Evaporator 101
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- Опубліковано 2 сер 2024
- In this quick Evaporator 101 talk, Bryan covers the basic purpose and function of the evaporator coil in the air conditioning system.
The evaporator is the heat absorber, and it's the component that many of us associate with HVAC; A/C units don't make cold air, but they remove heat from the air. A/C evaporators are typically cold, with the coil generally having a temperature of 40 degrees Fahrenheit (with some refrigeration evaporators being as cold as -40 degrees). The temperature is relatively low so that heat can move into the refrigerant with the evaporator.
Many evaporators have fins that increase the surface area, which gives air more contact time and enables heat transfer into the refrigerant within the coil. Generally, the refrigerant will enter the evaporator from the bottom and exit through the top as a gas; from there, it goes down the suction line.
Before the evaporator coil, a metering device drops the pressure of the liquid refrigerant. That's what allows the evaporator to be relatively cool (compared to the relatively warm liquid in the condenser bottom and liquid line). The metering device also flashes off some of the liquid refrigerant and makes it become a vapor.
When the refrigerant absorbs heat inside the evaporator, there is a rapid change from the liquid state to the vapor state, which is called boiling. This boiling isn't actually hot; refrigerants have very low boiling points compared to water (which is what many of us have observed boiling). As such, we even have to manipulate refrigerant pressures to get them to boil at a temperature as high as 40 degrees. During the phase change from liquid to vapor, the refrigerant is at saturation and maintains a constant temperature until it has completely boiled.
We generally want to keep A/C evaporator coils above 32 degrees Fahrenheit (0 degrees Celsius), as water can freeze on the coil. Frost and ice buildup on the coil reduce the efficacy of heat transfer. Freezers need to have far colder evaporator coils, as heat needs to be able to move into the refrigerant even at a low temperature. Those coils will freeze, but refrigeration systems also rely on defrost strategies to melt ice off the coil.
Our goals are to control the temperature and feed most of the coil with boiling liquid refrigerant. The last (top) part of the coil is where superheating happens; the refrigerant has become 100% vapor, and the temperature begins to rise. We can measure the superheat to determine how far we're feeding that coil with liquid refrigerant. Reaching our target superheat would indicate that we're feeding the coil with the ideal amount of boiling liquid refrigerant.
We also need to make sure we're moving the correct medium (usually air, sometimes water) across the coil at the correct rate. For example, a dirty air filter can prevent the right amount of air from moving over a coil. If there's not enough air, then there's not enough heat, so the pressure will drop (and may lead to a frozen coil).
Read all the tech tips, take the quizzes, and find our handy calculators at www.hvacrschool.com/
Another excellent video
Make it simple human understand your topic
Just want to say as someone new coming into the industry I can’t tell you enough how much I appreciate these videos and also how you do them. Really helps. Thanks man.
You doing a separate short video for each specific component is helping me understand how the AC unit works much more
glad its helpful
Incredibly fascinating. The more I learn, the more in awe I am of the engineers who invented these technologies
In class we learn about a different component per day. First was the compressor, then the condenser, and next class is learning about the evaporator. Your videos give me such a helpful way to study and learn these components in school.
Your videos are fantastic. I'm in the process of getting my home's HVAC system replaced and your videos explain not only the mechanics but the physics behind how this all works, and in an easy to understand way.
Glad to help
i learned a lot. i. a begginer but with this kind of video it helps me motivate to learn even more. thank you bryan for making amazing videos hope to see more from your channel
I recently started working at an ice machine company and I knew very little about how they worked. I am getting some on the job training, but I am coupling it with what I am learning from your videos, and it is all starting to click for me. I still have so much to learn, but I appreciate the work you did with these videos, because I'm sure there are lots of people like me that you are educating. Thank you.
Im in school now for HVAC and your videos are very helpful. Thank you. Please continue making more!
Thank you sir for delivering this nice, brief explanation about evaporator. So the point is that the air must be sufficient passing through the evaporator to give enough heat for refrigerant to phase changing completely. Greetings from Indonesia. Well done sir. 👍🙂
Outstanding! These videos should be used in appropriate classrooms.
Thank you God bless you and your family
GREAT BREAKDOWN!! I'm a first term HVAC/R student. This definitely helps!!
