SophiA project: HKA Lab test progress

SophiA HKA Lab test is intended to provide a better understanding of the cooling system in the field.

 

It is built inside a small cooling chamber where the three different temperature levels are created with the same components as in the containers. In addition, thyristor-controlled resistance heaters are installed to simulate the higher heat fluxes at the four different demo locations.

 

Initially, it was planned to have a plate HX as a cascade heat exchanger since the cost would be much lower and the space needed would be less compared to a tubes-in-shell HX.

However, the lab tests showed that a height difference is required in order to push the liquid out of the plate, thus reducing the heat exchanging area. The tests also showed a sufficient and homogeneous ice growth in 8 hours and that the thermal energy storage could hold the ice for over 50 hours with no additional heat input into the chamber.

 

The design of the CO₂ cycle then changed after discussions with many experts. The fear was that the oil of the CO₂ compressor could be trapped at the lowest point of the cycle, which is the bottom of the thermosiphon. The flow velocity of the two-phase refrigerant is not sufficient at this point to entrain the oil and return it to the compressor.

 

The CO₂ system was therefore modified, and results of the -30°C room will be shown soon.

 

Sources :

SophiA project (Sustainable Off-grid solutions for Pharmacies and Hospitals In Africa) - Newsletter n°3 (october 2023)

Présentation of the cold room : https://sophia4africa.eu/hka-laboratory-test/