aqua-ammonia
aqua-ammonia
(OP)
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?





RE: aqua-ammonia
Good luck,
Latexman
RE: aqua-ammonia
The water content of various ammonia qualities can be seen in:
RE: aqua-ammonia
Most if not all absorption refrigerators have a means of condensing water from the NH3 vapour (after bubble pump) before the NH3 is condensed how is this possible?
RE: aqua-ammonia
NH3 + H2O <-----> NH4+ + OH-
Ammonium hydroxide is just a word/name that was invented and is synonomous to aqueous ammonia, ammonia water, ammonical liquor, ammonia liquor, aqua ammonia, i.e. a solution of ammonia and water.
Good luck,
Latexman
RE: aqua-ammonia
IMO, that's the apparent reason for water condensing before ammonia.
I think the professor is right. A 17% w/w (10 N) solution is ionized by much less than 0.5%. A very dilute solution can be ionized by more than 10%. In these cases ammonia molecules pick up H+ ion from neighboring water molecules to form ammonium and hydroxide ions.
It is OH- that turns phenolphthalein pink.
Both compounds in the ammonia-water mixture are very polar, making it a highly non-ideal solution.
Good examples of the non-linearity of mixture-functions with composition are an enthalpy-composition plot showing parabola-like isotherms with minima in the mid-range and solution dynamic viscosities showing peaks at about a 0.25 ammonia mass fraction.
The following link shows thermophysical properties:
www.mie.uth.gr/ekp_yliko/NH3_H2OProperties_1.pdf
RE: aqua-ammonia
RE: aqua-ammonia
RE: aqua-ammonia
Now, you're referring to a hydrogen-assisted ammonia absorption refrigeration system
As in your attached sketch, the reserve vessel acts as a "balance drum" receiving, as well as delivering, hydrogen, as the double-ended arrow shows. Hydrogen is coming in not only from the condenser but mainly from the absorber/regenerator after been cooled by heat exchange.
Therefore, there is no gas stratification effect. Am I right?
RE: aqua-ammonia
The vent tube keeps the condenser and evaporator at the same pressure, while the hydrogen keeps ammonia vapor from passing through the vent tube. The other and main purpose of the hydrogen is to cause ammonia to evaporate in the evaporator, just like blowing air over water causes cooling by evaporation. For more details study the link I provided. Bear in mind that there is a hydrogen flow loop, an ammonia flow loop, and a water flow loop.
RE: aqua-ammonia
Is the mixture homogeneous or stratified?o (Chemical)
RE: aqua-ammonia
It appears that the hydrogen stream contains some ammonia vapor (no stratification). If temperatures in the reserve vessel drop, some ammonia would condense and be drained back to the condenser or to a liquid trap connected with the evaporator.
That is probably the reason for the protruding hydrogen pipe and the sloping of the reserve vessel towards the condenser.
RE: aqua-ammonia
RE: aqua-ammonia
See fig. 13.4 in
http://www.parliament.vic.gov.au/images/stories/co...
RE: aqua-ammonia
RE: aqua-ammonia
This systen is called the Platen-Munters cycle. Hydrogen (or helium) is never pure. It contains various amounts of ammonia vapor depending on what part of the circuit is beeing considered.
The hydrogen reserve vessel acts as a presure equalizer by being connected to both the liquid coming out of the condenser and the gas returning from the absorber.
RE: aqua-ammonia
NXTCOLD
RE: aqua-ammonia
RE: aqua-ammonia
The following link may be of interest:
http://www.thaiscience.info/Article%20for%20ThaiSc...
RE: aqua-ammonia
RE: aqua-ammonia
RE: aqua-ammonia
RE: aqua-ammonia
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.
RE: aqua-ammonia
RE: aqua-ammonia
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 -30oC 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.
RE: aqua-ammonia
RE: aqua-ammonia
RE: aqua-ammonia
RE: aqua-ammonia
Yes, about 5 hp per 100 tons.
RE: aqua-ammonia
RE: aqua-ammonia