Pub Date : 2016-07-20DOI: 10.1109/ITHERM.2016.7517736
Z. Sárkány, Weikun He, M. Rencz
Besides the electric parameters of a semiconductor device, the lifetime is a key measure of quality. Overheating is one of the top failure causes in electronic systems. In this paper, a power cycling experiment done on silicon carbide (SiC) MOSFET devices is presented. The experimental setup and measurement conditions are described in detail and a discussion is given on the importance of the electrical setup and the control strategy. The data collected during the power cycling are analyzed, and the primary failure modes are identified. The high-resolution monitoring of the voltage drop on the device, in combination with other monitored parameters, enables the detection of a bond wire lift-off or breakage. With the help of the thermal transient measurement and structure function analysis, the structural changes in the heat flow path can also be identified. Finally, the results of the electric measurements are compared and verified by scanning acoustic microscopy tests.
{"title":"Temperature change induced degradation of SiC MOSFET devices","authors":"Z. Sárkány, Weikun He, M. Rencz","doi":"10.1109/ITHERM.2016.7517736","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517736","url":null,"abstract":"Besides the electric parameters of a semiconductor device, the lifetime is a key measure of quality. Overheating is one of the top failure causes in electronic systems. In this paper, a power cycling experiment done on silicon carbide (SiC) MOSFET devices is presented. The experimental setup and measurement conditions are described in detail and a discussion is given on the importance of the electrical setup and the control strategy. The data collected during the power cycling are analyzed, and the primary failure modes are identified. The high-resolution monitoring of the voltage drop on the device, in combination with other monitored parameters, enables the detection of a bond wire lift-off or breakage. With the help of the thermal transient measurement and structure function analysis, the structural changes in the heat flow path can also be identified. Finally, the results of the electric measurements are compared and verified by scanning acoustic microscopy tests.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"60 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129103371","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 : 2016-07-20DOI: 10.1109/ITHERM.2016.7517667
T. Hatakeyama, R. Kibushi, M. Ishizuka, T. Tomimura
For thermal management of electrical equipment, thermal contact resistance is one of the important parameters. However, thermal contact resistance is dependent on various factors, for example surface roughness, the contact pressure and the hardness of the material. Therefore, quantitative evaluation is difficult. Nowadays, CFD (Computational Fluid Dynamics) analysis is widely used in thermal design of electronics. However, unknown thermal contact resistance is always a problem for accurate temperature estimation. In this study, we examined surface roughness and material hardness dependence of thermal contact resistance and electrical contact resistance for simple estimation of thermal contact resistance. Measurement of thermal contact resistance takes a long time and electrical resistance measurement is much shorter. If thermal contact resistance can be estimated from electrical contact resistance, thermal contact resistance can be known in short time, and this method can support accurate CFD analysis. The materials to be measured are Al1070 and S45C, and three patterns (Ra = 0.2, 3.2, 12.5 μm) of surface roughness are examined. After the measurement of thermal and electrical contact resistance, we examined the ratio between electrical contact resistance and thermal contact resistance for the faster estimation of thermal contact resistance using the concept of Wiedemann-Franz law and Lorentz number like experimental constant.
{"title":"Fundamental study of surface roughness dependence of thermal and electrical contact resistance","authors":"T. Hatakeyama, R. Kibushi, M. Ishizuka, T. Tomimura","doi":"10.1109/ITHERM.2016.7517667","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517667","url":null,"abstract":"For thermal management of electrical equipment, thermal contact resistance is one of the important parameters. However, thermal contact resistance is dependent on various factors, for example surface roughness, the contact pressure and the hardness of the material. Therefore, quantitative evaluation is difficult. Nowadays, CFD (Computational Fluid Dynamics) analysis is widely used in thermal design of electronics. However, unknown thermal contact resistance is always a problem for accurate temperature estimation. In this study, we examined surface roughness and material hardness dependence of thermal contact resistance and electrical contact resistance for simple estimation of thermal contact resistance. Measurement of thermal contact resistance takes a long time and electrical resistance measurement is much shorter. If thermal contact resistance can be estimated from electrical contact resistance, thermal contact resistance can be known in short time, and this method can support accurate CFD analysis. The materials to be measured are Al1070 and S45C, and three patterns (Ra = 0.2, 3.2, 12.5 μm) of surface roughness are examined. After the measurement of thermal and electrical contact resistance, we examined the ratio between electrical contact resistance and thermal contact resistance for the faster estimation of thermal contact resistance using the concept of Wiedemann-Franz law and Lorentz number like experimental constant.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"113 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133386808","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 : 2016-07-20DOI: 10.1109/ITHERM.2016.7517734
Julian Anaya, Huarui Sun, J. Pomeroy, Martin Kuball
The integration of diamond in ultra-high power GaN HEMT devices has demonstrated to be a very promising strategy to increase the device lifetime and their thermal management. Typically polycrystalline diamond films rather than single crystal diamond are used for this purpose, however for this material the thermal transport in the near-nucleation site is strongly affected by the small grain size and the accumulation of defects in this region. Here we modeled the phonon thermal transport in diamond, including the effect of the polycrystalline structure, showing that its thermal conductivity exhibits very different properties to those observed in single crystal diamond; namely, the thermal conductivity is severely reduced, the grain structure may induce anisotropy in the heat conduction and also a strong variation of the thermal conductivity from the nucleation and following the diamond growth direction is observed. All these features are included in a full thermal model of a GaN high power amplifier, showing their impact on the thermal management of the device. We show that including the full description of the polycrystalline diamond thermal conductivity is fundamental to accurately assess the thermal management of these devices, and thus to optimize their design.
