A Brief Introduction to the Pinch Analysis

The economics of industrial production, limitation of global energy supply, and the realities of environmental conservation are an enduring concern for all industries. Wherever you turn, there’s another entreaty to save energy, reduce carbon emissions and protect the environment for posterity. Pinch analysis is a tools used to design a heat exchanger networks (HEN) that reduce the energy usage. This paper will be about brief introduction for the pinch analysis, application of the second law of thermodynamics in design heat exchanger network

Pinch Analysis:

Pinch technology is the technology that provides a systematic methodology for energy saving in processes and total sites. The methodology is based upon first low and second low of thermodynamic. Applying Pinch technology to heat exchanger network HEN synthesis.

The pinch analysis uses Temperature-Enthalpy (T-H) diagram, the composite curves. the temperature axis represents the available driving forces for heat transfer, while the enthalpy axis shows the supply and demand of heat. For processes with multiple cold streams, the individual process thermal duties can be combined into a single “cold composite curve” drawn on a Temperature-Enthalpy T-H diagram, which represents the enthalpy demand profile of the process. Similarly, all the thermal duties for hot streams can be combined into a single “hot composite curve”, which represents the enthalpy availability profile of the process.

Next step is recovering some heat from the hot streams to the cold streams. The optimum value of the Minimum Approach Temperature (∆Tmin) is first determined based on the economic tradeoff between cost savings from heat recovery and capital cost of the heat exchangers. The T-H curves are then ...

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...ollowing:

Hos stream Cols stream

Stream Tin(K) Tout (K) Cp (MW/KG) Stream Tin(K) Tout (K) Cp (MW/KG)

H1 204.4 65.6 1.3 C1 65.6 182 1.29

H2 248.9 158.6 1.66 C2 37.8 204 1.1

H3 158.6 121.1 1.66 C3 93.3 204 1.3

Result:

Utility used Total entropy

(MW/K) Average Area

m2

HP steam 0.846 3.36E+05

MP steam 1.049 1.92E+05

LP steam 1.201 1.63E+05

The result show the maximum total entropy is for networks used HP steam with less surface area needed and the minimum total entropy is for one use LP steam

Conclusion:

The second low of thermodynamic can be used as tool to minimize the cost of utility in a heat exchanger network problem. Total low productions of entropy show a better utilization of the energy quality but with a high area cost. This can help Mathematical Programming Mode to control the entropy of the system rather than cost of the utility.