proII里面蒸汽压问题？ 基于不同的测量办法 reid vapor pressure (rvp) calculations the rvp laboratory procedure provides an inexpensive and reproducible measurement correlating to the vapor pressure of a fluid. the measured rvp is usually within 1 psi of the tvp of a stream. it is always reported as "psi," although the astm test procedures (except for d5191 which, as mentioned below, uses an evacuated sample bomb) actually read gauge pressure. since the air in the bomb accounts for approximately 1 atm, the measured gauge pressure is a rough measure of the true vapor pressure. six different calculation methods are available. within each calculation method, the answer will depend somewhat on the thermodynamic system used. as with the tvp, the thermodynamic system for rvp calculations may be specified explicitly or, by default, the thermodynamic system used to generate the stream will be used. the apinaphtha method calculates the rvp from figure 5b1.1 in the api technical data book, which represents the rvp as a function of the tvp and the slope of the d86 curve at the 10% point. the graphical data have been converted to equation form by simsci. this method is the default for pro/ii's rvp calculations. it 2-32 component data is useful for many gasolines and other finished petroleum products, but it should not be used for oxygenated gasoline blends. the apicrude method calculates the rvp from figure 5b1.2 in the api technical data book, which represents the rvp as a function of the tvp and the slope of the d86 curve at the 10% point. the graphical data have been converted to equation form by simsci. it is primarily intended for crude oils. the astm d323-82 method (known as the d323 method) simulates a standard astm procedure for rvp measurement. the liquid hydrocarbon portion of the sample is saturated with air at 33 f and 1 atm pressure. this liquid is then mixed at 100 f with air in a 4:1 volume ratio. since the test chamber is not dried in this procedure, a small amount of water is also added to simulate this mixture. the mixture is flashed at 100 f at a constant volume (corresponding to the experiment in a sealed bomb), and the gauge pressure of the resulting vapor-liquid mixture is reported as the rvp. both air and water should be in the component list for proper use of this method. the obsolete astm d323-73 method (known as the p323 method) is available for compatibility with earlier versions of the program. the astm d4953-91 method (known as the d4953 method) was developed by the astm primarily for oxygenated gasolines. the experimental method is identical to the d323 method, except that the system is kept completely free of water. the algorithm for simulating this method is identical to that for d323, except that no water is added to the mixture. air should be in the component list for proper use of this method. the astm d5191-91 method (known as the d5191 method) was developed as an alternative to the d4953 method for gasolines and gasoline-oxygenate blends. in this method, the air-saturated sample is placed in an evacuated bomb with five times the volume of the sample, and then the total pressure of the sample is measured. in the simulator, this is accomplished by flashing, at constant volume, a mixture of 1 part sample (at 33 f and 1 atm) and 4 parts air (at the near-vacuum conditions of 0.01 psia and 100 f). the resulting total pressure is then converted to a dry vapor pressure equivalent (dvpe) using the following equation: (2-70) where: x = the measured total pressure pro/ii reference manual (volume 1) component and thermophysical properties 2-33 a = 0.548 psi (3.78 kpa) this number is then reported as the rvp. air should be in the component list for proper use of this method.查看更多
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