2016 IIAR Technical Papers
Orlando, FL
38th Annual Meeting

Quantitative Risk Analyses of Untreated, Vertical Pressure Relief Venting Using a Computational Fluid Dynamics Simulation 
Author: William Greulich and Olav Roald Hansen

This paper describes atmospheric anhydrous ammonia gas effects from an untreated pressure vessel relief vent discharging vertically to the atmosphere in an urban area. The primary effect, areal ammonia dispersion, is modeled using computational fluid dynamics software with wind speed and direction varied. In an urban area, where nearby buildings are equally tall or taller than the point of release, local wind fields can be chaotic and direct parts of the ammonia plume down to street level. The diffusion model’s ammonia concentration results are used to estimate public health effects. Assumptions concerning population distribution and likelihood of the release are examined. As a sensitivity study two vent heights were simulated. This work aims to assist the refrigeration community, including its regulators, in quantifying public health risks leading to improved relief vent placement and assessment of the need for relief vent discharge treatment.
Comparing Evaporative and Air-Cooled Condensing in Ammonia and HFC-507 Refrigeration Systems
Author: Doug Scott

Ammonia is the ideal industrial refrigerant, with high efficiency and broad utilization in industry and attractive environmental properties. Use of air-cooled ammonia systems is uncommon, though; almost all ammonia systems use evaporative condensers based on past practice and assumptions concerning efficiency and system performance. However, efficient use of air-cooled condensing could allow the benefits of ammonia to be realized more widely. As a follow-on to a previous IIAR paper, “Comparing Evaporative and Air Cooled Condensing for Ammonia Systems” (Scott 2014), this paper compares energy and operating costs of ammonia and hydrofluorocarbon HFC-507 refrigerants using evaporative and air-cooled condensing applied to similar refrigeration systems for refrigerated warehouses in 11 U.S. cities.
Executive and Top-Level Management Team Introduction to the NH3 System Process Safety Management Program
Author: Jet Tyson-Stiffler

The author interviewed several well-known top-level managers (some associated with large corporations) to provide management teams with information about ammonia refrigeration systems and how process safety management (PSM) affects their positions. Sincere thanks are offered to those individuals who cannot be named or publically recognized herein. Their input was invaluable. At the end of this paper is a list of common acronyms and terms used throughout the industry in relation to PSM and risk management programs (RMPs).
Hygrothermal Analyses of Ammonia Refrigeration Pipe Insulation Systems
Author: Gordon Hart, P.E. and Christian Bludau, Dipl.-Ing.

Hygrothermal computer analyses can be used to model how much moisture accumulation, in the form of both condensed water and ice, is likely to occur in a refrigeration pipe insulation system. Hence, these analyses may be a valuable tool to estimate the useful life of a refrigeration pipe insulation system. Such analyses can also be used to model various insulation systems exposed to different environmental conditions. To determine how several thermal insulation systems on ammonia refrigeration pipes would perform over time, a study used a computer model to perform hygrothermal analyses, thereby predicting simultaneous heat and moisture transfer. This study modeled several variables, including one pipe temperature and pipe size, three different insulation materials both without and with a particular film type vapor retarder, and a certain number of years, and input standardized annual hourly weather data from three U.S. cities.
Use of Natural Refrigerants in Europe:  A Long History, a Great Future, Perfect Now
Author: Bernd Kaltenbrunner

Natural refrigerants have been proven efficient well-known agents in refrigeration technology for more than a century. In recent decades, the refrigeration industry has faced many technological challenges related to refrigerants. Ozone depletion potential and global warming potential (ODP and GWP) have been hotly debated. Natural refrigerants like ammonia, hydrocarbons, carbon dioxide, air, and water have the potential to address challenges regarding the environment and efficient systems for users. In Europe—a so-called “classic” user of natural refrigerants—many different applications have entered the market. But what is new is the combination of already established technological ideas and new ones. Refrigeration systems are being combined, for example, ammonia/carbon dioxide cascades, secondary cooling systems, hydrocarbons in supermarket systems, and trans critical carbon dioxide systems. Refrigeration systems are also becoming the overall supplier in complex systems, taking over air conditioning, heating, and hot water supply. For example, systems for supermarket distribution centers, meat factories, and breweries with ammonia /carbon dioxide cascades also take over heating demand, while small ammonia applications work in supermarkets and in breweries. Thus, boundaries start to disappear as refrigeration systems also work as heat pumps, making it hard to decide whether it is a refrigeration system or a heat pump system. This paper describes some well-established applications of natural refrigerants.
Expanding the Use of Ammonia Refrigeration
Author: John D. Collins, P.E.

