tx valves and liquid recievers

[young gun]

do all tx valve systems NEED liquid recievers ? Even if a small charged system and no reason to ever have to pump down system... Is it absolutely vital ?

[monkey spanners]

A lot of the Serap milk tanks i work on have txv's and no recievers, even on big 9 HP models.
I have fitted a few txv's to cellar coolers when the capiliary has blocked up, just had to make sure the compressor had high starting torque electrics as txv don't equalise the pressure as quickly as capiliary when the system turns off.

Why do you ask?

[young gun]

i just have a senior tradesman at work trying to tell me ALL tx valves NEED liquid recievers with no exceptions.... I have never heard such rule just need to hear other peoples thoughts.... thanks

[martinw58]

i dont think all tev systems need recievers but you have to make sure the sysem is corectly charged as the condenser will have to hold the liquid when the valve starts to close

[Peter_1]

MArtinw58, I totally agree with you. Not needed if critically charged

[cool runings]

.

You need to understand how the TEV works.

It opens and closes so it needs more or less liquid.

If it needs liquid then the liquid will need to come from somwhere, if it does not need liquid then the liquid will need to be stored somewhere.

The liquid reciever is a good place but so is an oversized condenser..

Coolrunnings.

.

[Magoo]

Hi Young gun.
despite what everyone else has said, senior tradesmen generally have figured problems out way back. Thats why they are still tradesmen.

[young gun]

Hi Magoo,
Yes i defintly listen to and take in everything i can from what other tradesman ( especially senior ) tradesman say. But I also like to study and ask other opinions, as just because they say and believe that, doesn't make it 100% correct, or relevant to all situations.
Thanks Magoo

[mad fridgie]

Hi Magoo,
Yes i defintly listen to and take in everything i can from what other tradesman ( especially senior ) tradesman say. But I also like to study and ask other opinions, as just because they say and believe that, doesn't make it 100% correct, or relevant to all situations.
Thanks Magoo
Well done, and how true!
You should go far.

[Aik]

.

The liquid reciever is a good place but so is an oversized condenser..


You are right. If no reciever then part of condencer flooded (take part of reciever). Excess of thermal expansion of refrigerant are situated in condencer. In some systems after condencer (if no reciever) install pipe with bigger diameter.

[young gun]

Thankyou very much everyone for your thoughts.
I totally understand how a TXV system could function without a reciever.
So no one has ever been taught that ALL TXV systems MUST have a liquid reciever with no exceptions. Or no one has ever come across this in an old text book?

[young gun]

Just found another thread on this subject.
Receiver! Needed or not (Under Fundamentals)
This also agree's with the fact not ALL txv systems need recievers.
LOL Why am i having such a hard time trying to explain this at work.
Maybe ill keep my thoughts to myself, and let them believe what they want to believe?

[monkey spanners]

LOL Why am i having such a hard time trying to explain this at work.
Maybe ill keep my thoughts to myself, and let them believe what they want to believe?


For some people, winning an argument or discussion is more important to them than being correct, which is a shame because they never progress and just stay with the level on knowledge they have.

I love it when i find out i was wrong about something because thats when i stop being wrong and start being right :D

Jon

[Magoo]

Young gun.
OK ,you have a system that has a thermal expansion valve, aka TXvav. That txv is a constant modulating orifice, temp driven.
Next, at high load the TXV is wide oen looking for max perfomance, as in pull down situation.If lacking liquid to feed the vav, the vav hunts. [ open to closed rapid cycling.]
At design temp the TXV is at minimal open.
So if you charge system for pull down, where the hell is that excess liquid going to stored. In the condenser obviously. So now effective condenser HX has been seriously reduced, creating a false high discharge condition.
Problem: system can hydraulic. Conditions, ie overnight, winter, what ever. Now you have a vertual bomb at your disposal.
Next people killed, you are on a mission to know were, kiss the family good by and go straight to jail.
All for the sake of a friggen receiver.
Really a no brainer decission.

[lana]

Arguments given here are very interesting and also true.

WHAT IS CORRECT IS NOT ALWAYS POPULAR,
WHAT IS POPULAR IS NOT ALWAYS CORRECT :cool:

I have the same arguments with older engineers who know something (EITHER CORRECT OR INCORRECT) and they insist on it without any good reason.

Anyway, having receiver in a TEV system is a good thing and also saves a lot of time and worries.
In theory you may not need receiver BUT you have to charge the system critically, like cap tube system.
If it is overcharged then excess refrigerant will accumulate in the condenser and you may have high pressure problem.
Systems with water cooled condensers (shell & tube) usually don't have receivers because condenser also acts as receiver.

In my opinion the difference (or advantage) between TEV system and cap tube is this very reason. Life is more easy with TEV than cap tube. :o

Cheers

[dirk]

If you have constant load on the evaporator and relativly stable condensing it may not be neccessary to have a reciever. Under different load conditions there will be a varying amount of refrigerant in either the evaporator or condensor hence the need for the reciever.

[young gun]

Toyota, Isuzu airconditioning and other car manufacturers also have gone away from the traditional drier reciever concept, and use the condenser as liquid reciever. Although not quite sure how the pipes have been modified at the end of the coil because i have not cut one up, either way its still a condenser coil being used partly as a liquid reciever.

I think now it is quite obvious that ' you cannot generalize ALL tx valve systems as MUST NEED liquid recievers.'
Because quite obviously all systems are different, they all face different heat loads and heat load changes and also face different condensing loads/situations.
To generalize "ALL" tx valve systems with one rule, to me now sounds quite unprofessional and incorrect.

But once again, that is just my opinion, which doesnt make it right.

[bmundoorkote]

hi there,
not atall.mostly large refrigeration system some time using depends on the tonnage of the system. but small tonnage it is not required.
best rgds.
bm