Pub Date : 2017-05-01DOI: 10.1109/ITHERM.2017.7991853
Thomas L. Rougher, Luke Yates, Zhe Cheng, B. Cola, S. Graham, Ramez Chaeito, A. Sood, M. Ashegi, K. Goodson
Diamond has the highest known thermal conductivity of any known bulk material, but the properties of synthetic diamond films often fall far short of this high level. The DARPA program Thermal Transport in Diamond Films for Electronics Thermal Management brings together researchers from five universities to comprehensively characterize the thermal transport and material properties of CVD diamond thin films in an effort to better how to further improve the thermal transport properties and understand how accurately these properties can be measured using time domain thermoreflectance and Raman spectroscopy. Here we summarize the results of the thermal measurements of diamond conducted via time domain thermoreflectance (TDTR) using two different systems and discuss some difficulties of accurately measuring the thermal conductivity of micron-thick anisotropic films that often have high surface roughness. We also report that in certain cases the thermal conductivity and thermal boundary conductance of CVD diamond films has been improved to the point of making them highly attractive for thermal management of high power electronic devices.
{"title":"Experimental considerations of CVD diamond film measurements using time domain thermoreflectance","authors":"Thomas L. Rougher, Luke Yates, Zhe Cheng, B. Cola, S. Graham, Ramez Chaeito, A. Sood, M. Ashegi, K. Goodson","doi":"10.1109/ITHERM.2017.7991853","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7991853","url":null,"abstract":"Diamond has the highest known thermal conductivity of any known bulk material, but the properties of synthetic diamond films often fall far short of this high level. The DARPA program Thermal Transport in Diamond Films for Electronics Thermal Management brings together researchers from five universities to comprehensively characterize the thermal transport and material properties of CVD diamond thin films in an effort to better how to further improve the thermal transport properties and understand how accurately these properties can be measured using time domain thermoreflectance and Raman spectroscopy. Here we summarize the results of the thermal measurements of diamond conducted via time domain thermoreflectance (TDTR) using two different systems and discuss some difficulties of accurately measuring the thermal conductivity of micron-thick anisotropic films that often have high surface roughness. We also report that in certain cases the thermal conductivity and thermal boundary conductance of CVD diamond films has been improved to the point of making them highly attractive for thermal management of high power electronic devices.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"118 1-2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114030873","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992539
S. D. Marshall, R. Arayanarakool, L. Balasubramaniam, Bing Li, P. Lee, Peter C. Y. Chen
In order to improve upon a conventional straight microchannel heat sink, a range of curved, angular and wavy microchannels were designed in order to increase fluid mixing via the occurrence of secondary flow interactions, in particular Dean vortices, hence augmenting heat transport. Both numerical models conducted in FLUENT and laboratory experiments were employed to investigate the heat transfer enhancement of a range of geometries (single curved, wavy, sawtooth, U-turn and square-wave). In both studies, every channel demonstrated significantly higher Nusselt Numbers and Thermal Performance Factors (TPF) than an equivalent straight channel, despite an increase in pressure drop. The relative order of the channels in terms of TPF was the same for both experiments and numerical simulations, with the exception of the U-turn channel which performed better in the former. However, experimental TPF results were found to be 15–20% of those from the simulation — these differences are associated with the relative simplicity of the numerical model and additional non-linear impacts in the experiments. Overall, wavy channels were found to have superior performance, especially over angular channels with sharp turns, thus it is suggested that wavy microchannels are the most advantageous designs for the development of heat sinks, especially in terms of minimising pressure drop whilst still making use of the enhanced heat transfer properties of Dean vortices. Finally, for a given wavy channel, an optimal input flow rate condition is also determined.
