Which of the following is considered the most undesirable property in refrigerants?

The most undesirable property in refrigerants is a low latent heat, which refers to the amount of heat required to change a substance from liquid to gas at a constant temperature. Refrigerants with low latent heat require larger quantities to achieve the same cooling effect, making systems less efficient. This inefficiency often leads to higher operational costs and increased energy consumption, which is a significant concern in both commercial and residential HVAC systems.

In refrigeration applications, the efficiency and performance are heavily influenced by the latent heat of the refrigerant. A refrigerant with low latent heat requires frequent cycling of the compressor, consuming more energy and leading to higher wear and tear. This can significantly diminish the effectiveness of a refrigeration cycle, making it less desirable for use in practical applications.

In contrast, a high pressure drop, high cost, and high viscosity can all introduce challenges, but they might not have as direct and significant an impact on system efficiency and performance as low latent heat does. Therefore, low latent heat stands out as a critical factor in determining the suitability of a refrigerant for effective and economical refrigeration.