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ISSN Online: 2377-424X

ISBN CD: 1-56700-226-9

ISBN Online: 1-56700-225-0

International Heat Transfer Conference 13
August, 13-18, 2006, Sydney, Australia

CONTROL OF TINY DEW DROPLETS DEPOSITED ON A COPPER PLATE BY SCATTERED LASER LIGHT AND ITS MEASUREMENT BY USING A PHASE-SHIFT INTERFERENCE MICROSCOPE

Get access (open in a dialog) DOI: 10.1615/IHTC13.p12.550
9 pages

Abstract

Tiny dew droplets deposited on a copper plate were controlled at constant diameters by a developed control technique for studying initial dropwise condensation. The technique employs the proportional control added integral movement using scattered laser light from the surface of the copper plate and an optical fiber cable. The droplets were controlled constant in the range from few micrometers to tens micrometers in diameter and were almost a hemisphere form in initial condensation at room temperature. Also, the shape of a dew droplet was measured accurately by using an interference microscope that employed a phase-shift technique which can obtain the accurate height by numerical calculation using three interference images in which the phase value of interference fringe in each image is changed in steps by using a piezoelectric transducer. A simple method that uses a conventional speaker horn and an optical fiber cable was introduced to depress speckle noise in the interference images. The shape of a dew droplet deposited at dew point on the plate surface with 0.1 μm in average roughness was measured with an accuracy of ±3nm. The mass of a dew droplet could be obtained from the volume of its shape measured and was of the order of 10−9 g and the mass growth under the gentle wind velocity against time was also obtained.