Refrigerated ammonia research aims to safeguard society
As refrigerated ammonia gains attention as a cleaner fuel for heavy-duty applications, such as marine vessels, scientists are working to understand how it behaves in water and how to respond quickly to spills in order to protect people and the environment.
The research began in September 2023 as part of a collaborative effort between the American Bureau of Shipping through the Laboratory for Ocean Innovation and the Mary Kay O’Connor Process Safety Center (MKOPSC) at Texas A&M University.
Later-stage interaction showing the persistent gel-like interfacial layer above the bulk water after the intermediate ammonia-rich layer has dissolved.
Credit: Courtesy of Javier Ovalle Rosas
These groups identified knowledge gaps in handling and transporting refrigerated ammonia and investigated how it behaves when released into water. They conducted a detailed experimental study to investigate key factors, providing novel insights into spill behavior and informing risk assessment.
“The goal of this research was to understand the interaction and short-term behavior of refrigerated ammonia when it contacts water,” said Dr. Faisal Khan, chemical engineering department head and MKOPSC director.
When refrigerated ammonia and water interact, the process involves interfacial heat and mass transfer with rapid phase change. This means that when refrigerated ammonia spills, it instantly becomes a source of short- to medium-term ammonia vapor above the water surface.
Throughout the research, the team found that refrigerated ammonia can remain concentrated near the water surface and continue moving into the air over a longer period rather than mixing quickly throughout the water before evaporating.
“This matters for spill response because it means the vapor source doesn’t disperse the way people might expect,” said Dr. Edison Sripaul, senior research engineer at MKOPSC. “Responders need to know that ammonia can linger and keep releasing from the surface rather than getting diluted quickly by the water below.”
Another finding was the discovery of a distinct, gel-like ammonia-rich layer at the water surface. According to the paper, this gel-like phase remained stable and served as a source of ammonia release.
“What surprised us most was how organized and long-lasting this behavior was,” Khan said. “Instead of everything mixing quickly, the refrigerated ammonia and water formed different phases that stayed separate for a while. Understanding this behavior is an important first step toward managing ammonia spills effectively and protecting people and the environment.”
The team also found that the unusual ammonia-water behavior spanned different experimental sizes, suggesting it was not simply an effect of size.
“Our experiments showed that the interface between ammonia and water is an active region, not simply a boundary,” said Dr. Harini Gunda, a postdoctoral fellow at the MKOPSC. “Seeing the same behavior across different experimental sizes suggests that this interfacial mechanism is intrinsic to the ammonia–water interaction, rather than simply an effect of the system size.”
Khan said the research has expanded to include simulated seawater and larger experiments. Beginning in September 2026, the team plans to conduct additional experiments that more closely mimic real marine conditions. These studies will help researchers better understand what could happen if ammonia were accidentally released from a refrigerated system at sea.“Freshwater gives us a baseline, but seawater adds important chemical effects from salinity, buffering and dissolved minerals,” said Javier Ovalle Rosas, a Ph.D. student who participated in the research. “We want to understand how these factors influence ammonia transfer at the water surface and the overall evolution of a spill under realistic marine conditions.”
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