Pub Date : 2016-05-01DOI: 10.1109/ITHERM.2016.7517619
M. del Valle, Carol Caceres, A. Ortega
Hybrid air/liquid cooling systems used in data centers enable localized, on-demand cooling, or “smart cooling” using various approaches such as rear door heat exchangers, overhead cooling systems and in row cooling systems. These systems offer the potential to achieve higher energy efficiency by providing local cooling only when it is needed, thereby reducing the overprovisioning that is endemic to traditional systems. At the heart of all hybrid cooling systems is an air to liquid cross flow heat exchanger which regulates the amount of cooling that the system provides by modulating the liquid or air flows or temperatures. Understanding the transient response of the heat exchanger is crucial for the precise control of the system. In this paper a 12 in. × 12 in water to air heat exchanger, with similar characteristics to the heat exchanger commonly found in data centers, is modeled using three partial differential equations solved by the use of a finite difference approach. The model is validated against experimental data obtained from an experimental rig designed to introduce controlled transient perturbations in temperature and flow on the inlet air and liquid flows to the heat exchanger. Experimental data were obtained for step change, ramp change, and sinusoidal variation in the inlet water temperature and mass flow rate. Steady state heat transfer coefficients are used in the air and liquid side of the heat exchanger. The heat transfer coefficient inside the tubes is calculated by the use of the Gnielinski correlation. A steady state technique is used to extract the air side heat transfer coefficient. With these parameters, it was found that the dynamic heat exchanger model agrees remarkably well with the transient experimental data. The modeling equations also provide insight into the characteristic response times of the heat exchanger in terms of the major independent non-dimensional parameters describing its design and operating conditions.
{"title":"Transient modeling and validation of chilled water based cross flow heat exchangers for local on-demand cooling in data centers","authors":"M. del Valle, Carol Caceres, A. Ortega","doi":"10.1109/ITHERM.2016.7517619","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517619","url":null,"abstract":"Hybrid air/liquid cooling systems used in data centers enable localized, on-demand cooling, or “smart cooling” using various approaches such as rear door heat exchangers, overhead cooling systems and in row cooling systems. These systems offer the potential to achieve higher energy efficiency by providing local cooling only when it is needed, thereby reducing the overprovisioning that is endemic to traditional systems. At the heart of all hybrid cooling systems is an air to liquid cross flow heat exchanger which regulates the amount of cooling that the system provides by modulating the liquid or air flows or temperatures. Understanding the transient response of the heat exchanger is crucial for the precise control of the system. In this paper a 12 in. × 12 in water to air heat exchanger, with similar characteristics to the heat exchanger commonly found in data centers, is modeled using three partial differential equations solved by the use of a finite difference approach. The model is validated against experimental data obtained from an experimental rig designed to introduce controlled transient perturbations in temperature and flow on the inlet air and liquid flows to the heat exchanger. Experimental data were obtained for step change, ramp change, and sinusoidal variation in the inlet water temperature and mass flow rate. Steady state heat transfer coefficients are used in the air and liquid side of the heat exchanger. The heat transfer coefficient inside the tubes is calculated by the use of the Gnielinski correlation. A steady state technique is used to extract the air side heat transfer coefficient. With these parameters, it was found that the dynamic heat exchanger model agrees remarkably well with the transient experimental data. The modeling equations also provide insight into the characteristic response times of the heat exchanger in terms of the major independent non-dimensional parameters describing its design and operating conditions.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"50 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":"117147419","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.2016.7517724
K. Yazawa, A. Shakouri
Industrial energy consumption represents a large part of the energy flow in the United States and it would probably be similar in many other countries. Coal or gas fired furnaces are a major component of the energy consumption to supply high temperatures. Refractory wall is indispensable along the furnace pathway designed for melting or processing materials. Unfortunately, more than a fraction of the input energy diffuses across the refractory wall due to the high temperatures and the waste heat is dumped to the ambient. Thermoelectric power generator (TEG) has an ultra low profile and is widely scalable with arraying the modules. This configuration is matched very well with the requirement of harvesting energy from the waste heat through the refractory wall without any design change of the current furnaces. We propose a simple water-cooled TEG system replacing a fraction of the refractory wall thickness while maintaining the melt temperature and the heat flux would be the same as the current refractory wall with passive air cooling. Design optimization is conducted, trading-off the TEG module thickness and the furnace wall thickness maximizing the power output while maintaining the above heat flux. We will present a quantitative analysis based on an example of the conventional fire ports that produce furnace gases at a temperature of 1500 °C. The furnace is designed for melting glass pellets and maintaining the temperature of melt glass at 1000 °C in a pool. A facility with 500 ton/day capacity is modeled. There are four fire ports and 54 cm thick aluminum-zirconia-silica (AZS) refractory wall around the ports. The thermal optimization is conducted considering the design of TEG matched to desired heat flux of approximately 10 kW/m2. As shown in our earlier work, the TEG design with a smaller TE element fill factor down to 10% or below, will provide the most cost effective power generation. Interestingly, the additional material cost for the optimum TEG with 10% fill factor and a copper cold plate is much less expensive compared to the cost needed for the AZS refractory wall material that it is replacing. When the remaining thickness of the refractory wall is 25 cm, the power generation from TEG is 1.72 kW/m2 while maintaining the same heat flux. The total power output from the all four fire ports can be 66.1 kW and the cost for the TEG module is estimated to be $0.5 per Watt based on demonstrated robust high temperature TE material.
{"title":"Thermal optimization of embedded thermoelectric generators in refractory furnaces","authors":"K. Yazawa, A. Shakouri","doi":"10.1109/ITHERM.2016.7517724","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517724","url":null,"abstract":"Industrial energy consumption represents a large part of the energy flow in the United States and it would probably be similar in many other countries. Coal or gas fired furnaces are a major component of the energy consumption to supply high temperatures. Refractory wall is indispensable along the furnace pathway designed for melting or processing materials. Unfortunately, more than a fraction of the input energy diffuses across the refractory wall due to the high temperatures and the waste heat is dumped to the ambient. Thermoelectric power generator (TEG) has an ultra low profile and is widely scalable with arraying the modules. This configuration is matched very well with the requirement of harvesting energy from the waste heat through the refractory wall without any design change of the current furnaces. We propose a simple water-cooled TEG system replacing a fraction of the refractory wall thickness while maintaining the melt temperature and the heat flux would be the same as the current refractory wall with passive air cooling. Design optimization is conducted, trading-off the TEG module thickness and the furnace wall thickness maximizing the power output while maintaining the above heat flux. We will present a quantitative analysis based on an example of the conventional fire ports that produce furnace gases at a temperature of 1500 °C. The furnace is designed for melting glass pellets and maintaining the temperature of melt glass at 1000 °C in a pool. A facility with 500 ton/day capacity is modeled. There are four fire ports and 54 cm thick aluminum-zirconia-silica (AZS) refractory wall around the ports. The thermal optimization is conducted considering the design of TEG matched to desired heat flux of approximately 10 kW/m2. As shown in our earlier work, the TEG design with a smaller TE element fill factor down to 10% or below, will provide the most cost effective power generation. Interestingly, the additional material cost for the optimum TEG with 10% fill factor and a copper cold plate is much less expensive compared to the cost needed for the AZS refractory wall material that it is replacing. When the remaining thickness of the refractory wall is 25 cm, the power generation from TEG is 1.72 kW/m2 while maintaining the same heat flux. The total power output from the all four fire ports can be 66.1 kW and the cost for the TEG module is estimated to be $0.5 per Watt based on demonstrated robust high temperature TE material.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"39 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":"131271364","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.2016.7517697
H. Erden, M. Yildirim, M. Koz, H. Khalifa
Aisle containments in data centers help provide uniform server inlet air temperatures. This allows the cooling system to run at a higher evaporator temperature and more efficiently. On the other hand, CRAH units run at higher speeds to ascertain that racks receive sufficient air flow. Since CRAH fan power already constitutes an important component of data center power use, such increases in the fan power can overshadow the energy savings due to more efficient chiller operation. CRAH bypass configuration is proposed to achieve optimum operating condition for enclosed aisle data centers. This configuration utilizes fan-assisted perforated floor tiles to induce a fraction of tile flow from the room through bypass ports or leakage paths and help decreasing the amount of air flow passing through the large flow resistances of CRAH units. Experimental results show that there is an optimum operating condition for the specific data center test cell that is designed to represent an enclosed aisle data center utilizing the proposed CRAH bypass configuration. Here, the flow characteristics of major system components and experimental measurements have been used to calibrate a flow network model (FNM) for the design optimization and trade-off analysis of the proposed system. Calibrated FNM along with a thermodynamic model (TM) of the cooling infrastructure provides an estimate of the energy use at various fractions of CRAH bypass air and chilled water temperatures. This study introduces the design of the experimental setup for testing CRAH bypass configuration for enclosed aisles and for calibrating models to predict the cooling infrastructure energy saving potential of the proposed technique.
