Explanation of expansion devices.

[floshey]

Okay, so i've read sumthing about expansion devices, but i don't quite understand it, i hope you guys can help me get it all right.

TEV (Thermal Expansion Valve)
A device that regulates the superheated gas, you can combine it with a bulb that senses pressure on the suction/discharge line and can control the amount of regrigerant goint into the evaporator. You can buy these adjustable or premade for a certain refrigerant

(What is superheating, the way i understand it, it is the difference from the vapourized refrigerant(evap) and the gas in the suction line, which have absorbed energy)

EPR (Evaporator Pressure Regulator)
Uhm, i think i'm quite off the track here, but i'll try.
An EPR is placed on the suction line after the evaporator, and the device will only allow a certain amount of refrigerant to escape so it can maintain a certain working pressure = controlling the evaporating temperatur indirect.

(I have read refrigeration basics, downloaded the refrigaration handbook from SWEP, and read allmost every information on XS, vr-zone, phase-change.com and so on, but it is hard to understand it when it ain't written in your main language, so you have to convert it and then understand it, so i would be glad if you used simple words to explain the functions)

That is kinda it, also i don't know what "superheat" "supercooling" etc is, but i think it is the difference between the refrigerant when it has been cooled or heated by ie vapourization, condensing etc. Someone please explain/correct me

Thanks guys.

[FoxTrottZero]

Hey flosh...
Ok: when a refrigerant is boiling off in the evap (hopefully nowhere else lol) the temperature of the gas doesn't raise at all...
it reaches a critical boiling point and stayes there while it changes phase from a liquid to a gas... once all of the liquid has boiled off, the gas is all that's left to heat, so it begins to take in the thermal energy that was originally being taken up by the liquid...
superheated gas is simply refrigerant in it's gasseous state that is warmer than the boiling point...
supercooled is the opposite... the liquid is colder (has less heat in it) than it's liquified state...

hope that helps

[Scout255]

For example:

I have a sealed container of water at atmospheric pressure.

Lets say it is at -23.5'C, this would be a "Supercooled State" because it's temperature (-23.5'C) is lower than it's freezeing point (0'C).

Lets say I heat it up on a stove and bring the temperature up to 100'C and bring the water to a boil, and then wait until all the water has boiled off. If I then continue to add more heat to the water vapor, the temperature will now rise above water's boilding point of 100'C. Eventually it could get to say 120'C if I continue heating it. The ammount of superheat is simply the current temperature (120'C) with the boilding point subtracted from it (in this case, 100'C). In this example the super heat would be 120'C-100'C=20'C of superheat.

TXV's control the ammount of superheat leaveing from the evaporator suction line. Its senseing bulb allows this. i.e if the bulb senses that the superheat is too high (i.e their is far too little refrigerant in the evaporator) it will allow more liquid refrigerant into the evaporator. This will then lower the superheat coming out of the evaporator because the evaporator has to heat up and boil much more liquid and change it into a gas.

If the superheat is too low (i.e their is far too much refrigerant in the evaporator and it is not having enouph time to evaporate), the TXV will let less refrigerant into the evaporator.

I believe this is right, correct me if i'm wrong though.

[chilly1]

Okay, so i've read sumthing about expansion devices, but i don't quite understand it, i hope you guys can help me get it all right.

TEV (Thermal Expansion Valve)
A device that regulates the superheated gas, you can combine it with a bulb that senses pressure on the suction/discharge line and can control the amount of regrigerant goint into the evaporator. You can buy these adjustable or premade for a certain refrigerant

(What is superheating, the way i understand it, it is the difference from the vapourized refrigerant(evap) and the gas in the suction line, which have absorbed energy)

EPR (Evaporator Pressure Regulator)
Uhm, i think i'm quite off the track here, but i'll try.
An EPR is placed on the suction line after the evaporator, and the device will only allow a certain amount of refrigerant to escape so it can maintain a certain working pressure = controlling the evaporating temperatur indirect.

(I have read refrigeration basics, downloaded the refrigaration handbook from SWEP, and read allmost every information on XS, vr-zone, phase-change.com and so on, but it is hard to understand it when it ain't written in your main language, so you have to convert it and then understand it, so i would be glad if you used simple words to explain the functions)

That is kinda it, also i don't know what "superheat" "supercooling" etc is, but i think it is the difference between the refrigerant when it has been cooled or heated by ie vapourization, condensing etc. Someone please explain/correct me

Thanks guys.

Superheat is the refrence we use to indicate the amount that a refrigerant it heated above it's saturated temperature.

A TXV ans a spring and bellows balancing assembly, they are designed for a spefic temperature and refrigerant. The Bellows is filled with a gas mix so that it responds to temperature at the bulb and increases the pressure in teh bellows that balances so higher temperature raises the pressure and opens the valve more. The internal pressure also pushes in teh oppisite direction so that a rise in pressure closes the valve. So there is a P/T balance that is adjustable by increasing the pressure on the bellows as in CW rotation of the adjusting stem raises the roessure slowing the refrigerant flow and there by increasing the superheat by allowing less refrigerant into the evapor. The reverse is also true, loosen the spring (CCW Turn) and there will be more refrigerant in the system so the superheat will be less.

You got the EPR correct it regulates the pressure at its inlet by opening if there is a rise in pressure.

[floshey]

omg, thanks guys, i think im getting it now, so i wasnt completely off the track. THANK YOU for taking time to explain I LUV YOU GUYS :D
Just to check that i got everything right, lets say we have a CO2 system(example) the CO2 will evaporate at aprox. -80C, so we measure the temperature of the gas in the suction line to -71C, the superheat will then be 9C?

So to measure the superheat, we need to know the evap temperature and the suction line temperature(where would be the ideal place to mount the probe, how far from evap?)

Im not sure on the condenser though, the supercooling is the difference between ? and ?. And how do you measure it.

I am really glad you are taking your time to explain it to noobie me, can't appriciate your help enough :)

EDIT: So saturation means turning from gas to liquid?