2005 IIAR Technical Papers
  Acapulco, Mexico
 27th Annual Meeting

The Process of Optimizing and Fine Tuning Refrigeration Systems to Improve Efficiency and Lower Operating Costs
Author: Russell K. Uhl

The process of optimizing and tuning an industrial refrigeration system can be a daunting and difficult task that requires patience, hard work, and close attention to detail. However, a little perseverance and head scratching will make it possible to run a refrigeration system at a level of efficiency that may not have been thought possible. This paper discusses step by step the refrigeration optimization and tuning process for a production plant, and the gains in efficiency obtained all through the process.
Refrigeration Piping: A Simplified Guide to a Modern Approach
Author: Paul Danilewicz and Paul Orlando

The paper examines issues faced by engineers, contractors and owners when designing, installing and operating refrigeration piping. It reviews piping mechanical design by discussing applicable piping codes and the suitability of piping, castings, bolting and gasket materials as well as welding methods for low-, normal- and high-temperature service. It then analyzes pipe-sizing methods for a variety of applications, emphasizing the effects of undersizing or oversizing liquid piping, vapor lines and control valves. This evaluation is followed by a discussion on piping layout issues, in particular, layout of compressor suction mains, wet suction returns, elevated equipment and condensers. The paper concludes with a presentation of special cases such as thermal expansion in liquid CO2 and subcooled refrigerant lines, vapor condensation in hot gas and instrument tubing, liquid hammer, liquid carryover, internal and external corrosion, and a comparison of pumped and gravity-fed overfeed systems.
Making the Most of a VFD-Equipped Evaporative Condenser
Author: Michael S. Haller

Variable Frequency Drives (VFDs) have gained notoriety in the refrigeration industry over the last several years. However, it remains difficult to locate practical information with regard to the real-world efficiency benefits of and operational considerations for these drives as they are applied in refrigeration systems. This paper attempts to bridge the gap between the theoretical and real-world application of VFDs on evaporative condensers by discussing the optimization of a plant’s condenser cooling capacity and energy use. The paper first outlines how the effectiveness of VFDs at reducing operating costs depends on both system load and the underlying control strategy. The paper then proceeds to analyze all of the potential direct and indirect benefits of employing VFDs on evaporative condensers. Through this analysis, the feasibility of retrofitting older systems from simplistic start/stop fan operation to VFD control is considered.
Back to the Basics: What is the Right Liquid Feed Method For Your System?
Author: Alan Simchick

Many engineers and technicians select methods to feed ammonia liquid to evaporators based on traditional practices rather than using an analytical approach. Because of the wide acceptance of these methods, an engineer can survive in the industry for many years without ever fully understanding how these systems function. This paper illustrates an analytical approach to selecting the liquid feed system that is best suited for particular applications. A detailed appendix is also included to improve technicians’ and end users’ understanding of these systems. The appendix also reviews and compares five widely used liquid feed methods: direct expansion, gravity liquid feed (flooded), mechanically pumped recirculated liquid overfeed, gas pumped recirculated liquid overfeed, and controlled pressure recirculated liquid overfeed systems.
Machinery Room Ventilation for Industrial Refrigeration Systems: A Rational Engineering Analysis
Author: Rex Brown

Machinery room ventilation has long been recognized as one of the most important safety options available for ammonia refrigeration systems. This paper reviews current requirements for ventilation, discusses the basis for a rational engineering analysis of ventilation requirements, and assesses whether current requirements meet actual needs. First, the purpose of ventilation is discussed and compared to the criteria used to establish ventilation requirements over the past hundred years. Second, the paper reviews the history and evolution of current code requirements in the U.S. Third, the paper identifies the risks that the ventilation system should mitigate, including probability of particular incidents occurring, the resulting consequences, and design parameters that influence this risk. Finally, the paper defines the function and proper modes of ventilation operation, and makes recommendations on improving the current requirements.
Relief Vent Piping per ASHRAE 15-2004
Author: Don Faust and Brian Peterson

Sizing ammonia relief vents, once a simple process, has become more complicated as safety codes have evolved. In recent years, code officials have been scrutinizing vent pipe sizing much more heavily. The latest release of the ASHRAE Safety Standard for Refrigeration Systems devotes considerable ink to the sizing of relief vents, and provides the user with an equation for determining pressure drop in relief piping. This paper will show how to use the ASHRAE equation to solve for the pressure drop in relief vent piping, how to select a relief valve and three-way valve, and also show some strategies to bring existing nonconforming installations into compliance with the code.
Modern Evaporator Piping: Two-phase Riser & Gravity-Feed System Design
Author: David Ross

