Which refrigerant in commercial and industrial systems has the highest latent heat and refrigerating effect?

• A. R-134a
• B. Ammonia
• C. R-22
• D. R-410A

Answer: (B)

Latent heat of vaporization is the energy a refrigerant absorbs when it changes from liquid to vapor in the evaporator. The higher that latent heat per kilogram, the more cooling you get for each kilogram that evaporates, which means a stronger refrigerating effect for a given mass flow. Ammonia has a much larger latent heat of vaporization than the hydrofluorocarbon options listed, so it delivers substantially more cooling per kilogram and often higher volumetric efficiency in large industrial systems. That combination—very high latent heat and strong cooling per unit mass—explains why ammonia is favored for large commercial and industrial chillers. The other refrigerants have much lower latent heats, so they produce less refrigerating effect per kilogram, which is why they’re used in different applications or in smaller systems. Keep in mind ammonia’s advantages come with safety trade-offs, as it is toxic and flammable.