Pub Date : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190187
J. Vangilder, Yatharth Vaishnani, W. Tian, M. Condor
We propose a compact rack model which provides the capabilities of an explicitly-detailed model and the computational efficiency of a black-box model. The proposed model idealizes internal-rack airflows as conforming to a well-defined flow network topology. It predicts IT-equipment inlet temperatures (which depend on internal-rack recirculations) and pressure-driven leakage airflows. Consequently, it can model, for example, contained and uncontained architectures, the effects of under-rack cable cutouts, and ceiling-ducted racks (with a sealed rear door).The model is efficient and robust because it eliminates the need to explicitly model small-scale features in large-scale data-center CFD simulations while not appreciably increasing computational cost relative to the simplest black-box models. It has the potential for high accuracy as internal-rack flow resistances are taken directly from experimental measurements and inputs may be tailored to any rack population or application.
{"title":"A Compact Rack Model for Data Center CFD Modeling","authors":"J. Vangilder, Yatharth Vaishnani, W. Tian, M. Condor","doi":"10.1109/ITherm45881.2020.9190187","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190187","url":null,"abstract":"We propose a compact rack model which provides the capabilities of an explicitly-detailed model and the computational efficiency of a black-box model. The proposed model idealizes internal-rack airflows as conforming to a well-defined flow network topology. It predicts IT-equipment inlet temperatures (which depend on internal-rack recirculations) and pressure-driven leakage airflows. Consequently, it can model, for example, contained and uncontained architectures, the effects of under-rack cable cutouts, and ceiling-ducted racks (with a sealed rear door).The model is efficient and robust because it eliminates the need to explicitly model small-scale features in large-scale data-center CFD simulations while not appreciably increasing computational cost relative to the simplest black-box models. It has the potential for high accuracy as internal-rack flow resistances are taken directly from experimental measurements and inputs may be tailored to any rack population or application.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"10 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127218912","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190581
S. Panse, S. Ekkad
Additive manufacturing is proving to be a viable manufacturing technique to fabricate complex structures as it opens up the design space by providing improved design freedom and reduced geometric restrictions. Further, it assures to provide benefit to the heat exchanger industry which relies on novel geometric features to enhance performance and efficiency. This paper explores the heat transfer and pressure drop performance of additively manufactured microchannel heat sinks. Two types of microchannel heat sinks were tested, namely, single-pass and two-pass microchannels with heat flux provided on the bottom wall. Additionally, the microchannel geometry was enhanced by incorporating periodic secondary flow passages with an aim to enhance fluid mixing and disrupt boundary layer development. The enhanced microchannel configurations featured the oblique fin and trapezoidal fin heat sinks. Enhanced microchannels showed superior performance both thermally and hydraulically with 100% increase in heat transfer performance with negligible gain in pressure drop over the baseline straight microchannel geometry. Moreover, the performance gain was more evident for the single-pass microchannels than the two-pass configuration, which showed tremendously high pressure drop due to increase in flow length. Results showed 30% reduction in the overall thermal resistance for a constant pressure drop for the enhanced microchannels in the single pass configuration.
