Impact of airside fouling on microchannel heat exchangers

In this study, the performance of the microchannel heat exchanger (MCHX) in domestic refrigerators was tested before and after fouling. The louvre-fin and plain-fin heat exchanger (HX) with fin pitches from 1.5 mm to 3 mm were tested. It was found that, for louvre-fin HXs and plain-fin HXs with the same fin pitch, the former is more sensitive to fouling. Under the situations of dust injection of 100 g, the same air speed and the fin pitch of 2 mm, the airside pressure of louvre-fin samples and plain-fin samples would respectively increase by 42.4% and 25.5%; their airside heat transfer rates would decrease by 35.6% and 17.9%, respectively. For louvre-fin HXs, according to test results, it seemed that airside pressure drop increased more quickly when fin pitch was smaller than 2.5 mm, and the trend would be slower if fin pitch was bigger than 2.5 mm. Detailed observation of fouling was done, and the types of fin structures played a prominent role in fouling as well. For instance, fouling on plain-fin HXs usually happened on front surfaces. However, the interior of louvre-fin HXs was more vulnerable to fouling. Furthermore, same heat exchangers were tested under the conditions of two different types of dust and the dust injection up to 200 g. At the same time, fouling mechanism was analyzed, and key factors in fouling process were proposed.