Shock Wave Through Water, Temperature and Pressure

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aXiom K Associate Join Date: Dec 2005 Location: Right here in Australia Posts: 27	Shock Wave Through Water, Temperature and Pressure 10/20/2006 2:08 AM
	So, I have a manifold block with a solenoid pump (50hz) and a release valve hanging off it, a length of pipe runs to an air filled pressure vessel. We pump water into the system, compress the air and then at a timely juncture release the water from the system at a greater rate than the pump can achieve on its lonesome. This unfortunate setup is causing some resonance and hammering which is bouncing the seal in the release valve off its seat. One fix is to have a stub pipe, pointing down with no air in it, hanging off the manifold. I'm guessing the sock wave bounces down this pipe and cancels itself on its way out. I want to get a more quantitative idea of what's going on here. What will happen when we run this system at 60Hz, or with hot water? I want some easy to use equations relating water temp, shock wave speed and ummm whatever else I need to know. Thanks. __________________ Do or do not, there is not try, but there is failure...
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	Pathfinder Tags: fluid Shock wave wave propagation

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aurizon Guru Join Date: Jun 2006 Location: Toronto Posts: 3968 Good Answers: 120	#1 Re: Shock Wave Through Water, Temperature and Pressure 10/20/2006 11:23 PM
	install a water hammer suppressor. A cheap and dirty one is a vertical pipe with air in it. This is often used in houses. Sometimes the air gradually dissolves in the water and the pipe fills and the hammer returns. Commercial products have a membrane that keep the gas there and the membrane expands and contracts, using the trapped air a a spring to dampen the hammer. Adding a small hole in the pipe connecting the water to the suppressor make it more like a car shock absorber and reduces long term waves. __________________ Per Ardua Ad Astra
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aXiom K Associate Join Date: Dec 2005 Location: Right here in Australia Posts: 27	#2 Re: Shock Wave Through Water, Temperature and Pressure 10/23/2006 9:38 PM
	Input appreciated. We have had differing success with hammer arresters, baffles, and resonators. Though the ones that fullfill other system requirements, like not changing the water volume when under pressure, fail at different operating temperatures. Why is this? __________________ Do or do not, there is not try, but there is failure...
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aurizon Guru Join Date: Jun 2006 Location: Toronto Posts: 3968 Good Answers: 120	#3 In reply to #2 Re: Shock Wave Through Water, Temperature and Pressure 10/24/2006 12:32 AM
	A water hammer suppressor that does not change volume. In that case you need a multipath suppressor. That means you divide the flow from the main path into 8 paths and then recombine them after a few feet, but you make sure that each path is different from the other.. Let us say, direct path is 3 feet. Make a 5 foot, 6 foot,7 foot, 8 foot,9 foot, 10 foot, 11 foot. Use coiled copper tubing and solder it all up and remove all air. Then this will supress water hammer by stretching out the hammer into 8 smaller hammers and with the mixed phases you will get cancellation. That is the only way I can see of having an incomprssible water hammer suppressor. The essence of water hammer suppression is expansion, so this will not be 100% effective. Why must it be zero compression. As for hot water, that expands air volumes?? __________________ Per Ardua Ad Astra
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aXiom K Associate Join Date: Dec 2005 Location: Right here in Australia Posts: 27	#4 In reply to #3 Re: Shock Wave Through Water, Temperature and Pressure 10/24/2006 1:40 AM
	I imagine the hot water would expand the air volume in the pressure chamber, and increase its affective spring rate, or pre-load or something, making the hammer stronger, or changing the frequency of the hammer to match the excitation from the pump. But, could it also be the speed that the shock wave travels is dependant on the density of the water? I am trying to narrow in on the factors that are in play for the geometry I have.... PS. It really helps to talk out loud about this stuff. Cheers. __________________ Do or do not, there is not try, but there is failure...
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