Hey guys this is AC Service Tech and today what we're looking at is the basic
refrigeration cycle. Alright, so you can take this as looking at it as if it's a
it's a standard air conditioning system. Alright, so you have two items that
separate the low pressure and the high pressure on this system and the one is
the compressor that's up high and then the other is the metering device where
in this picture you see it's down low. So how the refrigeration cycle
works is it takes low pressure and low temperature vapor refrigerant, it comes
into the compressor, and out of the compressor it comes out as a high
temperature, high pressure vapor refrigerant. In fact it's at its hottest
spot on the entire system right there. As it enters into the condenser coil it
starts rejecting heat. As it rejects heat it starts turning into a saturated state
in the middle of the condenser coil. Alright, a saturated state is where vapor
and liquid both exist at the same time. So right there, right after the
saturated state where it turns into a complete liquid until where it comes out
right next to the service valve, the temperature decrease as its rejecting
heat, the temperature decrease in liquid form is called the subcooling.
The saturated state is is where it's transferring most of its energy at.
Alright, the refrigerant is what is carrying the heat and moving it,
rejecting it and absorbing it in the refrigerant itself. And most of that
energy transfer occurs right in that saturated state. Alright so it comes from
the saturated state in the middle of the condenser coil, it continues to reject
heat as a complete liquid, until it comes out of the condenser coil. Then it comes
down in the picture here and then it makes a left and then it goes in through
the filter dryer. The filter dryer is there to absorb any moisture in the
system. It has a fixed capacity and that's it. It goes through
that and then it hits the metering device. The metering device allows for a
pressure change. When you have a pressure
change so you have high temperature, high pressure liquid refrigerant coming into
the metering device and then it turns it into a low pressure then what happens is
it automatically makes it a low temperature as well. So if you decrease
temperature then pressure will decrease. If you decrease pressure then
temperature will decrease. So in this case we have a high pressure, high
temperature liquid refrigerant coming through and hitting the metering device.
The metering device is only going to allow a small amount through
and then it turns into a low pressure, low temperature eighty percent liquid
20% flash gas mix but it's mainly going to be a low temperature, low pressure
liquid until it gets to the middle of the evaporator coil. So the
refrigerant is actually absorbing heat once it enters into the evaporator coil.
As it absorbs enough heat it turns into that saturated state in the middle of
the evaporator coil, where most of the energy absorption is taking place
and then right after that is where it turns into a low pressure, low
temperature vapor. Right after the saturated state it turns into that low
pressure, low temperature vapor until where it comes out of the
evaporator coil. It's still absorbing heat. As it comes out of the evaporator
coil, right at that point right there, the temperature increase from the saturated
state in vapor right at the end of the saturated state in vapor to where it
comes out, that's called the superheat. If you continue along you keep coming up as
a low pressure, low temperature vapor. You come up and then you make a right
and then you come over to the service valve. So that's where we take
a superheat reading at. So if you took right in the middle of the
evaporator coil right after the saturated state where it turns into a
complete vapor the temperature increase from there, all the way over to the
service valve, next to the compressor that's called the total superheat.
After that it just enters back into the compressors and low pressure, low
temperature vapor refrigerant and the refrigerant cycle starts all over again.
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