2017 IIAR Technical Papers
  San Antonio, TX
39th Annual Meeting

New Refrigerant Quality Measurement and Demand Defrost Methods
Author: Michael Elstroem

New measurement methods make it possible to design energy-efficient Low Charge Evaporator Systems Controlling both the injection of refrigerant according to the Evaporator load and Defrost cycle “demand defrost” while also increasing safety aspect when using natural refrigerants as Ammonia. Requirements to reduce global warming (GWP) and CO2 emissions lead to a desire to use natural refrigerants. This has initiated numerous new efforts and developments worldwide. Application of new measurement principles and design methods in the refrigeration industry may significantly impact the achievement of lower global electrical energy consumption by realizing reductions of 20 to 40% (Jensen, 2015). At the same time safety may be increased by minimizing the refrigerant amount through “LOW CHARGE SYSTEMS” with a charge reduction factor of 30 to 50 times for Ammonia DX systems (Nelson, 2013). The heat transfer coefficient within the evaporators is highly dependent on the flow pattern, mass flux and the Vapor Quality. This paper describes a new sensor system for optimizing Evaporator Control including description of the measurement principle for measuring the phase of refrigerant as Vapor Quality with an “X” sensor that measures degree of dryness and a demand defrost sensor measuring ice build-up on the air cooler surface. The paper also provides information about sensor design, laboratory testing, system design, field testing, application, summary and conclusions.

The Design of CO2 Refrigeration System  Using Ammonia System Design Principles 
Author: K. Visser, Hon.M.IIR, FInstR, M.IIAR, M.ARA, M.KNVvK, M.euramon

This paper demonstrates that the application of evaporative condensers, which are commonly used in ammonia refrigerating systems, to condense subcritical CO2 and gas cool transcritical CO2 fluid will permit the efficient application of CO2 refrigeration worldwide if ammonia design principles are followed. By using the ambient wet bulb design temperature (AWBDT) as the condensing and gas cooling base temperature instead of the ambient dry bulb temperature, all CO2 refrigeration applications are brought within the scope of efficient applications worldwide. CO2 refrigeration that employs evaporative condensers and gas coolers, if used with parallel compression, will be at least as efficient, if not more efficient, than ammonia refrigerating systems.

Parallel Operation of  Screw Compressor Packs
Author: B. Pijnenburg and J. Ritmann 

Ammonia screw compressor packs utilizing parallel operation of two or three smaller industrial NH3 screw compressors offer the optimum way to fulfill maximum part load efficiency, increased redundancy, and other highly desirable features in the industrial refrigeration industry. Optimized parallel operation can secure continuous operation and can in most applications be configured to improve overall operating economy. New compressors have been developed to meet requirements for flexibility in operation and have intelligent controls. The intelligent control system must focus on all external demands and strive to offer always the lowest possible absorbed power, including future scenarios with connection to smart grid. This paper builds on and includes most of the results of an earlier investigation to show how to implement a series of compressor packs following basically the results of these findings.

Code Requirements for the  Evaluation and Design of  Rooftop Equipment Supports
Author: Robb N. Davis, P.E.

Placing ammonia piping and equipment on the roof of a building presents additional loading challenges that the pipe designer may not typically address. General loading concerns including; service loads, gravity loading, and where applicable seismic loads, should be addressed for any above ground pipe system. However, wind loading on rooftops or exterior exposed piping can present a unique design challenge for the pipe systems and the support components. This paper will review current code requirements specifically associated with wind and seismic loading on rooftop applications. Even if addressing this loading is outside the scope of work, a knowledge of the requirements can aid in better system coordination and design.

Assessment of Lubricants for  Ammonia and Carbon Dioxide  Refrigeration Systems
Author: Glenn D. Short

Ammonia (R717) and carbon dioxide (R744) have received increased recognition as non-ozonedepleting and low global warming potential refrigerants. In some cases, both of these refrigerants are used in a cascade system. Some properties of refrigerant-lubricant mixtures are very important for the design and performance of compressors and the refrigeration cycle. Low solubility of a lubricant with a refrigerant can improve the compressor’s performance. The use of miscible or nonmiscible lubricants can bring different technical advantages for the performance of the refrigeration cycle.
Examination of a lubricant’s chemistry, miscibility, solubility, and viscosity with a refrigerant helps system engineers find the best overall balance of good compatibility, lubricity/load-carrying performance, and system performance. R717 data are presented with immiscible mineral oil and synthetic hydrocarbon lubricants and a miscible polyalkylene glycol lubricant. R744 data are presented for miscible polyol ester and polyalkylene glycol derivative lubricants and immiscible synthetic hydrocarbon lubricants.