{"title":"Evaluation of Additively Manufactured Single-Pass and Two-Pass Enhanced Microchannel Heat Sinks","authors":"S. Panse, S. Ekkad","doi":"10.1109/ITherm45881.2020.9190581","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190581","url":null,"abstract":"Additive manufacturing is proving to be a viable manufacturing technique to fabricate complex structures as it opens up the design space by providing improved design freedom and reduced geometric restrictions. Further, it assures to provide benefit to the heat exchanger industry which relies on novel geometric features to enhance performance and efficiency. This paper explores the heat transfer and pressure drop performance of additively manufactured microchannel heat sinks. Two types of microchannel heat sinks were tested, namely, single-pass and two-pass microchannels with heat flux provided on the bottom wall. Additionally, the microchannel geometry was enhanced by incorporating periodic secondary flow passages with an aim to enhance fluid mixing and disrupt boundary layer development. The enhanced microchannel configurations featured the oblique fin and trapezoidal fin heat sinks. Enhanced microchannels showed superior performance both thermally and hydraulically with 100% increase in heat transfer performance with negligible gain in pressure drop over the baseline straight microchannel geometry. Moreover, the performance gain was more evident for the single-pass microchannels than the two-pass configuration, which showed tremendously high pressure drop due to increase in flow length. Results showed 30% reduction in the overall thermal resistance for a constant pressure drop for the enhanced microchannels in the single pass configuration.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127455974","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190361
G. Damoulakis, M. J. Gukeh, Theodore P. Koukoravas, C. Megaridis
The term "vapor chamber" has been used to describe a device that spreads heat, as opposed to the term "thermal diode" that has been assigned to a device technically designed to prevent heat flow along a specific direction. In this study, a vapor chamber with a wickless, wettability-patterned condenser is fabricated and tested. The device takes advantage of the phase-changing properties of water, inside a closed loop comprised of a classical wick evaporator opposing a wickless wettability-patterned condenser. The wettability pattern facilitates spatially-controlled dropwise and filmwise condensation, and provides an efficient way to transport the condensate with specially-designed wedge tracks using capillary forces. The vapor chamber can also act as a thermal diode if the wickless condenser has a higher temperature than the wick, thus blocking heat flow in the opposite direction. When the device is performing as a vapor chamber (VC), the working medium evaporates from the hot superhydrophilic copper wick and condenses on the cold wickless condenser. The condensed water returns to the hot side of the device from strategically-placed superhydrophilic wells on the condenser, where condensate droplets accumulate, grow and ultimately bridge between the evaporator and the condenser. However, when the device is performing as a thermal diode (reverse mounted), evaporation must be initiated on the wickless plate and condensation occurs on the opposing wick of the condenser. In this way, the fluid circulation in the device is choked and heat transfer is impeded. The device diodicity is tunable by changing the wettability pattern and can be adjusted as needed for different thermal applications. When the device operates as a VC, heat is effortlessly pumped out of the heat source; at the same time, the device blocks the undesirable heat backflow while working as a thermal diode. The present VC thermal diode apparatus could prove beneficial in a wide spectrum of thermal-management applications, such as aerospace, spacecraft, building materials, protection of electronics, packaging, refrigeration, thermal regulation during energy harvesting, thermal isolation, etc.
{"title":"Vapor Chamber with Wickless Condenser - Thermal Diode","authors":"G. Damoulakis, M. J. Gukeh, Theodore P. Koukoravas, C. Megaridis","doi":"10.1109/ITherm45881.2020.9190361","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190361","url":null,"abstract":"The term \"vapor chamber\" has been used to describe a device that spreads heat, as opposed to the term \"thermal diode\" that has been assigned to a device technically designed to prevent heat flow along a specific direction. In this study, a vapor chamber with a wickless, wettability-patterned condenser is fabricated and tested. The device takes advantage of the phase-changing properties of water, inside a closed loop comprised of a classical wick evaporator opposing a wickless wettability-patterned condenser. The wettability pattern facilitates spatially-controlled dropwise and filmwise condensation, and provides an efficient way to transport the condensate with specially-designed wedge tracks using capillary forces. The vapor chamber can also act as a thermal diode if the wickless condenser has a higher temperature than the wick, thus blocking heat flow in the opposite direction. When the device is performing as a vapor chamber (VC), the working medium evaporates from the hot superhydrophilic copper wick and condenses on the cold wickless condenser. The condensed water returns to the hot side of the device from strategically-placed superhydrophilic wells on the condenser, where condensate droplets accumulate, grow and ultimately bridge between the evaporator and the condenser. However, when the device is performing as a thermal diode (reverse mounted), evaporation must be initiated on the wickless plate and condensation occurs on the opposing wick of the condenser. In this way, the fluid circulation in the device is choked and heat transfer is impeded. The device diodicity is tunable by changing the wettability pattern and can be adjusted as needed for different thermal applications. When the device operates as a VC, heat is effortlessly pumped out of the heat source; at the same time, the device blocks the undesirable heat backflow while working as a thermal diode. The present VC thermal diode apparatus could prove beneficial in a wide spectrum of thermal-management applications, such as aerospace, spacecraft, building materials, protection of electronics, packaging, refrigeration, thermal regulation during energy harvesting, thermal isolation, etc.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"31 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125938351","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190541
Sougata Hazra, Alisha Piazza, K. Jung, M. Asheghi, M. Gupta, E. Jih, M. Degner, K. Goodson
3D Manifolded embedded Micro-Coolers (3DMMC) devices are becoming increasingly attractive and thereby, sought after active cooling solutions for high power density electronic components and devices. 3D-MMCs have shown the potential to effectively cool extreme levels of heat flux, characteristic of high- power density electronics and microprocessors. Despite numerous studies that have experimentally demonstrated promising performance of small area (25 mm2) micro-coolers, the challenges associated with fabrication of large area (>500 mm2) have not been adequately discussed or documented. This study discusses in details, a well validated, repeatable and reliable process flow for making 3D-MMC devices of sizes ranging from 10 mm2 to 1000 mm2 hotspot area via Silicon wafer microprocessing. Specifically, this study delves deep into the high aspect ratio (>10) anisotropic Silicon etching that is characteristic of such microfluidic devices. Additionally, we have provided insight into process development in Deep Reactive Ion Etching (DRIE) by discussing several issues that are frequently encountered during this deep Si etching step, namely, formation of black Si by photoresist micro-masking, high surface roughness resulting from deep etching and etch rate drop off. We have demonstrated the importance of tweaking etching and passivation cycle times during etching, by showing that merely 10% change in cycle times can eliminate these problems completely - this information is widely valuable to the Silicon microfabrication community. This study aims to document and disseminate a reliable high aspect ratio deep Si etching recipe that can be used to fabricate high performance large area microcooler devices, and will hopefully act as a starting point for fabrication efforts and new recipe development.
{"title":"Microfabrication Challenges for Silicon-based Large Area (>500 mm2) 3D-manifolded Embedded Microcooler Devices for High Heat Flux Removal","authors":"Sougata Hazra, Alisha Piazza, K. Jung, M. Asheghi, M. Gupta, E. Jih, M. Degner, K. Goodson","doi":"10.1109/ITherm45881.2020.9190541","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190541","url":null,"abstract":"3D Manifolded embedded Micro-Coolers (3DMMC) devices are becoming increasingly attractive and thereby, sought after active cooling solutions for high power density electronic components and devices. 3D-MMCs have shown the potential to effectively cool extreme levels of heat flux, characteristic of high- power density electronics and microprocessors. Despite numerous studies that have experimentally demonstrated promising performance of small area (25 mm2) micro-coolers, the challenges associated with fabrication of large area (>500 mm2) have not been adequately discussed or documented. This study discusses in details, a well validated, repeatable and reliable process flow for making 3D-MMC devices of sizes ranging from 10 mm2 to 1000 mm2 hotspot area via Silicon wafer microprocessing. Specifically, this study delves deep into the high aspect ratio (>10) anisotropic Silicon etching that is characteristic of such microfluidic devices. Additionally, we have provided insight into process development in Deep Reactive Ion Etching (DRIE) by discussing several issues that are frequently encountered during this deep Si etching step, namely, formation of black Si by photoresist micro-masking, high surface roughness resulting from deep etching and etch rate drop off. We have demonstrated the importance of tweaking etching and passivation cycle times during etching, by showing that merely 10% change in cycle times can eliminate these problems completely - this information is widely valuable to the Silicon microfabrication community. This study aims to document and disseminate a reliable high aspect ratio deep Si etching recipe that can be used to fabricate high performance large area microcooler devices, and will hopefully act as a starting point for fabrication efforts and new recipe development.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"221 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126038886","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190337
