A dynamic model of failure scenarios of the dry cooler in a liquid cooled chiller-less data center

Author(s):  
Tianyi Gao ◽  
Milnes David ◽  
James Geer ◽  
Roger Schmidt ◽  
Bahgat Sammakia
Keyword(s):  
Author(s):  
Sami A. Alkharabsheh ◽  
Bahgat Sammakia ◽  
Saurabh Shrivastava ◽  
Michael Ellsworth ◽  
Milnes David ◽  
...  

This study presents the results of a detailed parametric study for a data center that is air cooled using a set of four CRAC units in a cold/hot aisle raised floor configuration. The fans of the CRAC units and the servers are calibrated using their practical characteristics fan curves. A commercial CFD code is utilized for this purpose in which the buoyancy forces are taken into account. The k-epsilon model and the Boussinesq approximation are used to model the turbulent airflow and the buoyancy effect, respectively. A dynamic model is developed to take into account the changes in flow rates and power dissipation in the data center environment. The current dynamic model does not take into account the thermal mass of the CRAC units or the servers. The effect of the CRAC fan speed, instantaneous change in power dissipation, tiles perforation ratio, and servers fan speeds on the total flow rate in the room and the inlet temperatures of the racks are investigated. In the transient model, we investigate the effect of different CRAC failure scenarios on the time history of the temperatures and the flow pattern in the data center. Time constants and safe time are estimated from this study. A fundamental understanding of the effect of different data center entities on the flow and the temperatures is developed. Interesting flow patterns are observed in the case of different CRAC failures that could be used to recommend general design guidelines.


2008 ◽  
Vol 45 ◽  
pp. 147-160 ◽  
Author(s):  
Jörg Schaber ◽  
Edda Klipp

Volume is a highly regulated property of cells, because it critically affects intracellular concentration. In the present chapter, we focus on the short-term volume regulation in yeast as a consequence of a shift in extracellular osmotic conditions. We review a basic thermodynamic framework to model volume and solute flows. In addition, we try to select a model for turgor, which is an important hydrodynamic property, especially in walled cells. Finally, we demonstrate the validity of the presented approach by fitting the dynamic model to a time course of volume change upon osmotic shock in yeast.


1980 ◽  
Vol 41 (C8) ◽  
pp. C8-284-C8-288 ◽  
Author(s):  
V. A. Poluchin ◽  
M. M. Dzugutov ◽  
V. F. Uchov ◽  
R. A. Vatolin

Author(s):  
S. R. Rakhmanov ◽  
V. V. Povorotnii

To form a necessary geometry of a hollow billet to be rolled at a pipe rolling line, stable dynamics of the base equipment of the automatic mill working stand has a practical meaning. Among the forces, acting on its parts and elements, significant by value short-time dynamic loads are the least studied phenomena. These dynamic loads arise during transient interaction of the hollow billet, rollers, mandrel and other mill parts at the forced grip of the hollow billet. Basing of the calculation scheme and dynamic model of the mechanical system of the ТПА 350 automatic mill working stand was accomplished. A mathematical model of dynamics of the system “hollow billet (pipe) – working stand” within accepted calculation scheme and dynamic model of the mechanical system elaborated. Influence of technological load of the rolled hollow billet variation in time was accounted, as well as variation of the mechanical system mass, and rigidity of the ТПА 350 automatic mill working stand. Differential equations of oscillation movement for four-mass model of forked sub-systems of the automatic mill working stand were made up, results of their digital calculation quoted. Dynamic displacement of the stand elements in the inter-roller gap obtained, which enabled to estimate the results of amplitude and frequency characteristics of the branches of the mill rollers setting. It was defined by calculation, that the maximum amplitude of the forced oscillations of elements of the ТПА 350 automatic mill working stand within the inter-roller gap does not exceed 2 mm. It is much higher than the accepted value of adjusting parameters of the deformation center of the ТПА 350 automatic mill. A scheme of comprehensive modernization of the rollers setting in the ТПА 350 automatic mill working stand was proposed. It was shown, that increase of rigidity of rollers setting in the ТПА 350 automatic mill working stand enables to stabilize the amplitude of forced oscillations of the working stand elements within the inter-rollers gap and considerably decrease the induced nonuniform hollow billet wall thickness and increase quality of the rolled pipes at ТПА 350.


2009 ◽  
pp. 70-93
Author(s):  
V. Manevich

The paper considers the monetary dynamic model developed by J. Tobin, the leader of Keynesian economic thought in 1970-1990. Particularly, the author examines q-theory of investment proposed by Tobin which allows to expose the relationship between supply of monetary assets and investment in real capital. Application of various tools of monetary and financial policies is also considered in its different forms. The author aspires to use Tobin's model for the analysis of processes existing in the Russian economy and to test theoretical propositions and relationships elaborated by Tobin on Russian statistics.


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