Awesome video, thanks for making it easy to understand.
Just wow!! A lot of great information.... Thank You.
God bless you sir
You are a Great Instructor Thank You.
Excellent video and wonderful presentation.
Thank you for making easy to understand videos.
I’ve learned so much from this gentlemen 👑🙌🏾, to help me in my field which is home inspection.
He actually makes sense , I took a class and let tel you I can’t understand a word he is saying .. to technical ..
Thank you keep it up ..
Best explanation I have seen, nice job.
Great explanation.
Thanks, Brian.
FOR THE READERS:
Ah, but water boils at near freezing at low pressures.. In fact, the freezing point of water is also its triple point. But at such low pressures, the flow rate per ton would require compressors with ridiculously large displacement... so a workaround is using an absorption cycle, using something like lithium bromide and calcium chloride brine. But water is an excellent refrigerant at higher temperatures. It is instructive to note that in chilled water loops, water is not the refrigerant, but the transfer medium. Same with glycol chillers. Also, water is used as an absorbent in ammonia absorption systems, where ammonia is the refrigerant. Confusing, to say the least, to the uninitiated... and let's not even get started on ammonia chillers with flooded evaporators...
Very nice presentation. Thank you!
Excellent channel for people like me whi wanna be HVAC technician.
thank you for these videos
Great lecture, thanks! 👍👍
Ty 4 sharing your knowledge
My boss allowed me to join the refrigerant team at work and im under training but i want an in depth understanding so ive been watching countless videos on the system. I loved your explanation definitely made things a lot more clear!
excellent explanation. love it🙏
Thanks alot for taking the time to make these great videos😁
Glad you like them!
The slight difference in temperature between saturation temp and coil surface temp is about 5 degrees and it is called evaporator skin temperature. This difference is due to the coil heat transfer being affected by oil circulation, and the material that the coil is made out of.
this is brilliant (video and the concepts)
Very informative lesson. Thank you sir
That was a good class! Thank you
Phenomenal video thank you
Excellent. Thank you.
Learned lots 👍🏾
Very informative video thank you
Great video!
Awesome job
Excellent video
As an hvac student this right here was fucking great.
very interesting. I always wondered the direction of refrigerant flow, surprised to learn it hits the compressor first.
Very detail. Thank you awesome
THIS is the explanation I needed.
Love your content. Really helpful to noobs .
Great information 👍
That awesome ..
God bless..👍
Great stuff
Thank you. I’m a PLC certified 2 programmer. I want to switch professions and jump to HVACR. I know PLC are being implemented into HVACR. I’ll fit right in.
Thank you!
Whish I had an instructor like Bryan when I went to HVAC school👍👍👍👍👍👍👍👍
WONDERFUL
And light is the absence of darkness.
Thank you
NICE , VERY NICE BRYAN .... AS USUAL .
SLOWLY BUT SURELY I AM GETTING THERE ...
Since you work primarily in Florida, you mostly refer to the equipment in terms of cooling. I live in Oregon and for us, heating is as much or more important than cooling. It would help if you could also refer to the heating cycle when describing these HVAC systems and components. Thanks for the great videos.
thank you
Great job and video
Glad you enjoyed it
This is great
Can you make a detailed video of the heat pump process?
Thank you, well exolain,
Thanks
man hvac school is the best
Great video...
75/25 liquid & vapor thru the TXV
Evaporator absorbs LATENT & SENSIBLE heat
ALSO the heat exchange that happens in the EVAP. occurs thru CONVECTION...correct me if I'm wrong...
It would be convection is there was no fan. In forced air, convection is a MINOR factor in heat transfer, where CONDUCTION and RADIATION take over. The same thing happens at the condenser (if it is air cooled), except for the opposite direction of heat transfer. Enthalpy is lost or gained along the surfaces of the tubes and fins.
well said
Man I wish you guys lived near my home. I have a Trane XR17 (2019)and I have a Delta T of 10. 55 percent humidity in the home.
What are your pressures, subcool, superheat readings, anemometer or static pressure readings, a delta t of 10 degrees is very low, the clear result app we use has a target range of a minimum of 14 and a maximun amount of 20.
