2015 IIAR Technical Papers
San Diego, CA
37th Annual Meeting

Economic Justification for Replacing Ice-laden Refrigerant Pipe Thermal Insulation with New Insulation
Author:  Gordon H. Hart, P.E.

In 2011, following a severe hail storm, the owner of a large food processing plant discovered that the thermal insulation systems on his roof-top ammonia refrigeration pipes had been badly damaged. A subsequent inspection conducted soon after the storm by the building owner revealed that the pipe insulation was ice-laden and/or soaked with water, following its fifteen years of continuous service. To remedy the situation, the owner hired an insulation contractor to replace the ice-laden and wet insulation over the course of several years, as his budget and schedule would allow, using a different insulation system design. After the owner made this decision to replace the old insulation system with new materials, an energy analysis was conducted to determine the cost effectiveness of that replacement based on the value of energy saved and the cost of replacement. The decision to replace the original insulation system with a new one, of a different design, was made solely by the facility owner. This author had no role in that decision or recommendation. It should also be noted that the type of replacement insulation used, polyolefin, is no longer commercially available for industrial refrigeration applications.
Operating Experience with NH3 Dry Expansion Systems Servicing Refrigerated Distributed Centers
Author:  Stefen S. Jensen

Several jurisdictions of the World have either already legislated a phase-down of high global warming (GWP) refrigerants or are in the process of doing so. In June 2013 Presidents Xi and Obama entered into an agreement to work together towards a phase-down of Hydrofluorocarbon (HFC) refrigerants. On the 6th of September during the G20 assembly in Russia, around twenty nations agreed to participate in an HFC phase-down using the Montreal Protocol as a phase-down tool provided other nations would agree to participate. In December 2013 the European Parliament decided overwhelmingly in favor of a 79% reduction in HFC emissions by 2030. Aside from being powerful contributors to global warming, high GWP synthetic refrigerants also feature relatively poor vapour compression cycle efficiencies compared with natural refrigerants such as ammonia. Costs of electrical energy are rising rapidly. In Australia recent cost increases (22.6% as at July 2013 and 13.6% as at July 2014 in Queensland) are mainly the result of changes to the demand for network assets. The rapid uptake of solar panels has given rise to reductions in electricity demand from the grid. In some jurisdictions, demand on some days is below the power plant base load. The unit costs of electricity must therefore rise in concert with reductions in demand to ensure network maintenance can be funded. This is also referred to as the death spiral. The uncertainty with respect to the future of synthetic refrigerants and the rapidly rising electrical energy costs have renewed the focus of refrigerated warehouse operators towards future proofing of new installations and refrigeration system energy performance. By way of two case studies and references to a third installation in a food factory, this paper details the end-user business benefits associated with employing ammonia refrigerant and dry expansion refrigerant feed in small to medium size refrigerated distribution centers. In the case of one study, the energy consumption cost difference between a new dual stage NH3 dry expansion system and a single stage HFC based system servicing a similar sized facility owned by the same end-user in the same suburb is shown. One study describes a fully factory assembled NH3 based engine room comprising compressors, vessels, electrical equipment, engine room ventilation, PPE, controls and weatherproof enclosure ready for positioning on a prepared slab on site. This concept reflects the need to minimize site installation time and post-commissioning maintenance in small rural jurisdictions of Australia. Finally the paper describes future design areas (wish list) that will require attention by contractors as well as product/equipment suppliers in order to make NH3 systems more attractive to those end-users who have traditionally favored HFC systems.
Refrigerant and Regulatory Developments: Change Impacting the Opportunities for Natural Refrigerants
Author:  Rajan Rajendran, Ph.D.

In the years since the Montreal Protocol went into effect in 1989, the global refrigeration and air conditioning industry has met the challenge of phasing out ozone depleting chemicals and adapted well to achieving increasing efficiency for their equipment using synthetic hydrofluorocarbons (HFCs) in most common applications. In large industrial applications, ammonia has become the standard refrigerant of choice, even though HFCs are used in some installations. In recent years, the alarming growth and emissions of HFCs into atmosphere has caused concern that, if left unchecked, these HFCs could become a major contributor to global warming gases in the atmosphere. Starting with some European countries, and followed by Australia and eventually the rest of Europe, governments have started taking action to curb this growth and emission of large quantities of HFCs. More recently, the United States Environmental Protection Agency (EPA) announced proposed rules to remove some of the HFCs by application from their approved list of refrigerants. The refrigerant landscape has changed significantly and continues to evolve as these factors come into play. In response to a demand for refrigerants with lower climate impact, natural refrigerants have seen resurgence, made possible in large part due to the advent of electronics and software to make natural refrigerant systems more efficient. New synthetic refrigerants have also been developed, more efficient than existing HFCs and having less impact on the climate. We are looking at a future with more options than we have ever had before – which means that we have to be careful in how we make our choices to minimize or eliminate unintended negative consequences.

Optimizing Evaporator Runtime and Defrost Frequency
 Author: Bruce I. Nelson, P.E.

When cooling air to temperatures below freezing, the surfaces (fins and tubes) of evaporators unavoidably accumulate frost which must periodically be removed by defrosting. The defrosting process is inherently bad because it: a) reduces system refrigeration capacity by interrupting the air cooling process, and b) increases system power consumption by adding heat to the space which must then be removed by the refrigeration system. The room temperature and relative humidity in combination with the evaporating temperature defines the Sensible Heat Ratio (SHR) for the air cooling process. The SHR in turn indicates exactly how much moisture will be removed from the airstream and end up as frost on the evaporator (the "frost load"). To date, manufacturers of evaporators have not really offered much guidance to refrigeration system designers regarding how to properly select evaporators for a given frost load. Most of the time, manufacturers’ application guidance consists of "Well, when the frost load is heavy increase the number of defrosts, Oh and by the way, watch out."
The paper quantifies the rate of moisture removal as a function of SHR and shows the effect of frost accumulation on evaporator airflow and cooling capacity. The predicted reduction in evaporator cooling capacity over time is used to determine an appropriate value for runtime hours (hours/day) used for equipment selection as well as selecting an appropriate defrost frequency (no. of defrosts/ day).

Regulatory & Code Implications for Low Charge Ammonia Systems
 Author:  Kurt Liebendorfer

How is the regulatory burden impacted by installing low charge ammonia refrigeration systems? With the rapidly growing interest, development and application of limited or low charge ammonia systems, there is an increasing need for market awareness and definition of what the benefits and/or implications are from a regulatory and code perspective for such a system, as compared to larger traditional or existing ammonia systems. For example, codes and standards such as OSHA, IIAR, ASHRAE, IBC, IMC and UMC all have various design references and/or criteria related to the quantity of refrigerant in a system, and specify actions or designs that must be undertaken as a result of their specific refrigerant threshold quantity (TQ). This paper will seek to identify these regulated threshold quantities among the various applicable codes or standards so that designers, contractors and end users can better understand the fact or fiction of the various threshold requirements.
This is a very large and broad undertaking because there are so many regulations, codes and standards that may or may not apply to all users. Therefore, the paper is also meant to set the stage for continued investigation, collaboration and validation on the subject matter. Many of the regulations and codes have been coordinated over the years and contain some common requirements. However, as shown in this paper, there is a lack of refrigerant threshold quantities related to charge management, as well as a lack of discussion on refrigerant quantity guidelines. Nevertheless, technological advances and industry awareness now provide a real opportunity to incorporate new TQ’s into the regulations and codes. This continued work needs to influence regulatory agencies and code writing bodies to update their documents and to keep pace with the tremendous benefits that low charge technology provides the ammonia refrigeration industry.

Industrial Refrigeration Vapor Valve Sizing- an Updated Approach
 Author:  Robert Sterling

Calculation of pressure drop in vapor flows through valves has made substantial advancements in the past half-century. Currently-used methods for determining pressure drop through valves with vapor flows (assumed to be either saturated or superheated refrigerant vapor states) were identified and evaluated. Attempts at providing a standard means for industrial ammonia system engineers to calculate vapor valve pressure drops have been undertaken in the past, notably by the IIAR. At present, the IIAR makes available an explicit set of equations, based on CV , and provided in the Ammonia Refrigeration Piping Handbook (2004). It is often the case that in HVAC&R, valves are sized based on capacity in Tons of Refrigeration. This does not allow for accurate sizing for types of valves not rated in those terms and will often not predict the correct valve for a specific application. This study recommends the use of widely-standardized methods for calculating vapor flow valve pressure drops be adopted in the industrial refrigeration industry on the part of engineers and contractors.
Applying Evaporative Condensers to Subcritical CO2 Condensing and Transcritical CO2 Gas Cooling  
 Author:  John Ball and Klaas Visser

A mathematical model of an evaporative condenser that allows for unusual properties of CO2 has been constructed to show that subcritical CO2 can be condensed at 30 degrees Celsius (86 degrees Fahrenheit) with ambient air at 35 degrees Celsius (95 degrees Fahrenheit) dry bulb and 24 degrees Celsius (75 degrees Fahrenheit) wet bulb. World-wide climate conditions are examined to show that evaporative condensers can be used to condense subcritical CO2 at 30 degrees Celsius (86 degrees Fahrenheit) for the entire or most of the year in large areas of many countries such as USA, China, Canada, Australia almost all of Europe including Spain, Italy, Greece, and Turkey. Reduction in water consumption is demonstrated using a dry cooler in conjunction with an evaporative condenser. It is also demonstrated that evaporative CO2 gas cooling of transcritical fluid results in high electrical energy efficiency signified by high Coefficients Of Performance (COP) at supercritical pressures of 7.5 MPa (1088 psia) and higher, particularly when employing parallel compression for medium temperature and low temperature refrigeration duties in, for example, supermarkets by providing AC cooling as part of the parallel compressor operation at 5 to 10 degrees Celsius (41-50 degrees Fahrenheit) CO2 evaporating temperatures.
Long Term Field Trial of Alkylbenzene (AB) Lubricant in an NH3 System
 Author:  Manuel Munoz-Alonso

Alkylbenzene lubricants have been a good solution in ammonia plants to increase the oil drain interval and reduce the amount of residues in the system when using mineral oil. Nowadays there are more synthetic oils that can be used to do this job. This paper tries to show that these alkylbenzene lubricants are still valid and give a good performance at reasonable prices.

2015 International Technical Program
All International Technical Papers are available in their original presented language and English. 

Perspectivas del futuro de sistemas de conversion de energia termica oceanica (OTEC)
 Author: Zahid Ayub, Ph. D., P.E. and Samuel Sami, Ph. D.,  P.E.

Este trabajo examina el potencial del uso de amoníaco en la conversión de energía térmica oceánica (OTEC). Se analizan diferentes tipos de equipo de transferencia de calor avanzado para utilización como vaporizador, condensador y regenerador. Se discuten brevemente las ventajas y desventajas de cada opción. Se presenta una comparación general entre un sistema con amoníaco y otro con R-134a usando un ciclo Rankine de baja temperature.

Un análisis comparativo de varios componentes del ciclo usando amoníaco y R-134a bajo las mismas condiciones de entrada en el evaporador y el condensador mostró que el amoníaco tiene eficiencia de recuperación de calor mejor que R-134a. Además, el ciclo de amoníaco tiene mucho menos caudal másico comparado con R-134a, que resulta en un sistema mucho más pequeño comparado con el de R-134a.

Prospects of Ammonia Based Ocean Thermal Energy Conversion (OTEC) Systems
 Author: Zahid Ayub, Ph. D., P.E. and Samuel Sami, Ph. D.,  P.E.

This paper explores the potential use of ammonia in Ocean Thermal Energy Conversion (OTEC). Different types of advanced heat transfer equipment are discussed for use as vaporizer, condenser and regenerator. Pros and cons of each option are briefly discussed. An overall comparison between ammonia and R-134a based system is presented using a low temperature Rankine cycle.
A comparative analysis of various components of the cycle using ammonia and R-134a under the same input conditions at the evaporator and condenser showed that ammonia has better heat recovery efficiency compared to R-134a. Furthermore, the ammonia cycle has significantly less mass flow rate compared to R-134a, which results in much smaller system compared to that of R-134a.

