Stream parameters

Table 3 Effects of straightening and structural controls on selected river/stream parameters (acc. to [55], amended)...

TABLE 2. CRYOGENIC UPGRADING OF NATURAL GAS—STREAM PARAMETERS COMPOSITION—MOL.%... 

Minimum number of stream variables (iteration stream parameters). 

Equation (3) above—or more generally by Equation (13) of Reference 7—including any required "utilization function costs" as described in Requirement 3 below) is a minimum with respect to all decision variables of that component—including stream parameters such as H, T, or P upon which the essergy may depend (say via Equation 2, through the familiar dependence of enthalpy and entropy upon temperature T and pressure P—if M, T, or P are not state variables, in which case their value would result from decisions in another component). 

For each stage j, the inlet streams are assumed to be of known rates, compositions, and thennal conditions, while outlet stream parameters are unknown. Thus, and Hj i are known quantities. The column or stage pressures are usually fixed and are therefore known, which renders Equation 5.10 redundant. This leaves nine equations for each stage with nine unknowns Lj, Vj, Xj, Yj, hj, Hj,... 

Provided that we know all kinetic data, ay, k, and a, these two equations carry only one new variable V since temperatures can be derived from suitable enthalpies. Provided that we know how to calculate the averaged driving forces, the model now can be solved and exit stream parameters and volume of the dryer calculated. The success, however, depends on how well we can estimate the averaged driving forces. 

Fischer et al. (1979) list numerous predictive equations for longitudinal dispersion, and perhaps not inconsequentially, estimates of from stream parameters are notoriously inaccurate. Fischer et al. state that the recommended relationship, i.e., Eq. (20.10), will generally predict only within a factor of 4. 

Estimates of volatilization rates from stream parameters are also notoriously inaccurate. Moog and Jirka (1995) found that even the best empirical relationships have a 95% confidence interval of greater than a factor of 3. Values of for a given river reach can be measured by conducting a gas tracer study when greater accuracy is desired (Kilpatrick et al., 1989 Hibbs et al., 1998). 

Values of can be obtained indirectly from stream parameters using Eq. (20.13), or... 

In order that this equation can be used, a functional relationship between (Ri/R ) and known stream parameters must be found. Experimental data of Martinelli [1] and Baker [3] were used, therefore, to establish this relationship for two-component flow. TWs relationship was found using a trial and error approach. Applying (21) together with existing data, the ratio Ri/R vras calculated. Various combinations of stream properties were plotted against It was... 

We obtain the expression for dg in terms of known stream parameters as follows... 

The form serves for streams parameters input via a keyboard or from DCS. Usually, the form contains data for a single subsystem (not necessarily). For making the input faster, most (or all) of the inputs for material, nodes and type of measurement are "pre-printed". 

Note that the complex balance of a larger system of units is set up just according to this input/output scheme. At a fictitious cross-section the system is cut, and the stream parameters refer to this cross section (our... 

For each stage j, the inlet streams are assumed to be of known rates, compositions, and thermal conditions, while outlet stream parameters are unknown. Thus, L, V,+i, Xj, and... 

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