Hi all- I come asking for fluid dynamic advice- other forums I've posted to have been fruitless, and I know there are a ton of brilliant folks here. I'm not sure how best to explain it, so I'll lay it out as a physics problem.
I need to automate the control the flow of water, both cold pressurized (from the hose bib, estimated pressure is 80 PSI), and hot (<180F) gravity fed (column height is no more than 36"). Both the in-flow and out-flow needs to pass through a pulse-sensor water meter (a vane connected to a magnet read by a hall effect sensor). My problem is: valves are either pressure-actuated (requiring a differential pressure of >=3-5psi from inlet to outlet), or gravity-feed (can open with up to 7ft of column pressure, but if greater than that, it fails closed and will not open). Additionally, my flow meter cannot be pressurized, so it has to be protected from city water. My plumbing is all 1/2" rigid copper, and my vessel is a converted beer keg (legally acquired, and amazingly tough stainless steel). It was so much work to put the holes in it that I have already, and don't want to have to put any more in it (please, I know I can easily solve this by adding a second hole to the bottom of the vessel, but doing that is simply not possible). I've come up with the following solution, but I don't trust my engineering chops enough to know if it's valid. My thought process: both valves are normally closed, and when the pressurized valve is open (lower), it will supply a small degree of pressure to the gravity feed valve (right), but given that the gravity feed valve fails closed if pressure limits are exceeded, it will not 'leak'. Once the supply valve (pressure side) is closed, and water is heated up, the gravity valve can be opened since the column height is much less than minimum spec. This way I can use the existing orifice I drilled a decade ago in the keggle, and modernize it with my arduino-based update. Figure 1 is a photo of my brewery: the vessel in question is the farthest left, on top. It has a large opening in the back to admit a 220VAC heating element, and a bulkhead fitting in the bottom for the fluid input and output. Figure 2 is my recreation of my design idea- the one on which that I need confirmation/correction.
Any design flaws that will prevent this from being successful? I'm not at the point of discussing coding, just the physical requirements.
Figure 1:
Figure 2:
I need to automate the control the flow of water, both cold pressurized (from the hose bib, estimated pressure is 80 PSI), and hot (<180F) gravity fed (column height is no more than 36"). Both the in-flow and out-flow needs to pass through a pulse-sensor water meter (a vane connected to a magnet read by a hall effect sensor). My problem is: valves are either pressure-actuated (requiring a differential pressure of >=3-5psi from inlet to outlet), or gravity-feed (can open with up to 7ft of column pressure, but if greater than that, it fails closed and will not open). Additionally, my flow meter cannot be pressurized, so it has to be protected from city water. My plumbing is all 1/2" rigid copper, and my vessel is a converted beer keg (legally acquired, and amazingly tough stainless steel). It was so much work to put the holes in it that I have already, and don't want to have to put any more in it (please, I know I can easily solve this by adding a second hole to the bottom of the vessel, but doing that is simply not possible). I've come up with the following solution, but I don't trust my engineering chops enough to know if it's valid. My thought process: both valves are normally closed, and when the pressurized valve is open (lower), it will supply a small degree of pressure to the gravity feed valve (right), but given that the gravity feed valve fails closed if pressure limits are exceeded, it will not 'leak'. Once the supply valve (pressure side) is closed, and water is heated up, the gravity valve can be opened since the column height is much less than minimum spec. This way I can use the existing orifice I drilled a decade ago in the keggle, and modernize it with my arduino-based update. Figure 1 is a photo of my brewery: the vessel in question is the farthest left, on top. It has a large opening in the back to admit a 220VAC heating element, and a bulkhead fitting in the bottom for the fluid input and output. Figure 2 is my recreation of my design idea- the one on which that I need confirmation/correction.
Any design flaws that will prevent this from being successful? I'm not at the point of discussing coding, just the physical requirements.
Figure 1:
Figure 2:
