It usually refers to the weight of the column of atmospheric air above the unit surface area. Atmospheric PressureĪtmospheric or air pressure is the pressure of air in a given environment. Measuring devices often show gauge pressure, although absolute pressure sensors are also in use. This is known as gauge pressure, and it is the pressure measured when determining the air pressure in car tires. In some cases, pressure of gases is measured as the difference between the total or absolute pressure and the atmospheric pressure. The SI unit for pressure is the pascal, which is a newton per square meter. If, on the other hand, you use a blunt knife, you will not be able to cut through because the area is greater and the pressure is lower as a result. The area where the force is applied is small, so the pressure is high enough to cut through the object. For example, if you try pushing a sharp knife down through a carrot or a tomato, you will cut it. You will probably agree that it is less scary to be stepped on by someone wearing running shoes than by someone wearing stilettos. If the same force is applied to two areas, a smaller and a larger one, the pressure would be greater for the smaller area. Pressure is defined as force per unit of area. Department of Energy, THERMODYNAMICS, HEAT TRANSFER, AND FLUID FLOW. DOE Fundamentals Handbook, Volume 1, 2 and 3. Fundamentals of Engineering Thermodynamics, Fifth Edition, John Wiley & Sons, 2006, ISBN: 978-7-0 Thermodynamics in Nuclear Power Plant Systems. Nuclear Systems Volume I: Thermal Hydraulic Fundamentals, Second Edition. Nuclear Reactor Engineering: Reactor Systems Engineering, Springer 4th edition, 1994, ISBN: 978-0412985317 Stacey, Nuclear Reactor Physics, John Wiley & Sons, 2001, ISBN: 0- 471-39127-1. Baratta, Introduction to Nuclear Engineering, 3d ed., Prentice-Hall, 2001, ISBN: 8-1. Lamarsh, Introduction to Nuclear Reactor Theory, 2nd ed., Addison-Wesley, Reading, MA (1983). In relative units it is a negative gauge pressure of about – 0.92 bar, – 92 kPa, or – 13.54 psig. at 0.08 bar or 8 kPa or 1.16 psia) and in a partially condensed state. On the other hand condensing steam turbines (at nuclear power plants) exhaust steam at a pressure well below atmospheric (e.g. For instance, an absolute pressure of 80 kPa may be described as a gauge pressure of −21 kPa (i.e., 21 kPa below an atmospheric pressure of 101 kPa).įor example, a car tire pumped up to 2.5 atm (36.75 psig) above local atmospheric pressure (let say 1 atm or 14.7 psia locally), will have an absolute pressure of 2.5 + 1 = 3.5 atm (36.75 + 14.7 = 51.45 psia or 36.75 psig). It is certainly possible to have a negative gauge pressure, but not possible to have a negative absolute pressure. A perfect vacuum would correspond to absolute zero pressure. When the local atmospheric pressure is greater than the pressure in the system, the term vacuum pressure is used.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |