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Muhammad Anwer
11-07-2017, 10:44 AM
Dear all,

Hello to every one, I am new in this forum and I am trying to learn ammonia refrigeration and its valves selection for evaporators.

To all respected members, I need your help, what is the Saturated suction temperature and how would i decide it.

I need to install a ammonia evaporator to maintain a room temperature at -20 degC and I have a liquid ammonia supply at -42 degC. So I need to know that what would be its evaporation temperature ?? What would be its SST ?? and also how would I select the valve station for this evaporator ??

Any help in this matter would be highly appreciable, looking forward for your help.

Thank you.

RANGER1
13-07-2017, 02:19 AM
Dear all,

Hello to every one, I am new in this forum and I am trying to learn ammonia refrigeration and its valves selection for evaporators.

To all respected members, I need your help, what is the Saturated suction temperature and how would i decide it.

I need to install a ammonia evaporator to maintain a room temperature at -20 degC and I have a liquid ammonia supply at -42 degC. So I need to know that what would be its evaporation temperature ?? What would be its SST ?? and also how would I select the valve station for this evaporator ??

Any help in this matter would be highly appreciable, looking forward for your help.

Thank you.

Muhammad,
Suggest you hire a refrigeration company to work this out for you & asses your plant.
Can you explain the -42 deg C liquid, is it from a liquid pump on a low temperature accumulator?
Saturated suction pressure is probably -42 C & the suction pressure should be -36kpa, is this correct?
If you want your room temperature of -20 C you need ammonia to be colder by 6 to 10 deg C, so -26 to -30 deg C.
You have -42 C liquid so no problem.
You have to be able to defrost it as well, hot gas, water or electric defrost, so then you can narrow down what valve stations you need.
You also need room load in kilowatts to select correct evaporator & correct fin spacing for room temperature otherwise it can frost up to quickly.


https://www.agas.co.uk/media/2425/r717-pt-chart.pdf

saturated pressure is what you see in this chart, ignore second column.

NH3LVR
13-07-2017, 09:27 PM
There could be a problem with Nh3 at -42C being fed into a evaporator operating at a suction temp of -26C.
Depending on the coil design, the cold liquid has to be warmed up to Suction temp before any meaningful work can be done. Biggest problem is with top feed coils as I remember.