Hey there guys. Paul here from theengineeringmindset.com. In this video we're going
to be discussing heat pumps, the different types and how they work. Coming up: How heat pumps work, air to air heat pumps, air to water heat pumps, ground source heat pumps, water source heat pumps, as well as animations and systems schematics for each of these. I just want to take a moment to thank our partner Danfoss
for sponsoring this video. A critical aspect of heat pumps is how energy-efficient they are, and Danfoss has everything
you need to make sure your heat pump is running at what they call 360
degree energy efficiency. They even built a heat pump website that has business cases,
case stories, e-lessons, and they even have a fun diagram, similar to the ones you
see on this channel, so you can see how it all comes together. Just click the link in
the video description below to see what 360 degree
energy efficiency is all about.
Okay, the first thing we're going to look at is the air to air heat pump. These are the most common heat pump types. They often look very similar to a standard air conditioning split unit, with the unit located outside
& another unit located inside. These can either work
as a heating-only device or, alternatively, the
more popular choice is to have a device which
can provide both heating or cooling by making use
of the reversing valve. We've covered reversing
valves in our previous videos. Links to that can be found in
the video description below. There are a few different ways to configure a reversing valve heat pump. I'll show you a simple, typical example. The main components we'll
have in this type of system are the compressor, the reversing valve, the indoor heat exchanger,
an expansion valve with a non-return valve bypass, a bi-directional filter drier, a sight glass, another expansion valve with a non-return valve and bypass. Then we have the outdoor heat exchanger. We also have a controller and a number of temperature and pressure
sensors around the system. In heating mode, the refrigerant
leaves the compressor as a high-pressure,
high-temperature vapour and passes to the reversing valve.
The reversing valve is
positioned in heating mode, so the refrigerant passes through this and heads to the indoor unit. Cool air is then blown over the
indoor unit's heat exchanger to remove some of the thermal energy and provide heating to the room. As heat is removed, the refrigerant will
condense into a liquid. Having given up some of its energy, the refrigerant leaves as a high-pressure,
slightly cooler liquid. The refrigerant then comes to the expansion valve and bypass. In this mode the
expansion valve is closed, so the liquid refrigerant passes through the non-return valve.
It then passes through the
filter drier and sight glass, and then passes to the
second expansion valve. It will then pass through
this expansion valve because the non-return valve on this side is preventing flow in that direction. As the refrigerant passes
through the expansion valve, the refrigerant expands in volume and turns into a part-liquid,
part-vapour mixture. This expansion in volume reduces the temperature and pressure. We've covered how thermal expansion valves and electronic expansion valves work in great detail in the previous videos. Do check those out. Links are in the video description below. The refrigerant then heads to
the outdoor heat exchanger. Here, a fan is blowing outside ambient air over the coil and adding
heat to the cold refrigerant. The refrigerant boils at
a very low temperature, and as it boils it will carry
away the thermal energy. As an example, we know that water will carry thermal energy
away as steam when it boils, and we know that it boils at 100 degrees Celsius or
212 degrees Fahrenheit. Well, if we then look at some
common heat pump refrigerants, R134a for example, has a boiling point of minus 26.3 degrees Celsius or minus 15.34 degrees Fahrenheit.
Refrigerant R410a has a boiling point of minus 48.5 degrees Celsius or minus 55.3 degrees Fahrenheit. So, it's very easy to
extract thermal energy even at very low outdoor temperatures. We've covered how refrigerants work, also in previous video. Again, links to that can be found in the video description below. So the refrigerant picks
up the thermal energy from the outside air and leaves
the outdoor heat exchanger as a low-pressure, low-temperature, slightly superheated vapour, and then heads back to
the reversing valve.
The reversing valve then diverts this to the compressor to repeat the cycle. If this system is then
switched into cooling mode, the system then acts like a
normal split air conditioner. The compressor forces the high-pressure, high-temperature vapour refrigerant
into the reversing valve The reversing valve diverts
this to the outdoor unit. The fan of the outdoor unit blows ambient air across
the heat exchanger.
This air will be a cooler temperature, so it carries the thermal
energy of the refrigerant away. The refrigerant condenses as
it loses its thermal energy. Having given up some of its energy, the refrigerant leaves as a high-pressure,
slightly cooler liquid. It then heads to the expansion
valve, but this is closed, so the refrigerant passes
through the non-return valve. It then passes through the sight glass and the bi-directional filter drier. The next non-return valve is then closed, so the refrigerant passes
through the expansion valve. As it passes through the expansion valve, the refrigerant changes to a part-liquid, part-vapour mixture, which causes it to drop in
pressure and temperature. It then flows into the
indoor heat exchanger.
