Pressure drop through the suction line accumulator?

[frank721]

Now I am using a suction line accumulator (R134a) between my evaporator and compressor. I measured that the pressure of evaporator is about 3 bar but the inlet pressure of compressor is about 1bar. That means accumulator caused the pressure drop of 2 bar.

My dear friends, is it normal that accumulator results in such big pressure drop? I am not quite clear about the inner structure of accumulator. Is there any bolck or mesh in the accumulator which could induce the pressure drop?

Thanks a lot!

[nike123]

Pressure drop of suction accumulator is about 0.3°C.

What is make and model # of your accumulator?

[Peter_1]

Full of liquid.
Debris is almost not possible, most don't have mesh filters in it.

[frank721]

Pressure drop of suction accumulator is about 0.3°C.

What is make and model # of your accumulator?

You mean the pressure drop is 0.3bar nomally, right?
I am using Emerson A-AS-597

Thanks a lot.

[frank721]

Full of liquid.
Debris is almost not possible, most don't have mesh filters in it.

What do mean by "full of liquid"?

I found there is a so-called oil return orifice at the bottom of the U tube. But I can't see the exact posion and structure clealy there. Would you please elaborate it?

Thanks a lot.

[lowcool]

design kw rating of evap & comp at what suction temp would be good to see.sounds to me your suction line is undersized,only accumulator prob ive had is the tube falling off inside.

[nike123]

You mean the pressure drop is 0.3bar nomally, right?
I am using Emerson A-AS-597

Thanks a lot.

No, I mean equivalent pressure drop of 0,3°C!

[nike123]

I found there is a so-called oil return orifice at the bottom of the U tube. But I can't see the exact posion and structure clealy there. Would you please elaborate it?

Thanks a lot.

http://contractingbusiness.com/images/archive/82643accumulato_00000054796.gif


I don't think that "full of liquid" state could make pressure drop in range of 2 bar.

[desA]

R-134a @ 0.3'C dP

= (0.3/1.1)*13.3 kPa
= 3.63kPa
= 0.0363 bar

Source 'Application Guide AG 31-011' "Refrigerant piping design guide", McQuay

[Peter_1]

I don't think that "full of liquid" state could make pressure drop in range of 2 bar.[/QUOTE]
In another thread on this forum, you will find this actual situation which isn't resolved yet. Even a bigger pressure drop Nike of 2 bar

[desA]

In another thread on this forum, you will find this actual situation which isn't resolved yet. Even a bigger pressure drop Nike of 2 bar

Could the inlet & outlet be connected incorrectly? :D

[Gary]

I suspect there is something else between the evap and the compressor. Perhaps a suction drier or an EPR valve... or maybe a kink in the line.

Check the suction line temperature from the evap to the compressor. Where you find a temperature drop you will find the pressure drop.

[nike123]

In another thread on this forum, you will find this actual situation which isn't resolved yet. Even a bigger pressure drop Nike of 2 bar

Could be, but I still don't see how liquid could make any effect to that pressure drop if accumulator is in perfect condition.

[frank721]

design kw rating of evap & comp at what suction temp would be good to see.sounds to me your suction line is undersized,only accumulator prob ive had is the tube falling off inside.

the diameter of the suctionline is fixed by the port of the accumulator.

What do you mean by "only accumulator prob ive had is the tube falling off inside"?

Thanks

[Argus]

.


Many heat pumps of Far Eastern or Japanese manufacture incorporate a wire mesh filter in the inlet pipe at the top of the accumulator.

These are mostly unmarked, little more than the diameter of the pipe and often block with debris.

You need to cut the whole thing out to locate it.

I have also seen them be fitted the wrong way around (i.e. reversed flow) at the factory.


.

[Yuri B.]

Hello Frank.
? Are you speaking about that L'Unite Hermetique from your thread: http://www.refrigeration-engineer.com/forums/showthread.php?t=18967
If yes, could you please give other parameters, such as room temp, evap dT, SH, presupposing 3 Bar is evap pressure.

