2019 IIAR Technical Papers
  Phoenix, Arizona
41st Annual Meeting

Operating Cost Comparison Between Transcritical CO2 and Ammonia Recirculation Systems in a Cold Storage Warehouse
Author: Chris Herzog and Peter Lepschat

This paper examined operating costs of two similar cold storage facilities: one with a modern and efficient recirculated NH3 system, the other with a transcritical CO2 system. Analysis goes deeper than utility costs; other operating costs such as insurance, maintenance, personnel, compliance, water, chemical, and drainage are also reviewed.
The LOGAS Hot Gas Defrost System
Author: Stefan Jensen

This paper describes the development of a new hot gas defrost system primarily intended for central type, dual-compression-stage, low-NH3-inventory refrigeration systems for refrigerated storage facilities and other applications. The defrost concept described may also be considered for transcritical CO2 refrigeration systems and unitary low-charge NH3 plants of the packaged type. In these systems, the defrost method of choice is often electric due to difficulties associated with accommodating the refrigerant condensate returning to the package(s) during defrost. Conventional hot gas defrost in ammonia refrigeration systems, designed for low refrigerant inventory, requires a refrigerant reservoir that can accommodate the condensate returning from the evaporators during defrost. The LOGAS defrost system eliminates this requirement by employing a phase-change defrost fluid that utilizes several heat sources, including the glycol loop commonly used for subfloor heating in refrigerated warehouses.
Personal Protective Equipment Applications for Ammonia Refrigeration
Author: Ed Johnson

This paper gives guidance for assessing workplace hazards and selecting and maintaining the personal protective equipment (PPE) that allows ammonia refrigeration professionals to work in a regulated facility safely. Specifically, this paper addresses the following items:
(1) PPE assessments for process technicians, appropriate types of PPE for a given facility, and
safety equipment that employers are required to provide;
(2) Advantages and disadvantages of each PPE type;
(3) Regulatory and training requirements for each PPE type;
(4) PPE inspection, care, and maintenance;
(5) Service life of PPE;
(6) Physical changes to a facility that could lead to a change in PPE program;
(7) Recommendations for annual review and re-assessment of a PPE program; and
(8) Real-world examples of regulatory compliance and employee safety.


The purpose of this paper is to
(1) Provide enhanced awareness of the type of PPE that should be used,
(2) Identify the United States Occupational Safety and Health Administration (OSHA)–required
PPE that must be provided to technicians in a stationary process that utilizes anhydrous
ammonia,
(3) Give a better understanding as to which ANSI certifications are required for which PPE,
(4) Offer guidance regarding maintenance of PPE, and
(5) Offer guidance regarding proper respirator selection.


Developing and Implementing Effective Ammonia Refrigeration System Operating Procedures
Author: Michael Keller

This paper provides guidance on developing and implementing operating procedures for ammonia refrigeration systems. The regulatory information is based on the U.S. Occupational Safety and Health Administration (OSHA) Process Safety Management (29 CFR 1910.119) standard (1992), the Environmental Protection Agency (EPA) Chemical Accident Prevention Provisions’ (40 CFR part 68) Risk Management Plan Rule (1996), and the IIAR standards for Developing Operating Procedures for Closed-Circuit Ammonia Refrigeration Systems (ANSI/IIAR 7-2013). Other focus areas include a step- by-step guide and recommendations for effective technical writing, training, and various related topics.
Optimizing Your Remote PHA Experience
Author: Stephanie Smith

Although the basic brainstorming concepts in performing a Process Hazard Analysis (PHA) Study have not changed over the years, changes in the way business is conducted and the availability of modern communications technologies provide opportunities to enhance the implementation flexibility of a PHA Study. In addition, today’s personnel are more comfortable and effective with long-distance communications that include video and computer screen sharing. Nothing is as efficient and engaging as a PHA Team being present in the same room together, but the savings in travel costs, avoidance of the challenges associated with personnel travel, and the ability to quickly convene and implement a PHA review can allow a remote PHA to become an attractive option that can increase overall efficiency, without compromising quality. The use of contemporary technologies is changing the way PHAs are conducted and allow for experts in the field to reach out farther geographically. A core part of this paper is to focus on guidance that can directly be used by the PHA facilitator to optimize the logistics to get the most out of a remote PHA, where some or all team members are geographically distant.
Avoiding Brittle Fracture When Repressurizing Carbon Steel CO2 Vessels That Have Lost Pressure
Author: Jason Haley
A vessel containing liquid CO2 may form dry ice and be at a temperature below -100°F (-73.3°C) if a leak or control malfunction causes its pressure to drop to atmospheric pressure. If the upset condition is corrected and the vessel is repressurized too quickly with warm high-pressure CO2, there is a possibility of brittle fracture if the vessel material of construction is carbon steel. The industrial gas industry has developed safe and acceptable methods of depressurizing carbon steel CO2 vessels that have lost pressure. These are described in the Compressed Gas Association guideline CGA- 6.7. This paper describes the metallurgical and thermodynamic issues, and the methods used for repressurization in the industrial gas industry.
Predictive CFD Modelling of Condensation-induced Water Hammer in Two-phase Ammonia Systems

Author: Chidambaram (Chidu) Narayanan, DSc and Lane Loyko


The condensation induced hydraulic shock (CIHS) problem is a safety issue which requires the accurate prediction of the risk of pipe rupture due to formation of a hydraulic shock. The prediction of the formation of hydraulic shock depends on accurate modelling of slug formation for given conditions of vapor flow rate, liquid height, liquid subcooling, and piping geometry. This study presents results from the detailed three-dimensional CFD modelling of this problem applied to twelve different cases from the experimental study of Martin et al. (2007) with different liquid levels, vapor injection rates, and saturation conditions. The results show remarkable match to experimental results in terms of slug formation, slug propagation, and also in terms of shock formation times and shock amplitudes. The results yield rich information about the mechanisms associated with the formation of interfacial waves as a function of vapor flow rates and liquid level. It also reveals the necessity of condensation to trigger the formation of a slug and the possible modes of condensation such as interfacial/wall condensation that result in the propulsion of the slug eventually resulting in the hydraulic shock. This is the first time such a complex problem has been successfully simulated using a three-dimensional compressible multiphase CFD model demonstrating the utility of such a tool to increase the operational safety of industrial refrigeration systems.
Prediction of Void Fraction and Pressure Drops in Vertical Ammonia Risers

Author: John R. Thome, DPhil

 
Accurate prediction of pressure drops over a wide range of operating conditions in vertical riser piping in ammonia refrigeration systems is an important aspect for their reliable and trouble-free operation. The vertical flow of ammonia in a riser is a mixture of liquid and vapor whose pressure drop is composed of primarily two components, static pressure head and frictional pressure drop, and to a lesser extent a momentum pressure drop. For prediction of the static and momentum pressure drops, the void fraction of the two-phase flow is required, which is defined as the fraction of the cross-sectional area of the riser occupied by the vapor in the flow. Presently, the combined database of two recent experimental studies that measured the two-phase pressure drops for ammonia in 2 and 4 in. pipes will be used to back out values of the void fraction to create a void fraction database. This database has then been analyzed and compared to leading void fraction methods. It was found that a new void fraction method proposed here and the method of Yashar et al. (2001) accurately predicted the data, the latter one being recommended for use. Combining these with the Friedel (1979) frictional pressure drop correlation used to reduce the data, the original experimental total pressure drops were well predicted over their entire range, even down to very low flow rates. In this case, the Yashar et al. (2001) method gave the better total pressure drop statistics and is thus recommended here for use. Finally, the threshold of flow reversal was analyzed and a tentative prediction criterion was proposed.
OSHA: Walking-Working Surfaces and Working at Height
Author: Ken Kempa

The condensation induced hydraulic shock (CIHS) problem is a safety issue which requires the accurate prediction of the risk of pipe rupture due to formation of a hydraulic shock. The prediction of the formation of hydraulic shock depends on accurate modelling of slug formation for given conditions of vapor flow rate, liquid height, liquid subcooling, and piping geometry. This study presents results from the detailed three-dimensional CFD modelling of this problem applied to twelve different cases from the experimental study of Martin et al. (2007) with different liquid levels, vapor injection rates, and saturation conditions. The results show remarkable match to experimental results in terms of slug formation, slug propagation, and also in terms of shock formation times and shock amplitudes. The results yield rich information about the mechanisms associated with the formation of interfacial waves as a function of vapor flow rates and liquid level. It also reveals the necessity of condensation to trigger the formation of a slug and the possible modes of condensation such as interfacial/wall condensation that result in the propulsion of the slug eventually resulting in the hydraulic shock. This is the first time such a complex problem has been successfully simulated using a three-dimensional compressible multiphase CFD model demonstrating the utility of such a tool to increase the operational safety of industrial refrigeration systems.
Emergency Action Plan "Non-Response" Policy Can Be a Mistake
Author: Gary Smith

The Caifornia Occupational Safety and Health Administration (Cal-OSHA) is challenging the non-response and no respiratory protection strategy for an Emergency Action Plan (EAP). Cal-OSHA inspectors are citing companies that do not have a minimum of two escape respirators or SCBA's (self-contained breathing apparatus) outside the compressor room. They want the EAP to include an employer's explanation of how rescue, decontamination, medical care, and emergency shutdown (listed topics in EAP) will be accomplished. Employers using industrial refrigerants like ammonia, hydrocarbons, and CO2 need to prevent, protect (mitigate), and prepare for the rescue, medical, and decontamination consequences of loss of containment of their refrigerants. 

2019 Programa en español

Regulación de Refrigerantes Sintéticos para Latinoamérica
Author: Gildardo Yañez Angli
< Coming Soon!
En esta presentación analizaremos el por qué y el cómo el sector de aire acondicionado y refrigeración debe de adaptar los cambios mundiales y re-visitar el uso seguro de refrigerantes naturales y de nuevos refrigerantes que reemplazarán los refrigerantes sintéticos. Los refrigerantes naturales son de bajo potencial de calentamiento global. Esto significa que debemos armonizar eficiencia en  consumo energético y medidas de seguridad . Hay también una nueva generación de refrigerantes que incluye refrigerantes inflamables, refrigerantes tóxicos y refrigerantes de alta presión de operación.
Enfriadores de líquido y Condensadores Aire-Adiabáticos-híbridos. Que tecnología es más viable para cada aplicación? Factores de decision
Author: David Sanchez
< Coming Soon!
En la actualidad hay disponibles en el mercado una variedad de nuevas tecnologías de disipación de calor y condensación, tanto enfriadores de líquido, e.i: agua/glicol (también llamados aeros, dry coolers o fluid coolers), como para condensadores de refrigerante, que funcionan tanto en seco como en operación húmeda: sistemas adiabáticos e híbridos. Esta presentación analizará la decisión a favor o en contra de una de estas tecnologías durante la etapa de diseño de un proyecto; y cuál será el impacto en el costo de inversión, y los costos operativos posteriores; así como la seguridad higiénico-sanitaria de la planta en su conjunto, durante todo el ciclo de vida.
Ventilación Mecánica para salas de máquinas para sistemas de Refrigeración Industrial. Aplicando un Análisis Ingenieril
Author: Didier Altamirano Calderon
< Coming Soon!
La ventilación mecánica, ha sido reconocida como una de las medidas de seguridad más importantes disponibles para la operación segura de los sistemas de refrigeración de amoniaco. Todos los sistemas de refrigeración, utilizan un gas químicamente puro;  consecuentemente, la liberación de cualquier refrigerante podría dar como resultado una concentración de gas que puede convertirse en una amenaza para la vida de cualquier persona expuesta al escape del gas.  El propósito de esta discusión es revisar los actuales  requisitos y determinar si satisfacen las necesidades de la industria, y si recomiendan cambios a los códigos y normas actuales.
Consideraciones De Eficiencia Energética En Refrigeración Industrial Con Amoníaco
Author: Mario Mora Carli
< Coming Soon!
La ventilación mecánica, ha sido reconocida como una de las medidas de seguridad más importantes disponibles para la operación segura de los sistemas de refrigeración de amoniaco. Todos los sistemas de refrigeración, utilizan un gas químicamente puro;  consecuentemente, la liberación de cualquier refrigerante podría dar como resultado una concentración de gas que puede convertirse en una amenaza para la vida de cualquier persona expuesta al escape del gas.  El propósito de esta discusión es revisar los actuales  requisitos y determinar si satisfacen las necesidades de la industria, y si recomiendan cambios a los códigos y normas actuales.
Proceso de Deshielo por Gas Caliente. Recomendaciones para mejorar la eficiencia y seguridad
Author: Roberto Badillo
< Coming Soon!
Durante esta presentación se estudiarán dos métodos de deshielo: control de presiones y  drenaje de líquido;  con el propósito de explicar los beneficios y los ahorros energéticos que se notan al usar el método de drenaje de líquido.

2019 Commercial Technical Papers 

Natural Refrigerant System Selection Comparisons in Commercial Systems
Author: Dustin Lilya

When natural refrigerants were new to commercial refrigeration, the competitive landscape for system selection was between traditional system types that used synthetic refrigerants or natural refrigerant technologies. Now that natural refrigerant technologies are becoming mainstream, we have begun to see the system selection process shift to comparisons between the various natural refrigerants. This paper will provide a brief historical review and comparison of early systems, and then provide a technical comparison of current popular 100% natural refrigeration systems being adopted. How do CO2, NH3, and R290 compare to each other in terms of market penetration, cost, and design options for commercial applications?
Case Study: The First Commercial Propane/Carbon Dioxide Cascade Refrigeration System in North America
Author: Tristam Coffin, Keilly Witman and Tom Wolgamot

In 2016 the Northern California Region of a prominent U.S. supermarket company opened the first and only supermarket in North America that uses a commercial R290/carbon dioxide (R290/R744 or C3H8/CO2) cascade refrigeration system. The store is located in Santa Clara, CA, and it is part of the company’s strategy to pilot the full range of natural refrigerant technology options for research and development purposes.
Fire Hazards and Mitigation Measures of ASHRAE Class A3 Refrigerants in Commercial Refrigeration Applications
Author: Scott Davis, PhD

This study evaluates the flammability hazards of R-290 releases from a refrigerated display case and explores the effectiveness of using the condenser fan to mitigate the formation of flammable clouds in the event of an accidental release. The results of the study show how severity changes with charge size and demonstrate the potential for continuous condenser fan operation to mitigate the hazard posed by leaks external to the conditioned space. When a flammable refrigerant is released from a refrigeration cycle, there are several factors that affect the potential severity of the event including properties of the refrigerant, characteristics of the leak, properties of the equipment, and aspects of the environment. This paper focuses on releases outside the conditioned space of refrigeration units (i.e., from the condenser unit) and presents full scale testing results that quantify the severity of various refrigerant releases and associated post-ignition events for different charge sizes. In addition, the present study presents computational fluid dynamics (CFD) results which show: (1) how different factors influence the outcome of a leak; and (2) the effectiveness of condenser fan operation in mitigating the flammability hazard of leaks from condensing units.