Ive came across systems that use 2 evaps with only one compressor and condenser.. they were laid out with the freezer evap first in series then the fridge after and to the compressor. So that would imply the reliance on the refrigerant to move in the vapor form after the freezer , into the warmer environment which would condense it back into a liquid somewhat allowing it to absorb more heat from the warmer environment of the fridge.. right? Or am i recalling it wrong and the fridge part should be first then the freezer? Pretty sure the freezer would be first.. now ive only came across this maybe twice in my life and were on built in units that were separated from eachother which allowed space between the coils. Guessing there would have been a metering device between them but wasent able to see exactly how they worked before were torn out and replaced with a newer single unit.. always wondered how those worked and if they just had some crazy plumbing routing to make it work. But i remember there only being one beefy sealed compressor and one big condenser with 2 evaps.. one smaller and one bigger.. i would think the unit would section off the single condenser into 2 that would allow both evaps to be independent.. where the refrigerant would cycle through the compressor before going to the other coil but thatd be a ton of extra plumbing and the capillary tube would be a head scratcher.. for me at least. Still trying to learn..
A cooling effect is produced when refrigerant enters an evaporator due to state change correct??
Evaporator freezing question. I assume when evaporator coils freeze it is from the bottom up (earliest input after metering device). I have a dirty coil (hair, particles and seemingly some biofilm that I have been brushing out) and some freezing (near the bottom inch). All of the small lines branching out after the metering device have frost uniformly as they enter the coils. However not all the coils are freezing uniformly across (some bottom loops are just sweaty). Does this suggest that my coil freezing problem is mostly a flow issue in certain parts? Or could it still be a refrigerant issue?
I'm doing a project on ocean energy and i have to explain how (OTEC) work and I didn't know how an evaporator works thanks.
Cool temperature 18C but high humidity 70-90. Could this also be caused by oversized ac (not enough heat)?
Thx
What's the difference between a vehicle mechanical compressor vs an electric mini split or refrigerator compressor. Can a mini split compressor be replaced with a mechanical compressor?
8:55 Does having a higher superheat means the system is more or less efficient?
ie, Does higher superheat imply the system was able to extract more heat from the room?
X Y Z the lower the superheat, the higher the efficiency, due to more active surface area of the evaporator. We can’t run zero superheat, because we need to protect the compressor. Carrier tried to run zero superheat with its flowtronic chillers, about 20 years ago, because they thought they had good control with their electronic stepper motor driven expansion valves. Well, those units lost a lot of compressors which were 6 cylinder O6D semi hermetic compressors.
I have an Evaporator which only has 1/3 is cold (showed condesed water around the copper tubes). I have cleaned the metering device piston and the screen before the piston and replaced the liquid line filter drier and the evaporator coil. Do you have any idea what's wrong with it?
The suction line has two kinked turns which are less than 90 degree. Do you think that lead to the starved evaporator? The owner said he used to get temperature lower than 77F. Right now I measure the supply temperature from the closest register it has temperature around 80F.
I have checked the pressures (R-22 3 tons unit) and subcooling and superheat. Pressures are in good ranges. The superheat is around 34F. Subcooling is around 10. Any idea about what caused this symptom? Thank you
What’re the numeric values for your pressure man...amp draw
Hi! A few weeks ago a tech from an ac company came over to check my gas pack unit I'm not sure if it's called like that the unit has both the ac and heater in the same unit and it is in the roof of my house, and he removed the sensing bulb from the place it was and said to just leave it there it is not touching the pipe I believe is the evaporator's exit any more. Do you have any idea why he might have done that? Is it safe for my ac unit? I live in Tucson Arizona. Thank you. Great video by the way 👍👍
Checked the sheet shart... if the bulb is loose which regulates the superheat, that means more refrigerant will go through the evaporator.
If the evaporator is unsuccessful at turning all that extra refrigerant into vapor, the compressor could be receiving liquid and destroying itself, right?
/Plumber from Sweden studying to be an HVAC technician aswell :-)
How do you get to a temp so cold like -20? What is done differently?
Refrigerate work to decrease the inside temperature of refrigerate box upon mountain it will require less power to decrease of temperature
Can someone help? First off great video! I’m finding water droplets on my filter, I have proper drainage for the pan , so it’s not that. Any ideas? Thanks.
