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“How much water would it take to do that?” This question is the basis of two notable government-sponsored experiments conducted in 2018. Water was the chosen substance to reconstruct the beaches of the Grand Canyon and keep a rocket platform cool. What flow rates would you need to accomplish these tasks?
Hydronics and HFE
An advantage of building a dam in a river is the ability to generate electricity with the controlled flow of water as it passes through the turbine generators. A disadvantage of building a dam is there is now a big dirt strainer in the river. All the mineral-rich silt and sand that used to flow down the river gradually now settles in the bottom of the man-made lake. Silt and sand carried by an unobstructed river are helpful nutrients for the riverside plants and animals when they are deposited on the banks.
The Glen Canyon Dam is at the point in the Colorado River directly before water enters the Grand Canyon. Researchers noticed that the beaches have gradually been eroding. Generally, the bank of a river is always changing shape, but without a steady supply of sandy water, beaches are washed away.
If the beaches disappear, the tourists will camp higher up the canyon, damaging additional ecosystems near the river. However, as one might imagine, rebuilding the beaches at the bottom of the Grand Canyon isn’t as easy as pulling a dump truck full of sand right up to the edge of the river.
The dam has metered the natural flow of the Colorado River as it enters the Grand Canyon to generate electricity. Occasionally, the Department of the Interior will turn the valves at the bottom of the Glen Canyon Dam wide open.
NPS.gov explains, “Between Nov. 5-10, 2018, the Department of Interior increased the release of water from Glen Canyon Dam for a high-flow experimental release (HFE) of approximately 38,100 cubic feet/second (cfs) for three days.” That flow rate converts to about 17 million gallons/minute, to put it into a hydronics context.
This HFE simulates an enormous flood, which washes dirt from the banks down into the river, where they build new beaches. The Department of Interior conducted seven HFEs in the past. The 2018 HFE was about 60 percent the volume of the initial 1996 experiment. Worries of drought are a reason the agency doesn’t release as much water as it has in the past. DOI tracks its beach-building success, before and after, with wildlife cameras.
Elevated flow rates also are important to recognize and utilize in hydronics systems. If the normal operation flow rate of your system is too high, the particles in the water can start to erode the pipe, fittings and valves. Continuous, elevated flow conditions can pinhole copper pipe. That is part of the reason the HFE in the Grand Canyon is only done for a few days every few years.
If you are trying to purge or flush out a hydronics system, think about the HFE. You need the high flow rates to carry debris through the pipe. A flush-and-purge flow velocity is much different from normal system operation velocity, which is why it can be frustrating to try to purge a system with the system pump. A single-speed pump won’t be great at both tasks.
Heat absorption properties of H2O
Switching to the cooling properties of water, NASA is using a controlled flood in its Space Launch System project. To keep rocket launch pad 39B from burning to a pile of ash, as if it were Wile E. Coyote in a Roadrunner cartoon, they are planning to drench the platform with water mid-launch of a rocket. This system is being designed to launch the largest rocket NASA has ever built, scheduled for 2020.
It takes a lot of energy to get a rocket into space. The payload also increases as we launch heavier things through our atmosphere. If we are going to venture further into space, we are going to need to bring more than a couple of carry-on suitcases. Heavier rockets require more thrust, which creates a dangerously hot platform.
Here is the background of the project from NASA: “When NASA's new Space Launch System (SLS) rocket lifts off, its four RS-25 engines and two solid rocket boosters will produce a combined 8.4 million pounds of thrust. With it comes a torrent of heat and noise. To help protect the SLS rocket, Orion spacecraft, Mobile Launcher and launch pad from the extreme acoustic and temperature environment, water will spray onto the launch pad during ignition and liftoff.”
Water can absorb an incredible amount of energy. The specific heat capacity of water makes this NASA project a possibility; it also allows us to carry heating and cooling wa-ter around a house in networks of small piping.
The SLS deluge system also keeps the liftoff noise down. The sound created by this rocket is going to be unimaginably loud. Beyond that, the sound waves bouncing off the concrete below the rocket and bouncing back up alone would be enough to jeopardize the mission. Essentially, the water sponges away some of the noise that could literally shake the rocket apart as it launches.
The process of deluging the rocket platform creates an incredible geyser. At peak flow, the system will spray 450,000 gallons of water on the platform. NASA moves all this water from the holding tanks to the platform in one minute! During a system test, a column of water sprayed 100 feet in the air. NASA has a great YouTube channel where you can see some of these systems in action.
Water keeps the RS-25 engines cool, even in conditions that can hit 6,000 degrees. The combined power of this rocket is about 8.8 million pounds of thrust. To put thrust into context, Howstuffworks.com has a good description: “A 'pound of thrust’ is equal to a force able to accelerate 1 lb. of material 32 ft./second/second ([the] equivalent to the ac-celeration provided by gravity). Therefore, if you have a jet engine capable of producing 1 lb. of thrust, it could hold 1 lb. of material suspended in the air if the jet were pointed straight down.”
The RS-25 is scheduled to launch a 6-million-pound rocket into space.
The next project you work on may not involve 6,000 degree cooling loads. However, radiant cooling may be a good fit. Water is an excellent way to sponge the sensible heat out of a space.
Water in motion is an incredibly useful tool. The coordinated, high-flow conditions created by the Department of the Interior and NASA projects are calculated to complete incredible tasks. In the day-to-day hydronics and plumbing worlds, it is important to know what flow rates are required for the job. Fluid velocity is an important part of all systems and shouldn’t be left to design rules of thumb. l
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