Today’s world is putting new demands on refrigeration systems. Environmental concerns are driving regulatory changes, creating uncertainty around the use of synthetic refrigerants. Public awareness of the environmental impact of refrigeration is also higher. New technology offers new capabilities and options for refrigeration system design, presenting opportunities to use ammonia in applications and markets where it has not been used in the past. This technical paper describes how ammonia can become a significant refrigerant in new markets, including the commercial arena. The paper will  • Summarize regulatory factors affecting refrigerant selection, including the total equivalent warming index (TEWI); • Summarize technology now available that makes ammonia refrigeration feasible in new applications; • Present potential new applications and markets for ammonia refrigeration, including a case study of a recent ammonia/CO2 cascade system installed at a retail grocery market; and • Suggest steps the industry can take to support these new applications. Ammonia can become a more widely used refrigerant and serve markets in applications where it has not been traditionally used. This will take a change in thinking about how to use the refrigerant and how to design safe and effective systems. In taking this step, the commercial sector has some lessons for the industrial sector on making refrigeration systems user friendly and cost effective.
Revisiting Refrigerant Release Estimates
Author: Douglas T. Reindl, Ph.D., P.E. and Todd B. Jekel, Ph.D., P.E.

In 2008, we presented a paper titled “Estimating Refrigerant Release Quantities,” which recommended techniques for estimating the quantity of refrigerant released in incidents involving vapor only, low temperature liquid only, and high-temperature liquid that would include flash gas formation in the expansion to atmospheric pressure. In Appendix A of this paper, we provide a reprint of that 2008 publication, including minor corrections. In this paper, we revisit the topic of estimating refrigerant release quantities using two past incidents to demonstrate the complexities that can arise in this process. Finally, we include a set of tables that provides estimates of refrigerant release rates for both vapor and flashing liquid flows over a range of pressures for increments of leak opening sizes.
Low Recirculation Rate Evaporators
Author: Jeff Welch

Fin coil evaporators with enhanced internal tube surfaces allow for optimum performance with a minimal overfeed rate. Reducing the overfeed rate requires less pumping power and smaller line sizes to the evaporator. Additionally, less compressor power is required for the same refrigeration capacity because the wet suction line pressure drop is reduced. Lower compressor power results in substantial electrical power savings over the life of the facility. With internal tube enhancement, top fed evaporators can perform as well as bottom-fed evaporators while using a reduced refrigerant charge during full and part load operation.

2016 Programa en español

Arranque y aseguramiento de la calidad de instalaciones de refrigeración por amoníaco
Author: Silvio Toro Toro

Las instalaciones nuevas y ampliaciones de plantas de refrigeración por amoníaco deben ser sometidas a un proceso de arranque (start-up) y aseguramiento de la calidad (commissioning) que garantice la operación del sistema según su diseño, especificaciones y nomas. Asegura la utilización de materiales certificados para operar con amoníaco y bajo normas de montaje establecidas en cada país. Este trabajo describe varios aspectos de este proceso incluyendo metodología, normativas para el aseguramiento de la calidad, protocolos de pruebas, documentación, protección ambiental y seguridad.
Diseño de sistemas de CO2 en cascada con amoníaco
Author: Ole Christensen and Ricardo Mardones

