Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892325
S. Ogata, Eiji Sukegawa, Takahiro Kimura
An ultra-thin polymer pulsating heat pipe (PPHP) was developed by forming with UV curable polymer resin on polyethylene terephthalate films and hydrofluoroether was used as a working fluid. The casing materials were selected in consideration of compatibility between case materials and the working fluid and also the heat and pressure durability. A new apparatus was constructed to evaluate the thermal resistance of the PPHP without the heat dissipation caused by natural convection, and a simple model was developed to estimate the heat dissipation and identify their influence on the thermal performance measurement. Comparing experimental results in this apparatus with the results calculated by the model, we found that the uncertainty of the thermal resistance measurement caused by the heat dissipation could be reduced to the range of measurement error. The steady state operation of the PPHP in the horizontal orientation was confirmed by the temperature response to various heat loads and the observation of the working fluid pulsations. Performance evaluation of the PPHP using this apparatus showed that the thermal resistance of the PPHP decreased as heat load increased and reached a minimum value comparable with that of a copper plate of the same thickness.
{"title":"Performance evaluation of ultra-thin polymer pulsating heat pipes","authors":"S. Ogata, Eiji Sukegawa, Takahiro Kimura","doi":"10.1109/ITHERM.2014.6892325","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892325","url":null,"abstract":"An ultra-thin polymer pulsating heat pipe (PPHP) was developed by forming with UV curable polymer resin on polyethylene terephthalate films and hydrofluoroether was used as a working fluid. The casing materials were selected in consideration of compatibility between case materials and the working fluid and also the heat and pressure durability. A new apparatus was constructed to evaluate the thermal resistance of the PPHP without the heat dissipation caused by natural convection, and a simple model was developed to estimate the heat dissipation and identify their influence on the thermal performance measurement. Comparing experimental results in this apparatus with the results calculated by the model, we found that the uncertainty of the thermal resistance measurement caused by the heat dissipation could be reduced to the range of measurement error. The steady state operation of the PPHP in the horizontal orientation was confirmed by the temperature response to various heat loads and the observation of the working fluid pulsations. Performance evaluation of the PPHP using this apparatus showed that the thermal resistance of the PPHP decreased as heat load increased and reached a minimum value comparable with that of a copper plate of the same thickness.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"12 1","pages":"519-526"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91123563","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892375
Omidreza Ghaffari, M. Dogruoz, M. Arik
Thermal management has become a critical part of advanced micro and nano electronics systems due to high heat transfer rates. More constraints such as compactness, small footprint area, lightweight, high reliability, easy-access and low cost are exposed to thermal engineers. Advanced electronic systems such as laptops, tablets, smart phones and slim TV systems carry those challenging thermal needs. For these devices, smaller thermal real estates with higher heat fluxes than ever have created issues that current thermal technologies cannot meet those needs easily. Therefore, innovative cooling techniques are necessary to fulfill these aggressive thermal demands. Synthetic jets have been studied as a promising technology to satisfy the thermal needs of such tight electronics devices. The effect of nozzle-to-surface distance for a synthetic jet on its cooling performance has neither been studied extensively nor been well-understood. In a few available experimental studies, it was reported that synthetic jet performance is very sensitive to this distance and when the jet gets closer to the hot surface its performance degrades. Therefore, a computational study has been performed to understand the flow physics of a small-scale synthetic jet for a jet-to-surface spacing of H/Dh=5. Spatial discretization is implemented via a second order upwind scheme and a second order implicit scheme is used for temporal discretization to ensure stability. It is found that pulsating flow at the nozzle exit generates vortices and these vortices seem to have minimal effect on the target surface profiles. Local surface pressure, velocity, turbulence profiles and heat transfer coefficient distributions are determined, then the effects of jet frequency as well as near-wall vortices are discussed.
