Transient Thermal Response of Servers Through Air Temperature Measurements

2013 ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa ◽  
Roger R. Schmidt
Keyword(s):  
Thermal Conductance ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Operating Conditions ◽  
Cfd Analysis ◽  
Capacitance Measurements ◽  
Thermal Capacitance ◽  
Transient Thermal ◽  
Transient Thermal Response ◽  
Unsteady Conditions

Transient CFD analysis of data centers requires appropriate representations of the transient thermal characteristics of servers. Thermal conductance and thermal capacitance are two determining characteristics for the response of servers under unsteady conditions. Previous studies proposed tests that require detailed temperature and thermal capacitance measurements for each of the server component, requiring access to individual components inside the server. In this paper, we propose a method for obtaining the transient thermal characteristics of a server from server inlet and outlet temperatures under transient operating conditions.

Parameter Estimation for Lumped Capacitance Modeling of CRAH Units During Chilled Water Interruption

2015 ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa
Keyword(s):  
Data Center ◽  
Thermal Response ◽  
Experimental Methodology ◽  
Model Parameters ◽  
Thermal Mass ◽  
Sufficient Information ◽  
Thermal Capacitance ◽  
Chilled Water ◽  
Transient Thermal ◽  
Transient Thermal Response

Lumped capacitance models have been introduced to study transient thermal response of data centers. Chilled water interruption of a Computer Room Air Handling (CRAH) unit is one of several failure scenarios of data center cooling infrastructures. In such a scenario, predicting the transient thermal response of the CRAH unit depends requires the determination of the CRAH lumped capacitance model parameters: the thermal capacitance (thermal mass) and the time constant. In this paper, we propose an experimental methodology to extract sufficient information for the lumped capacitance modeling of CRAH units. The method requires measurements of inlet and exit air temperature, air flow rate and CRAH fan power. If the chilled water supply to a CRAH unit is intentionally interrupted in a data center with multiple redundant CRAH units, sufficient information to estimate the CRAH lumped capacitance parameters can be obtained without disturbing the data center operation.

Determination of the Lumped-Capacitance Parameters of Air-Cooled Servers Through Air Temperature Measurements

2014 ◽  
Vol 136 (3) ◽  
Author(s):  
Hamza Salih Erden ◽  
H. Ezzat Khalifa ◽  
Roger R. Schmidt
Keyword(s):  
Experimental Data ◽  
Air Temperature ◽  
Mathematical Formulation ◽  
Thermal Conductance ◽  
Thermal Characteristics ◽  
Thermal Response ◽  
Transient Behavior ◽  
Operating Conditions ◽  
Temperature Measurements ◽  
Inlet Temperature

Computer servers can be represented by lumped thermal capacitances for the purpose of simulating server and data center transient thermal response to changes in operating conditions or equipment failures. Two parameters are needed to characterize the transient behavior of a lumped-capacitance server: its thermal capacitance and its thermal conductance, heat transfer effectiveness, or time constant. To avoid the laborious task of obtaining these parameters from measurements or estimations of the thermal characteristics of internal components of the server, a method is proposed to derive these parameters from external measurements that can be easily obtained without performing an “autopsy” on the server. In this paper, we present the mathematical formulation underlying the proposed method and describe how the parameters are to be obtained from external air-temperature measurements using the mathematical model. We then present validation test cases using experimental data from server shut-down and inlet-temperature ramp tests. The experimentally obtained parameters are implemented into a computational fluid dynamics (CFD) case study of server shutdown in which the transient server exit air temperature is computed from the lumped-capacitance parameters via a user-defined function. The results thus obtained are in excellent agreement with the experimental data.

Two centuries of the thermal regenerator

2000 ◽  
Vol 214 (1) ◽  
pp. 269-288 ◽  
Author(s):  
A. J. Organ
Keyword(s):  
Thermal Response ◽  
Original Description ◽  
Thermal Capacity ◽  
Operating Conditions ◽  
Temperature History ◽  
Elementary Transformation ◽  
Fluid Temperature ◽  
Transient Thermal ◽  
Transient Thermal Response ◽  
Flow Reversals

The paper looks back over almost 200 years taken to convert Stirling's original description of the thermal regenerator into a quantitative picture of transient thermal response. The ‘regenerator problem’ is found to be essentially the conjugate heat exchange problem by another name, and thus the subject of a massive literature, none of which, however, has, until recently, successfully addressed the problem of repeated flow reversals at low flush ratios. The gap in the repertoire is ironic, given that these are precisely the operating conditions of Stirling's original invention. An elementary transformation overcomes the difficulty of solving for any number of flow reversals at any flush ratio. Temperature-time histories are presented for the ‘classic’ problem with fixed entry temperatures. For sufficiently high thermal capacity ratio a straightforward and explicit solution emerges for fluid temperature history at cyclic steady state. The approach is shown to be sufficiently versatile to permit extension to the complex cyclic operating conditions of Stirling coolers and prime movers. Along the way it is noted that heat transfer correlations ( NSt N2/3Pr versus NRe) for wire gauzes frequently thought inapplicable to the regenerator by virtue of a supposed ‘steady flow’ connotation in fact owe their very existence to an early part-solution of transient thermal response. To this extent the correlations are the proper data to use.

Influence of Phonon Dispersion on Transient Thermal Response of Silicon-on-Insulator Transistors Under Self-Heating Conditions

2006 ◽  
Vol 129 (7) ◽  
pp. 790-797 ◽  
Author(s):  
Rodrigo A. Escobar ◽  
Cristina H. Amon
Keyword(s):  
Computational Models ◽  
Phonon Dispersion ◽  
Thermal Response ◽  
Domain Size ◽  
Phonon Transport ◽  
Silicon On Insulator ◽  
Nonlinear Relation ◽  
Temperature Levels ◽  
Transient Thermal ◽  
Transient Thermal Response

Lattice Boltzmann method (LBM) simulations of phonon transport are performed in one-dimensional (1D) and 2D computational models of a silicon-on-insulator transistor, in order to investigate its transient thermal response under Joule heating conditions, which cause a nonequilibrium region of high temperature known as a hotspot. Predictions from Fourier diffusion are compared to those from a gray LBM based on the Debye assumption, and from a dispersion LBM which incorporates nonlinear dispersion for all phonon branches, including explicit treatment of optical phonons without simplifying assumptions. The simulations cover the effects of hotspot size and heat pulse duration, considering a frequency-dependent heat source term. Results indicate that, for both models, a transition from a Fourier diffusion regime to a ballistic phonon transport regime occurs as the hotspot size is decreased to tens of nanometers. The transition is characterized by the appearance of boundary effects, as well as by the propagation of thermal energy in the form of multiple, superimposed phonon waves. Additionally, hotspot peak temperature levels predicted by the dispersion LBM are found to be higher than those from Fourier diffusion predictions, displaying a nonlinear relation to hotspot size, for a given, fixed, domain size.

Transient thermal response in ultrasonic additive manufacturing of aluminum 3003

2011 ◽  
Vol 17 (5) ◽  
pp. 369-379 ◽  
Author(s):  
David Schick ◽  
Sudarsanam Suresh Babu ◽  
Daniel R. Foster ◽  
Marcelo Dapino ◽  
Matt Short ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Thermal Response ◽  
Ultrasonic Additive Manufacturing ◽  
Transient Thermal ◽  
Transient Thermal Response
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