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Homework Help: How ti increase R22 gas pressure in the tank?

  1. Dec 8, 2011 #1
    dear guys,

    first of all.., i'm sorry because i not sure my question suitable in this forum or not.
    if not, mr moderator please move my topics to correct section :redface:

    my problem is, how to increase the pressure of the r22 gas in the tank diameter 10 inch x 30 inc (length). my tank can hold pressure up to 600 psi. (specification)

    the pressure is : 150psi , i want to increase it up to 300.00 psi.

    i try to use heater and heat up until 60 deg c, but what i get is another 50 psi increase only.

    attached is the detailed picture..

    please share with if you have any opinion.



    Attached Files:

  2. jcsd
  3. Dec 8, 2011 #2


    User Avatar

    Staff: Mentor

    For a gas that follows the ideal gas laws, if you double its temperature (as measured in Kelvin) then you'll double its pressure. For example, from a room temperature of 20C (equating to 293 Kelvin), even if it were safe to heat the equipment fiercely, you'd have to heat it to double this temperature, i.e., 586 K, which equates to 313 Celcius. (For comparison, water boils at 100C, at sea level atmosphere.)

    What is r22 and why do you want to increase its pressure but not by adding more gas to the cylinder?
  4. Dec 8, 2011 #3
    dear NascentOxygen,

    thanks for the reply,

    first of all, Chlorodifluoromethane or difluoromonochloromethane is a hydrochlorofluorocarbon (HCFC). This colorless gas is better known as HCFC-22, or R-22. It was once commonly used as a propellant and in air conditioning applications.

    in my case, i need to simulate the pressure 300 psi same like discharge pressure ( 250-300 psi).
    normal condition , the pressure only 150psi, so after heat up to 60 deg c, it only rise to 200psi.
    the cyclinder tank is already full.

    i try use the isochoric process since the volume is contant.

    P2 = P1(T2/T1)

    by calculation p2 = is 400++ psi.
    by test , P2 = is 200 psi.

    back to the what i want to test.

    i want to do a test for new valve. ( picture attached)

    the testing procedure is , i need to charge the valve up to 300psi by using R22 gas then lock it.

    once complete, the valve will put it in the oven and heat cool to a certain standard testing temperature.

    but i still and stage one where i cant manage to get the 300 psi. maybe today i will try use a crankcase heater. heat up until i get the pressure. a bit risk.

    sorry, my english is bad, hope you can understand :smile:



    Attached Files:

    Last edited: Dec 8, 2011
  5. Dec 9, 2011 #4


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    Staff: Mentor

    That's what theory predicts it would do.
    Let's look at where you are going wrong. The mistake you are making is in your value of temperature. You are using degrees Celcius. WRONG!

    The formula requires temperature to be in degrees Absolute (also known as Kelvin). To convert from Celcuis to Kelvin, add 273. So at room temperature (lets say your store room is chilly and only 15C), this is 288 Kelvin. Then you heat the cylinder to 60C, this is 60 + 273 Kelvin, i.e., 333 Kelvin.

    So the new pressure,
    p2 = p1 * 333/288 = 1.16 * p1
    Just a predicted 16% increase in pressure for your heating to 60C. Not the 100% that you mistakenly believed.
    As I pointed out in my first reply, I don't think you can do it this way. You would have to heat it to the melting point of lead before the pressure would double. I doubt that the valve components and thread sealants (if any) would be designed for this level of abuse.

    I have no experience with compressed gasses, but I wonder is there a suitable inert gas one could add to an 80% full cylinder of r22 to raise the pressure? If the second gas was comparatively volatile, you might be able to bleed it off when the test was over to leave you with your original 80% level of r22.

    I'm guessing that you're wanting to test the valve but without losing the contents of the cylinder? Otherwise, wouldn't you empty the cylinder and fill it with a different higher pressure inert gas at around 300 psi for the test?

    This may not be the best forum for bottled refrigerant questions. Maybe you could try the chemistry forum before you risk injuring yourself.
  6. Dec 11, 2011 #5
    Look at your gas tables for R22
    Initial conditions at 150 PSI, 75 F is saturated vapor, Vol=1.36 FT^3, U1=30 BTU/Lb

    Finial condition at 300 psi is 604 F, superheated vapor, Vol=1.36 FT^3, Mass= 3.14 Lb, U2=190 BTU/Lb

    Amount of heat Q=ΔU=mass*ΔU=3.14*(190-30)=500 BTU plus you have to heat all the mass of the tank

    You may want to check my calc's
  7. Dec 13, 2011 #6
    dear RTW69 & NascentOxygen ,

    thanks guys...

    i learn alot from you guys..

    after calculate all turn wrong. can't use the degree c.

    only increase 18% if i heat up to 60 deg c.

    by looking at R22 table

    the temperature to increase pressure is 54.1 deg c is i am not mistaken, but i believe , that for refrigerant gas temperature. what i get rite now is only tank temperature.

    for this problem,

    i set up 1 unit 1 hp multi split air conditioning, tap the access valve at high side pipe line, then charge R22 to 70 psi ( low side ). the high side increase up to 315 psi. plug in the UUT( test valve ) then lock it.

    now my valve in chamber for temperature test. :)

    thanks guys
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