J. Sarkinen, Rickard Brännvall, Jonas Gustafsson, J. Summers
This paper analyzes the prospects of a holistic air-cooling strategy that enables synchronisation of data center facility fans and server fans to minimize data center energy use. Each server is equipped with a custom circuit board which controls the fans using a proportional, integral and derivative (PID) controller running on the servers operating system to maintain constant operating temperatures, irrespective of environmental conditions or workload. Experiments are carried out in a server wind tunnel which is controlled to mimic data center environmental conditions. The wind tunnel fan, humidifier and heater are controlled via separate PID controllers to maintain a prescribed pressure drop across the server with air entering at a defined temperature and humidity. The experiments demonstrate server operating temperatures which optimally trade off power losses versus server fan power, while examining the effect on the temperature difference, ∆T. Furthermore the results are theoretically applied to a direct fresh air cooled data center to obtain holistic sweet spots for the servers, revealing that the minimum energy use is already attained by factory control. Power consumption and Power Usage Effectiveness (PUE) are also compared, confirming that decreasing the PUE can increase the overall data center power consumption. Lastly the effect of decreased server inlet temperatures is examined showing that lower inlet temperatures can reduce both energy consumption and PUE.
{"title":"Experimental Analysis of Server Fan Control Strategies for Improved Data Center Air-based Thermal Management*","authors":"J. Sarkinen, Rickard Brännvall, Jonas Gustafsson, J. Summers","doi":"10.1109/ITherm45881.2020.9190337","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190337","url":null,"abstract":"This paper analyzes the prospects of a holistic air-cooling strategy that enables synchronisation of data center facility fans and server fans to minimize data center energy use. Each server is equipped with a custom circuit board which controls the fans using a proportional, integral and derivative (PID) controller running on the servers operating system to maintain constant operating temperatures, irrespective of environmental conditions or workload. Experiments are carried out in a server wind tunnel which is controlled to mimic data center environmental conditions. The wind tunnel fan, humidifier and heater are controlled via separate PID controllers to maintain a prescribed pressure drop across the server with air entering at a defined temperature and humidity. The experiments demonstrate server operating temperatures which optimally trade off power losses versus server fan power, while examining the effect on the temperature difference, ∆T. Furthermore the results are theoretically applied to a direct fresh air cooled data center to obtain holistic sweet spots for the servers, revealing that the minimum energy use is already attained by factory control. Power consumption and Power Usage Effectiveness (PUE) are also compared, confirming that decreasing the PUE can increase the overall data center power consumption. Lastly the effect of decreased server inlet temperatures is examined showing that lower inlet temperatures can reduce both energy consumption and PUE.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125267216","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190394
Jie Zhao, Xianguang Tan, Yajun Pan, Yong Sheng, Hongmei Liu, Jiajun Zhang, Jing Liu, Jun Zhang, Carrie Chen, N. Ahuja
Higher computing capability, higher density and better energy efficiency have always been the goal of data centers. Cross different factors, IT equipment, specifically as server is playing the crucial role in a data center development. CPU/GPU and other hardware ingredients’ computing capability keeps growth with innovated architecture and procedure upgrade, while comes along with increasing server power consumption as well as challenge for energy efficiency. Compared with conventional server system with dedicated fans and power supply units, design optimizations from rack level has been leading evolution to help data center to achieve those goals.This paper introduces an advanced rack scale power and thermal solution pilot deployed in Baidu new self-build data center. With the design, total rack power capacity is up to 36KW, which brings significant improvement for node density. Moreover,48V power distribution is implemented for better rack power efficiency, and centralized power shelf design with dual-input power source halves total PSU quantity for rack space saving and node density increase. Thermal solution is addressed from rack level as well, centralized fan wall provides air flow for whole rack, and thermosyphon heatsink is implemented in each node from higher heat dissipate efficiency perspective. With all the advanced technology integrated and optimized together, detailed energy efficiency contribution to Total Cost Ownership (TCO) is summarized and compared with conventional rack design and shows the advantages for data center energy efficiency.
{"title":"An Advanced Power and Thermal Optimized High Density Rack Solution for Data Center Energy Efficiency","authors":"Jie Zhao, Xianguang Tan, Yajun Pan, Yong Sheng, Hongmei Liu, Jiajun Zhang, Jing Liu, Jun Zhang, Carrie Chen, N. Ahuja","doi":"10.1109/ITherm45881.2020.9190394","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190394","url":null,"abstract":"Higher computing capability, higher density and better energy efficiency have always been the goal of data centers. Cross different factors, IT equipment, specifically as server is playing the crucial role in a data center development. CPU/GPU and other hardware ingredients’ computing capability keeps growth with innovated architecture and procedure upgrade, while comes along with increasing server power consumption as well as challenge for energy efficiency. Compared with conventional server system with dedicated fans and power supply units, design optimizations from rack level has been leading evolution to help data center to achieve those goals.This paper introduces an advanced rack scale power and thermal solution pilot deployed in Baidu new self-build data center. With the design, total rack power capacity is up to 36KW, which brings significant improvement for node density. Moreover,48V power distribution is implemented for better rack power efficiency, and centralized power shelf design with dual-input power source halves total PSU quantity for rack space saving and node density increase. Thermal solution is addressed from rack level as well, centralized fan wall provides air flow for whole rack, and thermosyphon heatsink is implemented in each node from higher heat dissipate efficiency perspective. With all the advanced technology integrated and optimized together, detailed energy efficiency contribution to Total Cost Ownership (TCO) is summarized and compared with conventional rack design and shows the advantages for data center energy efficiency.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116126515","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190438
K. Sridhar, Ryan Smith, V. Narayanan, S. Bhavnani
This experimental, terrestrial study is part of a larger effort to dissipate increased heat fluxes through enhanced pool boiling in spacecraft electronics prior to an extensive study to be conducted on the International Space Station under pristine microgravity conditions. The absence of buoyancy forces in microgravity causes vapor bubbles to grow to a very large size, leading to premature critical heat flux (CHF). Using an engineered surface modification, namely an asymmetric sawtooth ratchet, to create mobility of the vapor mass can alleviate this problem. The stainless steel (SS 316L) test surfaces were fabricated using powder bed fusion, a metal additive manufacturing process. Vapor mobility was observed in the downward-facing configuration for the asymmetric sawtooth structure explored in the stud y. A thin liquid film was observed underneath the vapor bubbles as they slid along the microstructure. The asymmetric nature of this liquid film is explored using high-speed imaging at the crest and trough of the sawtooth. The proposed asymmetric saw-tooth microstructure is a potential technique to induce motion of vapor bubbles across electronic components when reduced buoyancy forces do not detach vapor bubbles from the surface.