{"title":"Thermal management of GaN-on-diamond high electron mobility transistors: Effect of the nanostructure in the diamond near nucleation region","authors":"Julian Anaya, Huarui Sun, J. Pomeroy, Martin Kuball","doi":"10.1109/ITHERM.2016.7517734","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517734","url":null,"abstract":"The integration of diamond in ultra-high power GaN HEMT devices has demonstrated to be a very promising strategy to increase the device lifetime and their thermal management. Typically polycrystalline diamond films rather than single crystal diamond are used for this purpose, however for this material the thermal transport in the near-nucleation site is strongly affected by the small grain size and the accumulation of defects in this region. Here we modeled the phonon thermal transport in diamond, including the effect of the polycrystalline structure, showing that its thermal conductivity exhibits very different properties to those observed in single crystal diamond; namely, the thermal conductivity is severely reduced, the grain structure may induce anisotropy in the heat conduction and also a strong variation of the thermal conductivity from the nucleation and following the diamond growth direction is observed. All these features are included in a full thermal model of a GaN high power amplifier, showing their impact on the thermal management of the device. We show that including the full description of the polycrystalline diamond thermal conductivity is fundamental to accurately assess the thermal management of these devices, and thus to optimize their design.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131439305","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517677
M. Raudenský, I. Astrouski, T. Brozova, E. Bartuli
Cooling electronics boxes often requires extraction of high heat fluxes from closed boxes with many heat-producing components. The direct use of ventilation is sometimes limited by demands to use hermetic units or the need to extract heat from a specific place in a large and complicated system. A liquid system introduced inside of the electronic box can be used for this purpose. Unfortunately, metallic heat exchangers have a number of shortcomings in these applications, including significant weight as well as cost and space demands. Polymeric heat exchangers consisting of hollow fibers were proposed a decade ago and can be used as an alternative in such applications. Flexible polymeric hollow fiber heat exchangers were prepared and tested in liquid / air conditions. These heat exchangers use plastic capillaries with an outer diameter of 0.5 - 0.8 mm and a wall thickness of 10% of the outer diameter. They consist of flexible fibers and can be used in narrow slots and/or in shaped channels. These heat exchangers are effective even in natural convection applications because of their high heat transfer intensity on micro-objects. Experimentally obtained overall heat-transfer coefficients in water/air applications are up to 250 W/m2 K for forced convection and up to 80 W/m2 for natural convection. The use of plastic and non-corrosive materials is advantageous in electronic systems where high heat fluxes must be extracted safely from difficult to access spaces or from hermetically-sealed boxes.
