Pinch analysis is a systematic approach to analysing heat flow through an industrial process and has been used by industry for almost 30 years as a way of saving energy. The so-called 'pinch' occurs at the closest point between hot and cold streams in the network. Tools are available to visualise and then optimise processes to gain maximum output with minimum energy loss.   

For example, a temperature-enthalpy plot shows all hot and cold streams in a process and composite curves are obtained simply by adding hot or cold streams over the temperature range. After plotting both the composite curves in a temperature-enthalpy diagram, the total heating and cooling requirements for a process can be recorded.

The system is divided into two sections: above the pinch focuses on the hot stream (only the 'hot utility' is required), while below the pinch, only cold utility is required. Three golden rules apply to pinch techniques:

• No heat should be transferred across the pinch
• There should be no external cooling above the pinch
• There should be no external heating below the pinch

The pinch method can also be applied to materials, for example in water consumption and contamination analysis.