Trial calculations

A trial calculation shows that /in must be positive, and different authors recommend values ranging from 0.5 to 1.2. The value of kcN is sometimes taken as 0.8,... 

To apply the viscosity correction K, a preliminary or trial calculation should be made for the areas required using the equation of paragraph (e) above or the modified equation (still ASME conformance [33] but not... 

For final calculation use from Figures 7-23 or 7-24 and substitute in the above equation. Determine the needed Reynolds number, Re, using the next size larger orifice. Area is determined from that made in the first trial calculation [33]. 

The pressure balance is off by about 21 Ib/fP. In design, this can be corrected by a slight adjustment in liquid level or by adding pressure drop to the inlet line (e.g., a valve). It is assumed here that no further trial calculations are needed. 

Example 40 Trial calculations are done for Vanaiyt = (0.5) and Vprod = (0.9). .. (1.1) the required t-factors for p = 0.1 turn out to be 1.94. .. 1.66, which is equivalent to demanding n - 1. .. 120 calibration samples. Evidently, the case is critical and needs to be underpinned by experiments. Twenty or 30 calibration points might well be necessary if the calibration scheme is not carefully designed. 

Measuring and Using Numbers For each trial, calculate the heat released per gram of candle wax. 

Which components are the key components will normally be clear, but sometimes, particularly if close boiling isomers are present, judgement must be used in their selection. If any uncertainty exists, trial calculations should be made using different components as the keys to determine the pair that requires the largest number of stages for separation (the worst case). The Fenske equation can be used for these calculations see Section 11.7.3. 

Only sufficient trial calculations will be made to illustrate the method used. Basis 100 mol feed. 

A procedure for the selection of new values for the iteration variables for each set of trial calculations. 

The method starts with an assumption of the column temperature and flow profiles. The stage equations are then solved to determine the stage component compositions and the results used to revise the temperature profiles for subsequent trial calculations. Efficient convergence procedures have been developed for the Thiele-Geddes method. The so-called theta method , described by Lyster et al. (1959) and Holland (1963), is recommended. The Thiele-Geddes method can be used for the solution of complex distillation problems,... 

The specific heat at this temperature is 2.05 kJ/kg°C. A second trial calculation using this value gives t2 = 77.9°C and a new mean temperature of 58.9°C. There is no significant change in the specific heat at this mean temperature from the value used, so take the crude stream outlet temperature to be 77.9°C, say 78°C. 

These rate constants were the optimum values obtained using the STEPIT-CSMP combination, starting with initial values of koo kop kpp=27.7xlO 6M 1sec 1. The optimization required 74 trial calculations and 5.10 seconds of time on an IBM Model 158 Computer. 

The following trial dimensions and material proportions may be obtained from trial calculations, by inspection of similar structures, or from experience. The results of this dynamic calculation will determine the adequacy of the trial size. 

Analyze and Conclude For each trial, calculate the molar concentration of the base by dividing the moles of base by the volume of base in liters. 

With this method, unknown terminal temperatures are found without trial calculations. 

Using reasonable suggested values for AR, FA, and Ux, seldom are more than two trials required. Usually the first trial calculations are within reasonable tolerance of the assumed Ux value—say 15% error or less. Such error is tolerable if a 10 to 15% excess cooler bare tube area is allowed. Thus, having this tolerance of error, in many cases the first assumed Ux value is close enough for hand calculations and a second pass through steps 1 through 13 is not required. The DTA value first calculated in step 2 should also be adjusted for a second calculation... 

In the final analysis, processing time is the main criterion of batch-still design. To achieve optimal cost-effective performance requires a large number of trial calculations, such that the best combination of equilibrium stages, reflux ratio, batch size, and batch-processing time can be established. It is extremely difficult to successfully carry out such a procedure by hand calculation. 

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