{"title":"Flexible polymeric hollow fiber heat exchangers for electronic systems","authors":"M. Raudenský, I. Astrouski, T. Brozova, E. Bartuli","doi":"10.1109/ITHERM.2016.7517677","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517677","url":null,"abstract":"Cooling electronics boxes often requires extraction of high heat fluxes from closed boxes with many heat-producing components. The direct use of ventilation is sometimes limited by demands to use hermetic units or the need to extract heat from a specific place in a large and complicated system. A liquid system introduced inside of the electronic box can be used for this purpose. Unfortunately, metallic heat exchangers have a number of shortcomings in these applications, including significant weight as well as cost and space demands. Polymeric heat exchangers consisting of hollow fibers were proposed a decade ago and can be used as an alternative in such applications. Flexible polymeric hollow fiber heat exchangers were prepared and tested in liquid / air conditions. These heat exchangers use plastic capillaries with an outer diameter of 0.5 - 0.8 mm and a wall thickness of 10% of the outer diameter. They consist of flexible fibers and can be used in narrow slots and/or in shaped channels. These heat exchangers are effective even in natural convection applications because of their high heat transfer intensity on micro-objects. Experimentally obtained overall heat-transfer coefficients in water/air applications are up to 250 W/m2 K for forced convection and up to 80 W/m2 for natural convection. The use of plastic and non-corrosive materials is advantageous in electronic systems where high heat fluxes must be extracted safely from difficult to access spaces or from hermetically-sealed boxes.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115646960","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517618
Dan Comperchio
As data center designs continue to evolve, performance and reliability improves resulting in higher levels of uptime in the facilities. Often, this results in systems with additional capacity in power and cooling equipment to allow for concurrent maintenance, protection against equipment failures and can allow for more efficient operation. In addition to higher levels of reliability, data center designs are also pushing the envelope on efficiencies from the supporting infrastructure. While the design intentions are generally in the best interest of the buildings performance, data center designs can often suffer from overprovisioning power and cooling compared to the near-term or even long-term loading of the building. Further, the commissioning of systems often utilizes load banks to simulate ITE loads in the data center, typically done at design loads. Due to this, the low-load conditions in the data center may not be fully realized until the facility goes live. The low-load conditions can cause considerable inefficiencies to arise in the power and cooling systems and often the design conditions may not be met for a number of years, if at all. However, through careful planning and proper commissioning of the systems, design efficiency levels can be achieved and even exceeded.
{"title":"Addressing low and part load (in)efficiencies in data centers - real world examples from operating data centers","authors":"Dan Comperchio","doi":"10.1109/ITHERM.2016.7517618","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517618","url":null,"abstract":"As data center designs continue to evolve, performance and reliability improves resulting in higher levels of uptime in the facilities. Often, this results in systems with additional capacity in power and cooling equipment to allow for concurrent maintenance, protection against equipment failures and can allow for more efficient operation. In addition to higher levels of reliability, data center designs are also pushing the envelope on efficiencies from the supporting infrastructure. While the design intentions are generally in the best interest of the buildings performance, data center designs can often suffer from overprovisioning power and cooling compared to the near-term or even long-term loading of the building. Further, the commissioning of systems often utilizes load banks to simulate ITE loads in the data center, typically done at design loads. Due to this, the low-load conditions in the data center may not be fully realized until the facility goes live. The low-load conditions can cause considerable inefficiencies to arise in the power and cooling systems and often the design conditions may not be met for a number of years, if at all. However, through careful planning and proper commissioning of the systems, design efficiency levels can be achieved and even exceeded.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"115 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115700553","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517630
J. Kelley, K. Choo, V. Rao, S. Dessiatoun, M. Ohadi
An experimental and theoretical study was investigated on heat transfer and fluid flow characteristics of a photovoltaic p-Si cells array. The effect of three different type of collector geometries (Model A, B, and C) on thermal efficiency and pressure drop were considered. The theoretical model using a simple energy balance was well matched with experimental data within 11 %. Electrical generation is modeled by PVT in conjunction with an Organic Rankine Cycle. The results showed that the efficiency of model B boosts of up to 49.6% with the lowest pressure drop.
{"title":"Boosting electrical generation of a photovoltaic array by thermal harvest from p-Si cells: An experimental and theoretical study","authors":"J. Kelley, K. Choo, V. Rao, S. Dessiatoun, M. Ohadi","doi":"10.1109/ITHERM.2016.7517630","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517630","url":null,"abstract":"An experimental and theoretical study was investigated on heat transfer and fluid flow characteristics of a photovoltaic p-Si cells array. The effect of three different type of collector geometries (Model A, B, and C) on thermal efficiency and pressure drop were considered. The theoretical model using a simple energy balance was well matched with experimental data within 11 %. Electrical generation is modeled by PVT in conjunction with an Organic Rankine Cycle. The results showed that the efficiency of model B boosts of up to 49.6% with the lowest pressure drop.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127207651","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517684
M. Chowdhury, Sudan Ahmed, Abdullah Fahim, J. Suhling, P. Lall
Reliable lead free solders are needed for products exposed to extreme environments such as those used in the automotive, avionics, and oil-exploration industries, as well as in military applications. In this study, stress-strain curves have been measured for several doped Sn-Ag-Cu (SAC) solder materials at high temperatures up to 200°C, and their performances have been compared to those for standard SAC alloys. The doped lead free solder materials are referred to as SAC_R (Ecolloy), SAC_Q (CYCLOMAX), and Innolot by their vendors. SAC_R and SAC_Q are formulated with Sn, Ag, Cu, and Bi (SAC+Bi), while Innolot includes an engineered combination of six elements. Tensile specimens were formed in rectangular cross-section glass tubes using a vacuum suction process, and a water quenched (WQ) solidification profile was utilized. This profile resulted in extremely fine microstructures, and mechanical properties near the upper limit possible for each alloy. Uniaxial tensile testing was performed on the three doped alloys at temperatures of 25, 50, 75, 100, 125, 150, 175, and 200°C, and a strain rate of 0.001 sec-1. For the SAC_Q alloy, testing was also performed at strain rates of 0.0001 and 0.00001 sec-1, and the Anand constitutive parameters were calculated. The results for the doped solders were compared to standard SAC105 and SAC405 lead free alloys. The mechanical properties of SAC_R were found to exceed those for SAC105 at all temperatures, even though SAC_R does not contain any silver. In addition, the mechanical properties of SAC_Q and Innolot were found to match or exceed those of SAC405 at all temperatures. The new alloys show great promise for use in extremely harsh environments.
