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A.Mortezania
04-02-2017, 01:45 PM
Dear All,

In all of sources we see that for example 10% of end of evaporator (+ Suction line) is called super heater and it means when refrigerant comes out form evaporator it should be in superheat position on PH diagram.
But at low temperature evaporators even by using proper expansion valve and proper heat transfer area on evaporator and proper fan, Twice we have liquid floodback. This is one of reason that most of companies make accumulators for prevent liquid floodback to suction of compressor.

"I Think at low temperatures, If we do anything we can not prevent liquid floodback form evaporator and we should use accumulator to protect compressor".
It is true or even by using proper evaporator and proper expansion valve even at low temperature evaporators we have superheat at end ?

Sincerely yours.

Segei
04-02-2017, 04:50 PM
Sometimes you can have flood back when you have significant fluctuation of the refrigeration loads. Yes, mechanical TEV are slow and EEV react faster to load change. However, even with EEVs you can get flood back. Accumulator will prevent flood back to the compressors. Another solution to have compressor VFDs and compressors will unload fast enough when load change.

PaulZ
05-02-2017, 10:59 PM
Hi Mortezania
All evaporators using TX valves have superheat regardless of the temperature of the room.
It is advisable to have a suction accumulator to protect the compressor as TX valves will cause flood back for the following
# wrong orifice is selected (too big)
# superheat setting is incorrect
# orifice is damaged due to wire drawing, seat cut (valve still feeds liquid even when shut)
# bulb not secured to suction line properly
# bulb in wrong position on suction line
Regards
Paul