SUBJECT: Ph.D. Dissertation Defense
BY: Qihong Nie
TIME: Friday, August 8, 2008, 10:00 a.m.
PLACE: MRDC Building, 4211
TITLE: Experimentally Validated Multiscale Thermal Modeling of Electronic Cabinets
COMMITTEE: Dr. Yogendra Joshi,, Chair (ME)
Dr. Zhuomin Zhang (ME)
Dr. Samuel Graham (ME)
Dr. Martha G. Gallivan (ChBE)
Dr. Pui-Kuen Yeung (AE)


Thermal characterization of electronic cabinets is becoming increasingly important, due to growing power dissipation and compact packaging. Usually, multiple length scales of interest and modes of heat transfer are simultaneously present. A steady state reduced order thermal modeling framework for electronic systems such as electronic cabinets was developed to provide an efficient method to model thermal transport across multiple length scales. This methodology takes advantages of compact modeling at component level and reduced order modeling at subsystem and system levels. Compact models, which can be incorporated into system level simulation, were created for components, and reduced order models (ROM) were developed using proper orthogonal decomposition (POD) for subsystems and system. An efficient interfacial coupling scheme was developed using the concept of flow network modeling to couple the heat and mass flow rates and pressure at each interface, when interconnecting ROMs together to simulate the entire system. To achieve detailed modeling at component level, thermal information such as surface temperature and local heat transfer coefficients were extracted from the global modeling (system level modeling) and applied to the component model for detailed simulation. A boundary profile matching scheme for ROMs for each subsystem was provided to broaden the application of the multi-scale thermal modeling methodology. The output profiles of the subsystem upstream can be transferred to the input profiles of the subsystems downstream by adding necessary flow straightening duct during the snapshots generation process. The extension of the multi-scale thermal modeling approach to transients was investigated through an electronic enclosure with insulated gate bipolar transistor (IGBT) module. A general method to develop dynamic multi-layer compact models for components and modules was provided. These dynamic compact models were incorporated into enclosure level simulation. The dynamic reduced order model for the enclosure was developed using POD. To demonstrate the application of the multi-scale thermal modeling approach developed here to cabinets incorporating more advanced cooling techniques, a test vehicle with double-sided, hybrid forced air convection, thermoelectric cooling, and micro-channel liquid cooling was designed, constructed, and simulated. The multiscale thermal modeling methodology presented here was validated through experiments conducted on a simulated electronic cabinet and the test vehicle with hybrid cooling technique. The overall multi-scale modeling framework was able to reduced numerical models containing 107 DOF down to around 102, while still retaining an approximation accuracy of 90% over the domain.