Modern industry safety practices have, for the most part, moved the installation of vessels and valves outside of occupied spaces in order to reduce employee risk of accidental exposure to ammonia as well as to facilitate maintenance operations. The preferred location has been the roof, a location that in many cases is 15–35 feet above the evaporator. These higher elevations have resulted in dramatic changes to the velocities and pressure differences in both recirculated and flooded evaporator systems and the standard piping practices have not been updated to account for the liquid supply static head pressures and return riser flow issues. Historically, flooded evaporators had a liquid level usually no more than one or two feet above the evaporator outlet connection and the pipe sizes were relatively large for the mass flow. The large pipe diameters insured proper refrigerant flow in low head installations and allowed for oil separation and collection before the evaporator inlet. The return riser did not have turbulent flow by design. This paper presents a theoretical method for designing flooded systems that achieve proper flow conditions in the return riser and correctly predict the liquid line flow characteristics. The result is smaller sizes for lines and hand expansion valves, and evaporators with very similar saturated temperature conditions to the surge vessel many feet above it.
Actions Required During Ammonia Release Incidents: What Do Different Levels Require?
Author: Gary W. Smith

The changes in emergency response over the last 20 years have been significant. Regulatory mandates, including RMP, PSM, and OSHA’s training and personal protective equipment requirements, have required some very serious changes in the way we do business. We continue to improve management of ammonia releases — working on practical and effective strategies such as to stop the releases while they are small, to well-organized transitions of command among the four phases of emergency management. Today, the answer to emergency response readiness is in the basics and not in focusing on the fear-based worst-case scenarios. In 1986, we began to promote the fact that ammonia will burn, given the infamous Shreveport incident. Today, we have moved beyond fear-based logic to using prevention, mitigation, and preparedness to stop incidents small. The community threat from an ammonia release has been significantly reduced using practical approaches to managing ammonia. As a result, we are well on our way to making ammonia the safest managed hazardous material in the world.
The Basics of Refrigeration Control Valves for Liquid Make-Up Applications
Author: John Yencho

One of the most basic and important applications in industrial refrigeration systems is liquid refrigerant make-up and/or transfer to various vessels. The proper design, selection, and installation of piping and control valves serving this function will help to ensure the stable and reliable operation of a refrigeration system. It is worthwhile to give extra thought and attention when feeding high pressure liquid to intermediate-pressure vessels and intermediate-pressure liquid to low-pressure vessels. The entire system may shut down if this function fails or even if there is an upset in the operation of the system. This paper offers suggestions that reduce the likelihood of these problems.
Evaporator Performance in Carbon Dioxide Systems
Author: Andy Pearson

In several recent installations using carbon dioxide as the refrigerant, the performance of the evaporators has exceeded design expectations. To investigate this phenomenon this paper analyzes the air coolers in a cold store, the air coolers in a chill store and plate freezers in a meat processing plant. The analysis is based upon measured data from each site, which is compared with design expectations and contrasted with equivalent figures for ammonia evaporators. The paper gives some useful rules of thumb for selection of carbon dioxide evaporators, and suggests some other ways in which evaporator design might be modified in the future to optimize performance.
The Pressure/Enthalpy Diagram as a Teaching and Diagnostic Tool for Refrigeration Operators
Author: John Sherrill

The Pressure/Enthalpy or “Mollier” diagram has been used by engineers for many years. Up until recently, operators have had limited need for this tool. The Mollier diagram, when presented with the operator’s perspective in mind, becomes the perfect teaching tool for aiding in the visualization of many abstract refrigeration concepts. This paper overviews the terminology required and the basic refrigeration cycle, discusses use of the actual diagram, and reviews how to integrate the operator’s existing knowledge into a teaching program using the Mollier diagram. Using this method gives the operator the best chance of tying together his/her experience with the lessons to be learned in the classroom.
Oil Cooling Methods
Author: Wayne Wehber, Jean-Louis Picouet, and Mike Nielsen

Refrigeration systems using screw compressors require some method of cooling the compressors. This is usually accomplished by cooling the lubricating oil before injecting it back into the compressor. This paper provides a guide to all of the oil cooling approaches utilized on screw compressors from past to present, including an evaluation of the pros and cons of each.

