How minimizing pinch temperature improves heat transfer

A smaller pinch temperature difference can result in a larger heat transfer area but can also lead to higher capital costs. When designing heat exchangers, it's important to balance the thermodynamic performance with the economics.

Thermodynamics

A small pinch temperature can reduce the heat exchanger's irreversibilities and entropy loss. In a heat exchanger, the area around the pinch point contributes the most to entropy production and the required heat transfer coefficient. By overlapping the hot and cold composite curves and separating them by the minimum temperature difference, the maximum process heat recovery can be achieved. This indicates minimum hot and cold utility requirements for the process.

What is pinch technology?

Pinch technology is a process engineering technique that aims to reduce the amount of energy used in chemical processes. It's based on the idea that heat can be transferred from higher to lower temperatures, which can reduce the need for fuel and steam.

The origin of the word " pinch"

The term "pinch" in pinch technology comes from the pinch principle, which states that heat can be transferred from hotter to cooler temperatures to recover energy. The pinch method is a two-step process that calculates the maximum energy recovery in a system to minimize the amount of external energy needed.

Improved heat transfer

A small pinch temperature can improve heat transfer by minimizing the amount of heat that needs to be transferred across the pinch:

Pinch point

The pinch point is the minimum temperature difference at which heat can be transferred between two streams.

Pinch analysis

Pinch analysis is a technique that identifies the pinch point and helps to optimize heat transfer.

Heat transfer

Heat is always transferred from the higher-temperature object to the lower-temperature object.

Reduces energy consumption

Pinch analysis can help reduce the amount of energy required from outside, which can lower operating costs.

How to design pinch temperature?

To design pinch temperature, you can use the pinch method, which involves two steps:

Step by step

Calculate maximum energy recovery

Calculate the maximum energy recovery in the system to minimize the external energy needed.

Find the pinch

Use a graphical approach to find the pinch, which is the point where the hot and cold composite curves are closest in temperature on a temperature-enthalpy graph.

Here are some other things to consider when designing pinch temperature:

Minimum allowable temperature approach

The minimum allowable temperature approach, or ΔTmin, ensures that equipment sizes are reasonable.

A trade-off between equipment and operating costs

The selection of ΔTmin is based on the trade-off between the equipment and operating costs. Finally, pinch technology can help maximize heat recovery, which can lead to energy savings, reduced operational costs, and lower greenhouse gas emissions

Finally, pinch technology can help maximize heat recovery, which can lead to energy savings, reduced operational costs, and lower greenhouse gas emissions