Prueba de campo a largo plazo de lubricante alquilbencenio (AB)
 Author: Manuel Munoz-Alonso

Los lubricantes alquilbencénicos fueron una buena solución en las plantas de amoníaco para aumentar el intervalo de cambio de aceite, y reducir la cantidad de residuos en la instalación cuando se use lubricante mineral. Hoy día hay más lubricantes sintéticos disponibles, pero este trabajo intenta mostrar que los lubricantes alquilbencénicos son aún válidos y dan buenas prestaciones a precio razonable.

* English paper available in English Technical Program as Technical Paper #8
 Author: Yiqiang Jiang and Ian Zhao  



Energy Efficiency Improvement Strategies of Ammonia-Based Refrigeration Systems used in Indoor Snow Domes  
Author: Dr. Yiqiang Jiang and Ian Zhao

With reference to the design and operation of an indoor snow dome, many factors should be considered including the requirement of human body comfort, the quality of snow, energy saving operation and so on. As we know, the refrigeration system consumes most of the energy in an indoor snow dome and ammonia-based refrigeration systems are widely used in indoor snow domes. Therefore, the objective of this paper is to discuss the energy consumption and energy efficiency improvement strategies for ammonia-based refrigeration systems used in snow domes. First, it introduces four kinds of snowmaking methods and the principles of ammonia-based refrigeration systems used in the indoor snow domes. Second, it provides the refrigeration load and energy consumption of each system in a specified situation, followed by a discussion of different energy efficiency technologies: heat recovery technology and its application and thermal storage in snow base. Finally, a practical engineering example is given to show how to apply these energy efficiency strategies comprehensively to such aspects as energy efficiency, operation possibility, safety and economic viability.

Optimizando el tiempo de operacion y la frecuencia de desescarches de los evaporadores
Author: Bruce I. Nelson, P.E.

Cuando se enfría el aire a temperaturas de congelación, la superficie (tubos y aletas) de los evaporadores inevitablemente acumula escarcha la cual tiene que ser removida periódicamente mediante el deshielo. El proceso de deshielo es de por si malo porque: a) reduce la capacidad de refrigeración del sistema al interrumpir el proceso de enfriamiento de aire, y b) eleva el consumo de energía del sistema al agregar calor a la cámara que después debe ser eliminado mediante el sistema de refrigeración. La temperatura de la cámara y la humedad relativa en combinación con la temperatura de evaporación definen la relación de calor sensible (SHR de ahora en adelante, por sus siglas en inglés) para el proceso de refrigeración. El SHR a su vez indica exactamente cuanta humedad se eliminará del aire y terminará como escarcha en el evaporador. Hasta la fecha, los fabricantes de evaporadores en realidad no han ofrecido suficiente orientación a los diseñadores de sistemas de refrigeración con respecto a cómo seleccionar adecuadamente evaporadores para una carga de escarcha dada. La mayor parte del tiempo, una guía de aplicación de los fabricantes consiste en "Bueno, cuando la cantidad de escarcha en el evaporador es muy grande aumenta el número de deshielos, ah y por cierto, ten cuidado". El documento cuantifica la tasa de eliminación de la humedad como una función del SHR y muestra el efecto de acumulación de escarcha en el flujo de aire y capacidad del evaporador. La prevista reducción de capacidad en el evaporador con el tiempo se usa para determinar un valor apropiado para las horas de operación (horas/día) utilizadas para la selección del equipo, así como seleccionar una adecuada frecuencia de deshielo (no. de deshielos/día).

