most efficient way to supply ammonia to lowside recirculator

[RANGER1]

Not sure if this has been asked before, but see following description.

2 stage ammonia refrigeration plant
-40 C low side with liquid recirculator pumps
-10C intercooler/recirculator with liquid pumps

Several ways to maintain -40C liquid level
1/ high pressure liquid from receiver subcooled by separate internal coil in -10 C then feeds -40 C
2/ low pressure liquid transfer from -10C to -40C
3/-10 C liquid pump feeding -40C
4/ other methods don't know or can't think of on 2 stage plant

2 & 3 the same efficiency
What would efficiency difference be between 1 compared to 2 or 3, much?

[Segei]

1 is less efficient than 2 and 3, but difference is not significant. In 2 and 3 temperature of the liquid which is going to -40C vessel is -10C. In 1 this temperature is slightly higher probably from -5C to -7C. Evaporation temperature is intercooler is -10C and temperature of subcooled liquid will be higher than evaporating temperature.

[mbc]

Hi
as Segei told in 1 we have less efficient ( sub-cooling liquid )

But between 2 and 3
in 3 we have a little more efficient than 2 because of pump pressure .

also at 3 ) if we need more liquid in -40 it is better we use this feeding.

[RANGER1]

Thanks, I sort of figured some difference, it not significant.
A bit more flash gas on high pressure subcooled liquid that has to be compressed twice.

[Segei]

Hi mbc.
I don't see efficiency difference between 2 and 3. However, I agree with liquid feeding from intercooler to -40C vessel. To supply liquid in 2 example we have pressure difference around 30 psig. However, saturated liquid will be supplied. It means any pressure drop in liquid line will create flash gas and this gas will reduce capacity of metering valve. In 3 example liquid pump increase pressure difference to 60-80 psig and liquid will be subcooled. It means no flash gas in liquid line. Liquid pump will be able to supply 3-5 times more liquid to -40C vessel than just pressure difference.

[mbc]

Hi

if you see this PH diagrams you can see a little more efficiency

15028
From 6 to 17 is a our pump pressure

[Segei]

First, difference between 2 and 3 is fraction of 1% because of energy added by the pump. Second, 2 is more efficient(less flash gas) than 3 but difference is minimal.