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A tube-type evaporator requires capillary force in order to lift liquid refrigerant to circumference direction under a gravity field, which reduces thermal performance. Therefore, a capillary pumped loop with a plate-type evaporator was newly manufactured to improve the performance and reduce the thickness of the evaporator. The plate-type evaporator is flat disk shaped with an effective diameter...
This paper is a follow-up of a hard disk drive study presented at ITherm 2006 on thermal-acoustic optimization of a HDD placed inside an air duct with an axial fan. Today we present a benchmark study performed on a number of consumer products containing a HDD. We will show that it is possible to predict if a certain application design is close to its optimal, set-level design. This is important for...
Power dissipation levels in mobile electronics devices are heading towards five watts and above. With this power dissipation level, products such as mobile phones will require active cooling to ensure that the devices operate within an acceptable temperature envelop from both user comfort and reliability perspectives. To the authors knowledge no studies to date have been carried out to determine the...
This study examines numerically details of the flow and temperature fields of heat sinks with short plate fins cooled by impinging jet. The main focus is on the effect of fin shapes on the heat sink performance. Conjugate heat transfer between airflow convection and conduction inside the fin and base is considered. Three different shapes under study are rectangular, round-headed and elliptic, while...
Rapid development in the design of electronic packages for modern high-speed computers has led to the demand for effective methods of chip cooling. The primary concerns in thermal management applications are high thermal conductivity, large specific surface area and low weight. Graphite foams which possess predominantly spherical pores with smaller openings between the cells constitute a novel highly-conductive...
Boiling heat transfer enhancement for a two-phase cooling design is presented in this paper. The paper discusses an effective method of boiling heat transfer enhancement and its performance. The pool boiling heat transfer from the silicon surface is enhanced by combination of surface modification and micro machined structure. The effect of micro structure features like pore diameter, pore pitch, channel...
Porous metal foams, inserted into the channels of a liquid cold plate, can be used to enhance forced convection and flow boiling heat transfer and may be especially useful for direct, dielectric liquid cooling of electronic and photonic components. This study explores the thermofiuid characteristics of three porous copper foam configurations: 95% porosity and 10 PPI, 95% porosity and 20 PPI, and 92%...
Two-phase pumped-loop systems are being actively explored for the cooling of high-heat-flux electronics cooling because of their compactness and low thermal resistance. A typical two-phase pumped loop consists of a microchannel heat sink based evaporator, a finned-tube condenser, a reservoir, and a positive displacement pump. In the present study, the physics of operation of a two-phase pumped-loop...
This study examines the cooling performance of two hybrid cooling schemes that capitalize upon the merits of both micro-channel flow and jet impingement to achieve the high cooling fluxes and uniform temperatures demanded by advanced defense electronics. The jets supply HFE 7100 liquid coolant gradually into each micro-channel. The cooling performances of two different jet configurations, a series...
For a given heat sink thermal resistance and ambient temperature, the temperature of an electronic device rises fairly linearly with increasing device heat flux. This relationship is especially problematic for defense electronics, where heat dissipation is projected to exceed 1000 W/cm2 in the near future. Direct and indirect low temperature refrigeration cooling facilitate appreciable reduction in...
Thermal control of power electronics cabinets requires thermal characterization under multiple length scales and transport modes. Detailed numerical calculations or measurements are often time consuming or simply unfeasible. An efficient multiscale thermal modeling methodology is proposed for electronic cabinets with hybrid liquid, forced air convection, and thermoelectric cooling. Compact models...
The presence of multiple thermally resistive layers in power electronics packages diminishes the enhanced convective benefit of high-performance microchannel cold plates. One improvement reported here is the development of stereolithographically defined aluminum nitride (AlN) microchannel integrated coldplates as substrates for power electronics packages. High-resolution fabrication of green ceramic...
Boiling in microchannel heat sinks is attractive for high-performance electronics cooling due to the high heat transfer rates that can be achieved. However, the physics of flow boiling in microchannels, the flow patterns present, and the effect of microchannel size on the boiling regimes have not been investigated extensively, particularly with dielectric fluids. In the present work, experiments are...
Particle laden polymer composites are widely used as thermal interface materials (TIMs) in the electronics cooling industry. A critical need in developing TIMs is apriori modeling from first principles to predict the effect of particle volume fraction and arrangements. This in turn will help optimize the material. In general, TIM systems contain random distributions of particles of a polydisperse...
Shrinking chip feature sizes and increasing performance demands are resulting in non-uniform on-chip power dissipation. Sub-millimeter regions of high heat flux are developing with heat fluxes exceeding the average chip flux by a factor of six to ten and peak heat fluxes approaching 1000 W/cm2. These "flux-spots" can yield locally high temperatures ("hotspots") and extreme thermal...
There is a need for standard TIM characterization technique for notebook specific applications. The current standard method, ASTM D5470 tester neglects the usage conditions encountered in mobile specific applications. In addition, characterizing "Beginning of Life" performance of TIMs is not sufficient as performance can degrade with usage. This paper emphasizes the importance of considering...
Recent studies provide ample evidence of the effectiveness of two-phase spray cooling at dissipating large heat fluxes from electronic devices. However, those same studies point to the difficulty predicting spray performance, given the large number of parameters that influence spray behavior. This paper provides a complete set of models/correlations that are required for designing an optimum spray...
This paper presents the results of a numerical parametric analysis focusing on laminar microjet impingement cooling of electronics. A conjugate problem with the solid region representing an active IC chip and the fluid region encompassing the confined jet flow was solved with a commercial CFD software package based on the finite volume method. The flow parameters varied included the Reynolds number...
The conjugate steady-state and transient thermal performance of leaded package (30 Id HSOP) for automotive application in a custom environment is evaluated and further optimized using numerical simulation and experimental validation. The automotive industry deals on a daily basis with multiple packaging and module-level thermal issues when reducing the size of components, while managing the routing...
INTRODUCTION Maintaining the integrity of the heat dissipation path for high end microelectronic devices has become increasingly challenging as the industry migrates from ceramic to organic packaging. Typically, flip chip organic packages undergo significant thermal and mechanical stresses throughout the manufacturing process, including chip join, underfill, encapsulation, BGA attach and card join...
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