So in air-conditioning, we think a lot about how to diagnose things, but often we don't necessarily think about what it is. We're diagnosing like what's actually going on inside the system, and one of the things that we gloss over a lot is what happens inside the compressor. What's really going on with the refrigerant, so we've got this image over my shoulder, which is sort of the sexy scroll compressor. That's the patent art for what's going on inside the compressor, and you can see that as it goes through the scroll compressor, it traps it and smaller and smaller areas until it finally discharges out the discharge line.

And so when we say a compressor, we're not talking about a pump, I mean it does move. So if you're thinking of pumping as moving refrigerant through the system, it does do that. But it does it by taking the refrigerant vapour from a larger volume and compressing it down to a smaller volume. So it really is compressing.

It's changing the volume that the vapor occupies, and I use a metaphor to explain. What's going on inside that compressor all the time, but before we get to that lets just think very practically. You have this cool suction gas if you've ever grabbed a suction line. You know that it feels cool.

It's it's lower than the ambient temperature and often it'll build up condensation because it's cool and it's below dew point. So you can grab that suction line. You say: okay, that's cool, and then it goes into the compressor and the moment that it comes out of that compressor. It is much higher temperature, and so we think to ourselves.

Well, there must be a lot more heat in the refrigerant and there is more heat in the refrigerant, but it's not necessarily the way that you think so. Let's break this down just think of a air conditioning unit for a typical house, so the air conditioning unit that runs in your house, you have an evaporator coil somewhere inside and air runs over that of a vertical and as air moves over that evaporator coil heat Goes out of the air and into the refrigerant and the evaporator coil, and it travels down the suction line, and it goes back to the compressor and so from a very practical standpoint. All of the heat that was removed from the home from your house is traveling down that suction line, but you'll notice that that suction line feels cool and this sort of blows some people's minds. But the reason why that is is because the evaporator coil is even lower temperature, so it's the temperature, the evaporator coil plus superheat, that's the section line temperature and so that evaporator coil has to be a low temperature in order for heat to go into that evaporator Coil her hot goes to cold, so heat from the house goes into that lower temperature of a per cool and then ends up travelling down that suction line.

But what blows everyone's mind is they expect that when heats been absorbed from something that it should feel cold and it doesn't now you go into the discharge line and now it's blazing hot, so it goes into the compressor, cold, low temperature. It comes out of the compressor, hotter or higher temperature, and so what's going on inside, that compressor is that compressor somehow, just because the compressor is hot, it's just making the refrigerant hot, and the answer is a little bit and with a refrigerant cooled compressor, but primarily, What's happening is something called heat of compression, so the suction gas travels down the larger suction line. It's a low temperature, but it contains all of the heat from the inside absorbed in the evaporator coil. It's then dumped down into the compressor body.

It cools the compressor and then it's pumped out of the compressor body down the discharge line and then back out. So this is the discharge line going this direction suction line going this direction. The compression occurs right in the top here. So let's talk about this.

In metaphor, so imagine the room that you're in right now, whatever room you're in it's got two four walls that surround you and then it's got the ceiling and now imagine that this room that you're in that you're occupying is full of ping-pong balls. And these ping-pong balls they bounce around perpetually they're always bouncing, and these ping-pong balls they signify molecules and so the energy that these molecules contain. That causes them to bounce around that's heat, but the speed that these molecules or ping-pong balls are moving at. That is temperature.

In fact, temperature literally is average. Molecular velocity talk about this, a lot on the podcast and in these videos. So when you feel something as hot, what you're really feeling is you're feeling those molecules bouncing around or vibrating very fast, and that thing that you touch when you touch that hot stove, you're literally saying you're, coming into contact with molecules that are bouncing around really fast And that causes the molecules and your fingertips to bounce around really fast, which can be quite uncomfortable, cause burns right. So when we experience temperature, we are literally experiencing the molecular velocity of whatever substance.

So this you know this little bottle of water here that we've got the temperature that I feel of this water. My fingers are experience through conductance the molecular velocity of the speed that the molecules are moving so back to our room. You know this room. It's full of these ping-pong balls that are bouncing amount of overall energy that they contain is the heat.

The speed that they're moving is the temperature and the ping-pong balls themselves are the molecules and in this case its refrigerant so now imagine that one of these walls begins moving in so imagine it's sort of like the scene from you know, Star Wars or the where The room is getting smaller and smaller and they start to be crushed right, and so, as this wall moves in what happens to these ping-pong balls, do they speed up or do they slow down this wall as it moves in, is working against the force of those Balls bouncing off of it and as it does that the speed of those balls as they bounce against the wall and against each other start to increase. The molecular velocity begins to increase of these ping-pong balls, and so what happens? Is the temperature increases because again remember molecular velocity is temperature, the same thing, and so that's what's happening inside of a compressor and if you think of this scroll compressor behind my shoulder here, it goes in as vapour, in fact how it really works inside of a Compressor is that suction line, the refrigerant drops into a refrigerant cooled, compressors, shell. It cools the compressor kind of mixes with the oil, and then it's pumped out into the head. Where then, it's discharged, and so there is some heat added from the compressor itself, to cool it from the windings and from the different parts inside there were the friction, the the bearings and all that there is some heat generated there, but really the bulk of that Temperature change that we're seeing from say on average, an air-conditioner and an average suction line.

Temperature would be to say 50 degrees and then coming out of the compressor you'll commonly see about 165 170 degrees. And so that's a significant difference in temperature, say 120 130 degree differential and that differential is representative primarily of that heat of compression, which is, as the compression chamber gets smaller and smaller. The molecules in there are bouncing faster and faster, just like. If you imagine that room with the wall moving in the ping-pong balls are moving faster and faster, and so are you changing the amount of heat? The answer is yes, you are because there is work, that's being done against the forces, but primarily what you're doing is by compacting them into a smaller space you're taking the heat that was already in that suction gas that already came from inside the house.

You're packing those molecules closer together and you're, revealing that heat in the form of temperature so way of thinking about this is, when you add sure you increase temperatures. This is part of the gas laws. When you add pressure, you increase temperature and by increasing temperature. Now we can get that heat back out of the refrigerant in the condenser.

So what does the compressor do? Well, the compressors obviously like we said it, causes the refrigerant to occupy a smaller space in doing so that increases the temperature and by increasing the temperature of that suction gas. Now we can get the heat back out because hot goes to cold. So that's what that compressor does in addition to that, like we said with refrigerant cooled compressors, which is the majority of what you work on, if you work in air-conditioning or small refrigeration, that suction gas also does serve to cool that compressor, but primarily what's happening. Is you have that heat coming down that suction line at a low temperature goes into that room? That then squeezes those ping-pong balls together? The molecular velocity greatly increases, and now we can run it into the condenser where we can remove the heat from it again and they slow back down again and can then turn into a liquid.

So that's just a basic look and that's one of my favorite metaphors to explain. What's going on to into an compressor, because when you sit in that room and you imagine those ping-pong balls bouncing around and that's the refrigerant molecules, it just gives you kind of a picture a way to envision. What's going on and just remember. In that metaphor, the ping-pong balls are the refrigerant molecules bouncing around and the speed that they're moving or the velocity that equals the temperature all right.

Thanks for watching we'll catch you in the next one.