{"title":"Heat exchanger improvement via curved, angular and wavy microfluidic channels: A comparison of numerical and experimental results","authors":"S. D. Marshall, R. Arayanarakool, L. Balasubramaniam, Bing Li, P. Lee, Peter C. Y. Chen","doi":"10.1109/ITHERM.2017.7992539","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992539","url":null,"abstract":"In order to improve upon a conventional straight microchannel heat sink, a range of curved, angular and wavy microchannels were designed in order to increase fluid mixing via the occurrence of secondary flow interactions, in particular Dean vortices, hence augmenting heat transport. Both numerical models conducted in FLUENT and laboratory experiments were employed to investigate the heat transfer enhancement of a range of geometries (single curved, wavy, sawtooth, U-turn and square-wave). In both studies, every channel demonstrated significantly higher Nusselt Numbers and Thermal Performance Factors (TPF) than an equivalent straight channel, despite an increase in pressure drop. The relative order of the channels in terms of TPF was the same for both experiments and numerical simulations, with the exception of the U-turn channel which performed better in the former. However, experimental TPF results were found to be 15–20% of those from the simulation — these differences are associated with the relative simplicity of the numerical model and additional non-linear impacts in the experiments. Overall, wavy channels were found to have superior performance, especially over angular channels with sharp turns, thus it is suggested that wavy microchannels are the most advantageous designs for the development of heat sinks, especially in terms of minimising pressure drop whilst still making use of the enhanced heat transfer properties of Dean vortices. Finally, for a given wavy channel, an optimal input flow rate condition is also determined.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122895544","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992469
Farah Singer, D. Deisenroth, David M. Hymas, M. Ohadi
Recently additive manufacturing (AM) has brought significant innovation to thermal management devices and electronics. Among the most influential innovations are additively manufactured copper/copper alloy components and composites that benefit from the superior thermal, electrical and structural properties of the material. Cu is widely used in electronics, HVACR, radiators, charge air coolers, brazed plate heat exchangers, and oil cooling. Ongoing research is extensively studying, in parallel, Cu properties/characteristics and the different AM process parameters required to enhance the quality of the manufactured Cu components and to optimize their performance/applications. In this paper, we report various AM techniques and AM-based hybrid processes used to produce high-density Cu components. Selective heat exchanger/thermal management applications progress is also reviewed. It is then shown that additively manufactured, dense Cu can generate low mass structures and polymer/metal composites that promise to revolutionize developments in thermal management applications. Studies on the effect of the material properties such as the Cu particle morphology and size distribution are also reported. The major studies that report using Cu to address the challenges of electronics fabrication and cooling, which directly affect system-level performance and reliability, are also discussed. A novel AM process that facilitates microchannel cooling with Cu structures and new processes that allow embedding copper wires into thermoplastic dielectric structures are discussed to further emphasize the potentially transformative advances in additively manufactured electronics and thermal management devices using Cu/Cu alloy composites.
{"title":"Additively manufactured copper components and composite structures for thermal management applications","authors":"Farah Singer, D. Deisenroth, David M. Hymas, M. Ohadi","doi":"10.1109/ITHERM.2017.7992469","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992469","url":null,"abstract":"Recently additive manufacturing (AM) has brought significant innovation to thermal management devices and electronics. Among the most influential innovations are additively manufactured copper/copper alloy components and composites that benefit from the superior thermal, electrical and structural properties of the material. Cu is widely used in electronics, HVACR, radiators, charge air coolers, brazed plate heat exchangers, and oil cooling. Ongoing research is extensively studying, in parallel, Cu properties/characteristics and the different AM process parameters required to enhance the quality of the manufactured Cu components and to optimize their performance/applications. In this paper, we report various AM techniques and AM-based hybrid processes used to produce high-density Cu components. Selective heat exchanger/thermal management applications progress is also reviewed. It is then shown that additively manufactured, dense Cu can generate low mass structures and polymer/metal composites that promise to revolutionize developments in thermal management applications. Studies on the effect of the material properties such as the Cu particle morphology and size distribution are also reported. The major studies that report using Cu to address the challenges of electronics fabrication and cooling, which directly affect system-level performance and reliability, are also discussed. A novel AM process that facilitates microchannel cooling with Cu structures and new processes that allow embedding copper wires into thermoplastic dielectric structures are discussed to further emphasize the potentially transformative advances in additively manufactured electronics and thermal management devices using Cu/Cu alloy composites.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122996233","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992520
S. Sudhakar, J. Weibel, S. Garimella