{"title":"Experimental investigation of CRAH bypass for enclosed aisle data centers","authors":"H. Erden, M. Yildirim, M. Koz, H. Khalifa","doi":"10.1109/ITHERM.2016.7517697","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517697","url":null,"abstract":"Aisle containments in data centers help provide uniform server inlet air temperatures. This allows the cooling system to run at a higher evaporator temperature and more efficiently. On the other hand, CRAH units run at higher speeds to ascertain that racks receive sufficient air flow. Since CRAH fan power already constitutes an important component of data center power use, such increases in the fan power can overshadow the energy savings due to more efficient chiller operation. CRAH bypass configuration is proposed to achieve optimum operating condition for enclosed aisle data centers. This configuration utilizes fan-assisted perforated floor tiles to induce a fraction of tile flow from the room through bypass ports or leakage paths and help decreasing the amount of air flow passing through the large flow resistances of CRAH units. Experimental results show that there is an optimum operating condition for the specific data center test cell that is designed to represent an enclosed aisle data center utilizing the proposed CRAH bypass configuration. Here, the flow characteristics of major system components and experimental measurements have been used to calibrate a flow network model (FNM) for the design optimization and trade-off analysis of the proposed system. Calibrated FNM along with a thermodynamic model (TM) of the cooling infrastructure provides an estimate of the energy use at various fractions of CRAH bypass air and chilled water temperatures. This study introduces the design of the experimental setup for testing CRAH bypass configuration for enclosed aisles and for calibrating models to predict the cooling infrastructure energy saving potential of the proposed technique.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"52 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":"122297832","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.2016.7517585
A. Mahmood, Trina Barua, Saylalee Sabne, A. R. Nazmus Sakib, D. Agonafer
Chip Scale Packages (CSP) are used more and more in the portable electronic devices with its growing popularity due to small form factor. Electrical, Thermomechanical and Mechanical loadings act simultaneously on the electronic products during their daily usage. Due to the market demand, new high-performance functions are continuously being integrated with these devices despite the decreasing from factor and generation of more thermal stresses inside. These smaller devices are more prone to accidental drop and experience impact load, causing board interconnect failure by the repeatability of the drop occurrences. Therefore, the reliability of these products due to various loadings are being researched by taking multi-dimensional approach. A computational study has been carried out in this paper to investigate the effect of impact loading on the solder joints of WLCSP component boards. Here, a more thorough understanding of the solder joint behavior is examined by carrying out drop test with respect to elevated temperature and using PCBs of varying thickness and layer stack-ups. The same WLCSP is used for different boards and subjected to drop test according to the JEDEC specifications [1]. Two different types of boards are used and to simulate the actual drop test modified Input G method, that is Direct Acceleration Input method, was followed. The comparison of the boards has been made to understand the effect of temperature on the reliability of solder interconnects and on the strain generation induced in the PCBs during the drop test. It has been found that due to decreasing elastic modulus at higher temperature the behavior of both the boards are similar except the fact that thin board experiences relatively more stress in its interconnects after crossing a threshold temperature.
{"title":"A computational study of PCB layer orientation of WCSP assembly under temperature dependent drop impact loading","authors":"A. Mahmood, Trina Barua, Saylalee Sabne, A. R. Nazmus Sakib, D. Agonafer","doi":"10.1109/ITHERM.2016.7517585","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517585","url":null,"abstract":"Chip Scale Packages (CSP) are used more and more in the portable electronic devices with its growing popularity due to small form factor. Electrical, Thermomechanical and Mechanical loadings act simultaneously on the electronic products during their daily usage. Due to the market demand, new high-performance functions are continuously being integrated with these devices despite the decreasing from factor and generation of more thermal stresses inside. These smaller devices are more prone to accidental drop and experience impact load, causing board interconnect failure by the repeatability of the drop occurrences. Therefore, the reliability of these products due to various loadings are being researched by taking multi-dimensional approach. A computational study has been carried out in this paper to investigate the effect of impact loading on the solder joints of WLCSP component boards. Here, a more thorough understanding of the solder joint behavior is examined by carrying out drop test with respect to elevated temperature and using PCBs of varying thickness and layer stack-ups. The same WLCSP is used for different boards and subjected to drop test according to the JEDEC specifications [1]. Two different types of boards are used and to simulate the actual drop test modified Input G method, that is Direct Acceleration Input method, was followed. The comparison of the boards has been made to understand the effect of temperature on the reliability of solder interconnects and on the strain generation induced in the PCBs during the drop test. It has been found that due to decreasing elastic modulus at higher temperature the behavior of both the boards are similar except the fact that thin board experiences relatively more stress in its interconnects after crossing a threshold temperature.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"50 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":"128896591","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.2016.7517521
Debora de O. Silva, R. Riehl
Heat pipes are a closed tube or chamber of different shapes whose inner surfaces are lined with a porous capillary wick, containing a saturated working fluid. It is a technology not restricted to aerospace applications, which is frequently used as thermal control devices of satellites and space vehicles. Some other sectors are finding interest on applying heat pipes to promote the thermal control of electronic equipment and heat exchangers performance augmentation. The use of heat pipes in such equipment allows the development of more compact and efficient heat exchangers compared to traditional designs, which increases the interest on applying them for industrial purposes. Heat pipes operating at mid-level temperatures have found several applications on both aerospace and industry segments. This work has the objective to present experimental results of heat pipes operation designed and manufactured in stainless steel and copper, using water as working fluid, operating on cycles at temperatures up to 200°C focusing on industrial applications. Test results showed reliable operation during the cycles, with fast start-ups and transients, achieving thermal conductances of up to 21.9 W/°C. Even though water-copper heat pipes present a better thermal performance when compared to the water-stainless steel heat pipes, there is a wide application not only for industry but also for aerospace.
{"title":"Thermal behavior of water-copper and water-stainless steel heat pipes operating in cycles","authors":"Debora de O. Silva, R. Riehl","doi":"10.1109/ITHERM.2016.7517521","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517521","url":null,"abstract":"Heat pipes are a closed tube or chamber of different shapes whose inner surfaces are lined with a porous capillary wick, containing a saturated working fluid. It is a technology not restricted to aerospace applications, which is frequently used as thermal control devices of satellites and space vehicles. Some other sectors are finding interest on applying heat pipes to promote the thermal control of electronic equipment and heat exchangers performance augmentation. The use of heat pipes in such equipment allows the development of more compact and efficient heat exchangers compared to traditional designs, which increases the interest on applying them for industrial purposes. Heat pipes operating at mid-level temperatures have found several applications on both aerospace and industry segments. This work has the objective to present experimental results of heat pipes operation designed and manufactured in stainless steel and copper, using water as working fluid, operating on cycles at temperatures up to 200°C focusing on industrial applications. Test results showed reliable operation during the cycles, with fast start-ups and transients, achieving thermal conductances of up to 21.9 W/°C. Even though water-copper heat pipes present a better thermal performance when compared to the water-stainless steel heat pipes, there is a wide application not only for industry but also for aerospace.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 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":"130948325","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.2016.7517615
M. Patterson, S. Krishnan, John M. Walters
HPC Data Center's performance and growth are now being limited by both cost and power. A cost-efficient data center and an energy-efficient data center are all too often mutually exclusive, but they do not have to be. Liquid cooling is one area that, when done right, can improve both costs and energy efficiency. The design for liquid cooling systems generally begins with the ASHRAE liquid cooling datacenter classes. These provide guidance to both datacenter facility cooling system designers and electronic equipment manufacturers by providing a common baseline and understanding of the interface conditions between the cooling and the IT equipment. Further, the liquid cooling classes also suggest possible cooling equipment for a given datacenter class. Due to the aforementioned cooling equipment prescription, perception exists that moving from W1/W2 class environments to W3 or W4 classes represent increased energy efficiency during IT equipment operation. In this paper we show this not to be the case universally and explore a more detailed, technical approach to optimizing both cost and energy efficiency. The range of parameters includes geographical and climate conditions, state of the existing data center cooling infrastructure (greenfield, retrofit, cluster change-out, expansion), and IT level liquid cooling architecture. Through this analysis we show that for energy efficient operation of the IT equipment there exists an optimum liquid operating temperature that can also provide the lowest TCO. This temperature can drive the right capital investment as well as reduce facility operational expense and IT operational expense. We also explore the impact on reliability, the controls architecture, use of efficiency metrics, cluster compute performance, and opportunities for energy re-use.
{"title":"On energy efficiency of liquid cooled HPC datacenters","authors":"M. Patterson, S. Krishnan, John M. Walters","doi":"10.1109/ITHERM.2016.7517615","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517615","url":null,"abstract":"HPC Data Center's performance and growth are now being limited by both cost and power. A cost-efficient data center and an energy-efficient data center are all too often mutually exclusive, but they do not have to be. Liquid cooling is one area that, when done right, can improve both costs and energy efficiency. The design for liquid cooling systems generally begins with the ASHRAE liquid cooling datacenter classes. These provide guidance to both datacenter facility cooling system designers and electronic equipment manufacturers by providing a common baseline and understanding of the interface conditions between the cooling and the IT equipment. Further, the liquid cooling classes also suggest possible cooling equipment for a given datacenter class. Due to the aforementioned cooling equipment prescription, perception exists that moving from W1/W2 class environments to W3 or W4 classes represent increased energy efficiency during IT equipment operation. In this paper we show this not to be the case universally and explore a more detailed, technical approach to optimizing both cost and energy efficiency. The range of parameters includes geographical and climate conditions, state of the existing data center cooling infrastructure (greenfield, retrofit, cluster change-out, expansion), and IT level liquid cooling architecture. Through this analysis we show that for energy efficient operation of the IT equipment there exists an optimum liquid operating temperature that can also provide the lowest TCO. This temperature can drive the right capital investment as well as reduce facility operational expense and IT operational expense. We also explore the impact on reliability, the controls architecture, use of efficiency metrics, cluster compute performance, and opportunities for energy re-use.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"35 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":"129801740","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.2016.7517624
D. Lorenzini, Y. Joshi
Flow boiling in surface-enhanced microgaps represents a promising thermal control method for the removal of relatively high heat fluxes in applications such as three-dimensional (3D) integration of microelectronics. Although a few experimental investigations have reported encouraging results for these types of cooling layers, the computational fluid dynamics (CFD) analysis of the involved physics has lagged behind due to a number of challenges. In the present study, a phase-change model is used with the Volume of Fluid (VOF) method for interface tracking to analyze the transient flow regime evolution due to boiling in a microgap with circular pin fins for area enhancement, where the simultaneous heat conduction is solved in the silicon medium. High-Performance Computing (HPC) is used for investigating two-phase flow and heat transfer in a relatively dense array of pin fins of 150 μm diameter populating a 175 μm height microgap, which is 10 mm long. The dielectric refrigerant R245fa is used as the coolant due to its negligible electrical conductivity, desirable for inter-tier cooling. Results provide useful insight on how the vapor phase is generated and distributed as a function of the axial direction, as well as the implication on heat transfer and resulting surface temperatures to identify trends and required conditions for the reliable operation in potential microelectronic applications.
{"title":"CFD study of flow boiling in silicon microgaps with staggered pin fins for the 3D-stacking of ICs","authors":"D. Lorenzini, Y. Joshi","doi":"10.1109/ITHERM.2016.7517624","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517624","url":null,"abstract":"Flow boiling in surface-enhanced microgaps represents a promising thermal control method for the removal of relatively high heat fluxes in applications such as three-dimensional (3D) integration of microelectronics. Although a few experimental investigations have reported encouraging results for these types of cooling layers, the computational fluid dynamics (CFD) analysis of the involved physics has lagged behind due to a number of challenges. In the present study, a phase-change model is used with the Volume of Fluid (VOF) method for interface tracking to analyze the transient flow regime evolution due to boiling in a microgap with circular pin fins for area enhancement, where the simultaneous heat conduction is solved in the silicon medium. High-Performance Computing (HPC) is used for investigating two-phase flow and heat transfer in a relatively dense array of pin fins of 150 μm diameter populating a 175 μm height microgap, which is 10 mm long. The dielectric refrigerant R245fa is used as the coolant due to its negligible electrical conductivity, desirable for inter-tier cooling. Results provide useful insight on how the vapor phase is generated and distributed as a function of the axial direction, as well as the implication on heat transfer and resulting surface temperatures to identify trends and required conditions for the reliable operation in potential microelectronic applications.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"18 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":"132297062","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.2016.7517652
Pablo A. de Oliveira, J. Barbosa
This paper introduces a compact vapor compression cooling system equipped with a small-scale oil-free linear motor R-134a compressor and a novel heat sink that integrates the evaporator and the expansion device into a single unit. At the present stage of the development, a single orifice was used to generate the high-speed two-phase impinging jet on the heated surface. The effects of the applied thermal load, orifice diameter, orifice-to-heater distance, hot reservoir temperature and compressor stroke on the system performance were quantified. The system performance was evaluated in terms of the temperature of the heated surface, heat transfer coefficient, coefficient of performance and second-law efficiency. The operating conditions that maximized the system performance for specific operating conditions have been identified.
{"title":"Two-phase jet impingement heat sink integrated with a compact vapor compression system for electronics cooling","authors":"Pablo A. de Oliveira, J. Barbosa","doi":"10.1109/ITHERM.2016.7517652","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517652","url":null,"abstract":"This paper introduces a compact vapor compression cooling system equipped with a small-scale oil-free linear motor R-134a compressor and a novel heat sink that integrates the evaporator and the expansion device into a single unit. At the present stage of the development, a single orifice was used to generate the high-speed two-phase impinging jet on the heated surface. The effects of the applied thermal load, orifice diameter, orifice-to-heater distance, hot reservoir temperature and compressor stroke on the system performance were quantified. The system performance was evaluated in terms of the temperature of the heated surface, heat transfer coefficient, coefficient of performance and second-law efficiency. The operating conditions that maximized the system performance for specific operating conditions have been identified.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 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":"132416451","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.2016.7517565
Kevin P. Drummond, J. Weibel, S. Garimella, Doosan Back, D. Janes, M. Sinanis, D. Peroulis
A hierarchical manifold microchannel heat sink is used to dissipate heat from a small hotspot region superposed on a larger region of uniform background heat flux. A 5 mm × 5 mm overall chip footprint area is cooled using a 3 × 3 array of intrachip silicon microchannel heat sinks fed in parallel using a manifold distributor. Each heat sink consists of a bank of 25 high-aspect-ratio microchannels that are nominally 30 μm wide and 300 μm deep. The uniform background heat flux is generated with a 3 × 3 array of thin-film heaters fabricated on the chip; temperature sensors placed in each of these nine heating zones provide spatially resolved chip surface temperature measurements. An individually powered 200 μm × 200 μm hotspot heater is centered on the chip. The heat sink thermal and hydraulic performance is evaluated using HFE-7100 as the working fluid and for mass fluxes ranging from 600 kg/m2s to 2070 kg/m2s at a constant inlet temperature of 60°C and outlet pressure of 122 kPa. Background heat fluxes up to 450 W/cm2 and hotspot fluxes of greater than 2500 W/cm2 are simultaneously dissipated. The chip temperature uniformity and maximum temperature rise during hotspot heating are assessed. For the case with the highest simultaneous background and hotspot heat fluxes, the measured heat sink pressure drop is ~75 kPa and the average chip temperature is ~30°C above the fluid inlet temperature.
{"title":"Evaporative intrachip hotspot cooling with a hierarchical manifold microchannel heat sink array","authors":"Kevin P. Drummond, J. Weibel, S. Garimella, Doosan Back, D. Janes, M. Sinanis, D. Peroulis","doi":"10.1109/ITHERM.2016.7517565","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517565","url":null,"abstract":"A hierarchical manifold microchannel heat sink is used to dissipate heat from a small hotspot region superposed on a larger region of uniform background heat flux. A 5 mm × 5 mm overall chip footprint area is cooled using a 3 × 3 array of intrachip silicon microchannel heat sinks fed in parallel using a manifold distributor. Each heat sink consists of a bank of 25 high-aspect-ratio microchannels that are nominally 30 μm wide and 300 μm deep. The uniform background heat flux is generated with a 3 × 3 array of thin-film heaters fabricated on the chip; temperature sensors placed in each of these nine heating zones provide spatially resolved chip surface temperature measurements. An individually powered 200 μm × 200 μm hotspot heater is centered on the chip. The heat sink thermal and hydraulic performance is evaluated using HFE-7100 as the working fluid and for mass fluxes ranging from 600 kg/m2s to 2070 kg/m2s at a constant inlet temperature of 60°C and outlet pressure of 122 kPa. Background heat fluxes up to 450 W/cm2 and hotspot fluxes of greater than 2500 W/cm2 are simultaneously dissipated. The chip temperature uniformity and maximum temperature rise during hotspot heating are assessed. For the case with the highest simultaneous background and hotspot heat fluxes, the measured heat sink pressure drop is ~75 kPa and the average chip temperature is ~30°C above the fluid inlet temperature.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"1 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":"130214598","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.2016.7517587
M. Janicki, T. Torzewicz, A. Napieralski
This paper presents the investigations of internal package structure based on the analyses of device dynamic thermal responses to power step excitation recorded in various cooling conditions. The analyses are carried out for two theoretically identical power devices representing different technological generations. As demonstrated in the paper, both thermal and electrical behaviors of these devices differ substantially. The time constant spectra and the cumulative structure functions calculated from the recorded thermal responses revealed deep internal differences between the devices. These results were confirmed also by measurements of device geometries taken after the disassembly of their packages. Owing to the proposed approach it was possible also to generate compact thermal models of both devices in the form RC Cauer ladders whose elements could be attributed some physical meaning. These models were finally validated with the measurements showing excellent accuracy of thermal simulation.
{"title":"Investigation of internal package structure based on the analysis of dynamic temperature response","authors":"M. Janicki, T. Torzewicz, A. Napieralski","doi":"10.1109/ITHERM.2016.7517587","DOIUrl":"https://doi.org/10.1109/ITHERM.2016.7517587","url":null,"abstract":"This paper presents the investigations of internal package structure based on the analyses of device dynamic thermal responses to power step excitation recorded in various cooling conditions. The analyses are carried out for two theoretically identical power devices representing different technological generations. As demonstrated in the paper, both thermal and electrical behaviors of these devices differ substantially. The time constant spectra and the cumulative structure functions calculated from the recorded thermal responses revealed deep internal differences between the devices. These results were confirmed also by measurements of device geometries taken after the disassembly of their packages. Owing to the proposed approach it was possible also to generate compact thermal models of both devices in the form RC Cauer ladders whose elements could be attributed some physical meaning. These models were finally validated with the measurements showing excellent accuracy of thermal simulation.","PeriodicalId":426908,"journal":{"name":"2016 15th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)","volume":"7 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":"114412346","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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