What type of refrigerant is typically used in direct expansion systems?

Direct expansion systems commonly use refrigerants with suitable thermodynamic properties that allow efficient heat transfer and vaporization, making R717 (Ammonia) an ideal choice. Ammonia is known for its high heat capacity and energy efficiency. It operates effectively at lower temperatures and has a favorable cooling effect, which is essential in industrial refrigeration applications where maintaining precise temperature control is critical.

Ammonia also has a low environmental impact concerning ozone depletion potential, though it is important to manage its toxicity and flammability correctly. This enhances its application in industrial settings, where safety protocols are established.

While options like R134a and R410A are employed in various commercial air conditioning systems, they are less common in industrial refrigeration due to their lower efficiency at lower temperatures. R22, although used in the past, is being phased out due to environmental regulations concerning ozone depletion. Given these considerations, R717 stands out as the most suitable refrigerant for direct expansion systems in industrial refrigeration contexts.