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Performance analysis and optimization of high capacity pulse tube refrigerator
, Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010 ; Volume 1 , 2010 , Pages 257-263 ; 9780791849156 (ISBN) ; Roshanghalb, F ; Jahanbakhshi, R ; Saidi, M. H ; Kazemzadeh Hannani, S ; Sharif University of Technology
Abstract
High capacity pulse tube refrigerator (HCPTR) is a new generation of cryocoolers tailored to provide more than 250 W of cooling power at cryogenic temperatures. The most important characteristics of HCPTR when compared with other types of pulse tube refrigerators are a powerful pressure wave generator, and an accurate design. In this paper the influence of geometrical and operating parameters on the performance of a double inlet pulse tube refrigerator (DIPTR) is studied. The DIPTR is modeled applying the nodal analysis technique, using mass, momentum and energy conservation equations. The model is able to compute instantaneous flow field throughout the system and calculate cooling capacity...
Experimental study of flow field on stepped airfoil at very low Reynolds number
, Article Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering ; Volume 231, Issue 9 , 2017 , Pages 1706-1717 ; 09544100 (ISSN) ; Ghassemi, H ; Ebrahimi, A ; Ghasemi, B ; Sharif University of Technology
Abstract
In this article, the flow field around NACA0024 airfoil with step at lower and upper surfaces is experimentally investigated. For this purpose, particle image velocimetry technique based on the instantaneous flow structures is used to investigate the flow field around the airfoil at different times. All the experimental measurements in current study are conducted at very low Reynolds number condition based on the chord of the airfoil (Re=2000) and at angles of attack at 0° and 5° where the flow around airfoils is separated. The differences between vortical structures, mean streamlines, sizes of the wake regions, and vortex shedding of the stepped airfoils compared to unmodified airfoil are...