Receiver to Discharge Balance Line

[Superfridge]

Hi all

Could some one please shed some light on sizing and installation of the HP receiver to discharge balance line.

I have been reading the ASHRAE handbooks and now have a better understanding of this rather inportant component but could find no sizing data.

Thanks in advance

[RANGER1]

Someone may add correct method , but our engineers would say the bigger the better.
A decent size plant would have anything from 50-80mm balance line.

If t/syphon its bigger again , probably same size as main discharge header.

[lawrence1]

On Supermarket racks we use a 5/8'' from the condenser to receiver with a check valve.
Lawrie

[mbc]

size is not important is is usually 1/2
in NH3 and R and it is for balancing pressure in winter and summer times,
in winter it is open (keep liquid in condenser to bring dawn capacity of condenser in winter and rise of discharge pressure)
it is install discharge line goes to condenser and top of receiver with regulator valve (stop valve not recommended).

[Superfridge]

Quote; "The vent line flow is from receiver to condenser when receiver temp is higher than condensing temp. Flow is from condenser to receiver when air temp around receiver is below condensing temp. Flow rate depends on temp difference as well as on the receiver surface area. Vent size can be calculated from this flow rate"


This must only be the case when pressures are equal between condenser and receiver? A correctly designed system?

Have also read "a check valve can be fitted in the direction of the condenser when piping configeration is "unknown" ie unknown pressure drops and/or velocity pressure entering line to receiver"

[RANGER1]

http://www.irc.wisc.edu

Superfridge,
Please find link posted by Sergei .
It has a download to calculate balance line. Unfortunately its in psi ,tons etc

[Superfridge]

Thanks for the link RANGER1, a good find.

I would like to know how to calculate the pipe sizing long hand/old school so if anyone know's and is prepared to share this valuable information..........

My recent investigation has proven some of the plant I work on have this line incorrectly installed.
Just go's to show that a plant can be in service for 20 odd years and still have fundamental improvements done.
The comments like "it's always been like that" and "it always struggles in summer" now makes me think "let's have a closer look":D

[mad fridgie]

There are a number of ways at looking at this.
Sized upon max displacement,
imagine you are pumping down (no liquid leaving the reciever) so to keep the system balanced, vapour has to be released back to the cond. So if you are inserting 1 litre of liquid, you must have to release one litre of vapour. You then need to know the length and height of the liquid and vapour balance, you need to ensure the presure drop is small to ensure flow.
Or you could calculate the temp difference between the reciever and the cond, (how much energy is being absorbed by the reciever) Calculate how much flash gas is being produced, size you line again with little pressure drop.
You could also condisider fitting a check valve in the liquid drop line. If there is a large difference between the reciever temp and the cond, then raising vapour can go up the dropper stopping liquid leaving the cond (liquid hung up!) add ing the check valve allows a liquid head to be produced over the check valve, allowing the pressure to equalize via the balancing line and allowing flow.

[RANGER1]

Surerfridge try this , but the main problem will be connection size on liquid reciever.
www.irc.wisc.edu/file.php?id=133 (http://www.irc.wisc.edu/file.php?id=133)

[Superfridge]

Thanks again RANGER1,

I see what you mean about the HP receiver connection size being a limiting factor.

All good