TEV range & minimum pressure diff issue

[Lc_shi]

HI Sirs
Pls give your ideas:)

Need to select a TEV for a R22 system of capacity 56KW(16USRT)at Te=10C ,Tc=48C. I choose Emerson Alco TEV HFE valves(nominal 15USRT),it's a litter higher than norminal at this condition.
It's a parellel compressor system,while single compressor is working. The capacity is 50% of full load.
If the TEV adapt to the change,the mass flow across the valve decrease and the pressure drop should become small,then the evaporative pressure and condenser pressure difference should be small.
I wonder if there's minimum pressure diff requirement across the valve. if so, can the TEV properly work at 50% loading situation:confused:

regards
LC

[Renato RR]

I have similar situation on Rhoss chiller but compressors in paralell are 120 000 + 160 000BTU.So it can be done.However check with valve company.

Renato

[US Iceman]

I wonder if there's minimum pressure diff requirement across the valve?

YES. The minimum differential pressure is what you will need for the valve to provide it's rated capacity. The valves should have a 50% turn down capacity. If the valve you are using is a balanced port valve I'm sure it will be OK.


...then the evaporative pressure and condenser pressure difference should be small.

If you have one evaporator and one condenser for two compressors, the suction pressure will increase slightly because you are using all of the heat transfer surface with only one compressor.

At the same time, the discharge pressure will reduce slightly for the same reason.

The differential pressure the TXV will see does decrease some, but should not significantly reduce the differential pressure or the capacity of the valve.