*English paper available in English Technical Program as Technical Paper #4
Avaliacao Experimental do Processo de Drop-in do R22, Propano, Propileno e HFC438A em um Sistema De Refrigeracao
Author: Enio P. Bandarra Filho

O presente artigo relata uma investigação experimental do processo de drop-in do R22 substituindo-o pelos hidrocarbonetos propano e propileno, bem como pelo HFC438A em um sistema de refrigeração de 15 kW. A bancada experimental foi composta basicamente de um compressor semi-hermético, operado por um inversor de frequência, trocadores de calor de tubos concêntricos e uma válvula de expansão eletrônica. Os testes foram realizados por sucessivas substituições do refrigerante, sem alterar quaisquer componentes, nem mesmo o óleo lubrificante, retratando um típico processo de drop-in. Os principais parâmetros foram variados para verificar-se a faixa de operação e desempenho de cada refrigerante e, em seguida, estes resultados foram comparados à referência, R22. Os resultados experimentais mostraram que os refrigerantes naturais apresentaram os maiores valores de coeficiente de desempenho, COP, e os resultados para HFC438A permaneceram abaixo dos resultados do R22, obtendo-se o pior desempenho. Em relação ao impacto ambiental, utilizando TEWI, o propano e o propileno apresentaram os melhores resultados; entretanto, o HFC438A apresentou o maior impacto ambiental.

Experimental Evaluation of Propane, Propylane and HFC438A as Drop-in Replacements for an R22 System
Author: Enio P. Bandarra Filho

This paper describes an experimental investigation of the application of hydrocarbons propane and propylene as well as HFC438A as drop-in replacements for R22 in a 15 kW refrigeration system. The experimental system was composed basically of a semi hermetic compressor operated by a frequency inverter, tube in tube heat exchangers and an electronic expansion valve. The tests were performed by replacing the refrigerant without changing any components, not even the lubricant oil, as typical in a drop-in process. The main parameters were varied to verify the range and performance of each refrigerant and then compared to the reference, R22. The natural refrigerants presented the best coefficient of performance–COP–while HFC438A yielded the worst performance, below that of R22. Using TEWI as a benchmark for environmental impact, propane and propylene presented the best results while HFC438A had the worst impact.



Condensadores hibridos y sus ventajas en sistemas de amoniaco
Author: Raul Perea

Los costos de agua y energía eléctrica afectan la operación y el diseño de un sistema de refrigeración con amoníaco. Los condensadores enfriados por aire consumen más energía que los condensadores evaporativos, pero también incrementan el consumo del compresor al tener mayor presión de condensación. Sin embargo, aunque los condensadores evaporativos ahorran energía, también consumen agua. Cuando los costos del agua son altos, la solución de un condensador híbrido, enfriado por agua en horas de altas temperaturas y enfriado por aire en horas de bajas temperaturas, puede ser una solución viable. Este trabajo analiza y compara los consumos de 3 sistemas de refrigeración, uno con cada tipo de condensador, usando Bogotá, Colombia como ejemplo para calcular los consumos eléctricos y de agua en cada hora de un año ejemplo basado en la temperatura ambiente de cada hora. En el caso Bogotá, por sus altos costos de agua, y por sus temperaturas ambiente, la opción del condensador híbrido resulta ser la mejor, aunque el retorno de inversión comparado al evaporativo es de 8-10 años. Este retorno se reduce a la mitad cuando el costo del agua incrementa 10%. En el futuro, el costo del agua seguirá incrementando en muchas ciudades y el análisis de Bogotá se podrá aplicar más y más.


Hybrid Condensers and their Advantages in Ammonia Systems
Author: Raul Perea

Energy and water costs affect the operation and design of an ammonia refrigeration system. Air-cooled condensers consume more energy than evaporative condensers, but also increase the energy consumption of the compressor because of the higher condensation pressure. However, even though evaporative condensers consume less energy, they also consume water. When water costs are high, hybrid condensers, which are cooled by water when temperatures are high and cooled by air when temperatures are low, may be a viable solution. This paper analyzes and compares the energy and water costs of 3 refrigeration systems, each with a different condenser, using Bogota, Colombia as an example, to calculate the hourly consumptions based on the historical ambient temperatures for a sample year. In this case, because of the high water costs in Bogota and the distribution of ambient temperatures, the lowest operating cost option is the hybrid condenser. However, the payback period compared to an evaporative condenser is 8-10 years. This payback period depends on water costs and can be reduced to half if water costs increase by 10%. In the future, water costs will continue to increase in many cities making the analysis made for Bogota more and more relevant.