Summary and conclusions

Udvikling af et demonstrations- og testkøleanlæg, der anvender CO2 som kølemiddel

This project report describes design and test of a prototype chiller unit with CO₂ as refrigerant.

The fact that the transcritical system operates at a very high pressure has made it very hard to find the required main components applied in the prototype (compressor, heat exchangers, motor valves and relieves) - and at competitive prices.

The delivery time has been extremely long for most components - for instance, the compressor had a delivery time of 1 year.

The motor valve applied in the system is controlled by the pressure and the temperature after the gas cooler (air cooled condenser).

During the course of the project, a number of system solutions were analysed and at the end of the project a prototype was built and tested.

The tests carried out on the unit show that the COP is 3.4 – 4.0, which is not immediately satisfactory. However, considering the fact that the chiller unit is a prototype which will be optimised at a later stage, the result obtained now is relatively reasonable.

Proposal for improvements:

Improvement of gas cooler in order to obtain a lower discharge temperature
Evaporator with bigger surface (higher suction temperature)
Optimisation of refrigerant charge which suits the current gas cooler leaving temperature

Summary of Project result:

The project constructing a prototype chiller with CO₂ has been a success. Provided that the components are available at competitive prices and effectuating some minor technical adjustments, it will be possible to start production of a CO₂chiller unit.