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Hi,
I need the clarification on Expansion valve selection.
I have the capacity of 87KW
pressure drop 10 bar
Refrigerant R22
Expansion valve Danfoss TEX12 orifice no 4
This application used a compressor unit of tandem type.Each has the capacity of 41KW.
Now my question is :
During the part load application the only one compressor will be running.
Is this lead any problem to the compressor?
Basically i need the effect of oversized expansion valve?
Clarify it.
Best regards,
ravi perumal
The only problem I can see is the pressure difference over the valve.Quote:
Originally Posted by raviperumal
The pressure differece must remain about 5 or 6 bar or the valve will fail to work correctly.
I don't know if that helps but just a thought.
taz.
Hi TAz,
If valve fails how it will afect the compressor.
They will fail normaly in one of two ways.Quote:
Originally Posted by raviperumal
1 They fail closed, so they reduce the amount of refigerant flow through the system.
2 They fail open and flood the system with exess refrigerant.
Both have there own risks attached.
Cheers taz.
Hi,
That is the problem and you can not do anything about it. This is why with multiple compressors running in parallel, multiple cycles are used each with its own TEV.
Except when you use Electronic Expansion Valve.
Imagine this : The selected valve gives 87kW then when two compressors are running then there is no problem. When one is switched off then there is 43.5kW capacity, i.e. OVERSIZED TEV which will cause a major problem.
1- high suction pressure, if still there is no flood back to the compressor.:(
2- If the evaporator load is reduced more than 50% then you may have flood back to the compressor.:eek:
I have encountered with oversized TEV and it is not nice.:D
Hope this helps.
Cheers.:)
Hi,
When Evaporator load is reduced then the chances of flood back to compressor will be more.
If i am right,
In our case the compressor in the upstream line has got failed due to this kind of flood back.
Yha ....
Thanks to all.
Best regards,
ravi perumal
Hi,
I consider the better design is two EXPs in two branch circuits, and the valves normally should remain 1/3 allowance capacity.
how can I select an expansion valve for my design of refrigeratin system
If you give the right data to TEX manufacturer, they can advise you better though their software selection program .
You will also need an oil separator in case if you switch off one compressor & operate only one compressor with 50% evap load because your suction line is not designed for part load condition .
( on 50% evap load , oil return becomes a problem)
an oil separator means addition of two nrv in discharge line etc ; your accessories increase to protect the compressor . Hence two independent circuits will be simple to operate & maintain
Hi lana ,
the system will also need to have condenser capacity regulator to match the fall in evap load
An alternative may be to use an electronic expansion valve. some brands can control down to to well below 40% of total load. The siemens, emerson or sporlan will do the job. Its a matter of preference.
if you have any soft ware selection of TEV pls tell which will down load easyly.