I am studying hvac and was having problems with this area. But, doggonit you explained everything I need to know and more in 6 minutes. Great job soldier!!!
This was great, I’m in school and fell a little behind in all honesty and Im set graduate in 4 and a half months. Getting back into a studying routine which is a bit hard for me but taking notes on your video helped tremendously! Love the content!
Brian, I have a question for you. Ever since I started HVACR school August 18th of this year (2022), the entire process of the refrigeration cycle has really intrigued me. So much, in fact, that something in particular has been bothering me lately, and, for some reason, my own instructor has been unable to answer. This is what I have gathered so far: Going into the metering device is 100% liquid. Coming out of the metering device is a mixture of about 80% liquid, and about 10% vapor. How is it that the refrigerant turns into a mixture of liquid and vapor after it passes through the metering device if the metering device is reducing the pressure of the refrigerant (which, in turn, reduces its temperature)? Wouldn't reducing the temperature of a liquid refrigerant even further actually prevent it from turning into a vapor, and allow it to maintain its liquid state? After all, in order to cause a refrigerant to turn into a vapor, you would have to increase its temperature? Why is this confusing me?
It's confusing because it was oversimplified. It's actually an equation with three variables: PV = nRT. Generally you have to hold something constant to make sense of it. Check out a phase change diagram. A liquid can become a gas by heating it, OR by dropping the pressure on it. In a thermostatic valve, temperature is held constant (thus, "thermo-static") and pressure is decreased until the refrigerant is at the "critical line", right on the edge between liquid and gas. This is also called saturation temperature. Saturation depends on pressure; it's what that line is. So at this lower pressure, it's saturated now, and only takes a little bit of energy to turn the liquid into a gas, which is very energy efficient. Why does this happen? A liquid is a bunch of molecules bumping around, everything straining and struggling against each other to move. When parts of it boil, what's happening is those molecules got so much energy that they pushed everything around them away, and made personal space for themselves, a big empty area, called a bubble. The liquid is trying to close in on it, but the gas is too energetic and holds it back on all sides. Making it more energetic - ie, hotter - increases the strength and size of the bubble, but so does making the LIQUID WEAKER. If you decrease the pressure holding down the liquid, the liquid isn't pressing on itself so hard, and it's easier for bubbles to form with less energy. It doesn't have to try as hard to form some personal space. So increasing the volume decreases the pressure, and at that temperature and lower pressure, some of the molecules are able to escape the liquid's confinement and become vapor.
This are great type of video explanations. Thank you. I wish u can find someone that can animate your explanations in 3d or 2d to animate. That will be great
I just bought a new Goodman Evap Coil and it didnt come with a TXV valve. I saw you didnt install one either, do I not need one? its a 4-5 ton unit for r410a , model is chpf4860d6. I appreciate any tips, thank you!
Thanks for the useful content Bryan! I subscribed to your channel already. I have a question, can the TXV really control the needed pressure to meet the evaporator's pressure? is there any possibility that the TXV will feed too low pressure to the evaporator?
Lol rip you, buddy. But also rip me. Rip all of us. What a disaster.. pour one out for all the boys who didn't make it, and all the dreams that didn't make it either, because of that damn virus.
Is the metering device dropping the pressure of the sub cooled refrigerant and allowing it to cool even more or is it dropping the pressure of the the super heated vapor and allowing it to reach its condensing point?
I get the pressure dropper, but doesn't it also help increase the pressure? without the restriction the compressor would just pump. Think about the indoor metering device in heat mode.
Yes, because PV = nRT. So if Pressure goes up, Temperature goes up. The condenser only works because the refrigerant is colder than the air of the room it's trying to cool. If the refrigerant is already hot, then there's less room for it to take on heat before it evaporates. It still takes on heat as a vapor, but slower than as a liquid, so this is bad. now you're removing less heat from the room per cycle, so it's running hot.
Is it possible that the expansion valve fully closes to prevent refrigerant liquid flood back to the compressor when the evaporator coil has less heat load?
Being called a 'metering device' makes it sound as if measurement is the primary purpose of this component, because everyone thinks of a meter as a visual indicator. But as a pressure reduction device, shouldn't this vital component be called the pressure reducer, or just the 'reducer'? That would make so much more sense to apprentices, I would have thought.
Also it's really bad for the life of the valve. Water has the wrong material properties (heat capacity), and hose water usually carries little bits of unpurified dirt and impurities that will clog up the valve, and the rest of the line, and decrease heat transfer abilities.
You are not able to speak to the basics of something in such a simplistic and accurate way unless you have an overwhelming amount of knowledge and experience to allow you to describe something a layman can understand.
Can anyone explain to me how liquid enters the metering device, drops in pressure and becomes 25% vapor and 75% liquid? Drop in pressure is a drop in temperature so how does vapor result?
Correct me if I'm wrong: Should be the drop in pressure from the liquid going into the evap causing it to 'flash'; Quickly becoming part vapor & turning 100% as it exits the evaporator. Vapor results from the heat the refrigerant picked up being evaporated.
