Secondary refrigerants are usually?

Secondary refrigerants play a crucial role in refrigeration systems, particularly in applications where the primary refrigerant is not suitable for directly cooling the desired medium. They are typically used to transfer heat from the refrigerated space to the evaporator. Water and brine, which are both fluid substances, effectively absorb and transport heat due to their thermal properties.

Water, as a secondary refrigerant, is widely used because it is abundant, cost-effective, and has a high specific heat capacity, allowing it to carry a significant amount of heat with relatively small temperature changes. Brine, a mixture of water and salt, has a lower freezing point than pure water, making it suitable for applications where temperatures drop below freezing. This capability allows for efficient cooling even in low-temperature environments.

In contrast, options like chemical refrigerants are typically primary refrigerants that undergo phase changes to absorb and release heat directly in a refrigerating cycle. Air or gas can also be utilized in various cooling applications but are less efficient as secondary refrigerants compared to liquids. Solid refrigerants do not effectively facilitate heat transfer in the same manner as liquids, making them unsuitable in this context. Thus, water and brine emerge as the most effective and common secondary refrigerants in refrigeration practices.