{"title":"Phase Change Cooling of Spacecraft Electronics: Terrestrial Reference Experiments Prior to ISS Microgravity Experiments","authors":"K. Sridhar, Ryan Smith, V. Narayanan, S. Bhavnani","doi":"10.1109/ITherm45881.2020.9190438","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190438","url":null,"abstract":"This experimental, terrestrial study is part of a larger effort to dissipate increased heat fluxes through enhanced pool boiling in spacecraft electronics prior to an extensive study to be conducted on the International Space Station under pristine microgravity conditions. The absence of buoyancy forces in microgravity causes vapor bubbles to grow to a very large size, leading to premature critical heat flux (CHF). Using an engineered surface modification, namely an asymmetric sawtooth ratchet, to create mobility of the vapor mass can alleviate this problem. The stainless steel (SS 316L) test surfaces were fabricated using powder bed fusion, a metal additive manufacturing process. Vapor mobility was observed in the downward-facing configuration for the asymmetric sawtooth structure explored in the stud y. A thin liquid film was observed underneath the vapor bubbles as they slid along the microstructure. The asymmetric nature of this liquid film is explored using high-speed imaging at the crest and trough of the sawtooth. The proposed asymmetric saw-tooth microstructure is a potential technique to induce motion of vapor bubbles across electronic components when reduced buoyancy forces do not detach vapor bubbles from the surface.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122700499","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190262
Zhaoxi Yao, Yonatan Saadon, R. Mandel, F. Patrick McCluskey
Reduction of carbon emissions and energy savings are driving the development of lightweight, high efficiency, electric motor systems containing integrated power electronics. Thermal management is one of the major obstacles in high power density electric motor development. For high power interior permanent magnet motors, the heat loss is mainly generated in three locations: the stator core, the stator windings and the power electronics that are used to drive the motor. A compact thermal management system is developed and presented in this paper, which consists of a manifold microchannel cooling jacket, used for cooling both the stator core and power electronics, and a direct winding cooling approach employing hollow conductors.The cooling jacket has an overall ring-shaped structure, with the inner surface in contact with the stator core, and the outer surface in contact with the power electronics. A complex fluid path is designed inside the cooling jacket to lower the pressure drop and pumping power while increasing its thermal performance. For directly cooling the windings, hollow conductors allow the coolant to flow inside the conductor. This direct contact means it can handle very high heat loss. It also decouples the thermal and electrical aspects for choosing a wire insulation material. Since the heat generated in the conductor flows inwards without passing through the electric insulation, thermal conductivity doesn’t need to be a constraint to the choice of insulation material. Four different hollow conductor configurations, including one circular hollow conductor and three rectangular hollow conductor shapes, are evaluated and discussed in this study.
{"title":"Cooling of Integrated Electric Motors","authors":"Zhaoxi Yao, Yonatan Saadon, R. Mandel, F. Patrick McCluskey","doi":"10.1109/ITherm45881.2020.9190262","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190262","url":null,"abstract":"Reduction of carbon emissions and energy savings are driving the development of lightweight, high efficiency, electric motor systems containing integrated power electronics. Thermal management is one of the major obstacles in high power density electric motor development. For high power interior permanent magnet motors, the heat loss is mainly generated in three locations: the stator core, the stator windings and the power electronics that are used to drive the motor. A compact thermal management system is developed and presented in this paper, which consists of a manifold microchannel cooling jacket, used for cooling both the stator core and power electronics, and a direct winding cooling approach employing hollow conductors.The cooling jacket has an overall ring-shaped structure, with the inner surface in contact with the stator core, and the outer surface in contact with the power electronics. A complex fluid path is designed inside the cooling jacket to lower the pressure drop and pumping power while increasing its thermal performance. For directly cooling the windings, hollow conductors allow the coolant to flow inside the conductor. This direct contact means it can handle very high heat loss. It also decouples the thermal and electrical aspects for choosing a wire insulation material. Since the heat generated in the conductor flows inwards without passing through the electric insulation, thermal conductivity doesn’t need to be a constraint to the choice of insulation material. Four different hollow conductor configurations, including one circular hollow conductor and three rectangular hollow conductor shapes, are evaluated and discussed in this study.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"123 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122487675","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190372
S. Joshi, Feng Zhou, E. Dede, Danny J. Lohan, S. Sudhakar, J. Weibel
Silicon carbide (SiC) semiconductors have been identified to have potential to replace silicon devices due to superior electrical and thermal properties for a range of power conversion applications. For electrified vehicle applications, the device configuration leads to high current rates, and this in turn leads to high heat fluxes (~1 kW/cm2) over large bare dies (~1 cm2). SiC devices are capable of operating at higher junction temperatures than Si devices, which warrants revisiting air-cooling solutions that are more simple and reliable than liquid cooling. To enable air cooling for high heat flux dissipation, transformative heat spreading technologies must be developed to increase the heat sink footprint area considering the relatively low heat transfer coefficients available. An advanced vapor chamber technology is being investigated for spreading the high heat fluxes generated by next-generation wide band-gap power devices. For vapor chamber heat spreaders to operate at very high heat fluxes over large areas, the internal wick layer at the evaporator must simultaneously minimize the device temperature rise and the flow resistance to liquid resupply by capillary action during boiling. In this study, a vapor chamber is investigated having an embedded two-layer evaporator wick designed to decouple the functions of liquid resupply (through a cap layer) and capillary-fed boiling heat transfer (within a base layer). The performance of a 50 mm × 50 mm × 5.5 mm vapor chamber with an embedded two-layer evaporator wick is evaluated as the heat spreader under a straight pin fin heat sink cooled via air jet impingement for a 1 cm2 area heat source. The maximum dryout heat flux and thermal resistance are compared with that of a vapor chamber having a traditional monolayer evaporator wick. At a power dissipation of ~500 W, the air-cooled two-layer wick vapor chamber provides a 12% reduction in the thermal resistance compared to the monolayer wick vapor chamber assembly. The results indicate that the design of the evaporator wick of the vapor chamber plays a critical role in determining the overall thermal resistance of the heat sink plus spreader assembly.
