what is this?

[Mark]

chemi-cool
All the dx milk cooling tanks (ive seen) have had the suction line accumulator at the condensing unit end .With a high wattage heater tape wrapped round to aid the accumulators function ie fabdec,mueller tanks.(depends on field conditions)
Have you pumped the c/u unit down and looked whether theres any sort of expansion,or metering device,at the inlet of the vessel.(If its dx.)
It looks like the vessel pictured is some sort of liquid sub-cooler.
regards mark