Fluids property calculations

We will see that, as expected, the presence of charges in the matrix strongly modifies the long range (i.e. screening) behavior of the fluid-fluid correlation functions. In order to illustrate the effects of confinement on the dipolar fluid properties, calculations for the corresponding fully equilibrated system - i.e. an electrolyte with explicit solvent - have also been carried out in the hyper-netted chain (HNC) approximation. This is known to be accurate enough for the thermodynamic states under consideration. 

Hydrates. Programs have been developed for predicting hydrate forming conditions for the HLiG, HL1L2G, and HL1L2 equilibia. These use the approach developed by Parrish and Prausnitz (12) but with the PR equation used throughout for all fluid property calculations. Details of the method have been reported by Ng and Robinson (13). 

The factor enabling interpolation of reduced properties of a pure compound or mixture between two reduced properties calculated on two reference fluids merits attention in order to understand its meaning. 

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 heat requirements in batch evaporation are the same as those in continuous evaporation except that the temperature (and sometimes pressure) of the vapor changes during the course of the cycle. Since the enthalpy of water vapor changes but little relative to temperature, the difference between continuous and batch heat requirements is almost always negligible. More important usually is the effect of variation of fluid properties, such as viscosity and boiling-point rise, on heat transfer. These can only be estimated by a step-by-step calculation. 

Minimum Fluidizing Velocity U,nj, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one of the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen audYu [A.l.Ch.E.j., 610-612 (1966)] given below can then be used to back calculate d. This gives a particle size that takes into account effects of size distribution and sphericity. The correlation can then be used to estimate U, at process conditions, if U,nj cannot be determined experimentally, use the expression below directly. 

Djj. The Grashof number Nq, = Dj pgpAto/p" were is equivalent diameter, g is acceleration due to gravity, p is coefficient of volumetric expansion, p is viscosity, p is density, and Atg is the difference between the temperature at the wall and that in the bulk fluid. Nq, must be calculated from fluid properties at the bulk temperature. 

When you can determine that the overall coefficient U or fluid properties vary markedly from the inlet to the exit conditions of the unit, the arithmetic mean is no longer satisfactory for fluid property evaluation. For this case, the proper temperature of each stream is termed the caloric temperature for each fluid. The F fraction is the smallest of the values calculated and applies to both streams. Although the caloric temperature... 

Najjar, Bell, and Maddox studied the influence of physical property data on calculated heat transfer film coefficients and concluded that accurate fluid property data is extremely important when calculating heat transfer coefficients using the relationships offered by Dittus-Boelter, Sieder-Tate, and Petukhov. Therefore, the designer must strive to arrive at good consistent physical/thermal property data for these calculations. 

Shell-side fluid properties. From previous process calculations, the following properties were determined for the dry gas stream ... 

The fluid properties and porosity and permeability are determined independently. Boundary and initial conditions are specified for the particular experiment to be considered. With specified multiphase flow functions, the state equations, Eqs. (4.1.28, 4.1.5 and 4.1.6), can be solved for the transient pressure and saturation distributions, p (z,t) and s,(z,t), t= 1, 2. The values for F can then be calculated, which correspond to the measured data Y. 

Hence, Ub is a function of UbL, Db, and fluid properties. The equivalent diameter of the vapor blanket, Db, can be obtained from the correlation for the bubble departure diameter (Cole and Rohsenow, 1969). To calculate the liquid velocity, UbL,... 

In summary, the Gibbs ensemble MC methodology provides a direct and efficient route to the phase coexistence properties of fluids, for calculations of moderate accuracy. The method has become a standard tool for the simulation community, as evidenced by the large number of applications using the method. Histogram reweighting techniques (Chap. 3) have the potential for higher accuracy, especially if... 

Such performance curves are normally determined by the manufacturer from operating data using water at 60°F. Note from Eq. (8-6) that the head is independent of fluid properties, although from Eq. (8-4) the power is proportional to the fluid density (as is the developed pressure). The horsepower curves in Fig. 8-2 indicate the motor horsepower required to pump water at 60° F and must be corrected for density when operating with other fluids and/or at other temperatures. Actually, it is better to use Eq. (8-4) to calculate the required motor horsepower from the values of the head, flow rate, and efficiency at the operating point. The curves on Fig. 8-2 labeled minimum NPSH refer to the cavitation characteristics of the pump, which will be discussed later. 

First, the minimum fluidization velocity ( umj) is calculated from 23.2-5. After substitution of the particle and fluid properties provided, the resulting quadratic equation is ... 

How does u, change with changes in (a) fluid properties, and (b) solid properties Justify quantitatively without doing calculations. 

Minimum Fluidizing Velocity LO, the minimum fluidizing velocity, is frequently used in fluid-bed calculations and in quantifying one ol the particle properties. This parameter is best measured in small-scale equipment at ambient conditions. The correlation by Wen... 

For the semi-batch stirred tank reactor, the model was based on the following assumptions the reactor is well agitated, so no concentration differences appear in the bulk of the liquid gas-liquid and liquid-solid mass transfer resistances can prevail and finally, the liquid phase is in batch, while hydrogen is continuously fed into the reactor. The hydrogen pressure is maintained constant. The liquid and gas volumes inside the reactor vessel can be regarded as constant, since the changes of the fluid properties due to reaction are minor. The total pressure of the gas phase (P) as well as the reactor temperature were continuously monitored and stored on a PC. The partial pressure of hydrogen (pnz) was calculated from the vapour pressure of the solvent (pvp) obtained from Antoine s equation (pvpo) and Raoult s law ... 

For cooling of non-Newtonian fluids, the pressure drop should be calculated by use of fluid properties at the wall temperature. 

Assume magnitudes of the tube-diameter, D, mass velocity, G, and the fluid properties. Divide the length into equal increments of quality change, Ax, and calculate the heat-transfer coefficient, hz at the mid-quality magnitude of each Ax and assume that h2 is uniform in this quality range. Then the length required to change the quality Ax is... 

Assume a condenser built with a single tube if 12.5 mm I.D., which is fed with 150 kg/h of R-22 refrigerant (Du Pont). Calculate the tube length needed, assuming a wall at a constant temperature of 24.4 °C and a saturation temperature of 30°C. The fluid properties are shown in the Table 3.4-5. 

The second case is considered when a low density of solid phase and/or small sizes and concentration of solid is used. This allows considering the solid concentration uniform along the whole column and the slurry considered as a homogeneous phase with modified fluid properties. According to Deckwer [17] with dp<50pm and CSoiid<16% (in mass), we can use such simplification. The equivalent density can be calculated using the following expression ... 

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