Non-condensable

A substance, typically a gas, that does not change its physical state from gaseous to liquid under a specific set of conditions, such as temperature and pressure. In practical applications, it's often used to describe gases that remain in a gaseous phase when a cooling process aims to condense other components like water vapor or refrigerants. Understanding non-condensable gases is crucial in various fields, particularly in thermodynamics and process engineering where their presence can negatively affect the efficiency of equipment such as condensers and heat exchangers. These gases are often inert and don't readily interact with other components in the system. Their behavior is predictable, following gas laws such as Dalton's law of partial pressures. They play an important role in various industrial processes, including food processing and power generation.

Non-condensable meaning with examples

• In a refrigeration system, air and other gases that remain gaseous at the operating temperature and pressure of the condenser are considered non-condensable. These gases reduce the condenser's efficiency by occupying space and hindering the heat transfer from the refrigerant to the coolant. Thus the effectiveness is highly impacted negatively by the presence of non-condensables. This lowers overall system performance.
• Vacuum systems often encounter non-condensable gases released from leaks or outgassing of materials. These gases must be removed to maintain a high vacuum level. Specialized pumps and traps are employed for this purpose. The presence of non-condensable gases can impact experimental accuracy and the success of manufacturing processes sensitive to these gases, hence the removal is a critical process step.
• During steam generation, non-condensable gases, like dissolved air or nitrogen, can accumulate within the steam system. This accumulation can lead to corrosion, and a reduction in the heat transfer rate across the system. Their build-up negatively impacts the process. Steam traps and venting mechanisms are used to remove or limit the presence of non-condensable gases in industrial steam systems.
• In the context of food processing, nitrogen is used as a non-condensable gas for modified atmosphere packaging, which prevents spoilage of products. The non-condensable gas displaces the oxygen, thereby increasing the shelf life. This is crucial for product quality. Without non-condensables the shelf life of many food items is very short, hence its use is widespread.
• When natural gas is processed, non-condensable components such as nitrogen, carbon dioxide and helium, are removed. Their presence reduces the heating value of the gas. The removal improves the energy content and overall value of the fuel for sale. Processes like gas sweetening are employed to remove these gases from the produced gas stream.