[lowcool]

gday frank nikes photo depicts the said tube internally,you can hang any size suction line off the fitting ie lets say long pipe run requires larger size piping,size of accumulator ports is only relevant to capacity (kw) of system.5/8" accumulator with 1 1/8" pipe run

[nike123]

In another thread on this forum, you will find this actual situation which isn't resolved yet. Even a bigger pressure drop Nike of 2 bar

You mean this one (http://www.refrigeration-engineer.com/forums/showpost.php?p=142102&postcount=1)?

Pressure drop there is 1,9 Bar.;)

[El Padre]

Ciao,

Interesting debate, it appears to be a large pressure drop to be caused by an accumulator full of liquid, what is the pipe temperature at the accumulator inlet/outlet and the compressor inlet?

Cheers

[nike123]

frank721

As Gary already pointed out, when there is pressure drop, there is temperature drop.
Measure accumulator inlet pipe and outlet pipe temperature ((and post your findings here).
If difference is greater than 0,5°C you have restriction in accumulator. If not, your problem is elsewhere.

[Peter_1]

As Gary already pointed out, when there is pressure drop, there is temperature drop.
Not in the gaseous phase ;)

[nike123]

Not in the gaseous phase ;)

Why is then, when I making pressure test with nitrogen, nitrogen bottle is cooled?

[Gary]

Not in the gaseous phase ;)

That's true... but with this much restriction I'm thinking we can assume a liquid/vapor mixture before the restriction... especially if it has a liquid filled accumulator.

But then, we don't have enough information about the system.

Is this a cooler or a freezer?

Is it a cap tube system or a TXV system?

[Gary]

Why is then, when I making pressure test with nitrogen, nitrogen bottle is cooled?

Because the bottle has both liquid and vapor.

[nike123]

Because the bottle has both liquid and vapor.

I taught that nitrogen in bottle is at max 200bar and that all nitrogen is boiled at that pressure (and in gaseous phase) when at ambient temperature.

http://encyclopedia.airliquide.com/images_encyclopedie/VaporPressureGraph/nitrogen_vapor_pressure.gif

[fowlie]

why not fit shreader tails into inlet/outlet sides of accumulator,if anything it will tell you if it is the problem.dont like them myself as they ushally just become large oil traps on our old hot gas systems.

[Peter_1]

That's true... but with this much restriction I'm thinking we can assume a liquid/vapor mixture before the restriction... especially if it has a liquid filled accumulator.

But then, we don't have enough information about the system.

Is this a cooler or a freezer?

Is it a cap tube system or a TXV system?
That's also what I'm thinking about it.
Give us some more information.

What's your SH on the evaporator? What's the pressure inside your accumulator and what's its shell temperature? That's how we found out it was full of liquid.
Install schraeders as Fowlie suggested and share this readings
Nike, at least no noticeable temperature drop, perhaps you can see it with an IR imaged scanner, perhaps..
A pressure reduction of a gas can be perfectly isothermic

[Yuri B.]

My believe is any gas pressed, then cooled down to ambient, during sudden expanding will always consume SOME heat (insufficient however at all for refrigeration). And using nitrogen, we deal with a huge expansion - from 200Bg down to 20-30Bg (then to 0 Bg). But not so huge gas transition is here - only from 3B to 1B.
Frank meanwhile, is not giving the whole picture, having drawn onto the scene only that partricular part of his system.

[lowcool]

is the accumulator to small?a reply from the original poster would be good

[frank721]

dear freinds. sorry for late reply, since i was on leave in this period. it was not convenient for me to use internet.
now, let's continue. i feel so warm here because you are so kind.

[frank721]

http://contractingbusiness.com/images/archive/82643accumulato_00000054796.gif


I don't think that "full of liquid" state could make pressure drop in range of 2 bar.

