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Heat Pumps Explained - How Heat Pumps Work HVAC



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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.

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Once again, thanks for watching.