AC unit - air as refrigerant

[ssk1962]

I have a requirement to design, manufacture and test a stand alone, trailer mounted air conditioner unit - using Air (Reverse Brayton Cycle)
The spec outline is as follow
Gas = Air
Mass flow rate = 600 lbs/minute @ 40F.
Heat Mode = 750,000 Btu/hr
Ambient temp range = -40 to 140F

Is this commercially viable. Any input is very much appreciated
Why Air cycle - air conditioning has not picked momentum?

[Brian_UK]

There is a great deal of information about this on the web, has any of that given you any help?

[mad fridgie]

I have a requirement to design, manufacture and test a stand alone, trailer mounted air conditioner unit - using Air (Reverse Brayton Cycle)
The spec outline is as follow
Gas = Air
Mass flow rate = 600 lbs/minute @ 40F.
Heat Mode = 750,000 Btu/hr
Ambient temp range = -40 to 140F

Is this commercially viable. Any input is very much appreciated
Why Air cycle - air conditioning has not picked momentum?
try contacting Boeing or the like, as similar to what is used in commercial aircraft

[ssk1962]

Mad Fridge.......I know it works on a aircraft - aircycle machine with turbines and cold condition at high altitudes.
My question is i am trying to replicate it on the ground

[mad fridgie]

Mad Fridge.......I know it works on a aircraft - aircycle machine with turbines and cold condition at high altitudes.
My question is i am trying to replicate it on the ground
I had a look at something similar some years ago, (low temp freezer on a fishing boat) theory was not the issue, it was finding the equipment, all pointed to aircraft industry. The boat sank, so no further work was done.
We did also look into Turbo Chargers.

[Josip]

Hi, ssk1962 :)

welcome to RE forums...


Mad Fridge.......I know it works on a aircraft - aircycle machine with turbines and cold condition at high altitudes.
My question is i am trying to replicate it on the ground

as I know (maybe I'm wrong) ACM are working on the ground also....

"In addition to the engines, the Auxiliary Power Unit (APU) on the aircraft provides bleed air for use on the ground and, for some aircraft, in flight usually until just after take-off and from shortly before landing. With the B757, the APU is not used as a pneumatic source in flight. Again, the actual temperature and pressure of the air supplied will be dependent on ambient conditions and the running condition of the APU. The APU temperatures are nominally 177 deg. C /350 deg. F for the B757, as there is no precooler present in the APU system, and 200-230 deg. C for the BAe 146 aircraft."

http://www.advisorybodies.doh.gov.uk/pdfs/annex5tox0621add.pdf


seems it is possible to make it on the ground...;)

Best regards, Josip :)

[Hitech]

In aircraft The ACM provides cooling on the ground and heating at altitude, the problem is COP or rather lack there of, because it does not involve a phase change of the "refrigerant".:)

[ssk1962]

Josip and Mad Fridge,

I used Reverse Brayton Cycle. Theoritically it should work, But the efficiency is directly tied to the pressure ratio. it is mere 22 %. I am having problem Heat exchanger - lot of wasted heat.
Does any one know how to calculate moisture content of compressed air?

[Toosh]

Josip and Mad Fridge,

I used Reverse Brayton Cycle. Theoritically it should work, But the efficiency is directly tied to the pressure ratio. it is mere 22 %. I am having problem Heat exchanger - lot of wasted heat.
Does any one know how to calculate moisture content of compressed air?

Try here

http://www.uigi.com/air.html#Physical%20Properties%20of%20Air

Toosh

[MechAcc]

try contacting Boeing or the like, as similar to what is used in commercial aircraft
Actually Hamilton Standard or Airesearch makes the Environmental Control Units.

[Josip]

Josip and Mad Fridge,

I used Reverse Brayton Cycle. Theoritically it should work, But the efficiency is directly tied to the pressure ratio. it is mere 22 %. I am having problem Heat exchanger - lot of wasted heat.
Does any one know how to calculate moisture content of compressed air?


Usually during compression process of air water condense and we remove it, but remain air is always at 100%RH.... how much is that is not easy to say

.... btw is it possible to use some air dryer down to -40'C

... reuse of waste heat must be possible somehow


..... Most engines have a thermodynamic limit of 37%. Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18%-20% ... maybe your 22% is not mere...;)


Best regards, Josip :)

[dougheret0]

I have a requirement to design, manufacture and test a stand alone, trailer mounted air conditioner unit - using Air (Reverse Brayton Cycle)
The spec outline is as follow
Gas = Air
Mass flow rate = 600 lbs/minute @ 40F.
Heat Mode = 750,000 Btu/hr
Ambient temp range = -40 to 140F

Is this commercially viable. Any input is very much appreciated
Why Air cycle - air conditioning has not picked momentum?

My first job out of college was with Pan Am, working as a maintenance engineer on the first generation Boeing 707 passenger jets. These aircraft used air cycle refrigeration by expanding air from a compressor stage across a turbine. Downstream of the turbine was a "water separator", which was nothing but a bag. I expect you can get design data on these systems, possibly from Boeing, but certainly from some academic site on the web. Good luck.:)