1587415189PTE_POWERPOINT_1.ppt lecture slides
- 1. PTE 316 Piping Design Design Procedure: The problem of design procedure is to find a pipeline configuration and size within the constraints which is safe and economical. The steps in pipeline design are as follows: The determination of the problem , which includes the characteristics of the fluid to be carried, including the flow rates and the allowable head loss The location of the pipes, its source and destination, and terrain over which it will pass The design code to be followed and the material to be used. The determination of a preliminary pipe route, the line length and static head difference Pipe diameter based on allowable head loss Structural analysis such as wall thickness and stress analysis The stress analysis is performed in pipe configuration until compliance with the code is achieved.
- 2. Pipe types and applications • Seamless pipes (SMLs): These pipes are extruded and have no longitudinal seam. There is no weld and it’s the strongest of the three types • Electric resistance welded pipe (ERW): These pipes are manufactured from plates, where the seam weld is done by electric resistance welding. The welding efficiency is 0.8 • Submerged arc welded pipe (SAW): These pipes are manufactured from plates, normally rolled and steam welded together. The welding has a joint efficiency of 0.95.
- 3. Piping design equations. • Assuming steady state flow, there are a number of equations which are based upon the general energy equation, that can be employed to design the piping systems. Although piping systems and pipeline design can get complex, the majority of the design problems encountered by the engineers can be solved by the standard flow equations. Typical example is the Bernoulli equation.
- 4. What is Bernoulli's principle? • Bernoulli's principle is a seemingly counterintuitive statement about how the speed of a fluid relates to the pressure of the fluid. Many people feel like Bernoulli's principle shouldn't be correct, but this might be due to a misunderstanding about what Bernoulli's principle actually says. Bernoulli's principle states the following, • Bernoulli's principle: Within a horizontal flow of fluid, points of higher fluid speed will have less pressure than points of slower fluid speed.
- 5. How can you derive Bernoulli's principle? • Incompressible fluids have to speed up when they reach a narrow constricted section in order to maintain a constant volume flow rate. This is why a narrow nozzle on a hose causes water to speed up. But something might be bothering you about this phenomenon. If the water is speeding up at a constriction, it's also gaining kinetic energy • The only way to give something kinetic energy is to do work on it. This is expressed by the work energy principle.
- 6. Bernoulli equation Conti… Wexternal = Δk = mvf 2 - mvi 2 So if a portion of fluid is speeding up, something external to that portion of fluid must be doing work on it. What force is causing work to be done on the fluid? Well, in most real world systems there are lots of dissipative forces that could be doing negative work, but we're going to assume for the sake of simplicity that these viscous forces are negligible and we have a nice continuous and perfectly laminar (streamline) flow.
- 7. • Laminar (streamline) flow means that the fluid flows in parallel layers without crossing paths. In laminar streamline flow there is no swirling or vortices in the fluid. • Consider the diagram below which shows water flowing along streamlines from left to right. As the outlined volume of water enters the constricted region it speeds up. The force from pressure P_1P1 P, start subscript, 1, end subscript on the left side of the shaded water pushes to the right and does positive work since it pushes in the same direction as the motion of the shaded fluid. The force from pressure P_2P2 P, start subscript, 2, end subscript on the right side of the shaded fluid pushes to the left and does negative work since it pushes in the opposite direction as the motion of the shaded fluid.
- 9. We know that the water must speed up (due to the continuity equation) and therefore have a net positive amount of work done on it. So the work done by the force from pressure on the left side must be larger than the amount of negative work done by the force from pressure on the right side. This means that the pressure on the wider/slower side P1 has to be larger than the pressure on the narrow/faster side P2. This inverse relationship between the pressure and speed at a point in a fluid is called Bernoulli's principle. Bernoulli's principle: At points along a horizontal streamline, higher pressure regions have lower fluid speed and lower pressure regions have higher fluid speed.
- 10. • The idea that regions where the fluid is moving fast will have lower pressure can seem strange. Surely, a fast moving fluid that strikes you must apply more pressure to your body than a slow moving fluid, right? Yes, that is right. But we're talking about two different pressures now. The pressure that Bernoulli's principle is referring to is the internal fluid pressure that would be exerted in all directions during the flow, including on the sides of the pipe. This is different from the pressure a fluid will exert on you if you get in the way of it and stop its motion.
- 11. • Note that Bernoulli's principle does not say that a fast moving fluid can't have significantly high pressures. It just says that the pressure in a slower region of that same flowing system must have even larger pressure than the faster moving region. What is Bernoulli's equation? • Bernoulli's equation is essentially a more general and mathematical form of Bernoulli's principle that also takes into account changes in gravitational potential energy. let's take a look at Bernoulli's equation and get a feel for what it says and how one would go about using it.
- 12. • Bernoulli's equation relates the pressure, speed, and height of any two points (1 and 2) in a steady streamline flowing fluid of density ρ. Bernoulli's equation is usually written as follows, P1 + 1/2℮v + ℮gh1 = P2 + 1/2℮v + ℮gh2 The variables P1. v1, h1 refer to the pressure, speed, and height of the fluid at point 1, whereas the variables P2. V2, h2 refer to the pressure, speed, and height of the fluid at point 2 as seen in the diagram below. The diagram below shows one particular choice of two points (1 and 2) in the fluid, but Bernoulli's equation will hold for any two points in the fluid.
- 14. Derivation of Bernoulli's equation To conti….