Flow Computers / Totalizers for Liquids, Gases and Steam G Instruments flow computers / totalizers for liquids, gases and setam accuratelly measure volume, compensated volume and mass of various liquids and gases. They also measure volume and mass of saturated or superheated steam with high accuracy in very large range of temperatures and pressures. Liquids Many of the liquids are considered non-compressable for most applications. If a liquid can significantly expand or shrink in the temperature operating range the volume mesured needs to be compensated for that. The flow computer has to accuratelly measure the temperature and correct the volume. In order to do that the flow computer needs a thermal volume expansion coefficient for the specific liquid. There is a list of liquids in the flow computer / totalizer with preset data but the user can chose a ''generic'' liquid and enter his/her own coefficient. This would be the case when the liquid measured is not in the list or it is a mixture of two or more liquids. When the mass of the liquid is to be measured the flow computer / totalizer will also need its reference density. It can be entered manually for a generic liquid. The density can also come from a density meter connected to one of the analog inputs of the flow computer. Gases Gases are compressible and harder to measure accuratelly. Their volume depends on temperature and pressure so the volume measured needs to be compensated for both temperature and pressure. But the compressibility of the gases also depends on those two factors. So a compressibility factor is needed at any combination of temperature and pressure. If for a small range of temperatures and pressures the compressibility factor can be considered a constant it can be manually entered. If higher accuracy is needed and the temperature and/or the pressure can vary a lot then the compressibility factor has to be calculated accuratelly all the time and used for calculating the compensated volume or the mass of the gas. Ou flow computers for gases calculate the compressibility factor and the density of the gas with high accuracy in a very large range of temperatures and pressures. Like for the liquids the reference density of the gas can be manually entered or the actual density value can be received from a density meter connected to the flow computer / totalizer. Steam When the temperature of a liquid increases at a certain point it will start boiling and evaporating. If more heat is added with a constant pressure the temperature will not increase but the pecentage of the vapor will be increasing in the mixture. This will be wet saturated steam. The steam quality (dryness) is the mass of the vapor divided by the total mass of the two-phase mixture. Dry steam has a quality of 1.0, the liquid phase only has a steam quality of 0.0. If more and more heat (at a constant pressure) is added to the mixture, the quality will reach 1.0 (dry steam only) and after that the steam will be considered superheated. Adding more heat to a superheated steam changes both its temperature and its pressure. Because the steam is compressible its density changes with its temperature and pressure. It also changes with the quality of the steam (for saturated steam). Our flow computers for steam very accurately calculate the density of both saturated and superheated steam in a very large range of temperature and pressure providing accurate mass flow measurement. The calculations are by IAPWS-IF97 with the new additions from 2008.