{"title":"An investigation into momentum and temperature fields of a meso-scale synthetic jet","authors":"Omidreza Ghaffari, M. Dogruoz, M. Arik","doi":"10.1109/ITHERM.2014.6892375","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892375","url":null,"abstract":"Thermal management has become a critical part of advanced micro and nano electronics systems due to high heat transfer rates. More constraints such as compactness, small footprint area, lightweight, high reliability, easy-access and low cost are exposed to thermal engineers. Advanced electronic systems such as laptops, tablets, smart phones and slim TV systems carry those challenging thermal needs. For these devices, smaller thermal real estates with higher heat fluxes than ever have created issues that current thermal technologies cannot meet those needs easily. Therefore, innovative cooling techniques are necessary to fulfill these aggressive thermal demands. Synthetic jets have been studied as a promising technology to satisfy the thermal needs of such tight electronics devices. The effect of nozzle-to-surface distance for a synthetic jet on its cooling performance has neither been studied extensively nor been well-understood. In a few available experimental studies, it was reported that synthetic jet performance is very sensitive to this distance and when the jet gets closer to the hot surface its performance degrades. Therefore, a computational study has been performed to understand the flow physics of a small-scale synthetic jet for a jet-to-surface spacing of H/Dh=5. Spatial discretization is implemented via a second order upwind scheme and a second order implicit scheme is used for temporal discretization to ensure stability. It is found that pulsating flow at the nozzle exit generates vortices and these vortices seem to have minimal effect on the target surface profiles. Local surface pressure, velocity, turbulence profiles and heat transfer coefficient distributions are determined, then the effects of jet frequency as well as near-wall vortices are discussed.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"36 1","pages":"889-896"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91178033","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892419
Farzad Houshmand, Y. Peles
A High frequency wall temperature measurement approach at the microscale is demonstrated. This experimental approach was implemented to study the transient effect of bubbles in a slug flow regime. Air stream was injected into liquid water flow in a 210 μm deep and 1.5 mm wide horizontal microchannel to form a slug flow regime (with bubble frequency of ~280 Hz) and the associated wall temperature variations were recorded using the embedded resistance temperature detectors (RTDs) inside the channel-on the heater area. Synchronized images of the two-phase flow were simultaneously recorded by a high speed camera, and the recorded footage was used to interpret the observed trends. Three different regions with different heat transfer characteristics were identified for each cycle of bubble/liquid-slug passage.
{"title":"Transient wall temperature measurements of two-phase slug flow in a microchannel","authors":"Farzad Houshmand, Y. Peles","doi":"10.1109/ITHERM.2014.6892419","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892419","url":null,"abstract":"A High frequency wall temperature measurement approach at the microscale is demonstrated. This experimental approach was implemented to study the transient effect of bubbles in a slug flow regime. Air stream was injected into liquid water flow in a 210 μm deep and 1.5 mm wide horizontal microchannel to form a slug flow regime (with bubble frequency of ~280 Hz) and the associated wall temperature variations were recorded using the embedded resistance temperature detectors (RTDs) inside the channel-on the heater area. Synchronized images of the two-phase flow were simultaneously recorded by a high speed camera, and the recorded footage was used to interpret the observed trends. Three different regions with different heat transfer characteristics were identified for each cycle of bubble/liquid-slug passage.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"77 1","pages":"1215-1221"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90277787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892296
A. Sridhar, M. Sabry, David Atienza Alonso
The development of embedded and interlayer liquid cooling in integrated circuits (ICs) using silicon microchannels has gained interest in the recent years owing to the rise of on-chip heat uses that aggravate thermal reliability issues of the emerging 3D stacked ICs. Further development of such devices and their translation to commercial applications depend largely on the availability of tools and methodologies that can enable the “temperature-aware” design of liquid-cooled microprocessors and 2D/3D multiprocessor systems-on-chip (MPSoCs). Recently, two optimal design methods have been proposed for liquid-cooled microchannel ICs: one to minimize on-chip temperature gradients and the other, called GreenCool, to maximize energy efficiency in the coolant pumping effort. Both these methods rely upon the concept of channel width modulation to modify the thermal behaviour of a microchannel liquid-cooled heat sink. At the heart of both these methods is a new semi-analytical mathematical model for heat transfer in liquid-cooled ICs. Such a mathematical model enables the application of gradient descent approaches, such as non-linear programming, in the search for the most optimally performing channel design in a huge multi-dimensional design space. In this paper, we thoroughly quantify the impact and efficiency of the semi-analytical model, combined with non-linear programming, when compared against several numerical optimization mechanisms. Our experimental evaluation shows that nonlinear programming, alongside the semi-analytical model, is up to 23× faster than conventional randomized/heuristic design approaches such as genetic algorithms and simulated annealing using fully-numerical thermal models.
