Ohrid '09: 1st day key technical presentations

By Sabine Lobnig, May 08, 2009, 16:22 6 minute reading

The 3rd edition of the International Conference on Ammonia Refrigeration Technology in the Republic of Macedonia has welcomed about 95 experts in the ammonia refrigeration field. This first update on the event provides an overview of key technical papers presented during the first day of the conference.

The International Institute of Refrigeration in conjunction with the St. Cyril and Methodi University Faculty of Mechanical Engineering in Skopje have, despite the economic crisis, welcomed about 95 ammonia refrigeration experts (from 24 countries) at the 3rd edition International Conference on Ammonia Refrigeration Technology in Ohrid, Republic of Macedonia.

Choosing the Republic of Macedonia as the location for the event was not arbitrary: Ammonia refrigerant has been traditionally used in food processing and cold stores in South East Europe, where however such systems have more recently started to face increasing competition from HFC systems. New equipment in the region is needed, as well as education, training and possibly even a Fund. Last but not least, it is no coincidence that Gustav Lorentzen lived in the Republic of Macedonia for part of his life.

Key presentations

Ammonia Refrigeration Risk Assessment, Probability and Frequency, Anders Lindborg, Ammonia Partnership AB, Sweden

With this paper Lindborg demonstrates how ammonia’s dangers have been greatly exaggerated. Nonetheless, myths which depict ammonia as very dangerous continue to influence regulators and society at large. The author predicts that with good quality systems and reasonable amounts of charge, many new ammonia applications will be developed. Lindborg foresees that political pressure on HFCs will increase and this will result in new technical solutions with natural refrigerants such as ammonia. The author also notes that even though there are experts with long experience in ammonia refrigeration, these have little or no influence on the policy process because they do not interact frequently with governmental safety experts, code authorities, insurance companies, etc.

Modernization of Ammonia Refrigeration Systems in View of Reliability, Safety, Energy Consumption and Environmental Issues, Gert J. Koster, Grasso International B.V., The Netherlands

This paper gives an insight on ways to increase efficiency, reliability and safety when choosing to upgrade existing refrigerating plants. Koster concludes that proper maintenance on an average refrigerating plant as well as having a critical view to the day by day operation in all its aspects easily results in energy savings amounting to 15 up to 25 %. The energy costs of an industrial refrigerating plant are in the magnitude of 15 to 25 % of the investment costs per year, depending on among other things the number of yearly running hours. The author finally recommends keeping a data logging system or a logbook and analysing the data at a certain time interval, i.e. once per half year, as a good means of noticing possible decay.

Ammonia Safety by Design and Maintenance, Alexander C. Pachai, Johnson Controls Denmark

Pachai argues that merely fulfilling what standards and laws prescribe with regards to safe design, installation and maintenance of refrigeration plants is not always sufficient. Focusing primarily on ammonia plants, the intention of his paper is to show how one can take steps to improve the safety around refrigeration plants. Good practices for increasing safety are then discussed such as reducing the charge by using for example an indirect refrigerant such as CO2, adding an air scrubber to the ventilation system to prevent ammonia escaping outside the plant room, using the newest heat exchanger technology, ensuring that the valves are placed in a way that they are easily accessible, regularly inspecting the surface of vessels and pipes to identify potential corrosion, etc.

A Design Procedure for Energy Efficient Meat Carton Freezing Systems, Klaas Visser, KAV Consulting Pty Ltd, Australia

In this paper Visser discusses a design procedure to achieve minimum energy consumption when freezing cartons of meat by varying the time-temperature relationship. It is demonstrated that an energy efficient freezer design does not necessarily require a higher capital investment and frequently less. It is also shown that selection of the refrigeration compression plant on the basis of compressor COP is frequently poor practice in Air Blast Freezing Systems (ABFS). Rather, it is best practice to select equipment for the freezer operating conditions where the total energy input into the system is a minimum.

European Safety Standard EN 378-2008 In Combination with the German National Standard VDMA 24020-1 – Operating Requirements on Ammonia Refrigeration Systems, B. Schrempf, TÜV SÜD, Germany

The author discusses the updated European standard EN 378, as well as Part 1 of German national standard VDMA 2420, regulating safety requirements for refrigerating systems with ammonia refrigerant. Several paragraphs have been added to the former to address the mechanical hazards of vibration, protection against hot surfaces and protection against moving parts. Several useful annexes have also been added, providing additional guidance for ammonia systems (Annex A). At the German level, according to Part 1 of the German national standard VDMA 2420, specific attention needs to be paid to piping corrosion, trained personnel only should be assigned by the end user, while regular periodical inspections are mandatory. According to the German guideline, if requirements of standard EN 378 and the national Betriebssicherheitsverordnung (= German Ordinance on Industrial Safety and Health) are respected, no further measures for ammonia refrigeration systems concerning ex-ante safety are needed.

The Development of Azeotropic Ammonia Refrigerant Blends for Industrial
Process Applications, N. COX(a), V. MAZUR(b), D. COLBOURNE(c), (a) Earthcare Products Limited, UK, (b) Department of Thermodynamics, Academy of Refrigeration, Ukraine, (c) Re-phridge, UK

This paper reports on findings of a project seeking to design an azeotropic ammonia mixture to be employed for food blast freezing applications in the temperature range from - 55°C to + 50°C with higher pressure to avoid the disadvantages of pure ammonia. Property data available for the R717/R170 mixture was used to analyse performance with a property-based cycle model. Findings include: the COP is similar over the range of azeotropic compositions, albeit slightly lower than that of pure R717; the temperature of the refrigerant discharged from the compressor is significantly lower than R717, which favours system reliability; an improved heat transfer, particularly in the evaporator, was observed, resulting in higher evaporating temperatures, which equates to an incremental improvement in cycle efficiency; and the rate of degradation in system efficiency and refrigerating capacity as the heat rejection (or heat sink) temperature rises for the mixture is less than the rate of degradation of the pure components.

Applications of schickR723® Blend in Commercial Refrigeration Systems, J. Germanus(a), S. Römer(a), D. Kraiss(b), (a) Institut für Luft- und Kältetechnik gGmbH, Germany, (b) Schick GmbH + Co. KG, Germany

This paper discusses schickR723®, an azeotropic blend of ammonia and dimethyl ether - mixture of 60 weight% ammonia and 40 weight% dimethyl ether - as an alternative to ammonia. The characteristics and advantages of the blend compared to pure ammonia such as the potential to achieve lower discharge temperatures of approximately 15-25 degrees and improved solubility of the refrigerant in conventional oils are presented. The authors, then, discuss applications and examples where schickR723® is being used as working fluid under real working conditions with different components like compressors in refrigerating machines.


By Sabine Lobnig

May 08, 2009, 16:22

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