碳化硅(SiC)半导体由于在一系列功率转换应用中具有优越的电学和热学性能，已被确定具有取代硅器件的潜力。对于电动汽车应用，器件配置导致高电流速率，这反过来又导致大裸模(~1 cm2)上的高热通量(~1 kW/cm2)。SiC器件能够在比Si器件更高的结温下工作，这就需要重新考虑比液体冷却更简单、更可靠的空气冷却解决方案。为了实现高热流通量的空气冷却，必须开发变革性的散热技术，以考虑到相对较低的热传递系数，从而增加散热器的占地面积。为了扩散下一代宽带隙功率器件产生的高热流，研究了一种先进的蒸汽室技术。为了使蒸汽室换热器在大面积上以非常高的热流密度运行，蒸发器的内部芯层必须同时最小化设备温升和沸腾过程中毛细作用对液体补给的流动阻力。在本研究中，研究了一个具有嵌入式两层蒸发器芯的蒸汽室，该蒸发器芯设计用于解耦液体补给(通过帽层)和毛细管沸腾传热(在基础层内)的功能。在1 cm2面积的热源下，对带两层蒸发器芯的50 mm × 50 mm × 5.5 mm蒸汽室的散热性能进行了评价。并与具有传统单层蒸发器芯的蒸汽室进行了最大干热流密度和热阻的比较。在约500 W的功耗下，风冷两层灯芯蒸汽室与单层灯芯蒸汽室组件相比，热阻降低了12%。结果表明，蒸汽室蒸发器芯芯的设计对散热器加扩散器总成的整体热阻起着至关重要的作用。
{"title":"Thermal Performance Evaluation of a Two-Layer Wick Vapor Chamber for High Heat Flux Dissipation by Air Cooling","authors":"S. Joshi, Feng Zhou, E. Dede, Danny J. Lohan, S. Sudhakar, J. Weibel","doi":"10.1109/ITherm45881.2020.9190372","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190372","url":null,"abstract":"Silicon carbide (SiC) semiconductors have been identified to have potential to replace silicon devices due to superior electrical and thermal properties for a range of power conversion applications. For electrified vehicle applications, the device configuration leads to high current rates, and this in turn leads to high heat fluxes (~1 kW/cm2) over large bare dies (~1 cm2). SiC devices are capable of operating at higher junction temperatures than Si devices, which warrants revisiting air-cooling solutions that are more simple and reliable than liquid cooling. To enable air cooling for high heat flux dissipation, transformative heat spreading technologies must be developed to increase the heat sink footprint area considering the relatively low heat transfer coefficients available. An advanced vapor chamber technology is being investigated for spreading the high heat fluxes generated by next-generation wide band-gap power devices. For vapor chamber heat spreaders to operate at very high heat fluxes over large areas, the internal wick layer at the evaporator must simultaneously minimize the device temperature rise and the flow resistance to liquid resupply by capillary action during boiling. In this study, a vapor chamber is investigated having an embedded two-layer evaporator wick designed to decouple the functions of liquid resupply (through a cap layer) and capillary-fed boiling heat transfer (within a base layer). The performance of a 50 mm × 50 mm × 5.5 mm vapor chamber with an embedded two-layer evaporator wick is evaluated as the heat spreader under a straight pin fin heat sink cooled via air jet impingement for a 1 cm2 area heat source. The maximum dryout heat flux and thermal resistance are compared with that of a vapor chamber having a traditional monolayer evaporator wick. At a power dissipation of ~500 W, the air-cooled two-layer wick vapor chamber provides a 12% reduction in the thermal resistance compared to the monolayer wick vapor chamber assembly. The results indicate that the design of the evaporator wick of the vapor chamber plays a critical role in determining the overall thermal resistance of the heat sink plus spreader assembly.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"83 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122025411","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 : 2020-07-01DOI: 10.1109/ITherm45881.2020.9190379
