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Jacqueline Reinhold

on 12 October 2012

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Transcript of P.P.IIGp9NonTechAud

Fluid Mechanics for a
Non-Technical Audience Valves What are
Valves? Group 9 Different types of valves are used for different applications.

We will look at Check and Globe Valves These are a few types of valves: Globe
Lift Check
Swing Check
Plug Cock http://www.hnsa.org/doc/merchant/engineering/part5.htm Valves are pipe fittings that can be fully or partially opened and closed.

They regulate flow by stopping, slowing down or diverting it. Check valves typical valves that only allow the fluid to flow in one direction. A set of plates are present to allow to block fluid from enetering or leaving the system Check Valves...
The valve works when the plates move accordingly to stop, or allow the flow of fluid Check Valves... http://www.flosteer.com/checkvalves.htm#dualplate Are there different types? Globe Valves... The globe valve involves changing the direction of the flow by 90 degrees, thus eliminating the need for both an elbow and gate valve in some circumstances.

Globe valves are mostly used for purposes where the valve must be shut off frequently. If left open, damage is often found due to for force of the flow changing direction. Globe Valves... The Globe Valve includes a type of moveable disk that can be raised or lowered to open or shut the valve. http://profmaster.blogspot.com.au/2008/10/type-of-valves-globe.html When investigating valves we must look into... The Mechanical
Energy Equation!! The energy equation looks like this: Δ(P/p)+Δ(v^2/2)+gΔz+Δu =q+w Where: P - Pressure
p - density
v - velocity
g - gravity
z - height
u - internal energy
q - thermal energy
w - work done Considering an incompressible fluid with no kinetic energy changes..... The energy equation simplifies to: -Δ(P/p)-gΔz = q - Δu = energy loss The addition of major loss and minor loss in energy gives us the total loss due to friction.

Calculating the friction is important, as we do not want to have a weak jet of water while taking a warm shower! A fluid will lose energy due to friction as it moves along the pipe system and fittings. A pump is required to move the fluid across the system. Calculating the friction and using the appropriate pump is essential. Wait a minute... Yes! Your regular taps in your sink and garden are globe valves! Loss Coefficient The energy loss through a fitting can be expressed as: Why is it important? By calculating the loss coefficient and energy loss of the pipe systems, engineers will be able to determine the type of pump to use to send fluid across the system. Hmm... Ever wonder how waste flows out of a tap or how the flush system in a toilet works? Summary... Is it common at home? Yes! Our good old toilet flush system works by regulating the flow of water in and out of the toilet tank by using check valves. Diagram of the Toilet Tank http://www.lvvwd.com/conservation/ws_leaks_toilet.html http://www.buildingsheriff.com/outside-tap-cost.html Energy Loss Since the system is made up largely of pipes, energy loss due to friction in pipes are known as a major loss. Energy loss due to valves and fittings are called minor loss.
The addition of major loss and minor loss in energy gives us the total loss due to friction. Pipe fittings and valves are essential as they simplify our daily activities.

Engineers calculate energy loss due to pipe systems to efficiently transport fluid across the system at appropriate flow rates. Imagine trying to brush your teeth and no water comes out of the tap! Energy Loss = K(v^2/2) Where:
v = velocity
K = Loss coefficient The loss coefficient, K, varies for different fittings. The total system K is the sum of K for all fittings. Loss Coefficients of Fittings http://www.greenstone.org/greenstone3/nzdl;jsessionid=E9ED0144974E79BAE710370DCE74B40A?a=d&c=hdl&d=HASH011f05bf8734d88d1a080257.13.np&sib=1&p.s=ClassifierBrowse&p.sa=&p.a=b We will look at the calculation of minor loss caused by the valves. Hence... References: - http://www.flosteer.com/checkvalves.htm#dualplate
- http://www.lvvwd.com/conservation/ws_leaks_toilet.html
- http://www.buildingsheriff.com/outside-tap-cost.html
- http://www.hnsa.org/doc/merchant/engineering/part5.htm
- http://profmaster.blogspot.com.au/2008/10/type-of-valves-globe.html
- Young, Munson, Okiishi et. al. "Fundamentals of Fluid Mechanics" Sixth Edition Publiched 2009 by Wiley and Sons. United States of America
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