Hey thanks for watching this quick video is on the evaporator and the evaporator is probably, I don't want to say it's the most important component, because every component is critical to the operation of the basic refrigerant circuit. But it is the component that does the thing that we most relate to with air conditioning and refrigeration, which is, it is the part that absorbs heat. We would often think that the evaporator is the part that makes cold, but, as often is a you know, beat to death in the HVAC industry. You can't make cold cold is the absence of heat or a differential between something that is hotter and something that is colder.

It's an it's an explanatory word that we use. We call something cold, we're just saying it's cold in relationship to the temperature of our skin or the temperature that we would like it to be outdoors or whatever the case may be, but the evaporator, for all intents and purposes as far as we're concerned is cold. If you touch most of Aperta calls, they feel cold on air conditioners. The evaporator coils under normal sort of rated conditions are about 40 degrees Fahrenheit and, of course, that does vary depending on load conditions and in freezers.

You can get evaporator coils all the way down to minus. You know 30 minus 40 degrees, depending on the situation. So we have evaporator coils that are a wide range of temperatures, but they are all almost all as far as we're concerned cold. But when something is cold, that means it's a lower temperature than something else, so that way heat moves into it, which is why, in my basic refrigeration description, I talked about the evaporator as being the heat absorber, it pulls in heat and that's really what we're trying To do when we're attempting to cool something, because we make the evaporator coil of a lower temperature than either the room of the box, the air going over it.

So that way, heat goes out of that room or that refrigerator box or that freezer and the heat is attracted into that of Africa. Coil and often for most of the typical basic systems. We're working on we're just flowing air over the evaporator coil over those fins. On that evaporator coil and then, as it passes across that metal and the refrigerant moves through it's absorbing heat through the metal into the refrigerant, the fins on those coils.

That you'll often see act as additional surface area. To help give it a little bit more contact time so that, as that airs passing over, it has more contact time on the metal. So that way, that refrigerant inside that evaporator coil can absorb heat, and we like we talked about before the reason why the evaporator coil is cooler than lower temperature than the other components is because there's a pressure drop right before it. We're going to talk about the metering device separately, but the metering device provides a pressure drop going into the evaporator coil and so that evaporator coil can be a lower temperature.

The reason why we call it an evaporator coil is because the refrigerant inside boils or evaporates, and those two words don't mean exactly the same thing. I would rather that it was called the boil Raider instead of the evaporator, but if you remember it as a boiler ater that might help you remember what it does, because what's going on inside, there is the rapid change from liquid to vapor State. So it's a it's, this change from liquid to vapor right when it comes out of that metering device. It already has flashed off some of that refrigerant from liquid to vapor a lot of time.

A lot of books will say: you know approximately 70 to 30 percent. So 70 percent would be liquid. 30 percent would be vapor when it enters that evaporator coil, but that varies quite a bit and there's a lot of conditions that impact that but right as Ann enters, the evaporator coil, its are automatically changing state and it's boiling. If you imagine what water looks like when it boils in a pot, that's very similar to what its gon na look like as its flowing through the lines, it's gon na, be that changing state there's gon na, be you know, bubbles forming in it as it's boiling Going through that evaporator coil, now that's sort of blows our minds, because we imagine that's things that are boiling are hot and the only reason we imagine.

That is because the only thing we observe boiling in our day-to-day lives is water and water does boil at a high temperature compared to our skin at atmospheric pressure, 212 degrees, Fahrenheit or a hundred degrees Celsius is what water boils out at atmospheric pressure, whereas most the Refrigerants we work with, they boil at very low temperatures at atmospheric pressure. In fact, we have to kind of pressurize them above atmospheric pressure in order to manipulate them to boil at the temperatures that we want. So am i manipulating the pressure we can manipulate the temperature of that evaporator coil, you imagine this boiling refrigerant moving through it. We can manipulate the temperature at which it's changing State.

By manipulating the pressure like we talked about before higher pressure equals higher temperature. Lower pressure equals lower temperature, and that's also true, when you're dealing with what we would call a saturated refrigerant. That means that it's part liquid in part vapor together at this place at the same time otherwise known as boiling or condensing inside the evaporator coil it's boiling. It's changing state from liquid to vapor, like I said, fairly rapidly, as it circulates through the system now, just like sort of the opposite of the condenser, where we talked about how the refrigerant goes in the top and then as it becomes a liquid and kind of Settles down, it goes down to the bottom on an evaporator coil, we're generally gon na feed it into the bottom and then, as it boils off to a vapor.

