2007 IIAR Technical Papers
 Nashville, TN
 29th Annual Meeting

Optimizing Industrial Refrigeration Efficiency with a Kaizen Blitz
Author: Marcus Wilcox and Robert Morton

Company executives are increasingly focused on reducing energy use both for financial reasons and to exercise good corporate citizenship. Energy awareness at the executive level typically translates into issuing unfunded mandates to cut energy use by five or ten percent or more. Facility and/or maintenance managers therefore must accomplish this objective with ingenuity. In a large food processing or distribution company, it makes the most sense to wring these savings out of the biggest energy user — the industrial refrigeration system. A Kaizen Blitz can be used to help reduce energy consumption quickly with lasting results and minimal challenges.
Mechanical Integrity and Nondestructive Inspection for Ammonia Refrigeration Systems
Author: Jim Kovarik

Formulating specific requirements to inspect and test piping systems has particularly challenged end-users. Questions arising from an end-user’s perspective include: What test methods are applicable? What modes of failure are most common? What types of inspection equipment are most suitable? This paper reviews the different types of inspection technologies available to assess the condition of ammonia refrigeration equipment and highlights the merits and deficiencies of each technology. Elements of maintaining a viable PSM program and items to look for when selecting an inspection contractor are also discussed.
Comprehensive, System-wide Approach to Refrigeration Equipment Control for Maximum Energy Efficiency
Author: James Conant and Michael Ghan

Microprocessor control technology originally replaced electro-mechanical and solid-state programmable logic controller (PLC) devices, but did not take full advantage of data processing power. The first generation simply sought to capture and provide historical operating data to aid diagnostics and improve equipment operation. The next generation greatly advanced refrigeration energy efficiency, primarily at the individual equipment level. Examples include improved staging of multiple compressors, evaporator fan cycling, floating condenser and suction pressure control, defrost frequency reduction methods (e.g., liquid runtime, delta-T across the coil), and variable frequency drive motor control on compressors, condenser and evaporator fans. Today’s computer control technology delivers even higher energy efficiencies by employing a whole-system approach to individual refrigeration equipment operation. These efficiency improvements are made possible by the continuous monitoring of plant operating conditions and energy use, combined with a “Resource/Demand” perspective on refrigeration systems. This paper will detail different plant-wide management control methods and their benefits over the individual equipment control approach.
Stress Corrosion Cracking in the Ammonia Refrigeration Industry
Author: Rowe Bansch

Stress corrosion cracking (SCC) can occur on the inner surface of steel pressure vessels subjected to tensile stress, such as near major welds, in the presence of ammonia and oxygen. Such cracks may propagate through the vessel wall to create a pinhole leak, although cracks this severe are very uncommon in refrigeration applications. The paper reviews case studies of specific instances of known SCC, discussing failure modes, vessel applications, metallurgical analysis results, and methods of resolution. Finally, the paper presents methods of inhibiting SCC and makes specific recommendations for designing and inspecting vessels, and for repairing vessels that have experienced SCC.
Air Coolers, Air Currents and Temperature Distribution in Large Refrigerated Warehouses
Author: Heinz Jackmann

This paper concerns a case study of a refrigerated space holding 25,800 pallets within a height of 100 ft. The ductless design used a “reverse” airflow pattern with downward airflow against the wall and into the floor. Velocities were minimized to prevent room turbulence and allow natural air diffusion. Air returning from the product rose by natural convection within the refrigerated space. Computer simulation was used to analyze thermal effects within the space and optimize the design to specify coolers that ensured uniform air and temperature distribution.
High-Rise Warehouses: A Growing Trend for Controlled-Pressure Receiver Systems
Author: Jeremy J. Klysen and David J. Ross

Today’s refrigerated warehouses are growing “up” instead of “out” due to new warehouse technologies and for economic reasons. This paper will demonstrate that Controlled Pressure Receiver (CPR) overfeed systems coupled with modern controls have superior features which enhance the ability to properly feed liquid to evaporators. CPR systems cost less to build, operate and maintain than a mechanically pumped overfeed system. CPR systems use “free” gas energy from various parts of the system to feed liquid to evaporators located on 70 foot high roofs and as far away as 1,500 feet from the engine room. In addition to performing mechanical work, flash gas can also be used to perform thermal work throughout the system. Finally, CPR systems can easily identify excessive overfeed rates by tracking the number of transfer cycles, a problem that wastes compressor capacity by raising suction line pressure drop.
Troubleshooting Ammonia Refrigeration Systems with Plate Heat Exchangers
Author: Mats A.T. Stromblad

Semi-welded plate heat exchangers (PHEs) have found use in numerous ammonia systems since the 1980s because of their compactness, efficiency, low ammonia charge, resistance to pressure and temperature cycling, materials compatibility, and ease of modification. Industry has experienced a number of different kinds of non-performing cases involving PHEs and many lessons have been learned by equipment suppliers, contractors, and end users on how to set up systems and how to improve and handle ammonia applications with PHEs. This paper discusses the most important troubleshooting cases and provides suggestions on how to solve them. The paper also discusses challenges and troubles that end users face, and suggests that PHEs may be an option for meeting these challenges. PHEs can achieve greater thermal efficiency with their close temperature approaches. Dry expansion systems may promote the use of ammonia in air conditioning applications because of reduced system refrigerant charge; fusion bonding technology makes contributions in this area. Energy saving and energy recovery require efficient heat exchangers. Ammonia can find increased use for energy saving in absorption chilling and heating and in power production wherever close temperature approach heat exchangers can be used.
Minimization of Unit Freezing Costs for In-Line Freezing Systems
Author: Stefan S. Jensen and Marion Lehmann

