Which refrigerant is often used interchangeably with ammonia in certain refrigeration systems?

The refrigerant commonly used interchangeably with ammonia in certain refrigeration systems is carbon dioxide. This is due to the fact that both ammonia and carbon dioxide operate effectively at low temperatures and have high energy efficiency, making them suitable alternatives in specific applications.

Carbon dioxide, often referred to as R-744 in refrigeration, has become increasingly popular in commercial refrigeration systems due to its low environmental impact and natural occurrence. While ammonia is a well-established refrigerant in industrial settings due to its high cooling capacity and efficiency, carbon dioxide is preferred in scenarios where the system must comply with modern environmental regulations regarding global warming potential and ozone depletion.

This interchangeability is especially evident in systems designed for transcritical cycles, where carbon dioxide can perform efficiently at low temperature levels, similar to ammonia-based systems. It's important to note that the other options, while they may play roles in refrigeration, do not share the same direct applicability as substitutes for ammonia in industrial applications.