It's gon na come out the top so generally you'll notice that if Africa cools are fed with that boiling liquid refrigerant in the bottom and then the refrigerant comes out the top and then feeds down the suction line. It's very important in air conditioning that we control that temperature of the evaporator coil and keep it above the freezing temperature, because most air conditioners don't have any way of defrosting. So we've got to keep that coil surface temperature above 32 degrees to ensure that we don't start to build up, frost and ice now in practicality. You can actually get it a little below 32 and not have Frost, because there's a slight difference between the temperature of the refrigerant inside the coil and the actual surface temperature of the metal on the coil.

There's just like variance there and then also. If you have to have sufficient moisture and sufficient dwell time and order for it to start to freeze, so that's why, in a lot of arid environments, people won't get the same types of frost patterns that we get down in Florida, where we have very high relative Humidity and so there's different air flows that are needed in different circumstances, but regardless we generally want to keep that evaporator coil above 32 degrees Fahrenheit, so that we do not build up frost on that coil juxtapose that to say a freezer where we obviously have to Get that evaporator coil below 32 degrees temperature. Otherwise we would not get the product below 32. It wouldn't be a freezer unless it was below 32.

In fact, a lot of freezers are minus 10, minus 20 degrees Fahrenheit, and so you have to have an evaporator coil that is lower than the temperature of that desired temperature of the box or of the product inside the box. So if you open up the freezer at home - and let's say that it's minus 10 degrees inside that freezer, you have to have an evaporator coil, that is at least -9 degrees. Otherwise, heat isn't gon na move out of that box into that of Aperta quele, like we said, the evaporator coil is the heat absorber and it must be lower temperature than the air that's passing over it or than the space that it's in in the case of In the case of a freezer or a refrigerator in practice, you're actually gon na see more like a 10 to 20 degree. Lower temperature of a participation x' again very much depends on the particular equipment in order to absorb heat out of that space effectively.

So what we're doing with an evaporator coil, what we really care about, is we care about making sure that we control the temperature to the temperature that we want that of a protocol to be, and we also have to ensure that we flow refrigerant, let boiling liquid Refrigerant through most of the coil now the last part of the coil is what we call the super heating phase. If you remember what we talked about the condenser, you have D super heating, then you have condensing the change of state from vapor to liquid, and then you have sub cooling and an evaporator coil. You have the boiling phase or the flash gas or whatever you want to call it the the point at which it's changing state, its saturated state, it's boiling and then at the end you have the super heating phase. Super heating can only happen when it is fully vapor and, as that refrigerant finally makes its way all the way through that coil.

At the end, it's going to be fully vapor and that's when we, when you get further on and you learn what superheat is. That's all superheat is it's just using temperature and pressure in order to tell us how far through that evaporator coil that liquid refrigerant is boiling. So how long through that evaporator coil? Is that there's still some liquid, it's gon na start off at say 70 percent liquid refrigerant and then it's gon na go to a 60 50, 40, 30, 10 and then finally, we'll go to zero percent liquid refrigerant. And that's when we can start to superheat, that's when that temperature can start to rise, so we're gon na control, the temperature of that boiling through that evaporator coil through pressure, and then we're also going to control how far through the coil we're feeding the refrigerant.

Now everything in the air conditioning refrigeration system affects everything else, so the amount of refrigerant how well the compressor is moving that refrigerant. How well it's circulating it if it's compressing properly, whether or not your condenser coil is dirty or has problems or whether or not the airflow moving over. That of a protocol is too low. There's all kinds of factors that impact count of a protocol absorbs heat, but remember that when we're attempting to cool something.

That really is the point. So it's very important that we get all the situations correct. So that way we have a proper evaporator temperature and so that way we're feeding that boiling liquid refrigerant through the bulk of that coil till we hit what we call our target superheat the point at which it's it's designed to become a vapor before it goes back To that compressor again, because that compressor is a vapor pump. What's the point here, the point is: is that we have to control that temperature? How far it feeds through one thing about the evaporator coil itself is that we are moving the right medium across it.

Medium can be air or water or whatever it is that were cooling and that we're moving it across in the correct rates. So, for example, the really common example of this would be having a dirty air filter. If you have a dirty air filter, then there's not enough air moving over that of a protocol that evaporator coils job is to remove heat from the air and if there's not enough air, then there's not enough heat and the pressure in that evaporator coil will begin To drop and that's why you will find often that air conditioners that freeze up or even coolers or freezers that are freezing up too much many times, that's due to low air flow. So we have to control that airflow moving over that coil.

If it was a chiller where it was cooling water, then you'd have to control the amount of water that was moving across it because remember the evaporators job is to absorb heat. So we have to give it the right amount of heat for it to absorb for it to function properly. So that is just a very quick introduction. I could sit here and talk for hours about evaporator coils, but hopefully that gave you a sense of the evaporator coil.

The heat absorbing component of the basic refrigerant circuit will get you on the next video you.