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<br />. <br /> <br />18 <br /> <br />. <br /> <br />The conditions within the chamber were monitored by several <br /> <br /> <br />instruments. Several copper. constantan thermocouples were placed at <br /> <br /> <br />various points to make sure that the air temperature was uniform <br /> <br /> <br />throughout the chamber. The output of the thermocouples was fed into a <br /> <br /> <br />strip chart recorder to determine any temperature changes during the growth <br /> <br /> <br />period. Samples of air were taken from the chamber and forced through a <br /> <br /> <br />V-shaped tube filled with plaster of paris to measure the liquid water content <br /> <br /> <br />by the same technique used by Fukuta et al. (1979). <br /> <br /> <br />A standard pitot tube assembly positioned above the suction and <br /> <br /> <br />suspension chamber was helpful in ascertaining the updraft speed near the <br /> <br /> <br />suspended ice crystal. The pitot tube, oriented perpendicular to the flow, <br /> <br /> <br />produced a small pressure difference within the tube. This pressure <br /> <br /> <br />difference is a function only of the flow speed and therefore determines the <br /> <br /> <br />updraft velocity in the tunnel. Determining the rising speed of puffs of <br /> <br /> <br />smoke near the crystal position helped to establish the correspondence <br /> <br /> <br />between the pressure difference in a tube and the updraft speed. With the <br /> <br /> <br />help of a MKS Baratron Type 220B Electronic Differential Pressure <br /> <br /> <br />Manometer and a chart recorder, the pitot tube assembly continuouly <br /> <br /> <br />monitored the flow speed which was reported after 3, 4, 5, 6, 7, 8, 9, or 10 <br /> <br />minutes of growth. <br /> <br /> <br />The equipment attached to the top of the suspension chamber was the <br /> <br /> <br />suction system that secured the flow for the tunnel. The apparatus consisted <br /> <br /> <br />of a suction chamber, a control valve and a vacuum cleaner. Air leaving the <br /> <br /> <br />suspension tunnel first entered into the suction chamber, which was a box <br /> <br /> <br />15.2 an tall with a square cross section 20 em wide. The fog flowing through <br /> <br />the chamber has to pass through 2.5 an thick piece of foam rubber and then a <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br /> <br />. <br />