For vapor chamber heat spreaders to operate at very high heat fluxes, the internal wick layer at the evaporator must simultaneously minimize the device temperature rise and the flow resistance to liquid resupply by capillary action. Prior investigations in the literature have reported sustained capillary-fed boiling at heat fluxes as high as 1 kW/cm2 for small hotspots of significantly less than ∼1 cm2. However, the need to provide liquid feeding to avoid dryout prevents high levels of heat fluxes from being dissipated over areas any larger than localized hotspots. Thin layers of homogeneous evaporator wicks can help reduce the thermal resistance across the layer, but fail to sustain adequate liquid supply at high heat fluxes or over large areas. Thicker evaporator wicks offer greater flow cross-sections to better feed liquid to the evaporator by capillary action, but induce unacceptably large surface superheats due to the high thermal resistance across these thick layers. This work proposes and analyzes a hybrid two-layer evaporator wick for passive, high-heat-flux dissipation. A thick cap layer of wick material evenly routes liquid to a thin, low-thermal-resistance base layer through an array of vertical liquid-feeding posts. This two-layer structure decouples the functions of liquid resupply (cap layer) and capillary-fed boiling heat transfer (base layer), making the design scalable to heat input areas of ∼1 cm2 for operation at 1 kW/cm2. A model is developed to demonstrate the potential performance of a vapor chamber incorporating such a two-layer evaporator wick design and to establish the target sizes of critical wick features that must be fabricated. The model comprises simplified hydraulic and thermal resistance networks for predicting the capillary-limited maximum heat flux and the overall thermal resistance, respectively. The performance of the vapor chamber is analyzed with varying two-layer wick geometric feature sizes.
{"title":"An area-scalable two-layer evaporator wick concept for high-heat-flux vapor chambers","authors":"S. Sudhakar, J. Weibel, S. Garimella","doi":"10.1109/ITHERM.2017.7992520","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992520","url":null,"abstract":"For vapor chamber heat spreaders to operate at very high heat fluxes, the internal wick layer at the evaporator must simultaneously minimize the device temperature rise and the flow resistance to liquid resupply by capillary action. Prior investigations in the literature have reported sustained capillary-fed boiling at heat fluxes as high as 1 kW/cm2 for small hotspots of significantly less than ∼1 cm2. However, the need to provide liquid feeding to avoid dryout prevents high levels of heat fluxes from being dissipated over areas any larger than localized hotspots. Thin layers of homogeneous evaporator wicks can help reduce the thermal resistance across the layer, but fail to sustain adequate liquid supply at high heat fluxes or over large areas. Thicker evaporator wicks offer greater flow cross-sections to better feed liquid to the evaporator by capillary action, but induce unacceptably large surface superheats due to the high thermal resistance across these thick layers. This work proposes and analyzes a hybrid two-layer evaporator wick for passive, high-heat-flux dissipation. A thick cap layer of wick material evenly routes liquid to a thin, low-thermal-resistance base layer through an array of vertical liquid-feeding posts. This two-layer structure decouples the functions of liquid resupply (cap layer) and capillary-fed boiling heat transfer (base layer), making the design scalable to heat input areas of ∼1 cm2 for operation at 1 kW/cm2. A model is developed to demonstrate the potential performance of a vapor chamber incorporating such a two-layer evaporator wick design and to establish the target sizes of critical wick features that must be fabricated. The model comprises simplified hydraulic and thermal resistance networks for predicting the capillary-limited maximum heat flux and the overall thermal resistance, respectively. The performance of the vapor chamber is analyzed with varying two-layer wick geometric feature sizes.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124298260","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992570
S. Alkharabsheh, Bharath Ramakrishnan, B. Sammakia
This study presents an experimental and numerical characterization of pressure drop in a commercially available direct liquid cooled (DLC) rack. It is important to investigate the pressure drop in the DLC system as it determines the required pumping power for the DLC system, which affects the energy efficiency of the data center. The main objective of this research is to assess the flow rate and pressure distributions in a DLC system to enhance the reliability and the cooling system efficiency. Other objectives of this research are to evaluate the accuracy of flow network modeling (FNM) in predicting the flow distribution in a DLC rack and identify manufacturing limitations in a commercial system that could impact the cooling system reliability. The main components of the investigated DLC system are: coolant distribution module (CDM), supply/return manifold module, and server module which contains a cold plate. Extensive experimental measurements were performed to study the flow distribution and to determine the pressure characteristic curves for the server modules and the coolant distribution module (CDM). Also, a methodology was described to develop an experimentally validated flow network model (FNM) of the DLC system to obtain high accuracy. The measurements revealed a flow maldistribution among the server modules, which is attributed to the manufacturing process of the micro-channel cold plate. The average errors in predicting the flow rate of the server module and the CDM using FNM are 2.5% and 3.8%, respectively. The accuracy and the short run time make FNM a good tool for design, analysis, and optimization for DLC systems. The pressure drop in the server module is found to account for 56% of the total pressure drop in the DLC rack. Further analysis showed that 69% of the pressure drop in the server module is associated with the module's plumbing (corrugated hoses, disconnects, fittings). The server cooling modules are designed to provide secured connections and flexibility, which come with a high pressure drop cost.
