If you need the densities over a wider range of pressures, enter the range between PLow and PHigh along with a PIncrement that seems reasonable for your needs. NIST Electron Elastic-Scattering Cross-Section Database. XPS - NIST X-Ray Photoelectron Spectroscopy Database. Thermocouple - NIST ITS-90 Thermocouple Database. He also told the program that he wants the graph to be in increments of 1 psia, therefore, the graph will show densities for 19, 20 and 21 psia. Insulation - NIST Heat Transmission Properties of Insulating and Building Materials Database. In the example, we are only interested in one pressure, 20 psia, so he has selected a graph range of 19 to 21 psia, putting the desired 20 psia in the middle of the graph that will be given. The NIST program will generate a graph of density vs. After selecting the units you wish to use, click on the “ Press to Continue” button. If you are only planning on finding the density, you do not need to select viscosity units or any of the other units listed. He also selected cP for viscosity because it will show an optional calculation for viscosity. Select The Appropriate Units For this example, he has selected degrees F, psia, and lbm/ft3. For this example, he will find the density of propane gas at a temperature of 113☏ and a pressure of 20 psia. In this article, Jon Monsen has outlined the procedure for finding the actual density of a gas using the NIST Chemistry WebBook. To account for the difference between the Ideal Gas density and its actual density the ISA/IEC equation also requires the Compressibility Factor (symbol Z), which, unfortunately, is usually not easily found. Reaction thermochemistry data for over 8000 reactions. The most common of the ISA/IEC control valve gas sizing equations requires the pressure, temperature and molecular weight of the gas. To import this table into a software package, click the Download data as a tab-delimited text file link that appears under the. The NIST Chemistry WebBook provides access to data compiled and distributed by NIST under the Standard Reference Data Program. It is often of interest to process engineers, and to engineers who need to do control valve sizing calculations, to know the actual density of a gas rather than simply calculating the density based on the Ideal Gas equation using the molecular weight, the pressure and the temperature of the gas. In order to make full use of the WebBook, one must spend a good deal of time exploring its content and capabilities. Of particular interest to those who deal with chemical processes is the NIST Chemistry WebBook which contains a great deal of information regarding the properties of a broad range of chemicals. Department of Commerce. NIST provides a wealth of scientific information, most of which is beyond the scope of this article. The National Institute of Standards and Technology (NIST) is a part of the U.S.
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