The variables influencing how a given product freezes in an automatic in-line freezing system are time, temperature of the freezing medium, and heat transfer between the product and the freezing medium. This paper describes a design methodology to evaluate product freezing times, freezer capacity, and refrigeration load for such systems. The methodology estimates evaporator performance and product freezing time from first principles and determines the equilibrium between cooling load and evaporator capacity iteratively. The paper includes sensitivity analyses showing influence of evaporating temperature, product temperatures, air velocity, evaporator fouling, and product packaging on freezer performance. Finally, the paper shows a method to determine the minimum unit energy consumption point.
Thermal Analysis of Food Freezing Processes Using Variable Properties and Numerical Techniques
Author: John R. Masson

The key to designing effective food freezing processes is to understand correctly what actually happens when a non-homogeneous item is cooled from its initial freeze point to the final process temperature. ASHRAE’s Refrigeration Handbook provides calculation techniques and property correlations for food components which allow a much better understanding of the thermodynamic and heat transfer phenomena involved than that gained from traditional analyses based on assumed average constant properties. Using computer-based numerical techniques, consulting engineers can provide greater value to clients. By understanding the variability in food properties, end users and equipment designers can work together to design better food freezing processes with more predictable outcomes. Finally, future research into freezing processes can be better targeted.

2007 Programa en español

El Placer de Sistemas de Evacuación de Amoníaco
Author: Peter Jordan and Kris Hinds

La instalación del Nestlé Prepared Foods Division en la ciudad de Springville, Utah tiene más de 225,000 libras de amoníaco anhidro en su sistema de refrigeración. A traves de los años, esta planta ha pasado por modificaciones extensivas. Bajo condiciones normales, la transferencia y evacuación del amoníaco antes de estas modificaciones ocasionan paros de producción largos resultando en perdidas de producción y costos significantes. Sin embargo, esta planta tiene un sistema de evacuación a lo largo de la instalación que permite evacuaciones rápidas antes de modificaciones del sistema. Este trabajo examina el uso del sistema de evacuación de amoníaco desde la perspectiva de un usuario final. Repasa la historia del sistema de evacuación incluyendo la lógica usada para justificar la instalación del sistema y los costos relacionados con el sistema. El personal de la planta también describe los usos variados del sistema de evacuación subrayando la flexibilidad que prove.
Gerencia de refrigeración con amoníaco: ajustando el equipo de trabajo
Author: Lawrence F. (Tex) Hildebrand and Vern Sanderson

Cada año la industria gasta millones de dólares tratando de ajustar el equipo de refrigeración con amoníaco. Análisis de vibración, reinstalaciones, cambios de aceite, y ajustes de temperatura son unos pocos ejemplos. Sin embargo, asuntos de personal así como conflictos laborales, problemas personales, condiciones de trabajo adversas, una falta de percepción de importancia y salud mental también pueden tener potencialmente un impacto en la seguridad y el desempeño de los sistemas de refrigeración con amoníaco. De hecho, se puede argumentar que el operador del sistema de refrigeración con amoníaco es el factor más importante que contribuye al desempeño del sistema. Desde hace algunos años, ingenieros de refrigeración han asumido un dominio bastante grande de los sistemas que operan. Esta cultura no solo obtuvo mejoras en el desempeño del sistema y la seguridad, sino también ahorros de costos. Con la subida de los costos de energía, estos ahorros potenciales solamente pueden aumentar. Este trabajo reparte ejemplos verdaderos y filosofías para motivar a los empleados, incluyendo las etapas para lograr la meta fundamental que es el dominio o pertenencia de los empleados de su sistema de refrigeración con amoníaco.
Diseño del sistema termosifón
Author: Jeff Welch, P.E.

Debido a razones operativas y de mantenimiento, los sistemas termosifón se han convertido en un método muy popular de enfriamiento de aceite entre los diseñadores. A pesar de que se instalan muchos sistemas cada año, todavía existen problemas debido a una falta de comprensión sobre cómo deberían ser diseñados e instalados. Esta ponencia presenta un método teórico para el modelado de un sistema inundado o termosifón que puede ser usado por los diseñadores a la hora de obtener diseños más precisos y económicos, pero también para analizar sistemas que no rinden como se espera de ellos. Esta ponencia también presenta una lista de guías básicas de diseño y precauciones a tener en cuenta.
Las acciones requeridas durante incidentes de fuga de amoníaco: ¿Qué requieren niveles diferentes?
Author: Gary W. Smith

Cambios en las entidades que responden a emergencias durante los últimos 20 años han resultado significativos. Las regulaciones legales—incluyendo RMP, PSM, los requisitos de entrenamiento OSHA y los equipos de protección personal, han demandado ciertos cambios considerables en la forma que desarrollamos nuestra labor comercial. A pesar de que los cambios no resultan fáciles de entender o de cumplir por aquellos profesionales encargados de implementarlos. En la mayoría de los casos se ha conseguido evolucionar y conseguir un estatus mucho más seguro. De hecho, pasamos de una lógica basada en el miedo a una de prevención, mitigación y preparación para afrontar los riesgos y las amenazas asociadas con la refrigeración industrial a base de amoníaco y la estrategia de parar a los pequeños,” (“Stop them small,” en inglés) para un control de incidentes de emergencias.