Pressure calculation, initial

The bubble and dew-point temperature calculations have been implemented by the FORTRAN IV subroutine BUDET and the pressure calculations by subroutine BUDEP, which are described and listed in Appendix F. These subroutines calculate the unknown temperature or pressure, given feed composition and the fixed pressure or temperature. They provide for input of initial estimates of the temperature or pressure sought, but converge quickly from any estimates within the range of validity of the thermodynamic framework. Standard initial estimates are provided by the subroutines. 

Below is a typical oil PVT table which is the result of PVT analysis, and which would be used by the reservoir engineer in calculation of reservoir fluid properties with pressure. The initial reservoir pressure is 6000 psia, and the bubble point pressure of the oil Is 980 psia. 

The pressure developed by decomposition of acetylene in a closed container depends not only on the initial pressure (or more precisely, density), but also on whether the flame propagates as a deflagration or a detonation, and on the length of the container. For acetylene at room temperature and pressure, the calculated explosion pressure ratio, / initial > deflagration and ca 20 for detonation (at the Chapman-Jouguet plane). At 800 kPa (7.93... 

The. subsurface-pressure calculated for. this layer is bclOw the assumed-compressive strength iof 2,OOO b/W ihereforc. tKe initial foundation div isions are-acceptable relative, to the strength of this.subsurlace layer. ... 

The preceeding discussion was confined mostly to the carbon deposition curves as a function of temperature, pressure, and initial composition. Also of interest, especially for methane synthesis, is the composition and heating value of the equilibrium gas mixture. It is desirable to produce a gas with a high heating value which implies a high concentration of CH4 and low concentrations of the other species. Of particular interest are the concentrations of H2 and CO since these are generally the valuable raw materials. Also, by custom it is desirable to maintain a CO concentration of less than 0.1%. The calculated heating values are reported as is customary in the gas industry on the basis of one cubic foot at 30 in. Hg and 15.6°C (60°F) when saturated with water vapor (II). Furthermore, calculations are made and reported for a C02- and H20-free gas since these components may be removed from the mixture after the final chemical reaction. Concentrations of CH4, CO, and H2 are also reported on a C02 and H20-free basis. 

E3.7 A block of copper weighing 50 g is placed in 100 g of HiO for a short time. The copper is then removed from the liquid, with no adhering drops of water, and separated from it adiabatically. Temperature equilibrium is then established in both the copper and water. The entire process is carried out adiabatically at constant pressure. The initial temperature of the copper was 373 K and that of the water was 298 K. The final temperature of the copper block was 323 K. Consider the water and the block of copper as an isolated system and assume that the only transfer of heat was between the copper and the water. The specific heat of copper at constant pressure is 0.389 JK. g l and that of water is 4.18 J-K 1-g 1. Calculate the entropy change in the isolated system. 

Acetaldehyde (A) decomposes according to the reaction, CH3CH0 = CH4 + CO. Two sets of experiments were performed by Letort (Bull Soc Chim France 9 1, 1942) and the tabulated calculations were derived from them, (a) With a pressure of 183 torr, the data are of composition na/na0 and the corresponding rates (b) At several initial pressures the initial rates are given. Find the order of the reaction from the two sets of data. 

Calculate initial tray holdups and the pressure profile. 

C CALCULATE INITIAL PRESSURE PROFILE AND INITIAL ENTHALPIES PD=90. 

In the case of the bubble point pressure calculation (see Fig. 2.2-1), the liquid composition, xh and the temperature, T, are known and the vapour phase composition, y and the pressure, P, must be calculated. For the iterative calculations an initial guess for the bubble point... 

First, the initial trial value of bubble-point pressure is 247 psia since this is the bubble-point pressure calculated in Example 12-2 under the assumption of ideal-solution behavior. Determine Kj values at 150°F and 247 psia from Appendix A. 

Worked Examples 13.9 and 13.10. The same approach can be used to calculate equilibrium partial pressures from initial partial pressures and Kp, as shown in Worked Example 13.11. 

The value of the equilibrium constant for a reaction makes it possible to judge the extent of reaction, predict the direction of reaction, and calculate equilibrium concentrations (or partial pressures) from initial concentrations (or partial pressures). The farther the reaction proceeds toward completion, the larger the value of Kc. The direction of a reaction not at equilibrium depends on the relative values of Kc and the reaction quotient Qc, which is defined in the same way as Kc except that the concentrations in the equilibrium constant expression are not necessarily equilibrium concentrations. If Qc Kcr net reaction goes from left to right to attain equilibrium if Qc > Kc/ net reaction goes from right to left if Qc = Kc/ the system is at equilibrium. 

Figure 6 shows the calculated initial droplet sizes D0 which impact at each of the several sampling sites, as determined by the prevailing temperature, humidity, and barometric pressure (Ap/P). Having determined the volume fraction of the spray collected at each of the several sampling sites as previously described, interpolation from Figure 6 gives... 

