Icing/ ice deposits found at turbine

[spiderman]

hi all
im running a refrigeation system experiment using air as refrigerant.
this is a small model scale system designed at school for producing cold Air to go into a cold room. im trying to model a blast freezing application with my model.
my model using a primary compressor and secondary compressor is bootstraped to the turbine.
i left the system running for about a day and came back to find icing around the turbine exit.
how can i solve this problem without switching off the system altogther?
is there any new technologies out there in the market that i can use to solve this icing problem?:confused:
what does existing vapour compression systems use to solve icing problems?

someone suggested to me to use a 'dehumidifier in conjunction with evaporative spray cooling and regenerator'.

Does anyone know what this means and how it works?

Thanks for all your help.
cheers

[spiderman]

ps. this is a small model scale system designed at school for producing cold air to go into a cold room. im trying to model a blast freezing application with my model.

[LRAC]

Hi spiderman

Are you trying to produce an air cycle system and the compressors you are using are air compressors and not refrigeration compressors.

12 years ago i participated in an experiment with Bristol university on the design of such a system in the commercial field of refrigeration but the volume of air required to run the systems was astronimical and noisey.

Moisture in an air cycle system is the killer question as the air velocity and volume are large as well as noisey, we tried an air drier system plant bolted onto the turbine inlet (that was crap).

The only way we found to keep the turbine free of ice was to put a secound turbine in parallel and use the heat from the oil circuit of the turbine running to defrost the turbine that was in idle mode. This was done by duct work closers and dampeners and a small circulation fan within the closed off turbine.

We achieved a temp of -50C before 1 turbine left the building as the oil cooler packed up:D :D :D :D

Let me know and i'll see if i can help you?

regards
Lrac

[spiderman]

hi LRAC,
thank you for your reply.
Glad to get a reply from someone that has similar experience about what I am doing. :)

the primary compressor we used is an industrial air compressor from school.
i have been to the bristol university website.
they are doing similar research to what i am doing, although the scale of my project is not as big as their ACR projects.
yes you are right, the system is noisey.
the temperatures i could get was in the range of -30 to -50 degC.

Your solution to the icing problem in the turbine, is this available online or was it published in a paper or journal etc. so I can have a look at it. i assume you worked with the bristol university?

Just to check with you about your solution.
I assume at first you used 1 turbine and because there was ice forming you used two turbines?
The first turbine (which is running) creates a bit of heat and would defrost the second turbine (which is idle) in parallel to the running turbine.

What do you mean by ‘done by duct work closers and dampeners and a small circulation fan within the closed off turbine’?

The fan is located inside the idle turbine?
Could you explain this a little more?
Your solution is very interesting.:) :D

[Dan]

Gentlemen, I am quite interested in what you are doing and how your are going about it. Can you tell more? Turbine? What sort of compressor are you using? Is this transcritical process? Why use air?

[LRAC]

Gentlemen, I am quite interested in what you are doing and how your are going about it. Can you tell more? Turbine? What sort of compressor are you using? Is this transcritical process? Why use air?

Hi Dan

please find enclosed a simple air cycle system,this model does have limitations and is used for air con applications. refrigeration takes alot more thinking about as Spiderman says freezing of the moist air brings great problems.

Kind regards
Lrac

[NoNickName]

Contact IIR at http://www.iifiir.org/ and ask for a copy of "Holder, Brown and Gigiel, The effect of water and icing on the performance of open air cycle systems, Proc IIR congress, The Hague, August 1995".

[LRAC]

the temperatures i could get was in the range of -30 to -50 degC.

Your solution to the icing problem in the turbine, is this available online or was it published in a paper or journal etc. so I can have a look at it. i assume you worked with the bristol university?

Just to check with you about your solution.
I assume at first you used 1 turbine and because there was ice forming you used two turbines?
The first turbine (which is running) creates a bit of heat and would defrost the second turbine (which is idle) in parallel to the running turbine.

What do you mean by ‘done by duct work closers and dampeners and a small circulation fan within the closed off turbine’?

The fan is located inside the idle turbine?
Could you explain this a little more?
Your solution is very interesting.:) :D

Hi spiderman

I left the project 10 years ago in its infancy, the way the project was going was in the direction of air conditioning and not my own direction of refrigeration, + i had other plans. My commitment was wondering and the air cycle process was long winded, we solved 1 problem only for another to appear + i didn't think many customers would want a gas powered jet engine on the roof of their building to drive the system. Just imagine the maintenance schedule and gas costs to run it just to generate the air volumes required.

Quite a few questions in the above so here goes!

No papers were produced as i only produced papers on succesful results, there are some very clever people in the scientific world and they love to disagree with anything on paper, i was a more nuts and bolts guy and liked too see things actually work rather than publish papers on theoretical out comes.

Duct work was taken from the hot air heat exchanger back on to the expansion turbine casing, in simple terms encassing the turbine outlet in a warm environment so assisting in the impeller defrosting, we also tried using the heat from the oil cooled turbines circuit( the 1 left running).

1 big problem when the 2nd turbine comes back on line the moisture levels increased and we were back to square 1. Then you have to look at getting rid of the water droplets from the turbine casing.

You have alot of work ahead of you and the path is long and not exactly straight, if i can be of any assistance let me know. Believe me i made many a mistake and nearly ended up bald with the head scratching, but still quite interseting as people say nothing is more free than air, but the consumption of the air compressors didn't exactly make it top of the list for environmental concerns.

Nothing wrong with small scale applications but very limited on commercial and industrial applications.

I hope this answers some questions spiderman and hopefully Dan will read this post as well?

Kind regards
Lrac