Distributor orifices

[TB]

Whats the purpose of putting an orifice in the diffuser, right after the TXV ?

What would be the consequences if someone did not install it when installing the evap. ? Is it only used in refrigeration, or in AC coils too?

[R12rules]

I did that once.
The coil didnt get fed right.



what would happen if you took the main jet out of your carburator?


wouldnt feed the gas correctly? would it?

NO!


Same principle.

if ya want a more detailed explanation .. wait til Dave or Norm get here.

[LGM]

If you look into the distributor it has a cone ending in a sharp point. The nozzle serves the purpose of causing a solid column of liquid to hit the cone at the point equally dividing the liquid among the different distributor tubes. This way each circuit is fed equally.

If you leave it out, you tend to gravity feed the lower circuits and starve the upper circuits causing loss of capacity and frost problems.

[rayr]

Interestng.... On the HeatCraft coils I have installed, there is no such cone. The inlet of the distributor is flat. How can it gravity feed at aprox 150-250 Psi?? Russell coils require no orafice.

[wannafreeze]

I read on sporlan site that is has something to do with txv charge migration.

[westcoast refer man]

TB,

The orifice is there to cause pressure drop, which flashes more of the liquid into vapor. This pressure drop is in no way harmful to the performance of the system. At the same time, this flashing action mixes the remaining liquid and vapor together extremely well. Now when this mixture hits the so-called "cone", each circuit off the distributor tube gets the same amount of liquid and vapor. This is required for good evpaorator performance. Without the orifice there is no way to make sure each circuit recieves the same amount of liquid/vapor. Correct sizing of orifices can be critical.

There are manufacturers of distributors that don't use nozzles/orifices. This kind is referred to as a venturi type. There is no orifice in a venturi type distrbutor. Correct sizing of venturi type distributors is also important, but they have the disadvantage of not being able to up or down size without complete removal. With a pressure drop type, the orifice can be changed.

As far as TEV charge migration (where the charge in the TEV's bulb migrates to the power head because of a lower temperature) is concerned, since the orifice has a substantial pressure drop across it, the outlet temperature of the TEV is quite a bit higher than the evap coil temperature and bulb. This acts to keep the body temperature of the TEV warmer than the bulb temp, which in turn keeps the control point of the charge where it belongs-in the bulb.

[LGM]

Actually is more correct than I was. It is a liquid/vapor mixture.

Ray, I've worked for both Russell (with Witt) and Heatcraft and have been involved in a lot of nozzle selection. On some of the low velocity coils they still use what's called a venturi style distributor where the distributor is necked down to cause the pressure drop. In other evaps, if you remove the oriface you can see the cone. You can also look in one of the old Sporlan books and it shows you the inside.

By gravity feed, all I mean is that if the oriface is too large, it will not be evenly distributed to all circuits and will feed the lower circuits more than the upper circuits. May sound funny but believe me it happens. I've helped correct a bunch of them when at Heatcraft.

[rayr]

OK Thanks for the explanation. Usually get 2 or 3 orafices with the heatcraft. One for each flavor of refrig. LOL

[TB]

Thanks guys, I about had myself convinced the orifice was supplied with the coil so I could opt to not use a TXV. Don't make much sense, but neither did two metering devices in seriese.

Should the TXV be sized one size larger, like, say my box load is 7000 btuh, is a half ton valve good, or should I go with the 1 ton when using a distributor w/ orifice? Any problems with replacing a 30 yr old evap w/o an orifice type, with an evap that uses one?

I guess i'm thinking more as a service tech, what type things would I see that may suggest I suspect the orifice? ie. should be there and isnt, sized wrong, or valve before it sized wrong

[westcoast refer man]

Originally posted by TB

Should the TXV be sized one size larger, like, say my box load is 7000 btuh, is a half ton valve good, or should I go with the 1 ton when using a distributor w/ orifice? Any problems with replacing a 30 yr old evap w/o an orifice type, with an evap that uses one?

I don't remember any specific refrigerant for your system, but some TEV manufacturers make 3/4 ton valves. IMHO, asking a 1/2 ton valve to give an extra 16% to get 7000 btuh is pushing it. If a 3/4 ton is available go with that. Otherwise, a 1 ton valve shouldn't be a problem.

If an evap coil is a single circuit coil, then no distributor is used. However, once the coil has more than one circuit, a refrigerant distributor must be used as well an externally equalized TEV.

I guess i'm thinking more as a service tech, what type things would I see that may suggest I suspect the orifice? ie. should be there and isnt, sized wrong, or valve before it sized wrong [/B]

To keep it simple, orifice sizing is critical for good/equal distribution of refrigerant in coils that have more than one circuit. If the orifice is too big, equal distribution may not occur. This may be evident when comparing the leaving temperatures of the circuits. Too small and the pressure drop across the orifcie may be too great, which could lead to a loss of expansion valve capacity.

[R12rules]

Originally posted by westcoast refer man

Originally posted by TB

Should the TXV be sized one size larger, like, say my box load is 7000 btuh, is a half ton valve good, or should I go with the 1 ton when using a distributor w/ orifice? Any problems with replacing a 30 yr old evap w/o an orifice type, with an evap that uses one?


To keep it simple, orifice sizing is critical for good/equal distribution of refrigerant in coils that have more than one circuit. If the orifice is too big, equal distribution may not occur. This may be evident when comparing the leaving temperatures of the circuits. Too small and the pressure drop across the orifcie may be too great, which could lead to a loss of expansion valve capacity. [/B]

why isnt there more info on these suckers?

If it's out there ... I sure havent seen it.

This is a good thread.

[westcoast refer man]

Originally posted by R12rules

why isnt there more info on these suckers?

If it's out there ... I sure havent seen it.

This is a good thread. [/B]


Go to Sporlan's web site. Read their bulletin 20-10 when things slow down.

[icemeister]

I'll make it easy: Sporlan 20-10 (http://www.sporlan.com/20-10.pdf)

This is at least a two beer read. ;)

[LGM]

B I N G O!!!!!

[amazon]

One important point that must be done it to first choose the correct orifice , most of the time there are two or three sizes that come with the evaporator. then after you got the system charge and running , you will have to adjust the sub cool and super heat.......

Heat in the Amazon

[wannafreeze]

Originally posted by amazon
One important point that must be done it to first choose the correct orifice , most of the time there are two or three sizes that come with the evaporator. then after you got the system charge and running , you will have to adjust the sub cool and super heat.......

Heat in the Amazon

Do they come with instructions as to how to select the right one for the system.?

[westcoast refer man]

Originally posted by wannafreeze

Originally posted by amazon
One important point that must be done it to first choose the correct orifice , most of the time there are two or three sizes that come with the evaporator. then after you got the system charge and running , you will have to adjust the sub cool and super heat.......

Heat in the Amazon

Do they come with instructions as to how to select the right one for the system.?

Typically, there will be something to identify each orifice for use with a specific refrigerant. So, if you know what refrigerant you're going to put in, then you know which orifice to use.

[icemeister]

Originally posted by wannafreeze
.....Do they come with instructions as to how to select the right one for the system.?

The Heatcraft I&O Manual (http://www.heatcraftrpd.com/Maintenance/manuals/H-IM-64K.pdf) has a great dissertation on nozzle selection on pages 7-8.

It may be more than you wanted to know. ;)