The popping noise is intermittent noise that arises in domestic refrigerators seconds after the compressor on and has troubled clients from different manufacturers over the years. Such noise is very similar to pop popcorn, hence the name its distinctive name in English. The most likely cause for their outbreak is the phenomenon called Induced Shock Condensation (CIC), which is closely linked to the admission of vapor bubbles through vortices at the entrance of the capillary tube. Such bubbles come into contact with the cold suction line and collapse generating shock waves. These propagate toward the evaporator, making it reverberate generating noise. The solutions presented so far to solve the problem stand out: controlled injection of nitrogen, changing the filter diameter dryer or the inclination of the same, changing the mass flow rate by changing the compressor and / or capillary tube, etc. However, such measures or penalize the energy consumption of refrigerators or not eliminate noise in 100% of cases.

POLO tested these solutions in a conventional household refrigerator and sought a thermodynamically efficient alternative to eliminate noise. Therefore, accelerometers were used to detect the noise. Furthermore, the original filter dryer was replaced by an acrylic and a high-speed camera was used to record the flow pattern at the entrance of the capillary. The noise was completely eliminated with an additional heat exchanger, connecting the discharge line to the hair, which raised the refrigerator energy consumption by only 0.5%.