Modeling Behavior of Kiwifruit Falling at Terminal Velocity in a Flume

摘要

The terminal velocity of kiwifruit falling through a fluid is largely dependent on the density and hence the dry matter 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 kiwifruit for its 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. It is shown that below a density of 1020 kg m -3 (dry matter approximately 12.5% for kiwifruit), the standard error of the separation reaches 5 kg m -3 (~1% dry matter). This may be adequate to provide useful removal of low-quality kiwifruit from a line that fails grade standards. The flume sorting standard deviation increases with density, reaching 13 kg m -3 at 1045 kg m -3 (2.5% at 18% dry matter). This higher sorting error may limit the use of the technique for separating better tasting, high dry matter fruit from a product stream unless the fluid has its density artificially increased by the addition of salts, which introduces operational disadvantages