{"title":"A semi-analytical approach for optimized design of microchannel liquid-cooled ICs","authors":"A. Sridhar, M. Sabry, David Atienza Alonso","doi":"10.1109/ITHERM.2014.6892296","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892296","url":null,"abstract":"The development of embedded and interlayer liquid cooling in integrated circuits (ICs) using silicon microchannels has gained interest in the recent years owing to the rise of on-chip heat uses that aggravate thermal reliability issues of the emerging 3D stacked ICs. Further development of such devices and their translation to commercial applications depend largely on the availability of tools and methodologies that can enable the “temperature-aware” design of liquid-cooled microprocessors and 2D/3D multiprocessor systems-on-chip (MPSoCs). Recently, two optimal design methods have been proposed for liquid-cooled microchannel ICs: one to minimize on-chip temperature gradients and the other, called GreenCool, to maximize energy efficiency in the coolant pumping effort. Both these methods rely upon the concept of channel width modulation to modify the thermal behaviour of a microchannel liquid-cooled heat sink. At the heart of both these methods is a new semi-analytical mathematical model for heat transfer in liquid-cooled ICs. Such a mathematical model enables the application of gradient descent approaches, such as non-linear programming, in the search for the most optimally performing channel design in a huge multi-dimensional design space. In this paper, we thoroughly quantify the impact and efficiency of the semi-analytical model, combined with non-linear programming, when compared against several numerical optimization mechanisms. Our experimental evaluation shows that nonlinear programming, alongside the semi-analytical model, is up to 23× faster than conventional randomized/heuristic design approaches such as genetic algorithms and simulated annealing using fully-numerical thermal models.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"116 1","pages":"296-305"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79761434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892392
A. Merrikh, A. McNamara
Compact thermal modeling of hand-held and ultra-low power microelectronic systems has recently attracted a great deal of attention. In this study time-dependent evolution of heat transfer around a flat plate was numerically investigated. The flat plate is subjected to internal heat generation from the inner boundary via a discrete heat source. It is cooled on the outer boundary via buoyancy and radiation. The main objective of this work was to understand the limitation of a Foster RC-network in predicting transient behavior of a non-linear system as such. Non-linearity of the system stems from the physics of flow and heat transfer evolution around the flat plate, resulting time- and power-dependent boundary conditions. Special attention was paid to the characteristics and number of the network ladders for resolving the time-history of the temperature as a function of the input power. The studied system resembles a hand-held, fanless, device operating at room ambient.
