3 replies to this topic

[N.B.E.]

Hello everyone,,,

I'm a mechanical student and am trying to simulate an absorption system (Ammonia cycle).
We all know that heat absorption cycles are heat actuated; the heat source in my project is the engine block and its surroundings in a normal car.

It’s too costly to build it to see if it works. So I was wondering can I simulate this project in hysys knowing that am not using the ammonia as the absorbent, instead am using lithium bromide because it has a cooling limit of 5°C.

The cycle can be treated as if its and ammonia but can I modify fluids flowing like the refrigerant.

All I know is to use sour Pr instead of regular Peng Robinhson equation of state.
For streams I should use NBS or ASME.

If it’s possible which software package is best for me?
Can any body help?

I hope this project works because if we can eliminate parasitic load on engine cause by compressors, then less fuel will be needed since there is a significant load eliminated thus it will reduce emission gasses.
Another advantage is available power.
The system is economical for countries with high gas prices.

[Zauberberg]

In my opinion, using Sour PR or any other EOS is not likely to give you acceptable results. The system you have is highly non-ideal and contains an electrolyte - aqueous solution of lithium bromide. I would rather choose OLI package if available or, perhaps, NRTL.

The most critical part is simulation of water absorption in concentrated electrolyte solution, in the sense you'll need very accurate calculation of water vapor absorption rates in liquid LiBr medium - dependent on contacting volume/surface, absorbent load, system temperature, pressure and cooling capacity requirements. That is something you may wish to do manually, at least for the purpose of rough estimation.

The heart of process is evaporation-absorption cycle of refrigerant water with purpose to provide heat sink (cooling medium) at lower temperature levels than the one usually available (ambient air or cooling water), which is justified if you cannot remove heat from the system by using high-temperature sink, if surface area becomes too high for economic operation, or if coolant temperature rise without pre-chilling is unnaceptable. This should be your starting point in project assignment - evaluating the feasibility and applicability of such system: is it really required? And secondly, can it work as such?

The lowest temperature obtained by this cycle is in the range 5-10C and the most impressive application I have seen is huge external catalyst cooler system in RFCC regenerator units, with chilled water conditioned at 12C.

[N.B.E.]

thanks for the useful tips....
Am working on how i can simulate the project in the net two month to find out if it can work .I foulnd a hysys dealer in Doha (where I live) and I will ask about the OLI package or NRTL.

the emission gasses from cars are one of the major sources of green house gasses if we can ca reduce the amount of burned fuel in every car we will reduce the emission gasses perhaps this will give us longer time to work on other energy resources or maybe until all cars are electrical or so..
Knowing the target was set based on coefficient of performance for standard compression cycles.
C.O.P.= QL/W QL = cooling rate.
The C.O.P. for comparison is about 3 in all thermo books.
The compressor in the car I worked on needs 600 w or kj/s
There for QL = 1800 kj/s or W
The C.O.P. for ammonia is 0.5 there for the system will need 3600kj/sto be equivalent.
The main heat source is the exhaust pipe and it’s a co-current flow.
And I took measurements of the exhaust pipe surface in worst scenario when the engine is Idle and I got hi temperatures after the firs 15 min that reached 295˚C.

I will be pleased with your contributions....

You will also need the measurements of the exhaust mass flow, as welll as other heat sources (cooling water, oil, radiation) to have a better picture of your idea .Review the patents that already exist (1979,1995,2000). and expect lower COP. (0.2-0.4). I may have something helpful to save-time, an aplication for ACM's. once you have the streams values you can go on on the hysys simulation. mail me at papitodesanluis@gmail.com.