{"title":"Mechanical characterization of doped SAC solder materials at high temperature","authors":"M. Chowdhury, Sudan Ahmed, Abdullah Fahim, J. Suhling, P. Lall","doi":"10.1109/ITHERM.2016.7517684","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517684","url":null,"abstract":"Reliable lead free solders are needed for products exposed to extreme environments such as those used in the automotive, avionics, and oil-exploration industries, as well as in military applications. In this study, stress-strain curves have been measured for several doped Sn-Ag-Cu (SAC) solder materials at high temperatures up to 200°C, and their performances have been compared to those for standard SAC alloys. The doped lead free solder materials are referred to as SAC_R (Ecolloy), SAC_Q (CYCLOMAX), and Innolot by their vendors. SAC_R and SAC_Q are formulated with Sn, Ag, Cu, and Bi (SAC+Bi), while Innolot includes an engineered combination of six elements. Tensile specimens were formed in rectangular cross-section glass tubes using a vacuum suction process, and a water quenched (WQ) solidification profile was utilized. This profile resulted in extremely fine microstructures, and mechanical properties near the upper limit possible for each alloy. Uniaxial tensile testing was performed on the three doped alloys at temperatures of 25, 50, 75, 100, 125, 150, 175, and 200°C, and a strain rate of 0.001 sec-1. For the SAC_Q alloy, testing was also performed at strain rates of 0.0001 and 0.00001 sec-1, and the Anand constitutive parameters were calculated. The results for the doped solders were compared to standard SAC105 and SAC405 lead free alloys. The mechanical properties of SAC_R were found to exceed those for SAC105 at all temperatures, even though SAC_R does not contain any silver. In addition, the mechanical properties of SAC_Q and Innolot were found to match or exceed those of SAC405 at all temperatures. The new alloys show great promise for use in extremely harsh environments.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"09 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127217538","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517711
R. Abbaspour, David C. Woodrum, P. Kottke, Thomas E. Sarvey, C. Green, Y. Joshi, A. Fedorov, S. Sitaraman, M. Bakir
There are a number of emerging electronic applications that are thermally limited and may exhibit high overall power dissipation (“background”) combined with local very high power fluxes (“hotspot”). We have batch fabricated a microfluidic heat sink specifically designed to address both levels of heat removal. A microgap for hotspot cooling and micropin-fins are sequentially deep etched in a silicon substrate. The combined microfluidic heat sink is sealed by bonding another layer of silicon to the substrate. The coolant is injected into the combined heat sink from two distinct ports to dissipate the generated heat by micro-heaters. These micro-heaters emulate hotspot and background heat generation by active circuits as well as enable chip junction temperature measurement. Mechanical modeling is conducted to verify the reliability of the design and assess limits on the operating pressure of the fabricated system.
