Design, dependent factors

Having defined it is necessary to determine the design-dependent factors. The variables, shape complexity, tolerances, etc. modify the relationship between the curves. The relative cost coefficient in Equation (3.1) is one way in which these variables can be expressed. 

If data is not obtained, any estimate produced will be a lower bound only, the quality of the estimate will improve as more information is represented regarding the effect of the design-dependent factors. 

The quantity of catalyst used for a given plant capacity is related to the Hquid hourly space velocity (LHSV), ie, the volume of Hquid hydrocarbon feed per hour per volume of catalyst. To determine the optimal LHSV for a given design, several factors are considered ethylene conversion, styrene selectivity, temperature, pressure, pressure drop, SHR, and catalyst life and cost. In most cases, the LHSV is ia the range of 0.4—0.5 h/L. It corresponds to a large quantity of catalyst, approximately 120 m or 120—160 t depending on the density of the catalyst, for a plant of 300,000 t/yr capacity. 

Theoretical possible heat removal per pound of air circulated in a cooling tower depends on the temperature and moisture content of air. An indication of the moisture content of the air is its wet-bulb temperature. Ideally, then, the wet-bulb temperature is the lowest theoretical temperature to which the water can be cooled. Practically, the cold-water temperature approaches but does not equal the air wet-bulb temperature in a coohng tower this is so because it is impossible to contact all the water with fresh air as the water drops through the wetted fill surface to the basin. The magnitude of approach to the wet-bulb temperature is dependent on tower design. Important factors are air-to-water contact time, amount of fill surface, and breakup of water into droplets. In actual practice, cooling towers are seldom designed for approaches closer than 2.8°C (5°F). 

The report presents the findings from the analysis of the RCP failures. Estimates of the annual frequency for the spectrum of leak rates induced by RCP seal failures and their impact on plant safety (contribution to coremelt frequency) are made. The safety impact of smaller RCP seal leaks was assessed qualitatively, whereas for leaks above the normal makeup capacity, formal PRA methodologies were applied. Also included are the life distribution of RCP seals and the conditional leak rate distributions, given a RCP seal failure the contribution of various root causes and estimates for the dependency factors and the failure intensity for the different combinations of pump designers and plant vendors. 

The success of a laboratory design depends on many factors, not the least of which are health and safety considerations. When the team approach is implemented, each member brings to the design specific expertise essential to the element of proper design. 

The experiments are performed according to the chosen design and a response or a number of responses are measured. The sequence in which the experiments are performed can influence the estimation of the effect of a factor [36]. The reason for this lies in the fact that the measurements can be influenced by different sources of error. Each measurement is influenced by uncontrolled factors that cause random error. Measurements can also be influenced by systematic errors or by systematic errors caused by drift (linear drift due to time-dependent factors). The occurrence of systematic errors or of drift will affect the estimation of the effects of the factors fi om the design [36]. 

The architecture of a common NN is shown in Fig. 10.8. The design depends on the types of sensor responses, on their dynamic range, drift, and so on. In short, it depends on all the complexities of the transfer functions of different types of sensors. Once again there is an input layer containing m input elements. It is massively interconnected to the n nodes of the next hidden layer %n at which the weighing factors Wn operate on the signal. There can be more than one hidden layer, if necessary. The connection to the output layer 0O has the form of nonlinear transfer function /hid for example,... 

The selection of a particular system design depends on many factors number of use points requiring ambient and hot water, flow rates and frequency of usage, availability of capital, etc. " ... 

The number of gas-phase transfer units that exist in a given column design depends on a number of factors, including 1) slurry spray rate 2) droplet size and distribution 3) gas-phase residence time, which is controlled by the height of the spray zone 4) liquid... 

In an exothermic reaction the temperature increases as the conyersion increases. At low conversions the rising temperature increases the rate more than it is reduced by the fall in reactants concentration. Normally the conversion will be greater than for isothermal operation. However, undesirable side reactions and other factors may limit the permissible temperatures. In these cases successful design depends on effective removal of the heat of reaction to prevent excessive temperatures (hot spots). In general, the same methods are employed as for adding energy in endothermic reactions. 

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