Which of the following is NOT considered a refrigerant substitute in industrial refrigeration?

Water is not considered a refrigerant substitute in industrial refrigeration because it does not function as a refrigerant in the traditional sense. Refrigerants typically have specific thermodynamic properties that allow them to effectively absorb and release heat during phase changes between liquid and gas. While water can be used in certain cooling processes, such as in cooling towers or as a heat-transfer fluid, it does not undergo phase changes in the same way as traditional refrigerants under common operating conditions in industrial refrigeration systems.

In contrast, carbon dioxide, ammonia, and hydrocarbons are recognized substitutes because they possess appropriate thermodynamic characteristics for refrigeration cycles. Carbon dioxide can be used efficiently as a refrigerant in certain applications, allowing for low-temperature cooling. Ammonia is widely used in large industrial refrigeration systems due to its high efficiency and low environmental impact as compared to some synthetic refrigerants. Hydrocarbons, such as propane and isobutane, are gaining attention as refrigerants due to their low environmental impact and natural abundance, making them viable substitutes in various refrigeration applications.