{"title":"Combined finned microgap with dedicated extreme-microgap hotspot flow for high performance thermal management","authors":"R. Abbaspour, David C. Woodrum, P. Kottke, Thomas E. Sarvey, C. Green, Y. Joshi, A. Fedorov, S. Sitaraman, M. Bakir","doi":"10.1109/ITHERM.2016.7517711","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517711","url":null,"abstract":"There are a number of emerging electronic applications that are thermally limited and may exhibit high overall power dissipation (“background”) combined with local very high power fluxes (“hotspot”). We have batch fabricated a microfluidic heat sink specifically designed to address both levels of heat removal. A microgap for hotspot cooling and micropin-fins are sequentially deep etched in a silicon substrate. The combined microfluidic heat sink is sealed by bonding another layer of silicon to the substrate. The coolant is injected into the combined heat sink from two distinct ports to dissipate the generated heat by micro-heaters. These micro-heaters emulate hotspot and background heat generation by active circuits as well as enable chip junction temperature measurement. Mechanical modeling is conducted to verify the reliability of the design and assess limits on the operating pressure of the fabricated system.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125838108","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517696
J. Luttrell, Abhishek Guhe, D. Agonafer
Most data center cooling systems are designed to match installed cooling capacity to peak cooling demand at the most challenging ambient condition which typically occurs for only a period of the diurnal cycle. Evaporative coolers are provide economical cooling but use large quantities of water and are generally constrained to the ASHRAE A2 limits [1]. Direct expansion `topping' systems are a common technology to extend the temperature-humidity range, however, direct expansion systems require substantial electrical power which negatively affects the operating costs. Phase change materials have potential for economical thermal energy storage. Used instead of direct expansion, thermal energy storage can reduce the cost of cooling energy. By storing cooling capacity, thermal energy storage enables time-shifting of cooling demands and extends the temperature-humidity limits for evaporative cooling beyond the ASHRAE A2 limits. An added benefit, thermal energy storage with indirect/direct evaporative coolers reduces water consumption.
{"title":"Costs and benefits of thermal energy storage for augmenting indirect/direct evaporative cooling systems","authors":"J. Luttrell, Abhishek Guhe, D. Agonafer","doi":"10.1109/ITHERM.2016.7517696","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517696","url":null,"abstract":"Most data center cooling systems are designed to match installed cooling capacity to peak cooling demand at the most challenging ambient condition which typically occurs for only a period of the diurnal cycle. Evaporative coolers are provide economical cooling but use large quantities of water and are generally constrained to the ASHRAE A2 limits [1]. Direct expansion `topping' systems are a common technology to extend the temperature-humidity range, however, direct expansion systems require substantial electrical power which negatively affects the operating costs. Phase change materials have potential for economical thermal energy storage. Used instead of direct expansion, thermal energy storage can reduce the cost of cooling energy. By storing cooling capacity, thermal energy storage enables time-shifting of cooling demands and extends the temperature-humidity limits for evaporative cooling beyond the ASHRAE A2 limits. An added benefit, thermal energy storage with indirect/direct evaporative coolers reduces water consumption.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"329 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123223788","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 : 2016-05-01DOI: 10.1109/ITHERM.2016.7517678
J. Vangilder, Zachary M. Pardey, P. Bemis, David W. Plamondon
The small-diameter stanchions which support the raised-floor system are often neglected in CFD models. However, recent studies suggest that tile airflow predictions are substantially improved when stanchions are included. Further, it is anecdotally observed that the additional flow resistance imparted by the stanchions actually improves convergence of CFD simulations. While it is possible to model the stanchions explicitly, a compact-3D-distributed-resistance approach adds negligible computational overhead and is easy to specify in CFD tools. This paper recommends 3D distributed-resistance loss coefficient values to be used directly by data center modelers. Our primary approach is based on an interpolation between published loss coefficients for densely-packed tube bundles and a sparsely-packed model which we propose here. The model is validated by explicit CFD-wind-tunnel analyses, the results of which agree well with the interpolation model. Finally, we validate the model against tile airflow measurements taken in an actual data center.
{"title":"Compact modeling of data center raised-floor-plenum stanchions: Pressure drop through sparse tube bundles","authors":"J. Vangilder, Zachary M. Pardey, P. Bemis, David W. Plamondon","doi":"10.1109/ITHERM.2016.7517678","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517678","url":null,"abstract":"The small-diameter stanchions which support the raised-floor system are often neglected in CFD models. However, recent studies suggest that tile airflow predictions are substantially improved when stanchions are included. Further, it is anecdotally observed that the additional flow resistance imparted by the stanchions actually improves convergence of CFD simulations. While it is possible to model the stanchions explicitly, a compact-3D-distributed-resistance approach adds negligible computational overhead and is easy to specify in CFD tools. This paper recommends 3D distributed-resistance loss coefficient values to be used directly by data center modelers. Our primary approach is based on an interpolation between published loss coefficients for densely-packed tube bundles and a sparsely-packed model which we propose here. The model is validated by explicit CFD-wind-tunnel analyses, the results of which agree well with the interpolation model. Finally, we validate the model against tile airflow measurements taken in an actual data center.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2016-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125365356","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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