국내 최대 기계 및 로봇 연구정보

기술보고서

기술보고서 게시판 내용
타이틀	A LABORATORY STUDY ON THE PHASE TRANSITION FOR POLAR STRATOSPHERIC CLOUD PARTICLES
저자	Edward H. Teets, Jr.
Keyword	Cloud research; Crystals; Stratospheric circulation; Temperature effects; Thermodynamic properties of liquids
URL	http://www.dfrc.nasa.gov/DTRS/1997/PDF/H-2147.pdf
보고서번호	NASA-CR-198056
발행년도	1997
출처	NASA Dryden Flight Research Center
ABSTRACT	The nucleation and growth of different phases of simulated polar stratospheric cloud (PSC) particles were investigated in the laboratory. Solutions and mixtures of solutions at concentrations 1 to 5 m (molality) of ammonium sulfate, ammonium bisulfate, sodium chloride, sulfuric acid, and nitric acid were supercooled to prescribed temperatures below their equilibrium melting point. These solutions were contained in small diameter glass tubing of volumes ranging from 2.6 to 0.04 ml. Samples were nucleated by insertion of an ice crystal, or in some cases by a liquid nitrogen cooled wire. Crystallization velocities were determined by timing the crystal growth front passages along the glass tubing. Solution mixtures containing aircraft exhaust (soot) were also examined. Crystallization rates increased as "Delta"T(squared), where "Delta"T is the supercooling for weak solutions (2 m or less). The higher concentrated solutions (>3 m) showed rates significantly less than "Delta"T(squared). This reduced rate suggested an onset of a glass phase. Results were applied to the nucleation of highly concentrated solutions at various stages of polar stratospheric cloud development within the polar stratosphere.