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Ab.elb
05-10-2016, 08:34 AM
Hello guys,
I'm new to this forum and i need some help concerning the charging of AC systems:

I'm working on a project where i need to to charge the AC circuit of a car ( on a bench test) with liquid. I understand that we can do this by putting the refrigerant tank upside down. but what i m trying to achieve isto perform a very fast charging. so i'm thinking of a system to do so.


My thoughts are:
- Heat the refrigerant tank to 40 so that pressure will go up to (10 bar for R134a).
- Connect the ref tank to a compressor and a restriction to help build up my pressure, (then to a condensor), then to my benchtest.

The problem with that is there are risks of exploision while heating the tank.

I'm also wondering if pumps can be used to pump refrigerant from the tank ( r134a).

Do you guys have some ideas to help.
Thank you

Brian_UK
05-10-2016, 03:12 PM
Yes you can get liquid refrigerant pumps.

Intrigued, why the need for the fast fill?

Ab.elb
05-10-2016, 06:24 PM
Thank you for your answer Sir.
Can you help me for finding the pump. I ve looked into HERMETIC pumps and saw that they have pumps for big application (50m^3/h) , while i m looking just around 0.1 litter per second.




Intrigued, why the need for the fast fill?

It's for testing valves.

monkey spanners
05-10-2016, 07:09 PM
Most refrigerant recovery machines will pump liquid refrigerant, not sure on the flow rate though.

Ab.elb
06-10-2016, 09:56 AM
Most refrigerant recovery machines will pump liquid refrigerant, not sure on the flow rate though.

Thank you for your answer.
I've looked into some recovery machine and found that they pump liquid first out of the system. but won't this affect the compressor?

hyperion
06-10-2016, 01:32 PM
if you have created a good vacuum on the system and then charge it using your pre-heated R134A cylinder, your liquid transfer will be quite quick, as the total volume required of most modern cars A/C systems is only about 500grams.
Why is there a need to charge at a fast rate?
As you will have liquid charged, you will need to let the pressures equalise before setting the system in operation.
Only liquid charge into the high side and not into the suction or you could flood the compressor and wash out the oil.

Ab.elb
07-10-2016, 12:26 PM
if you have created a good vacuum on the system and then charge it using your pre-heated R134A cylinder, your liquid transfer will be quite quick, as the total volume required of most modern cars A/C systems is only about 500grams.
Why is there a need to charge at a fast rate?
As you will have liquid charged, you will need to let the pressures equalise before setting the system in operation.
Only liquid charge into the high side and not into the suction or you could flood the compressor and wash out the oil.

Thank you for your answer.
We need it fast just to test the filling valves on a bench test.
Yes I have found a tank heater blanket to wrap around the cylinder, but i have a question will i still have liquid when heating. I don't how my fluid behave under this heating on Mollier's diagram.

hyperion
07-10-2016, 03:33 PM
As you will be increasing the surface temperature of the cylinder and thereby the liquid refrigerant, the pressure will increase in alignment with the characteristics of the refrigerant.
As you are not allowing any of the refrigerant vapour to escape during the heating process, the liquid will increase its volumetric size in proportion to the pressure, as there is nowhere for the liquid to move to.
Provided that you are extracting the liquid from the cylinder via the deep dip port or inverting the cylinder to provide a full column of liquid. That is what you will get.
Make sure that you follow safe working practices when using liquid refrigerant as liquid burns can hurt!

Ab.elb
11-10-2016, 08:09 AM
Thank you for answer again.
I have also a thought that crossed my mind, I want to use a compressor between the refrigerant cylinder and another tank ( accumulator) to pressurise the refrigerant there. I have a question: I know that going through the compressor, I ll have all the refrigerant in vapor, but what about when i finish pressurising the refrigerant in the accumulator? will it condense there?

Thank you again for your help

hyperion
11-10-2016, 01:50 PM
Most compressors can only safely handle vapour.
Your accumulator is not designed as a condenser and the relative heat transfer to the ambient air will be quite slow.
If you are starting with an elevated temperature/pressure liquid refrigerant, why would you want to only take the vapour, compress and condense it, to then admit it to your 'test bench' system, which you mentioned needs to have a high transfer rate, to suit the tests that you are conducting.
You would be slowing down the refrigerant exchange quite considerably.
The transfer rates would be improved if you could increase the size of the connections and the associated transfer pipework, as there is a limit to the transfer rate you can achieve down a normal charging hose with schraeder fittings.

Tycho
11-10-2016, 06:56 PM
Hello guys,
I'm new to this forum and i need some help concerning the charging of AC systems:

I'm working on a project where i need to to charge the AC circuit of a car ( on a bench test) with liquid. I understand that we can do this by putting the refrigerant tank upside down. but what i m trying to achieve isto perform a very fast charging. so i'm thinking of a system to do so.


My thoughts are:
- Heat the refrigerant tank to 40 so that pressure will go up to (10 bar for R134a).
- Connect the ref tank to a compressor and a restriction to help build up my pressure, (then to a condensor), then to my benchtest.

The problem with that is there are risks of exploision while heating the tank.

I'm also wondering if pumps can be used to pump refrigerant from the tank ( r134a).

Do you guys have some ideas to help.
Thank you

As far as I can see, there is no "shortcut" to recharging a car AC using compressors or re condensing units

Car AC's should have a certain charge of refrigerant, so before recharging, old refrigerant should be reclaimed and the whole AC system should be pulled down to vacuum.

once the system is down on vacuum, it should be no problem recharging the system with the needed amount of refrigerant with the pressure difference of the bottle and the AC system.

if you want to charge it faster, it's all about pressure, so keep your refrigerant bottles in a temperate room and not out in the cold.

using any kind of machinery to try to charge the system faster is just a waste of electricity and time.



if you are looking to test the capacity of valves, I would get a high pressure washer pumping water, with an adjustable bypass valve on the discharge line so you can regulate the amount of liquid that is routed through the valve you want to test, then you can measure the pressure drop and the amount of water passing through the valve.
Liquid refrigerant, as water is uncompresable, so it should give you a 1:1 result