Ammonia-water refrigration system.

[Salah 1]

Hi guys:
I have an idea of using hot water (the water temp is about 50 celsuis if not more coming from water well) to run ammonia-water refrigeation unit. however in most of the articals I read about such process it looks like the minimum evaporator temperature we can get with such system is about +5 degrees celsuis which is nothing good for freezing purposes...
Can we get really freezing evaporator temperatures (like -10 or even lower).
With effeciency is not that crusial factor or this is not common in such systems..
Thank you

 

[georgeverghese]

If you want -10degC, use anhydrous ammonia. Otherwise, many plants are now switching out to trans critical CO2 refrigeration cycles to get higher eff.

 

[goutam_freelance]

Another possible option is to have a 2 stage refrigeration.

1. Step-1 achieve about 5 deg C temperature with low grade heat(say 50 deg C)
2. Step-2 achieve -10 deg C from 5 deg C temperature with high grade heat(steam or hot water, higher than 50 deg C by firing fuel etc.)

But the cost and economics need to be worked out.

 

[IRstuff]

https://en.wikipedia.org/wiki/Einstein_refrigerator had a variant that used ammonia and water

 

[BrianPetersen]

Are you trying to use an absorption cycle? If so, that's going to severely limit your options.

Minor digging suggests that temperatures well below 0 C are possible, but depend on both the high-side temperature and the heat-rejection temperature. https://bl-thermo.com/technical-information/

 

[goutam_freelance]

"Another possible option is to have a 2 stage refrigeration."

Another cheaper option in terms of first cost is to further heat the available fluid using a conventional or renewable source and use the higher temperature heat source using Vapor Absorption Refrigeration.