Recirculation Rate

[RefUser]

What does it mean exactly when you say 4:1 or 3:1 recirculation rate on a flooded Evaporator?
4 Parts liquid 1 part vapor??? or
4 Part Evaporated and 1 part still liquid on the suction pipe?

[RANGER1]

Refuser,
Send out 4 parts liquid, 3 parts liquid return, 1 part gas for 4 to 1 circulation.
Adjusted by hand regulating valve on each evaporator

[RefUser]

What would happen if I starve the evaporator?
running more like a dry system.
We have plenty of evaporators so I'm not worried about maintaining temp.

[Segei]

Capacity of these evaporators will be reduced and you should run more evaporators. Each evaporator has fans. These fans use energy and release it into refrigerated room as parasitic refrigeration load. Running additional evaporators will be bad for plant energy efficiency.

[Tycho]

Good read here:

http://www.ishraepune.org/documents/Liquid%20overfeed%20systems%20by%20R.%20P.%20Paranjpey.pdf

[RefUser]

we are actually running subcooled liquid to these evaps to the point that we aren't reaching saturation point in the unit with a 4:1 recirc rate. (brining). My theory was that I should be able to pinch back the HXV far enough to where we will achieve saturate state and actually absorb more heat, thus, disproving the need for more Evaps. however I am concerned about starving the evap. I Found that even with my HXV at half a turn I have more than enough capacity to remove the heat in this dock.

[NH3LVR]

Brining can be a problem if you are trying to use extremely subcooled liquid. especially with top feed coils.
Mike Fisher wrote an excellent article on this years ago, but I cannot find it at the moment.
One issue you may face, depending on your system, is oil trapping.

[RefUser]

We aren't having much issues with oil. And if you do find the article, I would appreciate if you could forward it to me. Thanks in advance

[RANGER1]

What would happen if I starve the evaporator?
running more like a dry system.
We have plenty of evaporators so I'm not worried about maintaining temp.

Any particular reason you want to starve it?

[RANGER1]

we are actually running subcooled liquid to these evaps to the point that we aren't reaching saturation point in the unit with a 4:1 recirc rate. (brining). My theory was that I should be able to pinch back the HXV far enough to where we will achieve saturate state and actually absorb more heat, thus, disproving the need for more Evaps. however I am concerned about starving the evap. I Found that even with my HXV at half a turn I have more than enough capacity to remove the heat in this dock.

So by saying liquid is sub cooled possibly to much means saturated suction pressure running lower than necessary in your plant, or for that room.
Can you raise suction pressure, especially if ambient low for maximum plant efficiency.
Does it have a BPR in suction line.
Liquid solenoid not passing, or set point to low.
Thermostat not calibrated.

Air infiltration from colder area?
Turn of a fan or two to reduce capacity.

Of course you can restrict amount going into evaporator, but does that mean you have to change setting seasonally.
Be interested in required room temperature & suction pressure.

[RefUser]

Just trying to get closer to Saturation Point by pinching back the HXV since our liquid is recirculated from a vessel that's tied to our low side.
not purposefully starve it but more of a byproduct.

[RefUser]

You are correct. We do not have a Back-Pressure Reg on the suction line, it goes to a recirculator and our compressors are maintaining 30psi on that vessel. Our Temp for that dock is 32 Deg. With the way we are running now we don't have issues but I might have to tweek it on summer.

[mbc]

Hi
We have
1- DX system
2 - Wet system
3 - flooded system,( over feed system)

If we compare these 3 system , we have:

In 1 one our cooling capacity in evaporator Max.0.7 of 2end .
2ed is 1
3rd is 1.25 time more than 2ed one.

Also we should look how we want to defrost the evaporator.
Hot gas
Hot water
Electric power.

[Segei]

Saturated temperature in your vessel is 17F. Liquid subcooling is 15F. This isn’t huge subcooling and your brining probably mild. To estimate starving of the coil look at frost formation. Underfed coil will have partial frost formation. Do you really need cooling in winter time? Many companies need dock heating for winter operation.

[RefUser]

I just got in a "data logger" to monitor the Delta temp across my evaps and am shooting for a 2:1 possibly 3:1 circulation rate. I'd like to thank all you guys for your valuable knowledge.

[Josip]

Hi, RefUser

here you can read about brining ...

http://www.refrigeration-engineer.com/forums/showthread.php?17160-how-to-increase-the-portion-of-liquid-after-TXV/page2

check post #63

Unfortunately Mike Fisher is not present on RE forums since 2014.
but his alias is US Iceman (http://www.refrigeration-engineer.com/forums/member.php?3487-US-Iceman)


.... not bad idea to read his posts (5300+)
.... a huge knowledge base :)


Best regards, Josip