{"title":"Parametric evaluation of foster RC-network for predicting transient evolution of natural convection and radiation around a flat plate","authors":"A. Merrikh, A. McNamara","doi":"10.1109/ITHERM.2014.6892392","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892392","url":null,"abstract":"Compact thermal modeling of hand-held and ultra-low power microelectronic systems has recently attracted a great deal of attention. In this study time-dependent evolution of heat transfer around a flat plate was numerically investigated. The flat plate is subjected to internal heat generation from the inner boundary via a discrete heat source. It is cooled on the outer boundary via buoyancy and radiation. The main objective of this work was to understand the limitation of a Foster RC-network in predicting transient behavior of a non-linear system as such. Non-linearity of the system stems from the physics of flow and heat transfer evolution around the flat plate, resulting time- and power-dependent boundary conditions. Special attention was paid to the characteristics and number of the network ladders for resolving the time-history of the temperature as a function of the input power. The studied system resembles a hand-held, fanless, device operating at room ambient.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"4 1","pages":"1011-1018"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83346600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892359
H. Alissa, S. Alkharabsheh, S. Bhopte, B. Sammakia
The purpose of under floor plenum in a typical raised floor data center is to route the supply of cold air to perforated tiles in the cold aisles, and hence, to the racks. However, the presence of under floor chiller piping and various wiring may have an adverse effect on flow rates if not placed based on physical considerations; the pressure drop caused by chiller piping and under floor blockages has not been investigated thoroughly in modeling of a fully representative real life data center, and in particular, in applications where some or all of the cold aisles may be contained. This effect on flow rate is expected to be even more profound in contained systems; this study aims to address the effect of under floor obstructions on data center performance. It was shown that when having blockages in critical locations, containment can act as a solution for the inlet temperatures at the racks, however, the blockage effect can still be seen on the racks outlet and the CRAC return temperatures. It was also observed that inadequate distribution of those blockages led to a change in the operating point of both the CRAC and severs fan curve reducing the flow being fed to the IT equipment, and hence the chiller cooling load is expected to increase, which results in a thermal deficiency of the data center.
{"title":"Numerical investigation of underfloor obstructions in open-contained data center with fan curves","authors":"H. Alissa, S. Alkharabsheh, S. Bhopte, B. Sammakia","doi":"10.1109/ITHERM.2014.6892359","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892359","url":null,"abstract":"The purpose of under floor plenum in a typical raised floor data center is to route the supply of cold air to perforated tiles in the cold aisles, and hence, to the racks. However, the presence of under floor chiller piping and various wiring may have an adverse effect on flow rates if not placed based on physical considerations; the pressure drop caused by chiller piping and under floor blockages has not been investigated thoroughly in modeling of a fully representative real life data center, and in particular, in applications where some or all of the cold aisles may be contained. This effect on flow rate is expected to be even more profound in contained systems; this study aims to address the effect of under floor obstructions on data center performance. It was shown that when having blockages in critical locations, containment can act as a solution for the inlet temperatures at the racks, however, the blockage effect can still be seen on the racks outlet and the CRAC return temperatures. It was also observed that inadequate distribution of those blockages led to a change in the operating point of both the CRAC and severs fan curve reducing the flow being fed to the IT equipment, and hence the chiller cooling load is expected to increase, which results in a thermal deficiency of the data center.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"11 1","pages":"771-777"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83424460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892271
S. Jules, D. Ryckelynck, C. Duhamel, Y. Bienvenu, Jean-Francois Bisson, R. Leon
The following study is motivated by the need to capture the elasto-viscoplastic behavior of a “real” industrial power module lead-free solder joint. In this work, we carried out a numerical design of experiments in order to forecast the ability of an experimental bending system to identify the specimen material properties. As a proof of principle, the micro-mechanical elastic behavior of power module copper substrates was then characterized thanks to the development of an innovative in-situ micro-mechanical bending test under an optical profilometer. An inverse Finite-Element Method has been applied in order to identify the material properties of test specimens designed directly out of industrial assemblies and not from bulk solder for good representativity. The results show that identified copper Young's modulus values are lower than that of a bulk material. It will be defined as such in the next identificatio n step targeting the solder joint.