Question, what will happen in a dehumidifier if the evaporator gets 60 degrees Celsius high humidity air from a dryer. Would you need to lower or increase the pressure to handle that since most dehumidifiers only seem to handle air up to 40 degrees Celsius ?
i have one dryer air..
works 3 to 40 c temp
i change filter and capillary tube but i haft to resize it...
so now i have
-7.5c entry to evaporator and exit 2.5c
after to the accumulator i have - 3.5 and entry to compressor 9c is that normal.... how much must be the Δτ to the evaporator? and with the temp room so the dryer ro works good??
thanks
So the air in the home is moist and humid all of a sudden!! I’ve had several techs look at it, changed the return plenum, had it level and cleaned. There was water built up in the supply duct work. And I opened it today. There is little water coming out of the drain line when running. And between the evap and blower had mold spores built up 3 days after cleaning. I’m interested in what it could be. Open to ideas. Currently turned the unit off cause I can’t take it anymore. Send help!
likes comments and a sub for the youtube algo, thanks for the refresher and clarification
Can you run cold water through this coil? Like a swamp cooler?
There are cold water air handlers but they’re part of a chiller system and way complicated nothing like a swamp cooler
Hey Bryan, Where does the image of the orbital scroll that you have behind you come from? Is it some scientific research?
Hi sir, which type or number alluminum rod are use to weld alluminum condenser and evaporator
"I could sit here and talk for hours about evaporator coils"
Couldn't we all
It’s a curse 😂
I like evaporators
Hello I have an evaporator r 717 with no data and I don’t know how to know it’s cooling capacity it’s dim is 2x2x1.2 fin spacing 10mm number of pipes is 244 and it’s diameter is 1.3 cm
Do we have an animation showing this cycle?
how does boiling occur than as refrigerator is closed and .......boilig doesn't take place in closed space???
If your up in the mountains will the boiling point of the refrigerant be lower or the same ? Lower right? 🤔
Water boils at 212F, at sea level, the higher altitude you go means less PRESSURE, so it takes LESS Energy/Heat to make the water boil..... (Temperature/Pressure relationship)
@@Progress24.7 so the Freon , the boiling point of like R-22 or R-410a any Freon would be lower right ? 🤔
@@tinymanthebeast No... it's not called freon, its referred to as *Refrigerant*, also R22 and R410 are two Different refrigerants so they boil at different temps, if you refer to a P/T Chart you will find the Temp/ pressure they need to be...
@@Progress24.7 if you're up in the mountains the super heat set point we'll be different right?
@@tinymanthebeast Good question. I believe it shouldn't make much of a difference because when dealing with A.C your working with a Pressurized system...also I believe there are special P/T charts that include what the temp needs to be at certain altitudes...ive never worked in the mountains so I'm not to familiar with this scenario....
Nice but how can fix almunium
I just had a brand new complete AC system installed, including the outside unit and the air handler and it failed immediately. It never cooled. The tech who installed it didn't even stick around to make sure everything was working properly. He turned the unit on and then left. This was very suspicious. Make me thing he knew the AC unit was bad. Now the company that contracted him is sending another tech out tomorrow to I guess clean up the mess he made. Fortunately I only paid half up front cost so if they don't make it right they aren't getting paid the balance.
So what would happen if I put a container of refrigerant inside a freezer? The refrigerant would boil inside the container and how would it evaporate would it blow the container?
Nothing will happen if you put a container of refrigerant in a freezer. I have containers of refrigerant stored in an outdoor shed and it gets below zero F every winter, nothing happens to the refrigerant. The refrigerant only changes state due to pressure changes, it only boils when pressure is reduced and in the container it remains under pressure.
@@onemoremisfit thanks for the answer ! Not sure I understand how it can boil without off gassing and building pressure but then again I don't know about the biology of refrigerant.
why do they call it saturated state? also dwell time?
they referring to heat?
You said Saturated refrigerant is part liquid and part vapor.
But saturated air is 100% vapor.
That's why I cannot understand the meaning of saturated.
I might understand this if I watched it 1000 times
Actually, 100% saturated air is at its "dew point". That means that at that temperature, water vapor will condense out of the air-water vapor mixture.