Pinch Golden Rules

Below the pinch, the system rejects heat and so is a net heat source. When a heat recovery system design does not have cross-pinch heat transfer, that is, from above to below the pinch, the design achieves the minimum hot and cold utility requirement under a given ATmin- 

FIGURE 9.10. Pinch principle penalty of cross-pinch heat transfer. 

Based on the eross-pineh heat transfer principle, if external cooling is used for hot streams above the pineh, it increases the hot utility demand by the same amount Similarly, extonal heating below the pinch increases the overall hot and cold utility requirement by the same amount. 

To summarize, there are three basic pinch golden rules (Linnhoff et al., 1982) that must be obeyed to achieve the minimum energy targets for a process  

Violating any of these rules will lead to penalty in both hot and cold utilities beyond the target. 

---