Hi, can you show me some more pictures or schematics with more detail? I am curious about it. Thanks a lot:)

[frank721]

I suspect there is something else between the evap and the compressor. Perhaps a suction drier or an EPR valve... or maybe a kink in the line.

Check the suction line temperature from the evap to the compressor. Where you find a temperature drop you will find the pressure drop.

Thanks for your suggestion. there is no other device between the accumulator and compressor. But you bring a good point: kink in the line. In fact, the diameter of outlet of accumulator is 7/8" and diameter of inlet of compressor is 5/8", but they are connected with a smaller tube of 1/4"
is it the reason that cause the big pressure drop?

[frank721]

.


Many heat pumps of Far Eastern or Japanese manufacture incorporate a wire mesh filter in the inlet pipe at the top of the accumulator.

These are mostly unmarked, little more than the diameter of the pipe and often block with debris.

You need to cut the whole thing out to locate it.

I have also seen them be fitted the wrong way around (i.e. reversed flow) at the factory.


.
wow... it's hard for me to cut it. anyway, it's a possible reason. thanks

[frank721]

Hello Frank.
? Are you speaking about that L'Unite Hermetique from your thread: http://www.refrigeration-engineer.com/forums/showthread.php?t=18967
If yes, could you please give other parameters, such as room temp, evap dT, SH, presupposing 3 Bar is evap pressure.
Hi, that thread is also posted by me. room temp is 31 degree C, SH is about 5 degree C
sorry, what do u mean by evap dT?:)

[frank721]

That's true... but with this much restriction I'm thinking we can assume a liquid/vapor mixture before the restriction... especially if it has a liquid filled accumulator.

But then, we don't have enough information about the system.

Is this a cooler or a freezer?

Is it a cap tube system or a TXV system?

it's cooler and TXV system

[frank721]

is the accumulator to small?a reply from the original poster would be good
i think it's already oversize according to my cooling capacity.:confused:

[Yuri B.]

Hi Frank.
What temp air off evap ?

[Yuri B.]

And what the RH of the 31C air by the way?

[Gary]

Thanks for your suggestion. there is no other device between the accumulator and compressor.

Are there any devices between the evaporator and the accumulator?

[Gary]

it's cooler and TXV system

After reading your other thread, I am even more confused. This is either an A/C system or it is a cooler system that you are trying to convert to an A/C system. Which is it?

[desA]

Thanks for your suggestion. there is no other device between the accumulator and compressor. But you bring a good point: kink in the line. In fact, the diameter of outlet of accumulator is 7/8" and diameter of inlet of compressor is 5/8", but they are connected with a smaller tube of 1/4"
is it the reason that cause the big pressure drop?

Are you serious? A 1/4" connecting line? :eek:

[Gary]

Are you serious? A 1/4" connecting line? :eek:

I read that several times and it just didn't register that anyone would actually do that... lol

[Gary]

In fact, the diameter of outlet of accumulator is 7/8" and diameter of inlet of compressor is 5/8", but they are connected with a smaller tube of 1/4"
is it the reason that cause the big pressure drop?

Yes... that would definitely do it.

[frank721]

Hi Frank.
What temp air off evap ?
hi, my evaporator is used for liquid cooling like cooling system in the desktop now. so, there is no air off evap

[frank721]

Are there any devices between the evaporator and the accumulator?


After reading your other thread, I am even more confused. This is either an A/C system or it is a cooler system that you are trying to convert to an A/C system. Which is it?


Are you serious? A 1/4" connecting line? :eek:


I read that several times and it just didn't register that anyone would actually do that... lol

yes, it is 1/4" really.
there is a needle valve between the evap and accumulator. but it is fully open. pressure drop is not significant when fully open.
it seems that we have found the cause of the 2 bar pressure drop:7/8" to 1/4"
thanks a lot, my friends:)

[frank721]

For discussing conveniently, i post the schematic of the evaporator. i measured the pressures at Point 1 and 2.

