aqua-ammonia 5

[aquafied]

Is the vapour given off during the generation cycle of an absorption refrigeration system basically pure Ammonia and does the Ammonia conform to the the saturation/pressure charts on the high temperature side and low temperature side of these systems?

 

[NXTCOLD]

COPs for the industrial systems run from about 0.2 @ -40 to 0.7 @ 40F. I should have noticed the topic was small enriched AAR.

 

[aquafied]

25362 (Chemical) In your third posting you suggested “there is no gas stratification effect” After much deliberation I can't believe that stratification doesn't occur in the "balance drum" otherwise Dalton's Law would be applicable and Hydrogen and Ammonia would be distributed equally throughout the system. Am I right?

 

[Compositepro]

NXTCOLD, I'm guessing that the "industrial" units you refer to use electricity to pump the water loop rather than a heat driven bubble pump. Is that correct?

aqufied, I don't understand your obsession with a "stratification effect". The whole refrigeration cycle is based on getting components separated (another word for stratified) from each other. Otherwise, nothing happens.

 

[aquafied]

Compositepro My obsession is a result of my need to convince my project partner that Hydrogen and NH3 are distributed evenly throughout the system before the liquid trap is established between the condenser and evaporator. Liberated NH3 vapour from bubble pump drives all the Hydrogen to the evaporator and traps it when enough NH3 condenses and closes the liquid trap. My colleague has an obsession with Dalton's Law and believes that Hydrogen still exists evenly throughout and the "balance drum" can't possibly work. He is the one with the brains

 

[25362]

To aquafied,

The pressure balance pipe (or reserve vessel) is not connected to the top of the ammonia condenser but to its liquid outlet, sometimes via a liquid trap to avoid hydrogen entering the condenser.

In this way the hydrogen rising from the absorber (with some remaining ammonia) mixes with the liquid ammonia "from" the condenser before entering the evaporator.

By then the ammonia vapor diffusing into hydrogen is ~ 26% w/w, which refers to a temperature of about -30^oC at the inlet to the "freezer" under a total pressure of say, 25 ata. At the outlet of the evaporator's "food chiller" the ammonia in the hydrogen stream reaches a concentration of about 50-55% w/w and enters the absorber with some liquid.

I hope the above amswers your query.

 

[aquafied]

25362 One more question. During the generation cycle is the Hydrogen pushed back to the evaporator or does it remain as a partial pressure on the condenser side and do you know where I can get technical info on this? My colleague is adamant that it does and none of my text books discuss this point.

 

[Compositepro]

The ammonia vapor coming from the generator is analogous to steam coming out of a tea kettle on a stove. The hydrogen is analogous to air in the room. As long as steam is being generated it is flushing all air out of the teapot. There is a tendency for air to try to enter the tea kettle by diffusion, but diffusion is a slow process that is far slower than the velocity of steam leaving the kettle.

 

[aquafied]

Thank you all for your patience and contribution for enhancing my knowledge of the technicalities the NH3/H absorption system.

 

[NXTCOLD]

Compositepro,
Yes, about 5 hp per 100 tons.

 

[25362]

http://nptel.iitm.ac.in/courses/Web...agpur/Ref and Air Cond/pdf/RAC Lecture 17.pdf

 

[Compositepro]

Here's an interesting insight from 25362's (any relation to THX1138?) latest link. Absorption systems that use electric pumps are not constant pressure systems, and do not use hydrogen.