Check out a phase change diagram. As pressure decreases, liquids turn into gasses. They also turn into gasses when you increase temperature. It depends on the non-ideal gas formula: (P+ (n^2 / V^2)) * (V-n) = nRT. It's an equation with two variables. Generally in thermo we try to hold one of them constant. That's why the thermostatic valve is called a thermo STATIC valve - it's designed in such a way that refrigerant temp remains reasonably constant. So when you hold temp constant, and decrease pressure, it passes over a critical point and partially vaporizes. High pressure liquid -> decrease pressure -> partially vaporizes The same happens when you go: High pressure liquid -> increase temp -> partially vaporizes. If you decrease pressure (by increasing the chamber) and increase temp (with an electric heater), it vaporizes even faster. Why does this happen? Because "low pressure material" is what a gas IS. Boiling happens when molecules have enough energy to push everything around them away and form bubbles and escape. Increasing the temp gives them more energy, but decreasing the pressure decreases the thing they're working AGAINST, because pressure is what's holding them in.
![FNAF vs TF2 - Episode 2 [SFM]](http://i.ytimg.com/vi/z5b3V2-VLb0/mqdefault.jpg)
I really like this series of videos. I’ve been playing them for my apprentice while we’re driving, then having a follow up discussion.
Well thanks buddy
Haha I do the same. Keep up the good work!
I am studying hvac and was having problems with this area. But, doggonit you explained everything I need to know and more in 6 minutes. Great job soldier!!!
Wait til he shows you the back of his bald head..... oh boy!
you still in or you working something else?
This was great, I’m in school and fell a little behind in all honesty and Im set graduate in 4 and a half months. Getting back into a studying routine which is a bit hard for me but taking notes on your video helped tremendously! Love the content!
Last night was my 2nd HVAC class and now this and other videos don’t seem like a foreign language. Can’t wait to get to this money!
Where are you taking your classes?
Thanks for u good work I listen to u podcast wen I drive to LA to visit my grandson 5 hours drive and it make it very enjoyable,
Neil it's Great way how you are
Explaining metering devices and
Superheat.
I just found your content and I am looking forward to checking out more. Thanks for sharing.
Thank u for this video. Opened my understand of a txv also the metering devices
Best explanation on RUclips, thanks.
Great series, hope to see more!
Brian, I have a question for you.
Ever since I started HVACR school August 18th of this year (2022), the entire process of the refrigeration cycle has really intrigued me. So much, in fact, that something in particular has been bothering me lately, and, for some reason, my own instructor has been unable to answer.
This is what I have gathered so far:
Going into the metering device is 100% liquid. Coming out of the metering device is a mixture of about 80% liquid, and about 10% vapor.
How is it that the refrigerant turns into a mixture of liquid and vapor after it passes through the metering device if the metering device is reducing the pressure of the refrigerant (which, in turn, reduces its temperature)?
Wouldn't reducing the temperature of a liquid refrigerant even further actually prevent it from turning into a vapor, and allow it to maintain its liquid state? After all, in order to cause a refrigerant to turn into a vapor, you would have to increase its temperature?
Why is this confusing me?
It's confusing because it was oversimplified. It's actually an equation with three variables: PV = nRT. Generally you have to hold something constant to make sense of it. Check out a phase change diagram. A liquid can become a gas by heating it, OR by dropping the pressure on it. In a thermostatic valve, temperature is held constant (thus, "thermo-static") and pressure is decreased until the refrigerant is at the "critical line", right on the edge between liquid and gas. This is also called saturation temperature. Saturation depends on pressure; it's what that line is. So at this lower pressure, it's saturated now, and only takes a little bit of energy to turn the liquid into a gas, which is very energy efficient.
Why does this happen? A liquid is a bunch of molecules bumping around, everything straining and struggling against each other to move. When parts of it boil, what's happening is those molecules got so much energy that they pushed everything around them away, and made personal space for themselves, a big empty area, called a bubble. The liquid is trying to close in on it, but the gas is too energetic and holds it back on all sides. Making it more energetic - ie, hotter - increases the strength and size of the bubble, but so does making the LIQUID WEAKER. If you decrease the pressure holding down the liquid, the liquid isn't pressing on itself so hard, and it's easier for bubbles to form with less energy. It doesn't have to try as hard to form some personal space.
So increasing the volume decreases the pressure, and at that temperature and lower pressure, some of the molecules are able to escape the liquid's confinement and become vapor.
Great explanation
This are great type of video explanations. Thank you. I wish u can find someone that can animate your explanations in 3d or 2d to animate. That will be great
I would honestly be down to do that =)
I just bought a new Goodman Evap Coil and it didnt come with a TXV valve. I saw you didnt install one either, do I not need one? its a 4-5 ton unit for r410a , model is chpf4860d6. I appreciate any tips, thank you!
Thanks for the useful content Bryan! I subscribed to your channel already. I have a question, can the TXV really control the needed pressure to meet the evaporator's pressure? is there any possibility that the TXV will feed too low pressure to the evaporator?