{"title":"Pressure drop analysis of direct liquid cooled (DLC) rack","authors":"S. Alkharabsheh, Bharath Ramakrishnan, B. Sammakia","doi":"10.1109/ITHERM.2017.7992570","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992570","url":null,"abstract":"This study presents an experimental and numerical characterization of pressure drop in a commercially available direct liquid cooled (DLC) rack. It is important to investigate the pressure drop in the DLC system as it determines the required pumping power for the DLC system, which affects the energy efficiency of the data center. The main objective of this research is to assess the flow rate and pressure distributions in a DLC system to enhance the reliability and the cooling system efficiency. Other objectives of this research are to evaluate the accuracy of flow network modeling (FNM) in predicting the flow distribution in a DLC rack and identify manufacturing limitations in a commercial system that could impact the cooling system reliability. The main components of the investigated DLC system are: coolant distribution module (CDM), supply/return manifold module, and server module which contains a cold plate. Extensive experimental measurements were performed to study the flow distribution and to determine the pressure characteristic curves for the server modules and the coolant distribution module (CDM). Also, a methodology was described to develop an experimentally validated flow network model (FNM) of the DLC system to obtain high accuracy. The measurements revealed a flow maldistribution among the server modules, which is attributed to the manufacturing process of the micro-channel cold plate. The average errors in predicting the flow rate of the server module and the CDM using FNM are 2.5% and 3.8%, respectively. The accuracy and the short run time make FNM a good tool for design, analysis, and optimization for DLC systems. The pressure drop in the server module is found to account for 56% of the total pressure drop in the DLC rack. Further analysis showed that 69% of the pressure drop in the server module is associated with the module's plumbing (corrugated hoses, disconnects, fittings). The server cooling modules are designed to provide secured connections and flexibility, which come with a high pressure drop cost.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"2672 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133929835","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992626
B. Wunderle, D. May, M. A. Ras, J. Keller
We have developed a novel, rapid, robust and non-destructive experimental technique for in-situ monitoring of delamination of interfaces for electronic packages. The method is based on a simple thermal transducer matrix of so-called THIXELS (thermal pixels) which allows a spatially resolved real-time image of the current status of delamination. The transducers are small metal wire meanders which are driven and electrically read out using the well-known 3-omega method. This method has special advantages over other thermal contrast methods with respect to robustness, sensitivity and signal-to-noise ratio. Notable is the absence of cross-effects. The proof of concept has been furnished on an industry-grade flip-chip package with underfill on an organic substrate. The technique is especially powerful for buried interfaces, where time-honoured methods like scanning acoustic microscopy (SAM) cannot be applied. As the technique effectively performs a thermal diffusivity sensitive scan, it may not only be useful for stress testing during package qualification, but sensor applications on other fields of health monitoring seem also possible.
