Reducing the Number of Heat Exchangers— Stream Splitting

Reducing the Number of Heat Exchangers—Stream Splitting 

When designing a HEN to meet its MER targets, stream splitting must be employed if (a) the number of hot streams at the pinch, on the cold side, is less than the number of cold streams or (b) the number of cold streams at the pinch, on the hot side, is less than the number of hot streams. In this way, parallel pairings that fully exploit the temperature differences between energy sources and sinks are possible. Moreover, stream splitting helps to reduce 

It is required to design a HEN, with a minimum number of heat exchangers that satisfy ATmin = 10°C and a hot utility MER target of 300 kW, for three streams on the hot side of the pinch  

To minimize lost work, as explained in Section 9.4, it is desirable to mix the split streams isothermally that is, to select 160°C, with x = 7.143 kW/°C. Unfortunately, isothermal mixing is infeasi- 

As illustrated in Example 10.10 and introduced by Linnhoff and Hindmarsh (1983), generalized rules for stream splitting on both sides of the pinch to satisfy MER requirements are 

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