PNachtwey said:
The pipe by it self does not create energy.
Neither does the pump. That is the whole point here. All of the parts of the system convert energy.
I will not be condescending and act like you don’t know that energy is neither created nor destroyed. I will, however, point out that you conveniently and, I can only assume, purposely ignore it in the attempt to make your point.
Whether we talk about a simple energy conversion device like a resistor or an antenna, or we talk about more complex energy conversion devices, such as steam engines or desk fans, the energy is only being converted from one form to another. You are correct to point out that pressure is an indirect measure of a part of total internal system energy.
With that in mind, what does a bridge abutment do to a speeding truck? Its kinetic energy is converted into noise, heat and metal deformation by the abutment. The truck did not make this energy conversion. The wall did.
Now consider a nozzle, yet another energy conversion device. This particular one converts potential energy into kinetic energy. A nozzle fitted to the plumbing at the bottom of a water tower will accelerate water based on the shape of the nozzle. When comparing dozens of shapes of nozzles, you will find the flow characteristics to be determined by the shape of the nozzle and the plumbing, as opposed to the water tower. The energy conversion device is the nozzle, not the water tower.
What about an injection pump, which, with no moving parts, uses the steam from a boiler to pull water from an outside tank into the boiler that is producing the steam to begin with? It seems impossible, but by carefully noting where the energy is and how it is converted back and forth from potential to kinetic and then back again, it is seen that pressure and flow are changing based on the confinement and release of potential and kinetic energies.
How about a resistor? How about an LED? What about a throttle? Where is the energy going in each of those systems? At the same time that resistors create heat, motors make rotation and light bulbs make light, none of these things are creating energy, which brings us to the heart of the issue. Neither a throttle nor a nozzle nor a motor nor a pump creates or destroys fluid energy, whether that energy is potential or kinetic. Your entire argument rests on the notion that because motive energy is imparted by the pump, that the pump is the origination of the pressure. And this is wrong, wrong, wrong. The pressure arises due to the overall system — whether that system is a plug or an accumulator stuck into the pump’s outlet port or any configuration of hoses, pipes and valves — converting kinetic energy into potential energy, heat energy or work outside of the fluid system. Kinetic energy is converted to a static pressure by the containment of the fluid that would otherwise continue with its imparted motion from the pump. It is this
resistance to flow that creates pressure. The system itself converts electrical energy to mechanical energy and from mechanical (rotating) energy to another form of mechanical energy (fluid) and without a containment system existing in some form or another, the kinetic energy is never converted to potential energy and pressure would never exist. The resistance to flow creates pressure.
To drive home the point, how is pressure created in systems that do not have pumps or motive force applied to the fluid, i.e., when the fluid itself is expanding or contracting? What occurs inside of a wax motor? Why is force only exerted at the end of a wax motor’s shaft when there is a rigid shell to resist flow in all other directions? What happens when water is contained in a rigid vessel and then frozen? Does the lack of a pump to apply motion mean that there is no pressure? Would there be any pressure at all if there were no resistance to movement? Finally, what happens to a pump when you run it without its case? You would get all kinds of fluid motion inside of your tank, but it does nothing useful because there is nothing to resist flow in any direction and no pressure is developed anywhere. This is the same as inducing eddy currents in a copper plate. It does nothing useful and no potential is created.
TL;DR: The containment of fluid, which converts kinetic energy to potential energy (pressure) is as much of an energy conversion device as a resistor, a motor or a pump. Ignoring that does not mean that a pump creates pressure.
Engineering is not the science behind building. It is the science behind not building.
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