Las restricciones en el uso de refrigerantes CFC, HCFC y hasta los HFCs están aumentando en la mayoría de los países. Potencialmente, esto deja los refrigerantes naturales como amoníaco, CO2, propano y butano como las únicas alternativas viables. Sin embargo, los refrigerantes hidrocarburos como propano y butano son muy inflamables y explosivos, por lo tanto su uso probablemente no será muy amplio. Para la mayoría de sistemas de refrigeración industrial, las alternativas serán el uso de amoníaco (NH3) o sistemas en cascada en el cual el refrigerante principal será amoníaco y el secundario CO2. Adicionalmente, en muchos países y estados, las autoridades gubernamentales están restringiendo la carga de amoníaco que un sistema puede tener así mismo muchos usuarios finales no quieren amoníaco en áreas de trabajo, proceso ni almacenaje. Tal reacción es motivada por accidentes ocurridos en algunas plantas donde el resultado ha sido que todo el refrigerante contenido en el sistema ha escapado a la atmosfera creando situaciones de alto riesgo personal. Acorde con esto el uso de CO2 en cascada con amoníaco es una alternativa cada vez más procurada. Este trabajo describe varias soluciones para la aplicación de CO2 con amoníaco en cascada. Se discute la selección de los componentes, dimensionamiento de válvulas, válvulas de alivio, tuberías y tanques. Finalmente el trabajo presenta precauciones de seguridad para operar y proveer servicio a los sistemas en cascada NH3/CO2.
Agentes contaminantes en un sistema de refrigeración con amoníaco: causas, efectos y su eliminación
Author: Mauricio Quiroga and Oscar Gomez

En todo sistema de refrigeración existe la posibilidad de que se encuentren agentes contaminantes como aire, agua y gases no condensables, que ocasionan efectos como congelación interna, cristales de hielo a partir de la presencia de agua, disminución en propiedades de lubricación de los aceites, altas presiones de operación, migración de aceite a evaporadores, deficiencias de transferencia térmica, sobrecalentamiento, y en algunos casos fallas y daños mecánicos a componentes, corrosión interna y en general pérdidas de eficiencia en todo el sistema. Se propone explicar en este artículo las causas más comunes que ocasionan la generación de estos agentes contaminantes, sus efectos y consecuencias tanto en la operación y desempeño del sistema así como también las recomendaciones para evitar, disminuir y/o removerlos del sistema.
Consideraciones de diseño para condensadores evaporativos en zonas sísmicas severas y con aplicaciones de carga de viento
Author: Jeffiey W. Nank, Bob Shriver, and Jorge Shriver

Experiencias desafortunadas del pasado han dejado en evidencia que, a pesar de que las estructuras son diseñadas siguiendo rigurosas y detalladas especificaciones de resistencia a cargas sísmicas y de viento, las especificaciones de los equipos mecánicos que en ellas se encuentran suelen ser vagas e incompletas. En las aplicaciones donde estas cargas pueden considerarse severas es de gran importancia asegurarse de que los equipos mecánicos soporten de igual forma las exigencias. En el presente documento se pretende explicar de forma detallada los procedimientos de cálculo recomendados en el Código de Construcción Uniforme (UBC) para la estimación de las cargas sísmicas y de viento para las cuales deben especificarse y diseñarse los equipos mecánicos en cada aplicación determinada, haciendo especial énfasis en los condensadores evaporativos. De igual forma se establecen algunas consideraciones de diseño  speciales que deben tenerse en cuenta para lograr que los equipos soporten dichas cargas severas de forma adecuada.
La importancia de contar con un programa PSM
Author: David Solis Moya

Este trabajo describe la Administración de la seguridad de los procesos (PSM), un sistema que está formalmente dirigido a la operación segura de cualquier proceso en donde exista el potencial de un hecho catastrófico. El amoníaco es una sustancia regulada y sistemas de refrigeración con 10,000 libras o más de amoníaco son procesos cubiertos por los requisitos del PSM. También describe los beneficios prácticos del PSM como garantizar que los riesgos en los procesos con amoníaco como refrigerante sean identificados; evitar incidentes significativos en las operaciones; asegurar que los requerimientos de seguridad sean considerados al evaluar decisiones comerciales; y evitar riesgos inaceptables a las personas, a la propiedad, a los productos y al medio ambiente.