Star Refrigeration at Gustav Lorentzen 2014

By Silvia Scaldaferri, Sep 15, 2014, 17:33 3 minute reading

At the 2014 Gustav Lorentzen Conference on Natural Refrigerants, Star Refrigeration presented three papers on ammonia refrigeration, focusing on charge reduction, safety and standards. According to Star Refrigeration, low pressure receivers could expand the use of ammonia as a refrigerant in smaller facilities, ranging from 100kW to 600kW, whilst improvements in the development of standards would facilitate their application and help to improve ammonia safety.

The Gustav Lorentzen Conference series has travelled around the world and continues to be a focal point for new research on natural working fluids, helping to further the worldwide acceptance of technology using CO2, ammonia, hydrocarbons and water as refrigerants.

Star Refrigeration, the UK’s number one industrial heating and cooling engineering company, was at the event to share its expertise on the latest ammonia developments.

Low pressure receiver (LPR) avoids adverse effects of charge reduction on refrigeration system efficiency

In GL 2014 paper 172, Andy Pearson from Star Refrigeration investigated the real versus perceived benefits of charge reduction in industrial refrigeration systems, illustrating the importance of system design capable of handling a wide variety of operating conditions. Pearson’s paper discussed different advantages and disadvantages of charge reduction, including:

  • Regulatory benefits (advantage): In the United States and France there are complex and onerous regulatory requirements on design, emergency planning and operation of large charge systems. In such countries, therefore, the benefit of regulatory compliance through charge reduction is attractive, particularly in medium-sized systems.
  • Lower water tolerance (disadvantage): A reduced charge ammonia system has less tolerance to water ingress than a traditional plant. Water build up lowers the evaporation pressure for a given evaporation temperature, requiring the compressor to work harder to compensate for the effect of water.

To reduce a system charge but maintain stable, reliable, efficient long-term operation, Person recommends using Low Pressure Receivers (LPR). These provide a means of warning of refrigerant loss before the capacity of the system is affected, avoids the adverse effects of refrigerant leakage or of water leakage into the plant.

Modular, packaged systems with lower ammonia charge and high efficiency

In another Star Refrigeration paper, Andy Pearson and Derek Hamilton further discuss Low Pressure Receiver (LPR) systems as components that enable charge reduction and the efficient operation of low charge ammonia systems for freezer applications.

Two recent innovations in particular have helped:

  • Aluminium evaporator tubes: instead of the stainless steel or galvanized steel aluminum has a thermal conductivity almost ten times that of stainless steel.
  • Internal surface enhancement: this encourages ammonia to wet the entire inside surface of the evaporator tube using a wicking effect. This improves the boiling heat transfer, which in turn ensures that the finned surface of the cooler is more effectively utilised.

Standards development process and the implication for ammonia systems

In Andy Pearson’s third Gustav Lorentzen paper he reviewed the processes involved in the development of safety standards, and the impact of the revision and update of ISA standards ISO817 and ISO5149, which unusually were both initially rejected at the national ballot in the approval stage.

With regards to ammonia, one of the reasons that the ISO5149 update was rejected was due to fact that the updated regulation appeared more restrictive than previously, due to a lack of clarity with regards to the use of ammonia in packaged chillers.

Pearson’s discussion of the difficult approval process for ISO817 and ISO5149 points to the problems that the present standards development process creates. There is a need for a better way to work within the standards process to better match current industry needs. If the ultimate goal is to facilitate a more effective use of safety standards and avoid a past accidents, it is essential that universal standards are easy to follow, and make the process of assessing conformity to the essential safety requirements of an installation simple, quick and cheap.

About Star Refrigeration

Founded in 1970, Star Refrigeration has become one of the leading companies in cooling and heating system innovation. It has expanded from an industrial refrigeration company to a multi-faceted engineering group. Today Star Refrigeration is a total solutions provider, active from design through to commissioning and maintenance of cooling and heating systems with a specific competence in the minimisation of refrigerant charge and leak-tightness.

It has over 350 employees working from nine branches throughout the UK and a network of overseas partners enabling the delivery of Star solutions around the world.


By Silvia Scaldaferri

Sep 15, 2014, 17:33

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