Nice job and video
now I know a bit about meetering devices. This will help me when I start classes up in May....provided this covid-19 dies down :/
Lol rip you, buddy. But also rip me. Rip all of us. What a disaster.. pour one out for all the boys who didn't make it, and all the dreams that didn't make it either, because of that damn virus.
Which book will you “HVAC School” recommend for self-teaching the hvac field for apartment complex industry
Great videos, thanks man!
Is the cause for that boiling that happens across the metering device the increase in back pressure?
Why two inputs from the suction line into the Thermostatic Expansion Control valve?
How does a capillary tube maintain superheat of a refrigerant at the outlet of an evaporator that has a very low heat load?
Is the metering device dropping the pressure of the sub cooled refrigerant and allowing it to cool even more or is it dropping the pressure of the the super heated vapor and allowing it to reach its condensing point?
It goes: hot gas -> meter -> cold gas, and it does that by dropping the pressure of the hot gas. PV = nRT
Superheated -> expansion valve -> supercooled
When a gas expands, it gets colder. When it compresses, it gets hotter.
I get the pressure dropper, but doesn't it also help increase the pressure? without the restriction the compressor would just pump. Think about the indoor metering device in heat mode.
I don't know what you mean by this
Can overfeeding an evap cuase high temp in a freezer? Since the pressure would go up.
Yes, because PV = nRT. So if Pressure goes up, Temperature goes up. The condenser only works because the refrigerant is colder than the air of the room it's trying to cool. If the refrigerant is already hot, then there's less room for it to take on heat before it evaporates. It still takes on heat as a vapor, but slower than as a liquid, so this is bad. now you're removing less heat from the room per cycle, so it's running hot.
Thank you
Is it possible that the expansion valve fully closes to prevent refrigerant liquid flood back to the compressor when the evaporator coil has less heat load?
Yes, depending on design of the valve.
So the compressor make the volume small which make it hotter and the meter device make the volume bigger so the temperature can drop???
yes! good job
txv - super heat axv - low side pressure?
Useful. Thanks
Does replacing a fixed orifice to a TXV increase the seer
It can in some load conditions but generally it won’t make a huge difference in EER and therefore SEER
@@HVACS thanks
Nice
I head superheat is the added heat after saturation is that correct?
Superheat is the number of degrees F above saturation temperature. It's like "left over" heat.
Being called a 'metering device' makes it sound as if measurement is the primary purpose of this component, because everyone thinks of a meter as a visual indicator. But as a pressure reduction device, shouldn't this vital component be called the pressure reducer, or just the 'reducer'? That would make so much more sense to apprentices, I would have thought.
Yeah. It does also have a meter on it, though.
😁👋👌😄😁😎😎🌴🌴🌴 thank you for making videos!👍👍👍
Can you run hose water through this valve?
Yeah but it will probably rust
Also it's really bad for the life of the valve. Water has the wrong material properties (heat capacity), and hose water usually carries little bits of unpurified dirt and impurities that will clog up the valve, and the rest of the line, and decrease heat transfer abilities.
your just awesome !
I’m just s regular guy but I’m glad you enjoy the videos
You are not able to speak to the basics of something in such a simplistic and accurate way unless you have an overwhelming amount of knowledge and experience to allow you to describe something a layman can understand.
That's not true, but it is true he has an enormous amount of knowledge.
🙌🤘🙌
Can anyone explain to me how liquid enters the metering device, drops in pressure and becomes 25% vapor and 75% liquid?
Drop in pressure is a drop in temperature so how does vapor result?
Correct me if I'm wrong: Should be the drop in pressure from the liquid going into the evap causing it to 'flash'; Quickly becoming part vapor & turning 100% as it exits the evaporator. Vapor results from the heat the refrigerant picked up being evaporated.
Hey buddy good question I'm trying to figure out the same thing lol . Did you figure it out ? Please let me know
Check out a phase change diagram. As pressure decreases, liquids turn into gasses. They also turn into gasses when you increase temperature. It depends on the non-ideal gas formula:
(P+ (n^2 / V^2)) * (V-n) = nRT. It's an equation with two variables. Generally in thermo we try to hold one of them constant. That's why the thermostatic valve is called a thermo STATIC valve - it's designed in such a way that refrigerant temp remains reasonably constant. So when you hold temp constant, and decrease pressure, it passes over a critical point and partially vaporizes.
High pressure liquid -> decrease pressure -> partially vaporizes
The same happens when you go:
High pressure liquid -> increase temp -> partially vaporizes.
If you decrease pressure (by increasing the chamber) and increase temp (with an electric heater), it vaporizes even faster.
Why does this happen? Because "low pressure material" is what a gas IS. Boiling happens when molecules have enough energy to push everything around them away and form bubbles and escape. Increasing the temp gives them more energy, but decreasing the pressure decreases the thing they're working AGAINST, because pressure is what's holding them in.
lose control? that mean system breaks? 6:20
Comment for the algorithm