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Simon Fehling joins EKA and will evaluate ejectors on CO2 systems in practice for his master thesis


As a relatively new technology in the refrigeration field, ejectors have been applied to CO2 refrigeration systems for reduction in energy consumption and increase in the refrigeration capacity. Another interesting new component is the liquid ejector, which is used to overfeed evaporators at medium temperature levels, usually used in supermarket refrigeration systems.

The work will be based on field measurements which is combined with literature studies and modelling. The system solutions with ejectors and/or liquid ejectors have been implemented but are not yet fully evaluated in practice. Based on field data that EKA and KTH have access to, these systems can be evaluated from a functional and performance point of view.


There are several supermarkets and ice rinks with integrated ejector and/or liquid ejector blocks to the refrigeration system – aiming to reduce the compressor power.

Both high-pressure and low-pressure side of CO2 refrigeration system are respectively connected to motivation inlets and suction inlets of ejector blocks. The intermediate pressure outlet from the ejectors will connect to the low-pressure side of the suction of the compressors. To take advantage of ejectors, there should be enough pressure lift between intermediate pressure and low-pressure. Similar conditions are required for the liquid ejector to function properly.

The described solutions have been implemented in a few projects but fails to work as expected. The heat recovery has been sacrificed for better performance of ejectors. Based on field data from two systems with ejectors, that EKA has access to, and other two systems with liquid ejectors, that KTH has access to, these systems should be analysed and improved.

Simon F. will carry experimental studies to:

  • Evaluate of the available CO2 systems using the existing instrumentation enabling monitoring the key system parameters.

  • Develop methods (or apply existing) to calculate and analyse the refrigeration system cooling capacity, performance, recovered heat and other key parameters for the systems.

  • Analyse the performance of integrated ejector and liquid ejector blocks and its impacts on refrigeration system.

The heat recovery function will of course be evaluated:

  • The heat recovery system design and functions.

  • The control strategies should be analysed theoretically and compared with the experimental systems.

  • The impacts of heat recovery design on ejector performance.

Modelling will be used in order to:

  • Illustrate the system function.

  • Simulate the system performance at different climate zones.

  • Evaluate energy consumptions.

We will keep you posted and wish Simon a warm welcome!


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