Heat exchangers rough rating

As a rough guide for plate heat exchangers, the rate of the hydrodynamic entrance length to the corresponding thermal entrance length is given by... 

If exchanger shell diameter is in doubt, see Chapter 2, Heat Exchangers, the Shell Diameter section. In addition, this book provides a rough rating method for air-cooled heat exchangers. 

The required relieving rates for these PR valves are based upon the steam rate to the turbine As a rough guide, the appropriate size can be checked against the following tabulation, which are recommendations of the "Standards of the Heat Exchanger Institute, Surface Condenser Section."... 

The preceding information will suffice to rough rate shell and tube units. For air-cooled heat exchangers, more is involved in rough rating. A suggested procedure is as follows 2 3... 

Comparison of Examples 2.1 and 2.2. Table 2.4 gives a measure of the effect of nonoptimum feed point on the column in this example, Table 2,4 shows that V and V, and therefore reboiler and condenser duties, increase by about 3 to 4 percent in Example 2.2. This roughly corresponds to a 3 to 4 percent increase in energy consumption and operat-mg costs. If the column or its heat exchangers are at a maximum capacity limit, the column feed rate will need to be reduced by 3 to 4 percent. If these consequences can be tolerated, a shutdown to change the column feed nozzle will be unnecessary. Note that in this example, the effect of nonoptimum feed was quite mild. In other casas, it may be far more detrimental,... 

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