orifice

[Ray Ang SM]

plea help,how to size expansion internal orifice,isit by compressor or evaporator coil temperature capacity.

[US Iceman]

...evaporator coil temperature capacity

What is this?

If you would have said evaporator coil capacity I see what you are asking for? However, the use of the word temperature in that description is confusing.

The TXV's have to be sized for the respective evaporator coil capacity at the specific operating parameters the evaporator will be operating at during normal conditions.

TXV orifices are rated on cooling capacity at a specific pressure differential and the temperature of the liquid refrigerant feeding the TXV.

Do not over-size the orifice capacity. If the orifice capacity is within 10% of what you need for the evaporator capacity you should be OK.

[powell]

Iceman,

I read the question somewhat different.

My answer would be that a TEV is sized according to the compressors btuh capacity at a given SST or as ray states, "evaporator coil temp".

regards...............powell

[US Iceman]

My answer would be that a TEV is sized according to the compressors btuh capacity at a given SST or as ray states, "evaporator coil temp".

That would work if.... you only have one evaporator.

What if you have more than one evaporator connected to a single compressor? Or, if the multiple evaporators each have a different capacity?

[powell]

That would work if.... you only have one evaporator.

What if you have more than one evaporator connected to a single compressor? Or, if the multiple evaporators each have a different capacity?

First, one would need to know the design SST and design TD of the evaps and then size the TEV accordingly, if by percentage, to the unit/compressors btuh capacity.

[Rajkumar]

Have you seen the Danfoss or Sporlan catalouge for selection of expansion valve.
If you required i will send.

raj

[US Iceman]

First, one would need to know the design SST and design TD of the evaps and then size the TEV accordingly, if by percentage, to the unit/compressors btuh capacity.

True, but... either way you need to know some information before you can make an informed decision. The assumption that needs to be defined is if the system has one or more evaporators.

You cannot size a TXV on a system containing multiple evaporators by using the compressor capacity though. If you get used to using the evaporator capacity then your selection will be accurate all of the time (if the valve is selected for the appropriate capacity in the first place by using the proper correction factors).

[Ray Ang SM]

thank guyfor helping alot.

[powell]

True, but... either way you need to know some information before you can make an informed decision. The assumption that needs to be defined is if the system has one or more evaporators.

Correct. I used the plural form of evaps in my statement.

You cannot size a TXV on a system containing multiple evaporators by using the compressor capacity though. If you get used to using the evaporator capacity then your selection will be accurate all of the time (if the valve is selected for the appropriate capacity in the first place by using the proper correction factors).

It seems we agree to disagree on how to explain the specifics of designing a valve. I'm sure that any valve that you and I design would probably match and work properly.

This discussion could evolve into a highly debated subject like the superheat/subcooling debates.

regards..................powell

[US Iceman]

This discussion could evolve into a highly debated subject like the superheat/subcooling debates.

Probably... just like the adjust or don't adjust TXV's thread.

I stand corrected on the issues of the plural use of evaps. I did not catch that on the first pass I made.

What I have been trying to say (and apparently failing) is that you need more information than the compressor capacity to size the TXV's. For a single compressor/evaporator system the compressor capacity has to equal both the TXV and evaporator capacity so no argument on that point. If the capacities don't match, something is wrong.

The point I was attempting to make is that if you base your decisions/selections for the TXV on the evaporator capacity and operating conditions that the TXV will work at you can't go wrong.

Then (on a multiple evap. system) the total evaporator capacity should equal the total TXV capacity and the total capacity of either one (evap.'s or TXV's) should match the total compressor capacity.

This way you don't have any accounting errors on something not adding up properly.

It seems we agree to disagree on how to explain the specifics of designing a valve.

We are not designing valves, the manufacturers do that. We are applying the valves to a specific operating condition. We may fully agree on the end result, but the methods I use and try to suggest are based on what I've done and been successful with.

And the most confusing thing to do is to try to explain how to do something. Look at the trouble we are having and we share a common language. Just imagine the person who is trying to read this and translate it into their native language. All we have to work with is pictures and language in trying to help someone. What one says, the others disagree with, but it's harder still for someone else who only has the written word to work from.