Heat exchanger networks costing equation

Calculate the capital cost target for the mixed specification heat exchanger network from Equation 17.11 using the cost law coefficients for the reference specification. 

If the capital cost of new heat transfer area is expressed in the form of Equation 18.6, then this will lead to poor retrofit projects. The problem with Equation 18.6 is that the optimization is likely to spread the new heat transfer area in the network in many locations, without incurring a cost penalty associated with the many modifications that would result. To ensure that new heat transfer area is not spread around throughout the existing heat exchanger network, a capital cost correlation should be used that is of the form ... 

By modifying heat transfer coefficients for streams requiring non-base-case operating conditions using Equation (15.141. the same cost equation can be used to calculate all exchanger costs in a given network. 

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