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Mechanical Engineering


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Everything posted by dudleybenton

  1. I am an engineer and applied mathematician who just happens to write software. I've written a lot of it since 1974—about three million lines of assembler, FORTRAN, and C. I have always written software to get some particular job done. If the subject matter didn't fall into one of my areas of expertise, I worked with someone who knew the important details. Examples of this cooperation include: geohydrologists, meteorologists, and biologists. I can't imagine writing software with no particular foundation. I have never sat through a single class in computer programming. Instead, I made a wager: I
  2. Sorry to have taken so long to respond… The main difference between spark-ignition (gasoline engine) and compression-ignition (diesel engine) operation is constant volume vs. constant pressure combustion. In a gasoline engine, combustion occurs so rapidly (the fuel and air are already in the combustion chamber with the plug fires) and near the top of the stroke so that the crank has little time to rotate and the piston moves only slightly with little change in volume. In a diesel engine, the fuel is sprayed into the cylinder as the piston is falling so that combustion occurs over a longer inte
  3. Sorry to rant, but… Just to give you a little appreciation for size… It takes the total output of Norris Dam just to run the fans on the cooling towers at Browns Ferry Nuclear Plant. Think fan on the radiator of your car compared to the engine. I have published multiple papers on BFNP and the cooling towers. Chuck Bowman designed those too (steam system thermal and cooling towers) plus Cumberland Steam Plant, Paradise Steam Plant Unit 3, Watts Bar Nuclear, Sequoyah Nuclear, Bellefonte Nuclear, Phipps Bend Nuclear, Hartsville Nuclear, and Yellow Creek Nuclear. CRC Press just released Thermal En
  4. Sorry for the long reply but the question is important and also complicated. Wind power is like a sneeze compared to a hurricane (supply to consumption). So is tidal power. I've been inside the power station at the Bay of Fundy, which has the largest tidal fluctuation in the world. Besides the fact that changing the resonance of the harbor (like stuffing a guitar with cotton) would diminish the tides, the thing is like a little lego toy compared to a real dam. I've crawled inside the turbines and generators of *real* dams, including: Norris, Fontana, and Chickamauga. The coal plant a mile from
  5. Did you measure the discharge pressure and/or head and how did you accomplish this? The discharge pressure (and head) will depend on several things, including where the fluid is coming from and going to.
  6. I can probably help you with data but I need more information about what you hope to accomplish. What type of reactor?
  7. Adjectives "high" and "low" are always relative terms. High or low may be compared to atmospheric on Earth or the critical pressure of the fluid in question. These terms might even be related to the capability of commonly available pumps. In this current discussion both water and CO2 have been mentioned, so "high" pressure would be in relation to the critical pressure of H2O (22 MPa) and that of CO2 (7 MPa).
  8. Recent power outages in California before the current fires reveal the weakness of "green" power solutions. While these sound good, in practice they are not resilient and have little reserve, thus falter when stretched. This trend will only worsen. Managing diverse power resources is a rapidly growing field creating jobs. You might want to explore this topic.
  9. Please repost with description. The pdf says "unavailable".
  10. I have seen this same thing many times. The overall surfaces are experiencing typical corrosion, which can be surprisingly difficult to prevent. The more extreme spots (especially the ones circled) were initiated by handling (bumped, scraped, dinged). The less extreme spots arise from debris that is no longer present, but facilitated and concentrated the chemical attach at those locations. These surfaces are not in the least unusual. Preventing this from happening requires considerable diligence and at least one of several available coatings. Note that if you coat a surface and it has any flaw
  11. If you're going to eventually make a living, ditch the Mac and get a Windows laptop. I am no fan of Bill Gates or Windows, but I accept the facts of life as they are. Unless you're going to work for the government or stay in academia, LINUX is also out. The vast majority of engineering software runs on Windows and most businesses circulate documents and spreadsheets created with MSO. There is no need to buy a new machine. Good reconditioned laptops are readily available on the Web for $200. After decades of industrial use, I can also say that Dell laptops significantly outlast all others. [No,
  12. There are many creative designs for cooling chips, especially graphics processors, created by users with available parts. I am surprised that you have not found images of these with a Google search. Try different search patterns and don't give up.
  13. If there is any way you could co-op (work for a company who builds agricultural mechanization devices for several months each year) that would be most enlightening. I know a recent graduate of the university here who has already participated in exciting implementations and has several job offers to choose from. This is a wonderfully productive and growing profession.