[lowcool]

frank if suction line diameter is fixed by size of accumulator port,what the hell happened.when anyone has a vague out i call it the autoduhh syndrome it can happen any time.

[lowcool]

interesting picture whats it of frank

[desA]

I think your compressor is going to suffer the world of pain, sooner, rather than later... :(

[Gary]

That's a flooded evaporator... and a whole different ball game.

[Magoo]

Interesting drawing, looks like a oil recovery bottle on a flooded ammonia evaporator.
If not ammonia, could be anyones guess.
I can see why you have a 2 bar delta P from evap to compressor, with 3/8 dry suction.

[Magoo]

OK, I went back and read the original ost again, its R134A. Could still be a scavenge oil recovery line that rises up in vessel to control level, the 1/4 "line would restrict flow and limit it. Also the 3/8 dry suction may be intentional to restrict carry over.
What controls liquid feed to flooded evaporator ?

[frank721]

frank if suction line diameter is fixed by size of accumulator port,what the hell happened.when anyone has a vague out i call it the autoduhh syndrome it can happen any time.
the inlet of accumulator is fixed, but you can use adaptor to reduce the diamter:confused:

[frank721]

I think your compressor is going to suffer the world of pain, sooner, rather than later... :(
why do you think so? sooner not later?:eek:

[frank721]

That's a flooded evaporator... and a whole different ball game.
as i said before, this system is taken over from other people. so i want to figure out the problem.
do u have any suggestion on this so-called flooded evaporator?
thanks a lot:)

[frank721]

OK, I went back and read the original ost again, its R134A. Could still be a scavenge oil recovery line that rises up in vessel to control level, the 1/4 "line would restrict flow and limit it. Also the 3/8 dry suction may be intentional to restrict carry over.
What controls liquid feed to flooded evaporator ?
what do u mean by "scavenge oil recovery line that rises up in vessel to control level"?
can u elaborate it?
before the evaporator, there is a manual valve to control the feeding liquid.

[desA]

why do you think so? sooner not later?:eek:

My concern is about liquid slugs getting into the compressor, if the system is not controlled carefully.

If that's all taken care of & guaranteed as a non-event, then rest easy - if not, then you may want to research further.

[lowcool]

dunno here we go years ago came across this sort of cascade system and i reckon that something like this was used on the expansion recovery,over run what ever circuit,come suction accumulator what ever to keep the feed up to the refrigerant pump.must say it was a little bit bigger on sizing but.ammonia blokes should have an idea
anybody else good for ideas

[D.D.KORANNE]

The 1/4 inch pipe you mentioned is usually a support pipe . I have in one instance noticed that one of the pipe tilts if you test the accumulator indepedently . So to my knowledge it is a support pipe . Just check with manufacturer . Besides, give me the following data to select the right model for you to compare.
Refrigerant
evap capacity
condensing temp
evaporation temp .

[frank721]

My concern is about liquid slugs getting into the compressor, if the system is not controlled carefully.

If that's all taken care of & guaranteed as a non-event, then rest easy - if not, then you may want to research further.
ok, then what do u think shoud be taken care?

[frank721]

dunno here we go years ago came across this sort of cascade system and i reckon that something like this was used on the expansion recovery,over run what ever circuit,come suction accumulator what ever to keep the feed up to the refrigerant pump.must say it was a little bit bigger on sizing but.ammonia blokes should have an idea
anybody else good for ideas
thanks, any experience on R134a?

[frank721]

The 1/4 inch pipe you mentioned is usually a support pipe . I have in one instance noticed that one of the pipe tilts if you test the accumulator indepedently . So to my knowledge it is a support pipe . Just check with manufacturer . Besides, give me the following data to select the right model for you to compare.
Refrigerant
evap capacity
condensing temp
evaporation temp .

Refrigerant : R134a
evap capacity:1~1.5kW
condensing temp:40~50 degree C
evaporation temp:15 degree C

Thanks a lot! by the way how to transfer cooling capacity in unit of "tons of R22" to "kW of R134a"?