A smali shell-and-tube exchanger with one tube pass [A = 4.64 m2 and U = 280 W/m2 °C] is to be used to heat high-pressure water initially at 20°C with hot air initially at 260°C. If the exit water temperature is not to exceed 93°C and the air flow rate i 0.45 kg/s, calculate the water flow rate. 

Chemical engineers make reaction-equilibria calculations to find the potential yield of a given reaction, as a function of temperature, pressure, and initial composition. In addition, the heat of reaction is often obtained as an integral part of the calculations. Because the calculations are made from thermodynamic properties that are accessible for most common compounds, the feasibility of a large number of reactions can be determined without laboratory study. Normally, thermodynamic feasibility should be determined before obtaining kinetic data in the laboratory, and if a given set of reaction conditions does not yield a favorable final mixture of products and reactants, the reaction-equilibria principles indicate in what direction one or more of the conditions should be changed. 

Use a series of 12 linear equations involving the assumed and calculated partial pressures to evaluate, by determinants, the errors in the three partial pressures assumed initially... 

The simulations reported here consisted of pressurizing an initially evacuated adsorber with four mixtures of different compositions. These simulations are very much like the traditional flash calculations of chemical engineering thermodynamics applied to an adsorption system. The first set of runs, which we refer to as set G-NVT, is equivalent to solving Eq. (4) with = 0, qf = 0, = y "AF > 0, closure condition... 

Elemental and isotopic fractionations by evaporation of silicate liquids, in particular limiting circumstances, can be simulated by equilibrium calculations, provided that an adequate thermodynamic model of the melt is available. In this approach, a particular starting temperature, pressure, and initial composition of condensed material are chosen and the gas in equilibrium with the melt is calculated from thermodynamic data. The gas is then removed from the system and equilibrium is recalculated. Repeated small steps of this sort can simulate the kinetic behavior during vacuum evaporation (i.e., the limit of fast removal of the gas relative to the rate it is generated by evaporation). This approach has been taken by Grossman et al. (2000, 2002) and Alexander (2001, 2002). 

The simplest models for vapor/liquid equilibrium, based on Raoult s law and Henry s law, are presented in Chap. 10, largely from an empirical point of view. The calculations by modified Raoult s law, described in Sec. 10.5, are adequate for many purposes, but are hmited to low pressures. The initial sections of this chapter therefore present two general calculational procedures for VLB, the first by an extension of modified Raoult s law and the second by equations of state. The theoreticalfoundationforbothproceduresispresentedinChap. 11. The remainder of tliis clrapter deals more generally witlr plrase equilibria, with consideration given in separate sections to liquid/liquid, vapor/liquid/liquid, solidlliquid, solid/vapor, adsorption, and osmotic equilibria. 

Weep test. In this test, unbraided samples of the tube are pressurized by filling them with a military fuel (MIL-S-3136, Type III and MIL-H-25579) consisting of 70% isooctane and 30% toluene. A 15 cm length of the tube is filled with the fuel with a small amount of red dye added to it to improve the visibility of the leak. The tube is pressurized to an initial pressure calculated from Eq. (5.2).00... 

Weep Test - This is a test to determine the integrity of a high pressure hose. In this procedure (MIL-S-3136, type III and MIL-H-25579) unbraided samples of the tube are pressurized by filling with a specified fuel (70% i-octane + 30% toluene) to a calculated initial pressure. Pressure is incrementally (0.035 MPa) increased until seepage occurs. This pressure is recorded as weep pressure. 

Initial conditions include Sw = 1, nf = 0, Cs = 0.83 wt%, and a fixed back-pressure. Calculations require less than 1 cpu minute on a VAX 6420 computer. The thesis of Kovscek provides additional numerical details (80). 

Calculate initial static state, (2) Determine parameters of dynamic model, (3) Calculate dynamic state, (4) Calculate pore water pressure increment and undrained residual strain, (5) Repeat steps of 2-4 till the end of cyclic loading, (6) Continue post-cyclic static analysis until the full dissipation of pore water pressure. 

While the Si-O-Si angles and the interpolyhedral 0-0 distances exhibit nonlinearities with pressure, these do not provide a quantitative measure for mechanical instability. With total energy methods, it is possible to calculate the elastic constants directly as a function of pressure. Under initial hydrostatic pressure, the elastic constants, Cy, are related to the energy variation, AF, to second order in the strains, through[31]... 

First, the reaction occurs at constant volume, so we calculate the partial pressures. The initial partial pressures of reactant and N2 (inert) are ... 

If the experiment would occur in a continuous system at constant pressure (initial pressure), calculate the space time for a conversion reached before at the end reaction. 

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