IIAR Conference Technical Paper Presentations to Cover Releases, Small Package Systems
“A common theme will be smallcharge ammonia systems applied to commercial and light industrial applications,” said Eric Smith, IIAR’s vice president and technical director.
Additional themes include dealing with releases, how to comply with regulations and the benefits of compliance.
Smith said he expects a good reception for the paper Quantitative Risk Analyses of Untreated, Vertical Pressure Relief Venting Using a Computational Fluid Dynamics Simulation written by William Greulich and Olav Roald Hansen.
“It examines what happens to ammonia when it is released and what the potential downwind effects could be,” Smith said. “The analysis takes a look at weather patterns, air temperature and how ammonia disperses under different scenarios and circumstances and whether or not people nearby might be harmed by a release.”
Smith said the paper is an example of the type of analysis that could be done to figure out whether or not an ammonia system could be used in any particular setting. “Where I think it has great potential are applications for commercial properties that are considering using an ammonia system instead of a synthetic refrigerant,” he said.
As part of Greulich and Hansen’s research, ammonia dispersion was modeled using computational fluid dynamics software with varied discharge height, wind speed and wind direction. “We’re not using the Gaussian model, which solves one simple equation. It works fairly well if you have nothing in the way. If you have obstructions, like buildings in the way, the model fails quickly,” Greulich said.
Greulich, one of the paper’s authors, said IIAR has heard papers on ammonia dispersion for a number of years, but that this one is different. “All of the previous authors have been stuck using similar methods that are inexpensive and easy to use but that comes with a price.
This is the first paper to step up to using computational fluid dynamics,” he said, adding that CFD is technically more robust but is expensive, slow and difficult to use. The paper digs deep into the effects of a release within an urban area, which is filled with buildings that would alter the flow of ammonia once it is released. “Ammonia is a buoyant gas when in equilibrium with the atmosphere. It should rise and go straight to the Moon, but everyone knows that the ammonia comes back because the winds and buildings bring it back,” Greulich said.
Greulich said the work is aimed at assisting the refrigeration community, including regulators, in quantifying public health risks, improving relief vent placement and assessing the need for relief vent discharge treatment. “We’re really trying to do this so owners and operators of systems and their regulators understand that this is a technical issue and is not something that is easily written in broad brush standards,” he said. “We want code officials to work in an informed way.”
Greulich said natural refrigerants are coming, and ammonia is one of the originals. He said he would like the paper to show that the risks associated with ammonia are calculable and that it is safe. “Up until now, no paper has told you what the risk actually means in useful quantifiable terms,” he said.
Also presenting during the conference is Doug Scott, who will discuss his most recent paper, Comparing Evaporative and Air Cooled Condensing for Ammonia and HFC-507 Refrigeration Systems, which is an encore paper to one he presented several years ago.
“It is expanding the case for air-cooled condensers,” Smith said, adding that Scott’s research examines the potential advantage for air-cooled condensers in areas where water is scare and, therefore, expensive.
Scott said that his paper includes additional citations and compares halocarbon-cooled systems, both air and evaporative, and used the synthetic refrigerant R-507 in the analysis.
“It is a four-way comparison of energy use and operating costs for a typical medium-sized refrigerated warehouse in 11 cities,” Scott said. “In general terms, when water is considered along with electric utility costs, the air-cooled systems are equal or less expensive in nearly all locations of the country.”
The findings surprised Scott, he said. “The prevailing logic would be that evaporative systems would use less energy,” he said. “They do during the peak hours of the year, but peak weather only occurs for a relatively small number of hours in the year. When you look at the year and operation over time, you get a different view and a different picture of the comparison.”
Smith said, “What I like about this paper is that there is not always a one-size-fits-all solution. It also demonstrates very clearly that ammonia has some very good operating efficiencies over R-507.”
Among Scott’s findings is that ammonia is more efficient even in very hot climates.
“The main takeaway from this is there is an opportunity for ammonia to be used where it hasn’t been used much before,” Scott said. “Historically if an owner wanted or needed to use air-cooled, the prevailing conclusion was you needed to use a halocarbon system. You didn’t automatically think of ammonia.”
Meanwhile, a paper presented by John Collins, Expanding the Use of Ammonia Refrigeration, looks at the regulatory factors affecting refrigerant selection and the development of new technology that offers new capabilities and options for refrigeration system design.
“Today’s world is putting new demands on our refrigeration systems. Regulatory changes driven by environmental concerns are creating uncertainty around the use of synthetic refrigerants. There is also a higher level of public awareness of the environmental impact of refrigeration,” Collins said.
Collins’ paper shows how ammonia has the potential to become a significant refrigerant in new markets, including the commercial arena, and outlines steps the industry can take to support these new applications.
Collins said that there have been significant developments in the design, fabrication and application of heat exchangers and controls for ammonia refrigeration. “This is enabling manufacturers to offer low-charge and small-capacity ammonia systems for commercial and retail applications,” he said. “This shift will require a change in thinking related to how we use the refrigerant and how we design our systems. In taking this step, the industrial sector can learn some lessons from the commercial sector in how to make refrigeration systems user friendly and cost effective.”
Collins’ paper includes a case study of a recent ammonia/CO2 cascade system installed at a retail grocery market, which demonstrates how ammonia can be used in a commercial setting. Collins said the ammonia industry needs to invest the money and effort to develop products and materials for small-capacity, low charge-applications to increase the use of natural refrigerants.
“Technology is part of the answer, but it will also take our industry to collectively build on our experience and to bring that knowledge to a broader market,” Collins said. “The infrastructure and institutions to develop and support trained and qualified designers, installers and operators is a major concern that cannot be overlooked. This will take the concerted effort of industry groups including end users, systems designers, manufacturers, contractors and also government agencies. Organizations like IIAR have an opportunity and an obligation to support the commercial sector of the refrigeration industry in addressing its need for natural refrigerant alternatives.”
A total of eight papers will be presented in English during the conference. In addition, there will be an International Program with six paper presentations in Spanish. All papers will have Spanish to English and English to Spanish translation.