{"title":"Non-destructive in-situ monitoring of delamination of buried interfaces by a thermal pixel (Thixel) chip","authors":"B. Wunderle, D. May, M. A. Ras, J. Keller","doi":"10.1109/ITHERM.2017.7992626","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992626","url":null,"abstract":"We have developed a novel, rapid, robust and non-destructive experimental technique for in-situ monitoring of delamination of interfaces for electronic packages. The method is based on a simple thermal transducer matrix of so-called THIXELS (thermal pixels) which allows a spatially resolved real-time image of the current status of delamination. The transducers are small metal wire meanders which are driven and electrically read out using the well-known 3-omega method. This method has special advantages over other thermal contrast methods with respect to robustness, sensitivity and signal-to-noise ratio. Notable is the absence of cross-effects. The proof of concept has been furnished on an industry-grade flip-chip package with underfill on an organic substrate. The technique is especially powerful for buried interfaces, where time-honoured methods like scanning acoustic microscopy (SAM) cannot be applied. As the technique effectively performs a thermal diffusivity sensitive scan, it may not only be useful for stress testing during package qualification, but sensor applications on other fields of health monitoring seem also possible.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132574708","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992595
Xingjian Yu, Yupu Ma, B. Shang, Bin Xie, Qi Chen, Xiaobing Luo
Dip-transfer phosphor coating method and its benefit on enhancing angular color uniformity (ACU) of white light-emitting diodes (LEDs) were previously reported, however, for applying this method in mass production, its fluid transfer mechanism and packaging consistency needs to be further investigated. The dip-transfer process is divided into two process, they are dipping process and transfer process. In our previous study, the dipping process were studied with experiments and simulations. In this study, we further studied the transfer process with numerical simulations based on combination of the volume of fluid (VOF) method and the dynamic mesh model, four parameters include post radius, withdrawal velocity, transfer height and phosphor gel viscosity were investigated. Besides, the packaging consistency of the dip-transfer phosphor coating method was studied with experiments. The simulated results show that the transfer volume decreases with the post radius, phosphor withdrawal velocity and phosphor gel viscosity, while keep the same with the transfer height. The experimental results show that the packaging consistency is highly rely on the transfer volume, with transfer volume varies from 0.71 μl to 6.12 ul, the maximum transfer volume deviation (MTVD) changes from 6.98% to 2.31%.
{"title":"Investigation on dip-transfer phosphor coating for light-emitting diodes: Experiments and VOF simulations","authors":"Xingjian Yu, Yupu Ma, B. Shang, Bin Xie, Qi Chen, Xiaobing Luo","doi":"10.1109/ITHERM.2017.7992595","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992595","url":null,"abstract":"Dip-transfer phosphor coating method and its benefit on enhancing angular color uniformity (ACU) of white light-emitting diodes (LEDs) were previously reported, however, for applying this method in mass production, its fluid transfer mechanism and packaging consistency needs to be further investigated. The dip-transfer process is divided into two process, they are dipping process and transfer process. In our previous study, the dipping process were studied with experiments and simulations. In this study, we further studied the transfer process with numerical simulations based on combination of the volume of fluid (VOF) method and the dynamic mesh model, four parameters include post radius, withdrawal velocity, transfer height and phosphor gel viscosity were investigated. Besides, the packaging consistency of the dip-transfer phosphor coating method was studied with experiments. The simulated results show that the transfer volume decreases with the post radius, phosphor withdrawal velocity and phosphor gel viscosity, while keep the same with the transfer height. The experimental results show that the packaging consistency is highly rely on the transfer volume, with transfer volume varies from 0.71 μl to 6.12 ul, the maximum transfer volume deviation (MTVD) changes from 6.98% to 2.31%.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133081976","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}
The development of newer and more efficient cooling techniques to sustain the increasing power density of high-performance computing systems is becoming one of the major challenges in the development of microelectronics. In this framework, two-phase cooling is a promising solution for dissipating the greater amount of generated heat. In the present study an experimental investigation of two-phase flow boiling in a micro-pin fin evaporator is performed. The micro-evaporator has a heated area of 1 cm2 containing 66 rows of cylindrical in-line micro-pin fins with diameter, height and pitch of respectively 50 μm, 100 μm and 91.7 μm. At the entrance of the heated area an extra row of micro-pin fins with a larger diameter of 100 μm acts as inlet restrictions to avoid flow instabilities. The working fluid is R1234ze(E) tested over a wide range of conditions: mass fluxes varying from 750 kg/m2s to 1750 kg/m2s and heat fluxes ranging from 20 W/cm2 to 44 W/cm2 while maintaining a constant outlet saturation temperature of 35 °C. In order to assess the thermal-hydraulic performance of the current heat sink, the total pressure drops are directly measured, while local values of heat transfer coefficient are evaluated by coupling high speed flow visualization with infrared temperature measurements. According to the experimental results, the mass flux has the most significant impact on the heat transfer coefficient while heat flux is a less influential parameter. The vapor quality varies in a range between 0 and 0.45. The heat transfer coefficient in the subcooled region reaches a maximum value of about 12 kW/m2K, whilst in two-phase flow it goes up to 30 kW/m2K.