Refrigeration Applications  Utilizing Liquid Desiccant  Dehumidification Systems
Author: Mark Piegay

The primary design for process air handling systems for the food and beverage industry is to use conventional cooling and reheat coils with a distributed refrigeration system. Often defrost is incorporated for coils operating at subfreezing temperatures. Occasionally desiccant wheels may be incorporated into the air handling unit or standalone systems to provide latent control to limit the amount of defrost required. One common drawback of the aforementioned designs is that they add heat to the refrigerated space. Defrost adds heat and moisture that ultimately adds load to the refrigeration system, and desiccant wheels add heat to the supply air stream supplied to the refrigerated space. In addition to the added heat, often the primary refrigerant is distributed to the air handling unit or fan coil that may be installed inside the space.
A liquid desiccant system can provide cooling for the refrigerated space and eliminate the need for defrost. This paper explains three different scenarios where a subfreezing (<32°F, 0°C) refrigerant is used to provide cool, humidity-controlled process air with a liquid desiccant system. Each of these cases includes a discussion on how the installation’s primary refrigerant is utilized and designed. The first case is a brewery’s fermenting cellar, the second is a meat cooler and packaging space, and the third is a cold storage staging area application.

Study of the Energy Consumption of a  CO2/NH3 Cascade Industrial Refrigeration  System Operating in Costa Rica and  Comparison with Direct Ammonia Systems  on One- and Two-Stage Configurations
Author: Mario Mora Carli

Many European and U.S. research papers claim that CO2 only offers energy savings over an ammonia system below a certain low-suction temperature. With the objective of providing additional knowledge and real case examples on this subject, this paper presents the study of a CO2/NH3 cascade industrial refrigeration system with more than three years of successful operation in Costa Rica and compares direct ammonia systems in one- and two-stage configurations.

Energy Performance of Low Charge, Central Type, Dual Stage NH3 Refrigeration Systems in Practice
Author: Stefan S. Jensen, B.Sc.Eng. FIEAust, CPEng, NER, RPEQ, F.AIRAH 

This paper describes the energy performances of several refrigerated distribution centers with storage volumes of approximately 10,000 to 50,000 m³ (353,000 to 1,766,000 ft³). The performance evaluations are based on the electrical energy consumption as measured by the electrical energy providers over representative periods of time. All systems are serviced by central, state-of-the-art low charge, dual stage NH3 refrigeration systems. In the case of one plant the contribution of the photovoltaic panels to the energy requirement of the facility as a whole is shown on a month-by-month basis.

Experimental Investigation on the  Performance and Environmental Impact  of a CO2 Cascade Refrigeration System
Author: Marcus Vinícius, Almeida Queiroz, Arthur Heleno Pontes Antunes, Enio Pedone Bandarra Filho, José Alberto Reis Parise 

This study evaluates the performance of cascade R744/R134 and R744/R290 systems, with CO2 in subcritical operation, by means of a drop-in operation. The experimental apparatus consists of two cycles. The low temperature cycle (LT) is formed by an R744 reciprocating variable speed compressor, an electronic expansion valve and a direct expansion air-source CO2 evaporator placed inside the cold room (2.3m x 2.6m x 2.5m). The high temperature cycle (HT) consists of a reciprocating compressor for R134a, an electronic expansion valve, and an air-cooled condenser. To connect both sides (cascadecondenser) a plate heat exchanger was used, acting, at the same time, as the condenser for the R744 and evaporator for the R134a. The degree of superheat for the R744 was varied from 5 to 15 K and the compressor operating frequency from 40 to 65 Hz. The drop-in operation was performed at the HT cycle, where the refrigerant R134a was replaced by R290, resulting in a charge reduction of 50%. The highest COP for the R744/R134a pair was 2.09 and the lowest, 1.81. Cooling capacity ranged between 4.30 and 5.58 kW and the air temperature inside the cold room varied from -17.7 °C to -0.8 °C. Finally, it was found that the results obtained for the R744/R290 system attended the air temperature conditions inside the cold room with similar COP values. However, the R744/R290 pair presented higher cooling capacities, from 5.20 to 5.88 kW. As for the environmental impact, based on the TEWI index, the best results were also obtained with the hydrocarbon option, with a reduction of approximately 10%.

2017 Programa en español

Investigação Experimental da Eficiência Energética e do Impacto Ambiental de um Sistema de  Refrigeração Cascata com CO2
Author: Marcus Vinícius , Almeida Queiroz, Arthur Heleno Pontes Antunes, Enio Pedone Bandarra Filho, José Alberto dos Reis Parise 

