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Under water

  1. Feb 18, 2014 #1
    Hello, new here looking for some help on a project I'm working on. First off, I am not an engineer, have no degree in anything and am a math moron.

    This is what I'm trying to achieve: deliver a proprietary substance overtime in 300' of water. The fantasy is to use Co2 gas to propel the substance. I realize that as chamber 'B' volume increases pressure will drop but that (I hope) does not matter as long as the propelling pressure stays (somewhere?) above the ambient pressure.

    I'm asking for what the volume and initial charge pressure should be for chamber 'B' in order to achieve this. The dimensions shown are from what material I've chosen to use to prototype and are otherwise meaningless and can be changed easily.

    I'd like to avoid discussing friction, viscosity and other obvious variables and assume whatever challenges they might represent can be more or less obviated.


    Attached Files:

  2. jcsd
  3. Feb 18, 2014 #2


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    Your design shows a syringe like apparatus to hopefully squirt some semi solid into the water.
    At 300 ft depth, the water is at higher pressure than the 130psi CO2 you show, so the piston won't budge.
    Once you fix that, you have to force the semi solid through a nozzle. Knowing the outside pressure is about 150 psi, your piston has to add the pressure needed to make that semi solid flow. Unless you can add more CO2 as the piston moves to keep the pressure up, the propelling pressure will drop as the piston advances. So you need to plan to have adequate pressure at the end of the stroke, not just at the start. That in turn means a big excess pressure at the start, so the ejection will be more a squirt than a controlled flow. Is that an issue?
  4. Feb 18, 2014 #3
    etudiant, thank you for the reply. Unfortunately, because of the new and idiotically named 'America Invents Act,' I must be circumspect about certain parameters, so I may not be able to be intelligent in some parts of my reply.

    Pardon me, I guess I did not make myself clear: It is the ambient that is 130 psi, not the Co2 charge in chamber B. That is what a chart told me the water pressure would be at 300'. The orifice, as I termed it, is a variable both environmentally and structurally - the exudate can be modified, as well as the configuration of distribution (orifice). I want to know what the Co2 pressure and volume needs to be to do the work. I see by the chart that at 40 F compressed Co2 has a pressure of around 567 psi. BUT! I would like to keep the volume and pressure in chamber B as low as possible to do the work.

    I realize that the action will be more forceful at the start and diminish towards the end. I'm searching to see if what I envision is practical.
  5. Feb 19, 2014 #4


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    Would a screw conveyer be a more effective alternative?
    The pace of product delivery could be controlled that way, even halted as desired. Of course the offset is greater manufacturing cost, because that approach needs a motor and a power supply.
  6. Feb 19, 2014 #5
    etudiant, it's not a matter of what would be more effective. The watery world is very different 300' below the surface and things like stored electrical energy, motors and the necessary usually extraordinary means to protect them are out of the question for this project.

    Absent any replies from the physics crowd, I'm gonna just experiment!
  7. Feb 20, 2014 #6


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    Experiment is indeed the best teacher.
    The control of your setup will be the long pole, imho.
    Wish you all the best.
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