{"title":"Flow boiling heat transfer and pressure drops of R1234ze(E) in a silicon micro-pin fin evaporator","authors":"C. Falsetti, M. Magnini, J. Thome","doi":"10.1115/1.4037152","DOIUrl":"https://doi.org/10.1115/1.4037152","url":null,"abstract":"The development of newer and more efficient cooling techniques to sustain the increasing power density of high-performance computing systems is becoming one of the major challenges in the development of microelectronics. In this framework, two-phase cooling is a promising solution for dissipating the greater amount of generated heat. In the present study an experimental investigation of two-phase flow boiling in a micro-pin fin evaporator is performed. The micro-evaporator has a heated area of 1 cm2 containing 66 rows of cylindrical in-line micro-pin fins with diameter, height and pitch of respectively 50 μm, 100 μm and 91.7 μm. At the entrance of the heated area an extra row of micro-pin fins with a larger diameter of 100 μm acts as inlet restrictions to avoid flow instabilities. The working fluid is R1234ze(E) tested over a wide range of conditions: mass fluxes varying from 750 kg/m2s to 1750 kg/m2s and heat fluxes ranging from 20 W/cm2 to 44 W/cm2 while maintaining a constant outlet saturation temperature of 35 °C. In order to assess the thermal-hydraulic performance of the current heat sink, the total pressure drops are directly measured, while local values of heat transfer coefficient are evaluated by coupling high speed flow visualization with infrared temperature measurements. According to the experimental results, the mass flux has the most significant impact on the heat transfer coefficient while heat flux is a less influential parameter. The vapor quality varies in a range between 0 and 0.45. The heat transfer coefficient in the subcooled region reaches a maximum value of about 12 kW/m2K, whilst in two-phase flow it goes up to 30 kW/m2K.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"205 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116390945","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 : 2017-05-01DOI: 10.1109/ITHERM.2017.7992556
Sevket U. Yuruker, Daniel G. Bae, R. Mandel, Bao Yang, P. McCluskey, A. Bar-Cohen, M. Ohadi
Two-phase microchannel cooling has demonstrated substantial performance enhancement for thermal management of high-power electronics, offering remarkable heat removal capability without imposing high pumping power penalties. However, similar to other bulk cooling methods, this method alone too has difficulty in addressing remediation of local hotspots. Thermoelectric coolers, on the other hand, are scalable and perfectly suited for localized cooling. Thus in this paper, we report our work on integration of a micro-contact enhanced TEC with FEEDS (thin-Film Evaporation and Enhanced fluid Delivery System) manifold-micro channel system. Combining these two thermal management schemes into a single system can provide effective heat removal over the entire electronic chip surface. Integration of these two methods, however, poses several challenges, including hermetic sealing, wiring of the TEC, excessive joule heating in electrical traces, and thermal/electrical short-circuits. Thus, the aim of this study was to integrate an optimized, 3 mm × 0.8 mm TEC into a FEEDS manifold-microchannel system to create a reliable high flux cooling mechanism on a silicon or silicon carbide chip for cooling of 5kW/cm2 hotspot and 1kW/cm2 background heat fluxes. The manufacturing, integration configuration, and assembly of the system are discussed in this paper. A numerical model of the system is built and simulated using the commercial finite-element analysis software ANSYS. Preliminary numerical results demonstrated that with 30 °C temperature rise at the SiC chip's background surface, less than 35 °C hotspot temperature rise with respect to the coolant fluid temperature (110 °C) can be achieved.