Adam A. Wilson, R. Warzoha, D. Sharar, A. Smith
Thermal resistance arises at the interface of two different materials. However, developers of sensors, electronics, and power conversion devices often ignore this effect. The additional thermal resistance imposed due to interface can enhance sensitivity of thermal sensors, and efficiency of thermal energy harvesting devices such as thermoelectrics. This work demonstrates that the effect of interfaces cannot, and should not, be ignored when dealing with many interfaces in a system. We use frequency-domain thermoreflectance to demonstrate that nanolaminate thin films significantly reduce the overall thermal conductance of the film stack. As an example, with 500nm total film thickness, a repeated period of 10nm each of high thermal conductivity aluminum (kbulk,Al = 212 Wm-1K-1) and silicon dioxide (kbulk,SiO2 = 1.4 Wm-1K-1) have measured effective thermal conductivity less than that of silicon dioxide alone (1.20 Wm-1K-1 vs 1.38 Wm-1K-1). While this is substantial, the diffuse mismatch model (which often over-predicts thermal conductance of single interfaces) predicts an even lower value of effective thermal conductivity (0.56 Wm-1K-1), meaning much lower nanolaminate thermal conductivity could be realized with appropriate treatment of the surface where an interface will form.
{"title":"Interface Density Effects on Cross-Plane Thermal Conductance of Nanolaminate Thin Films","authors":"Adam A. Wilson, R. Warzoha, D. Sharar, A. Smith","doi":"10.1109/ITherm45881.2020.9190379","DOIUrl":"https://doi.org/10.1109/ITherm45881.2020.9190379","url":null,"abstract":"Thermal resistance arises at the interface of two different materials. However, developers of sensors, electronics, and power conversion devices often ignore this effect. The additional thermal resistance imposed due to interface can enhance sensitivity of thermal sensors, and efficiency of thermal energy harvesting devices such as thermoelectrics. This work demonstrates that the effect of interfaces cannot, and should not, be ignored when dealing with many interfaces in a system. We use frequency-domain thermoreflectance to demonstrate that nanolaminate thin films significantly reduce the overall thermal conductance of the film stack. As an example, with 500nm total film thickness, a repeated period of 10nm each of high thermal conductivity aluminum (kbulk,Al = 212 Wm-1K-1) and silicon dioxide (kbulk,SiO2 = 1.4 Wm-1K-1) have measured effective thermal conductivity less than that of silicon dioxide alone (1.20 Wm-1K-1 vs 1.38 Wm-1K-1). While this is substantial, the diffuse mismatch model (which often over-predicts thermal conductance of single interfaces) predicts an even lower value of effective thermal conductivity (0.56 Wm-1K-1), meaning much lower nanolaminate thermal conductivity could be realized with appropriate treatment of the surface where an interface will form.","PeriodicalId":193052,"journal":{"name":"2020 19th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"111 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2020-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122085687","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：