2005 Programa en español

Plantas de refrigeración de amoníaco “con humedad”
Author: Norberto Aguilar Castillo

Se explica en este artículo como las reacciones naturales de amoníaco con el agua desencadena una reacción que contamina nuestras plantas de refrigeración afectando directamente en un mayor consumo de energía eléctrica y una baja de capacidad térmica además incrementando los costos de mantenimiento. El conocer la reacción con la humedad y controlarla nos ayuda a aumentar el rendimiento y bajar los costos de mantenimiento de nuestras plantas de refrigeración industrial. Además se presenta un estudio de humedad en una planta de refrigeración industrial en México.
El sistema de recirculación de líquido por presión de gas, desde un análisis en sus aplicaciones prácticas en la industria frigorífica
Author: Manuel Alarcon Lopez

El sistema de recirculación de líquido por presión de gas con recipiente de presión constante, destaca entre los métodos de alimentación a evaporadores como una alternativa que ha demostrado ser muy factible en los ámbitos técnico-económicos; además, proporciona soluciones redituables en sus diferentes aplicaciones en instalaciones frigoríficas monovalentes y polivalentes. Este trabajo presenta, desde un análisis en sus aplicaciones prácticas, al sistema antes mencionado, y propone una serie de conclusiones y recomendaciones útiles para el aprovechamiento óptimo de la tecnología frigorífica disponible. En la actualidad, resulta indispensable la difusión de ejercicios analíticos técnicos que fundamenten su seriedad en el hecho de aportar elementos de juicio a ingenieros de diseño y usuarios finales, en pro de una mejor elección del sistema de recirculación a utilizar.
Implementación de programas de seguridad
Author: Arturo Munguia Sanchez

El refrigerante amoníaco anhidro, cuya denominación comercial es conocida como R-717, ocupa actualmente un mercado muy importante y en pleno desarrollo en su uso para la refrigeración industrial en México, el cual ha demostrado tener ventajas comparativas respecto a otros refrigerantes como los denominados floró carbonados; pero éste, a diferencia de estos, debe ser empleado y manejado por personal calificado para su operación y mantenimiento. A pesar de ser un refrigerante que se anuncia por si solo al poseer un olor muy característico el cual puede hacer muy fácil el detectar cualquier fuga, es necesario tener una serie de implementaciones de seguridad en cuanto a instalaciones y medidas a tomar en caso de cualquier contingencia, las cuales nos impliquen correr el menor riesgo posible; el contacto con él en determinadas concentraciones puede ocasionar hasta la muerte. Este trabajo presenta los puntos más sobresalientes que nos permitan poder implementar un programa de seguridad para el manejo del amoníaco como refrigerante en la industria en México, así como el tener un conocimiento real de las medidas a seguir en base a las propiedades del mismo.
Opciones de modificación en el ciclo de refrigeración con impacto en el ahorro en consumo de energía
Author: Juan Carlos A. Lage Soto

Esta ponencia sistematiza el análisis de opciones de modificación del ciclo básico de refrigeración planteando alternativas en condensación y subenfriamiento de líquido, acoplamiento de compresores en serie (multietapas) y paralelo, efectos de sistemas de enfriamiento interetapas, acoplamiento de evaporadores a diversa temperatura de evaporación y opciones de sistemas de expansión de líquido y manejo del mismo a los evaporadores, extendiendo el análisis a los sistemas de absorción y a los principios de análisis de los sistemas en cascada. En cada caso se comenta el efecto sobre el nivel de consumo de energía y otros efectos colaterales. Al principio de la ponencia hacemos una reflexión sobre lo que llamamos Cuentas Integradas de Energía.
Sistema de enfriamiento indirecto con sistema cascada y tanque de estratificación
Author: Luis Macias Juarez

El amoníaco como refrigerante es de los más eficientes termodinámicamente tanto de los naturales como de los sintéticos; sin embargo por su nivel de toxicidad el uso de éste, en las instalaciones de sistemas de refrigeración, debe ser regulado. El objetivo de la presentación, es mostrar una alternativa para la reducción del volumen de amoníaco manejado en instalaciones de refrigeración, así como la ventaja de realizar el enfriamiento en cascada para el ahorro de energía.