两相微通道冷却已经证明了高功率电子产品的热管理性能的显著增强，在不施加高泵浦功率损失的情况下提供了卓越的散热能力。然而，与其他整体冷却方法类似，这种方法本身也难以解决局部热点的修复问题。另一方面，热电冷却器是可扩展的，非常适合局部冷却。因此，在本文中，我们报告了我们在集成微接触增强TEC与FEEDS(薄膜蒸发和增强流体输送系统)歧管-微通道系统的工作。将这两种热管理方案结合到一个系统中可以在整个电子芯片表面提供有效的散热。然而，这两种方法的集成带来了一些挑战，包括密封性、TEC的布线、电迹线中过多的焦耳加热以及热/电短路。因此，本研究的目的是将优化的3 mm × 0.8 mm TEC集成到FEEDS管汇-微通道系统中，在硅或碳化硅芯片上创建可靠的高通量冷却机制，以冷却5kW/cm2的热点和1kW/cm2的背景热流。本文讨论了该系统的制造、集成配置和装配。利用商用有限元分析软件ANSYS建立了系统的数值模型并进行了仿真。初步数值结果表明，SiC芯片背景表面升温30℃时，相对于冷却液温度(110℃)，热点温升可小于35℃。
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Pub Date : 2017-05-01DOI: 10.1109/ITHERM.2017.7992606
A. Hamed, S. Ndao
Probably the most trending technology in electronics today is wearable and flexible electronics. Flexible electronics are electronic circuits fabricated on flexible surfaces and offer many advantages. Similar to conventional electronics, thermal management of flexible electronics is a formidable challenge. In addition to high heat fluxes from the miniaturization of electronics' components, thermal management of flexible electronics must be adapted to the flexible and stretchable nature of the technology. In this work, we numerically study the thermal performance of thin film liquid metal PCMs for the thermal management of flexible electronics. Using 1-D (axial direction) transient conduction along with the enthalpy method, the temperature distribution within the liquid metal PCM was investigated as a function of length, thermal properties, and unsteady heat load. The results showed the existence of three important regions within which there exists an optimal PCM configuration and operating condition. Because PCMs are most suited for transient heat load applications, which is the case for many electronics, we studied the effects of transient heat load's periodicity and duration on the thermal performance of the liquid metal PCMs. The results showed that with a base load resulting in a chip temperature just below the PCM's melting temperature, optimal periodic heat loads can be achieved to maintain the chip at an acceptable operating temperature.
{"title":"Modeling of writable thin film liquid metal phase change material for electronics cooling","authors":"A. Hamed, S. Ndao","doi":"10.1109/ITHERM.2017.7992606","DOIUrl":"https://doi.org/10.1109/ITHERM.2017.7992606","url":null,"abstract":"Probably the most trending technology in electronics today is wearable and flexible electronics. Flexible electronics are electronic circuits fabricated on flexible surfaces and offer many advantages. Similar to conventional electronics, thermal management of flexible electronics is a formidable challenge. In addition to high heat fluxes from the miniaturization of electronics' components, thermal management of flexible electronics must be adapted to the flexible and stretchable nature of the technology. In this work, we numerically study the thermal performance of thin film liquid metal PCMs for the thermal management of flexible electronics. Using 1-D (axial direction) transient conduction along with the enthalpy method, the temperature distribution within the liquid metal PCM was investigated as a function of length, thermal properties, and unsteady heat load. The results showed the existence of three important regions within which there exists an optimal PCM configuration and operating condition. Because PCMs are most suited for transient heat load applications, which is the case for many electronics, we studied the effects of transient heat load's periodicity and duration on the thermal performance of the liquid metal PCMs. The results showed that with a base load resulting in a chip temperature just below the PCM's melting temperature, optimal periodic heat loads can be achieved to maintain the chip at an acceptable operating temperature.","PeriodicalId":387542,"journal":{"name":"2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123693212","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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