O presente trabalho apresenta uma comparação do desempenho de um sistema em cascata subcrítico usando o par R744 / R134a, com outro utilizando o par R744 / R290, através de uma operação de drop-in. O aparato experimental é composto por dois ciclos, o ciclo de baixa temperatura (BT) é formado por um compressor alternativo de velocidade variável para o R744 e uma válvula de expansão eletrônica que promove a evaporação direta do CO2 no interior de uma câmara fria (2,3m x 2,6m x 2,5m) para manter a temperatura interna de ar estável. O ciclo originalmente de alta temperatura (AT) é constituído por um compressor alternativo para o R134a, uma válvula de expansão eletrônica e um condensador arrefecido a ar. Um trocador de calor a placas, que é, ao mesmo tempo, o condensador do R744 e o evaporador para o ciclo AT, completa a bancada experimental. O grau de superaquecimento do R744 variou entre 5 e 15 K e a frequência de operação do compressor de R744 entre 40 e 65 Hz. A operação de drop-in foi realizada no ciclo AT, onde a carga do R134a foi substituída pelo R290 e reduzida em 50%. O sistema de refrigeração alternativo (R744 / R290) foi então submetido à outra etapa de testes, a qual permitiu a comparação energética entre os pares de refrigerantes. Por meio dos resultados obtidos, estimou-se um máximo COP equivalente a 2,09 e um valor mínimo de 1,81 para o par R744 / R134a. Os valores da capacidade de refrigeração estabeleceram-se entre 4,30 e 5,58 kW, demonstrando a aplicabilidade desse sistema cascata em condições de carga térmica variável. O valor mínimo da temperatura operativa do ar no interior da câmara foi -17,7 °C e o máximo -0,8 °C. Por fim, constatou-se que os resultados obtidos para o par R744 / R290 atenderam à condição de temperatura do ar no interior da câmara fria com valores de COP semelhantes. No entanto, o par R744 / R290 operou em capacidades de refrigeração até superiores, essas se estabeleceram entre 5,20 e 5,88 kW. Quanto ao impacto ambiental, baseado no parâmetro TEWI, os melhores resultados foram também obtidos com o hidrocarboneto, mostrando uma redução de aproximadamente 10%.

Amoníaco en sistemas de RSW
Author: Alberto Mayer U. 

La preeminencia en el uso del amoníaco como refrigerante en las instalaciones industriales pesqueras constituyó un hecho de la causa para su introducción en los sistemas de RSW (del inglés, refrigerated sea water) para sus respectivas flotas extractivas a partir de su fuerte irrupción en Chile a partir de 1990. Además, la entrada en vigencia del Protocolo de Montreal a fines de la década anterior, que colocó en entredicho a los refrigerantes artificiales en boga desde la década de 1930, fue un puntal de apoyo en ese proceso. Bajo esa perspectiva, la Refrigeración Industrial y en particular la Refrigeración Naval–enfrentadas a una aprensión casi atávica respecto al amoniaco–se vieron ante el desafío de reposicionarlo como alternativa viable, en términos de: desarrollar sistemas que además de eficientes fueran seguros. Este trabajo relata ese proceso, donde el compromiso por un diseño e instalación responsable de plantas de RSW fue acompañado por la industria fabricante de equipos en la reducción de la carga de refrigerante como respuesta a las demandas de seguridad.

Tratamiento de agua para  condensadores evaporativos
Author: Michael D. Sanders 

El propósito de este artículo es proveer un entendimiento básico del rol que juega el tratamiento de agua en los sistemas de condensadores evaporativos. Discutiremos aspectos específicos de las incrustaciones, la corrosión y el control biológico. Además, se discutirán métodos para simplificar el control y la alimentación del tratamiento de agua en sistemas de múltiples condensadores evaporativos.

Estudio del consumo energético real de  un sistema de refrigeración industrial en cascada CO2/NH3 que opera en Costa Rica y  comparación de la eficiencia energética con sistemas operando en una y dos etapas de compresión con amoníaco directo
Author: Mario Mora Carli

Hay una gran cantidad de trabajos de investigación en Europa y Estados Unidos que sostienen que el refrigerante CO2 puede ofrecer ahorro energético en comparación con un sistema amoníaco solo si opera por debajo de cierta temperatura de succión. Con el objetivo de proporcionar conocimiento adicional y ejemplos de casos reales de este tema, este trabajo presenta el estudio de un sistema de refrigeración industrial de CO2/NH3 en cascada con más de tres años de operación exitosa en Costa Rica y compara sistemas de refrigeración con amoníaco directos en configuraciones de una y dos etapas. 

Operación en paralelo de paquetes  de compresores de tornillo
Author: Bas Pijnenburg, John Ritmann

Los paquetes de compresores de tornillo para amoníaco aplicados en paralelo con dos o tres compresores de tornillo industriales de NH3 más pequeños ofrecen un camino óptimo cuando se trata de cumplir con la eficiencia máxima en carga parcial, aumento de la redundancia y otras características altamente requeridas por el sector de refrigeración industrial de hoy. La operación en paralelo es un camino óptimo que se puede optar en muchas instalaciones para asegurar un funcionamiento continuo y mayor ahorro económico operacional de toda planta. Los nuevos compresores han sido desarrollados para satisfacer los requisitos de flexibilidad operacional y son controlados de una manera inteligente. El sistema de control inteligente mantiene el foco en todas las demandas externas, pero aún se esfuerza por ofrecer siempre la potencia absorbida más baja posible, incluyendo los escenarios futuros con conexión a las redes inteligentes. Este trabajo se basa en una investigación anterior e incluye la mayor parte de sus resultados para mostrar cómo realizar una serie de paquetes de compresores siguiendo básicamente los resultados de estos hallazgos.