposes. Let's now have a look
at air cooled chillers.
So some of the pros for
using air cooled chillers is that they cost less to install and that's because they
use less equipment. Air cooled chillers require less space, they can set up on the
roof or out in a car park and they do not need a mechanical room. This means more space within the building for business purposes. Air cooled chillers
require less maintenance compared to water cooled chillers, again because they have less equipment.
Air cooled chiller
systems are much simpler and easier to design and do
not need another set of pumps for the condenser loop. Some of the cons for
using air cooled chillers is that air cooled chillers
sit outside the building, their fans and compressors
will create noise which the surrounding areas
might be able to hear. Although some measures can
obviously be implemented to reduce this. Air cooled chillers typically do not have as long service life compared
to water cooled chillers because they are exposed
to the sun, the rain, the frost, the snow, the wind, etc.
And this will all
deteriorate the materials. Air cooled chillers can suffer
from blockages much easier. They can be damaged and
they can also suffer from things like recirculation issues. So let's now have a look at some of the different compressor technologies that are currently available. Centrifugal chillers are used
for water cooled chillers. It's incredibly rare that
you would come across an air cooled centrifugal chiller. They're usually medium
to large cooling loads, typically available from
150 up to 6,000 tons of refrigeration or 530
to 21,000 kilowatts. They have a COP of around 5.8 up to 7.1. Typically they'll use only one compressor, sometimes two for
exceptionally large capacities. They work best at full loading, although VFDs can be fitted to improve the part load performance. They'll use one or two rotating impellers to compress the refrigerant and force it around the chiller and the capacity can be
controlled through speed control as well as vane guides.
Turbo call compressors
represent the latest in chiller compressor technology and they are an evolution on
the centrifugal type compressor and this is definitely
something to keep an eye on as they are becoming more common and you're going to start to see these more and more in buildings. Turbo call compressors can be used for air or water cooled chillers and they are used in all cooling loads from large to small buildings. They are typically available
in 60 to 1,500 tons or 210 to 5,200 kilowatts. They have a COP of 4.6 even up to 10.
Have one or more
compressors which are used and they can be staged or
the speed can be varied. They have variable speed controllers, they have soft starters, magnetic bearings and only have one moving part. They are oil free and
very low maintenance. They use rotating impellers
to compress the refrigerant and the capacity can be controlled through speed control
as well as vane guides. Reciprocating compressors
were used for air or water cooled chillers, although this is an older technology which is far less common now. They're used in small
to medium cooling loads although now the technology
is much more common in simple smaller low-cost refrigerators and refrigeration systems. For chillers they are typically available from 50 to 500 tons or
170 to 1,700 kilowatts. They have a COP of around 4.2 to 5.5 and they use a piston and chamber to compress the refrigerant. The capacity is controlled
through the compressor staging, cylinder unloading as
well as the speed control.
Scroll compressors are used for air or water cooled chillers. They are used in small
to medium cooling loads, typically available from
around 40 up to 400 tons or 140 to 1,400 kilowatts. Air cooled chillers typically
have 3.2 up to 4.6 COP. Water cooled COPs might be 4.45 up to 6.2. They'll use one or more compressors which can be fixed or variable speed and they can be stage or speed controlled. They use two spiral plates
to compress the refrigerant. One will be fixed in place and the other one rotates. Capacity is controlled via
momentarily separating the scrolls in a solenoid valve
and electronic modulation. Screw compressors can be used on air or water cooled chillers and they are used in small
to medium cooling loads. They are typically available
in 70 up to 600 tons or 250 to 2,100 kilowatts. The air cooled screw compressors
will typically have a COP of around 2.9 up to 4.15. Water cooled will have
a COP of 4.7 up to 6.07. Typically they'll have one compressor on a water cooled chiller or one to two compressors
on an air cooled chiller. They use two interlocking
rotating helical rotors to compress the refrigerant and the capacity is
controlled via speed control or a slider.
Absorption chillers, now
these use heat to drive the refrigeration process. They usually use steam or hot water. They're used in medium to large buildings, such as hospitals, swimming
centers and heat networks. They're ideal for using waste
heat or at least cheap heat. And they're sometimes used to offset peak electricity cost. They typically are combined
with mechanical chillers though. Now typically you can buy
these from 70 to 1,400 tons or 250 up to 4,900 kilowatts. They have a very low COP of 0.6 up to 1.9. They have no compressor. They are either direct or indirect fired and capacity is controlled
simply by varying the amount of heat which
is entering the chiller. That about wraps things up but before I go I just
want to thank Danfoss one last time for sponsoring this video. Don't forget to check out their wide range of chiller solutions over
at chillers.danfoss.com. Thanks for watching, I hope this has helped
you and you've enjoyed it.
If so, please don't forget
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TheEngineeringMindset.com. Once again, thanks for watching..