Modeling behavior of kiwifruit falling at terminal velocity in a flume.

摘要

Terminal velocity of kiwifruits falling through a fluid is largely dependent on the density and hence DM content of the fruit, but is also almost independent of fruit size and shape. This article shows how a water-based flume could be used to separate kiwifruits for their internal (taste-related) properties in bulk quantities and at high speed, obviating the need to use density-enhancing salts, which are less desirable. The mathematics of flume operation are discussed, and trials of a laboratory flume were conducted. Below a density of 1020 kg m-3 (DM approx. 12.5% for kiwifruits), the s.e. of separation was 5 kg m-3 (approx. 1% DM). This may be adequate to provide useful removal of low quality kiwifruits from a line that fail grade standards. The flume sorting s.d. increased with density reaching 13 kg m-3 at 1045 kg m-3 (2.5% at 18% DM). This higher sorting error may limit the use of the technique for separating better tasting, high DM fruits from a product stream unless the fluid has its density artificially increased by the addition of salts, which introduces operational disadvantages.