Popping noise in household refrigerators: Fundamentals and practical solutions

An intermittent noise that occurs around 30 s after compressor start-up has been disturbing customers of different domestic refrigerator manufacturers over the past 10 years. This noise is very similar to that produced by popcorn popping, being referred to as popping noise. The most probable cause of this strange and unpleasant noise is thought to be the CIS (Condensation Induced Shock) phenomenon. The aim of this study was firstly to check the possible occurrence of CIS in a specific household refrigerator and, secondly, to identify ways to avert it without affecting the product performance. To this end some changes were made to the refrigerator: i) the diameter of the filter dryer was altered; ii) the slope of the filter dryer was altered; iii) the compressor was replaced; and iv) an additional internal heat exchanger was installed. The noise was effectively eliminated only by placing the filter dryer horizontally or by installing an additional internal heat exchanger. Visualization studies were also carried out, making it clear that the occurrence of the popping noise is closely related to the flow pattern at the capillary tube inlet.