And in here, a fan blows the
warm indoor air over the coil. This causes the heat to transfer from the air into the refrigerant, and so the refrigerant boils
and takes its heat away. The refrigerant leaves the indoor unit as a low-pressure, low-temperature, slightly superheated state and flows into the reversing valve. The valve diverts this back to the compressor to repeat the cycle. Air to water heat pumps: These units work in a very similar manner to air to air heat pumps, but without the reversing valve. The high-pressure,
high-temperature vapour refrigerant leaves the compressor, but this time it heads into
a plate heat exchanger.
On the other side of the
plate heat exchanger, water will have been cycled through a hot water storage tank. Cooled water enters the heat
exchanger from the tank, and as it passes through
the heat exchanger, it absorbs heat from the hot refrigerant. The water will then leave
at a much hotter temperature and flow back to the hot water storage
tank to repeat this cycle. As the refrigerant gives
up its heat to the water, it will condense and it will
then leave the heat exchanger as a high-pressure,
lower-temperature liquid. We've covered how heat exchangers work in our previous videos. Links to these can be found in the video description below. The refrigerant then passes through the filter drier
and the sight glass, and then into the expansion valve.
The expansion valve causes the refrigerant to become part-liquid, part-vapour state. It'll be at a low
temperature and pressure. It then passes through the
outdoor heat exchanger, where the outdoor ambient air causes the refrigerant to boil. The refrigerant then
leaves at a low-pressure, low-temperature, slightly
superheated vapour and is then sucked back
into the compressor to repeat the entire cycle again. The hot water tank then provides hot water to the radiators, sinks, and
showers within the building. Ground source heat pump: There are two main types of
ground source heat pumps, that being the horizontal
and the vertical type. Both essentially work the same, it's just how they access the heat in the ground that varies. We'll look at when to
use the different types as well as the pros and cons
to these in our next video. This video, we're just gonna
focus on how they work. Ground source can be used
for heating air or water.
In the air type system, the heat pump can also have a reversing valve and then supply either heating or cooling. In both cases, the outdoor heat exchanger can be a plate heat exchanger with the refrigerant passing on one side and a mixture of water and antifreeze cycling on the other side. The water and antifreeze mixture is forced by a pump around the
pipes within the ground. This will allow it to
pick up the thermal energy in heating mode and bring
this to the heat exchanger. The refrigerant on the other
side of the heat exchanger absorbs the heat because it
has a very low boiling point, so as it boils it carries the heat away, which can then be used
within the building. In the air type system, there
can be a reversing valve. This will allow the refrigeration system to pull unwanted heat out of the building and transfer this into the
water-antifreeze mixture.
This water will then be pumped around the pipes in the ground, and it will transfer the
heat into the ground, thus returning cooler,
ready to pick up more heat. Water source heat pumps: Water source heat pumps
come in two main variations, closed and open loop. The closed loop sends a
mixture of water and antifreeze to collect thermal energy
from a pond or river, and transfers this through
the heat exchanger. The same water is then sent round again to repeat the cycle. Open loop pulls in fresh
water from an aquifer or from a river and pumps this into the heat exchanger
to collect the heat. Once it passes through, it is then released back
into the same water source. In a closed loop type, a
water and antifreeze mixture cycles around the pipes to
collect the thermal energy and bring this to the heat exchanger, where the refrigeration system will then would absorb the energy
and use it for heating. Alternatively, it will dump
the building's unwanted heat into the water-antifreeze mixture to provide cooling for the building.
The unit then works the same
as a ground source heat pump. In an open loop type, the
water is pulled in via a pump and sent directly to the heat exchanger. The heat exchanger then
pulls the thermal energy out of the water, or it dumps the unwanted
heat into the water. The water then passes
through the heat exchanger and returns to the source
some distance apart.
Before I wrap things
up, I just want to thank Danfoss one last time for
sponsoring this video. Don't forget to check out
their heat pump solutions by clicking on the link in
the video description below. Okay guys, that's it for this video. Thank you very much for watching. And I hope you enjoyed
this and it has helped you. If so, don't forget to
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