  14. I recently spoke to a friend who is hiring young engineers to work at several large power plants needing modernization. He said that the new hires know how to operate battling robots using their iPhone and 3D print useless plastic objects but don't understand thermodynamics or heat transfer. Please prove him wrong by mastering the foundations of industry! This website can help make that possible.
  15. We need more details to address this question. Do you mean an air powered siphon? Do you mean air bubbles rising in a vertical pipe producing an upward movement of the surrounding water? A picture of the device would help.
  16. Two months before my third birthday I changed all the light bulbs on the Christmas tree to be red yellow green red yellow green... I dismantled the radio at age seven and the television at eight. These were the old kind with vacuum tubes and did not survive the process. I rebuilt my first engine at eleven and was working as a professional mechanic by fourteen—before I could drive a car. I have a grandson who is three and destined for the same path. My father didn't know which end of a screwdriver to hold. The engineer gene came from my maternal grandfather.
  17. Fluids above the critical temperature are called "super critical." We sometimes call a liquid above the critical pressure "super critical." For example, in most large coal-fired steam power plants, the feedwater entering the boiler is about 4400 psia (30 MPa). The critical point is where the saturated liquid and vapor are indistinguishable; that is, a distinction is physically meaningless. There are no bubbles formed when boiling a liquid above the critical pressure. This is why you must have special equipment to clean (i.e., "polish") the feedwater in a supercritical coal-fired plant, as the
  18. The seawater probably flowed on the inside of the 90/10 Cu-Ni tubes at about 7 ft/sec (2 m/s), so multiply nD²π/4 to get volumetric flow then by density to get mass flow. You get surface area the same way. The overall heat transfer coefficient, U, is probably about 5 BTU/hr/ft²/ºF (25 W/m²/ºC). The delta-T is probably about 15ºF to 25ºF (8ºC to 14ºC). The specific heat of natural gas is about 0.5 BTU/lbm/ºF (2 kJ/kg/ºC). From that you can calculate the flow rate of natural gas and estimate the heat transfer capacity.
  19. There are several excellent texts on this subject. I always recommend Lindon Thomas' Heat Transfer because he's been a friend for many years. This is a large topic. To get a meaningful answer, you must further qualify your question. What type of heat exchanger? What do you expect it to do? What fluids? What temperatures? What flow rates? Heat exchangers are used for everything from natural gas to peanut butter.
  20. You will find many projects on ResearchGate where graduate students are investigating heat transfer within enclosures with a variety of conditions and fluids. You should be able to find something informative to your particular problem there. The complexity of the solutions varies considerably, so look for something on the level you're interested in pursuing.
  21. While pressure is clearly absolute (i.e., zero has a clear definition), temperature is most often with respect to some state (e.g., minimal crystalline structure). We can readily measure conditions and calibrate pressure instruments on an absolute basis. We don't have the same flexibility with temperature and so we recognize this in our measurements, calculations, and formulations. Also, heat is defined as that form of transient energy that crosses a system boundary by virtue of a temperature *difference*, not an *absolute* temperature.
  22. We know theoretically how pressure and density must interact at the critical point. Specifically, the first two partials (dP/drho and d²P/drho²) must be zero at the critical point for it to exist. This is mathematically equivalent to having three roots at the critical point. Simple equations of state (e.g., van der Waals) can reproduce this behavior, but may not fit data well anywhere else. In fact, the critical compressibility for a van der Waals fluid is Zc=3/8, which is larger than any known substance. The liquid densities are also off by a factor of 1/3 to 1/2 for the van der Waals EoS, as
  23. I cover this at some length in my book, "Thermodynamic and Transport Properties of Fluids." The Ebook is free on these days: 4/16,4/24,5/2 at this link https://www.amazon.com/dp/B07Q5L1CHT The software is always free at this link http://dudleybenton.altervista.org/software/index.html and one of the Excel AddIns (also free) may be helpful.
  24. You misunderstand the principle. Whether some working fluid is hot or cold compared to what humans consider normal atmospheric conditions isn't what determines whether or not a device is efficient. When I taught thermodynamics at university, I would always give a test question regarding a cup of coffee cooling to room temperature or a can of beer warming to room temperature. Both generate entropy (dS>0). I work out this example in my book, Thermodynamics. There are several reasons we build power plants using steam instead of air as the working fluid. The latent heat is a very important part
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