{"title":"Micro-mechanical characterization of lead-free solder joints in power electronics","authors":"S. Jules, D. Ryckelynck, C. Duhamel, Y. Bienvenu, Jean-Francois Bisson, R. Leon","doi":"10.1109/ITHERM.2014.6892271","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892271","url":null,"abstract":"The following study is motivated by the need to capture the elasto-viscoplastic behavior of a “real” industrial power module lead-free solder joint. In this work, we carried out a numerical design of experiments in order to forecast the ability of an experimental bending system to identify the specimen material properties. As a proof of principle, the micro-mechanical elastic behavior of power module copper substrates was then characterized thanks to the development of an innovative in-situ micro-mechanical bending test under an optical profilometer. An inverse Finite-Element Method has been applied in order to identify the material properties of test specimens designed directly out of industrial assemblies and not from bulk solder for good representativity. The results show that identified copper Young's modulus values are lower than that of a bulk material. It will be defined as such in the next identificatio n step targeting the solder joint.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"18 1","pages":"107-111"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91373937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892258
Daniel S. Meyer, B. Helenbrook, Wangkun Jia, M. Cheng
With the decreasing sizes of transistors and the increasing integrated circuit (IC) density, heat dissipation can be a limiting factor in developing emerging semiconductor technologies, such as silicon-on-insulator (SOI) based transistors and 3D-stacked ICs. To overcome this challenge, accurate thermal simulations are needed. The goal of this investigation is to explore the use of proper orthogonal decomposition (POD)-based reduced basis element methods (RBEM) for performing fast and accurate thermal predictions of ICs. The reduced basis element method (RBEM) is new type of reduced order modeling that takes advantage of repeated geometrical features. The RBEM uses a reduced set of basis functions to approximate the solution of a PDE on some geometrical subdomain or “block”. Once a reduced order model (ROM) has been created for a particular geometrical block it is a matter of “gluing” multiple blocks together and solving for equations governing the combined system. In this study, we examine the appropriate choice of “block” for the RBEM simulation of an IC. To determine the trade-offs between these choices, RBEM thermal simulations using single device blocks are compared to RBEMs that span multiple devices. It was found that larger blocks are more computationally efficient; however the advantage decreases if the devices within a block receive independent signals.
{"title":"POD based reduced basis element method for use in thermal modeling of integrated circuits","authors":"Daniel S. Meyer, B. Helenbrook, Wangkun Jia, M. Cheng","doi":"10.1109/ITHERM.2014.6892258","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892258","url":null,"abstract":"With the decreasing sizes of transistors and the increasing integrated circuit (IC) density, heat dissipation can be a limiting factor in developing emerging semiconductor technologies, such as silicon-on-insulator (SOI) based transistors and 3D-stacked ICs. To overcome this challenge, accurate thermal simulations are needed. The goal of this investigation is to explore the use of proper orthogonal decomposition (POD)-based reduced basis element methods (RBEM) for performing fast and accurate thermal predictions of ICs. The reduced basis element method (RBEM) is new type of reduced order modeling that takes advantage of repeated geometrical features. The RBEM uses a reduced set of basis functions to approximate the solution of a PDE on some geometrical subdomain or “block”. Once a reduced order model (ROM) has been created for a particular geometrical block it is a matter of “gluing” multiple blocks together and solving for equations governing the combined system. In this study, we examine the appropriate choice of “block” for the RBEM simulation of an IC. To determine the trade-offs between these choices, RBEM thermal simulations using single device blocks are compared to RBEMs that span multiple devices. It was found that larger blocks are more computationally efficient; however the advantage decreases if the devices within a block receive independent signals.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"8 1","pages":"9-17"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88301267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892417
F. Ejeckam, D. Francis, F. Faili, J. Dodson, D. Twitchen, B. Bolliger, D. Babic
AlGaN/GaN high electron mobility transistors (HEMT) semiconductor technology holds promise for revolutionary improvements in the cost, size, weight, and performance of a broad range of military and commercial microelectronics [1]. However, exploiting the true capabilities of GaN is a compromise between the desired RF performance and the realities of current thermal solutions. In this work we present modeling and integration details on performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated on freestanding and mounted, heat-spreading diamond substrates. The excellent thermal properties of diamond substrates grown by chemical vapor deposition (CVD) provide a superior heat spreading material for electronic packages. The successful on-wafer integration of diamond with gallium nitride (GaN) has emerged as a critical solution for the expected thermal challenges of the next generation of high power RF and microwave devices.
{"title":"Diamond for enhanced GaN device performance","authors":"F. Ejeckam, D. Francis, F. Faili, J. Dodson, D. Twitchen, B. Bolliger, D. Babic","doi":"10.1109/ITHERM.2014.6892417","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892417","url":null,"abstract":"AlGaN/GaN high electron mobility transistors (HEMT) semiconductor technology holds promise for revolutionary improvements in the cost, size, weight, and performance of a broad range of military and commercial microelectronics [1]. However, exploiting the true capabilities of GaN is a compromise between the desired RF performance and the realities of current thermal solutions. In this work we present modeling and integration details on performance of AlGaN/GaN high-electron-mobility transistors (HEMTs) fabricated on freestanding and mounted, heat-spreading diamond substrates. The excellent thermal properties of diamond substrates grown by chemical vapor deposition (CVD) provide a superior heat spreading material for electronic packages. The successful on-wafer integration of diamond with gallium nitride (GaN) has emerged as a critical solution for the expected thermal challenges of the next generation of high power RF and microwave devices.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"33 1","pages":"1206-1209"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87488348","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-05-27DOI: 10.1109/ITHERM.2014.6892361
J. Vangilder, X. Zhang
In an effort to improve the reliability and efficiency of data centers, racks and sometimes entire hot aisles are ducted to a dropped ceiling. The cooling performance of such systems strongly depends on IT and cooler airflow, the number and configuration of ducted objects and perforated ceiling tiles, the leakiness of the ceiling system, ceiling plenum depth, and other factors. Recently, a compact model has been proposed in which a Flow Network Model (FNM) representing the ducted equipment is embedded into a parent CFD model. By eliminating the need to explicitly model difficult-to-characterize leakage paths in CFD, this approach allows for realistic solutions while greatly improving the solutions speed and robustness of the CFD simulation. This paper employs the FNM (without CFD) to characterize and compare the cooling effectiveness of individually-ducted racks and ducted hot aisles subject to a given ceiling plenum pressure. Example resistance values needed in the FNM are provided. Additionally, an example data center layout is studied with the coupled FNM-CFD model to explore cooling performance as a function of ceiling leakiness, plenum depth, ratio of cooling to IT airflow, and rack density (IT airflow). Best-practice type recommendations for ducted equipment are provided.
{"title":"Cooling performance of ceiling-plenum-ducted containment systems in data centers","authors":"J. Vangilder, X. Zhang","doi":"10.1109/ITHERM.2014.6892361","DOIUrl":"https://doi.org/10.1109/ITHERM.2014.6892361","url":null,"abstract":"In an effort to improve the reliability and efficiency of data centers, racks and sometimes entire hot aisles are ducted to a dropped ceiling. The cooling performance of such systems strongly depends on IT and cooler airflow, the number and configuration of ducted objects and perforated ceiling tiles, the leakiness of the ceiling system, ceiling plenum depth, and other factors. Recently, a compact model has been proposed in which a Flow Network Model (FNM) representing the ducted equipment is embedded into a parent CFD model. By eliminating the need to explicitly model difficult-to-characterize leakage paths in CFD, this approach allows for realistic solutions while greatly improving the solutions speed and robustness of the CFD simulation. This paper employs the FNM (without CFD) to characterize and compare the cooling effectiveness of individually-ducted racks and ducted hot aisles subject to a given ceiling plenum pressure. Example resistance values needed in the FNM are provided. Additionally, an example data center layout is studied with the coupled FNM-CFD model to explore cooling performance as a function of ceiling leakiness, plenum depth, ratio of cooling to IT airflow, and rack density (IT airflow). Best-practice type recommendations for ducted equipment are provided.","PeriodicalId":12453,"journal":{"name":"Fourteenth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"5 1","pages":"786-792"},"PeriodicalIF":0.0,"publicationDate":"2014-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79490706","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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