Aqueous ammonia in refrigeration applications
Aqueous solutions with ethylene glycol or salt are the most commonly used fluids in ice rinks but they have less favourable thermophysical properties implying higher pumping power demand.
Project summary
The proposed system solution using aqueous ammonia (ammonia-water, aqua ammonia) as secondary refrigerant in refrigeration applications has been used for some time but is not yet fully evaluated and documented. This implies that the theoretical background in a refrigeration context as well as the practical considerations are not widely known. There is a need for further assessments to convince the market as to the advantages as well as informing about the corresponding risks. The work will include analysing data from field measurements combined with literature studies, experimental work and calculation/modelling. EKA has access to field data where a couple of systems can be evaluated from a functional and performance point of view. The cooperation with KTH will include some experimental tasks related to the investigation of thermophysical properties as well as corrosion.
Background
EKA, Energi & Kylanalys, provide services within the ice rink business such as energy and technology inventories, energy saving counselling, design and specification of new energy systems as well as procurement support. In order to provide energy calculations and to give best possible support to our customers we need to have a leading knowledge and command of all aspects of the energy systems in ice rinks. This applies to technical performance, durability, energy usage, investment as well as life cycle cost.
Ice rink refrigeration systems are often designed as indirect systems to reduce the refrigerant charge and therefore they require secondary fluids. In these applications the pumping energy of the secondary fluids typically corresponds to 10-20% of the total refrigeration system energy usage. Aqueous solutions with ethylene glycol or salt are the most commonly used fluids in ice rinks but they have less favourable thermophysical properties implying higher pumping power demand. There is a growing interest in using ammonia-water as secondary fluid in ice rinks for both new construction and retrofit. This is an environmentally friendly and very energy efficient fluid which offers low corrosivity to steel components and very low pumping power. Material compatibility and safety must be considered when designing the systems. Ammonia-water uses only about 50% of the pumping power compared with ethylene glycol. Field measurements show that in modern systems using ammonia-water the share of pumping power in the total energy usage is often less than 5%.
Preliminary tasks:
Literature study:
- Ice rinks, secondary fluids, energy usage, etc
- Properties, corrosion, safety, material compatibility,
- Design criteria, components, retrofit, operation, degassing,
Field measurements analysis:
- Compile known systems using ammonia-water by category and application
- Evaluate energy performance
- Pump power, energy, control, temperature differences in practice
- Energy benefit of retrofitting existing systems
Experimental studies (KTH):
- Degassing effect on ammonia concentration over time
- Sealing small leakages with “Rink Seal Pro” (Barr’s Leak Stop) – possible or not?
Retrofit:
- Practical cases, interviews, study visits
- Cleaning procedures, requirements on cleanliness,
- Which retrofit procedures are available today?
- Bad cases - what can go wrong?!
- Develop guidelines for retrofit.
Degassing:
- Effect of degassing, is it necessary, long term effects in real systems, control, etc.
- What equipment is available on the market, operating principles,
- Cost of equipment
Safety aspects:
- What does the code say today, how to interpret different codes (EU, North America, …)?
- What happens in case of leakage - ammonia in the air, ground water, etc.
- What is the health/medical effect of physical contact with ammonia-water (+/-15%)
- Safety measures, equipment, etc.
Leakages:
- What causes leakages?
- How can a leaking system be repaired?
- Can small leakages be handled with “Rink Seal Pro” or corresponding?
- What are the options if a leak appears?
Cost:
- How does the use of ammonia water affect the life cycle cost?
- Which parameters affect the investment as well as the operating cost?
Report:
- Document and visualise - the results, information acquired, methods developed
- The collected knowledge will serve as guideline for the ice rink market; therefore this work should be well documented in a report (English language).
Work plan
The work is supervised in close cooperation with Jörgen Rogstam, EKA, and Monika Ignatowicz, KTH. Regular meetings are expected to keep good pace in the project.
Supervisors
University supervisor at KTH
Industrial supervisor and contact person
Jörgen Rogstam VD/Managing Director EKA - Energi & Kylanalys AB
The project is in academic collaboration with the Royal Institute of Technology, Energy Technology – Applied Thermodynamics and Refrigeration, KTH, Stockholm.