Symbols, abbreviations, or full names for units of length,Īrea, mass, pressure, and other types. You can find metric conversion tables for SI units, as wellĪs English units, currency, and other data. The unit is named after Blaise Pascal, the eminent French mathematician, physicist and philosopher.Ĭonversion calculator for all types of measurement units. The pascal (symbol Pa) is the SI unit of pressure.It is equivalent to one newton per square metre. The definition of a pascal is as follows: The SI prefix "mega" represents a factor of MPa to KN/(mm^2), or enter any two units below: Enter two units to convert From: June 1992.You can do the reverse unit conversion from 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. In the English system, the force unit is the pound-force ( l b f) and is defined as the force required to accelerate a mass of 32.174 l b m (1 slug) at a rate of 1 f t s 2. CRC Press 2 edition, 2012, ISBN: 978-0415802871 In SI units, the force unit is the newton ( N ), and it is defined as the force required to accelerate a mass of 1 k g at a rate of 1 m s 2. 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. Negative Gauge Pressure – Vacuum Pressure.The Standard Atmospheric Pressure is defined at sea-level at 273 o K (0 o C) and is: The Standard Atmospheric Pressure approximates to the average pressure at sea-level at the latitude 45° N. The atmospheric pressure varies with temperature and altitude above sea level. Atmospheric pressure is the pressure in the surrounding air at – or “close” to – the surface of the earth. Gauge pressures are positive if they are above atmospheric pressure and negative if they are below atmospheric pressure. The latter pressure scale was developed because almost all pressure gauges register zero when open to the atmosphere. The term gauge pressure is applied when the pressure in the system is greater than the local atmospheric pressure, p atm. When pressure is measured relative to atmospheric pressure (14.7 psi), it is called gauge pressure (psig). Since atmospheric pressure at sea level is around 101.3 kPa (14.7 psi), this will be added to any pressure reading made in air at sea level. Pounds per square inch absolute (psia) is used to make it clear that the pressure is relative to a vacuum rather than the ambient atmospheric pressure. When pressure is measured relative to a perfect vacuum, it is called absolute pressure (psia). Although absolute pressures must be used in thermodynamic relations, pressure-measuring devices often indicate the difference between the absolute pressure in a system and the absolute pressure of the atmosphere existing outside the measuring device. But in engineering we often deal with pressures, that are measured by some devices. In this article the term pressure refers to absolute pressure unless explicitly stated otherwise. Often it will be important to distinguish between absolute pressure and gauge pressure. Pressure as discussed above is called absolute pressure.
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