Flow boiling in small diameter channels

Many studies have been carried out on two-phase flow heat transfer in channels with hydraulic diameter bigger than6 mm, but relatively little work has been done for small diameter channels in the meso and compact range (diameterfrom 0.1 to 3 mm). The use of exchangers with small channels in refrigeration units, which are very numerous besides,could bring a significant reduction of the internal volume of the exchanger, and therefore diminish the refrigerantcharge of the whole refrigerating system. One can imagine the interest to widen knowledge on the flow and the heattransfer in small-diameter tubes. This paper examine the thermal behavior of refrigerants boiling in small pipes. Thecorrelations available for in-tube evaporation heat transfer coefficient are discussed and evaluated, when possible, andnew research areas of relevance than can contribute to expand the use of small-diameter channels evaporators inrefrigeration units are suggested.