Optimal Design Of The Diffuser Length For An Ejector
Date Issued
2012
Date
2012
Author(s)
Chung, Wei-Yi
Abstract
The ejector is the most essential component in an ejector cooling system affecting its performance. Thus, designing the best ejector has long been the objective of research by many scholars. Since the early application of one-dimensional theory could not be used to analyze the length of the component, this study instead used computational fluid dynamics (CFD) to investigate the impact of the process of shortening and elongating the length of the diffuser section of the ejector on the injector flow field. This study further analyzed methods for minimizing the length of the diffuser section without affecting the performance of the ejector under various operating temperatures and changes to the throat area of the primary nozzle, so as to meet the criteria of cost and maximum benefit to performance. The following conclusion can be drawn.
The larger cross-sectional area of the diffuser exit, yielding the slower exit velocity, makes the critical temperature higher. And if the diffuser angle is too large, the boundary layer separation in the diffuser may occur, that limits the size of cross-sectional area to increase the critical temperature. Therefore, the cross-sectional area of the diffuser exit has the optimal size range. The constant cross section area length and diffuser length have a specific size range that does not affect the performance of the ejector. The case study of a variable throat nozzle ejector for operating with the range of the generator temperature, Tg, from 90℃ to 110℃, evaporator temperature, Te, from 8 to 15℃ and condenser temperature, temperature, Tc, from 35 to 40℃, the constant cross section area length and diffuser length can be 25.6% shorter than that of the original design.
Subjects
Ejector
Type
thesis
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