Compact Modeling of Fractal Tree-Shaped Microchannel Liquid Cooling Systems

2011 ◽  
Author(s):  
Cheng Chen ◽  
Emad Samadiani ◽  
Bahgat Sammakia
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Maximum Flow ◽  
Heat Fluxes ◽  
Compact Model ◽  
Temperature Fields ◽  
Compact Modeling ◽  
Liquid Cooling ◽  
Cooling Systems ◽  
Full Field

Demands for higher computational speed and miniaturization have already resulted in extremely high heat fluxes in microprocessors. Fractal tree-shaped microchannel liquid cooling systems are novel heat transfer enhancement systems to keep the temperature of the microprocessors in a safe range. Due to the complexity of these systems, their full field numerical modeling for simulation of the flow and temperature fields is too time consuming and costly, particularly to be used within iterative optimization algorithms. In this paper, a quick but still accurate compact modeling approach based on Flow Network Modeling (FNM) is introduced for analysis of the flow filed in fractal microchannel liquid cooling systems. The compact method is applied to a representative fractal microchannel cooling system and the obtained velocity and flow rate distribution are validated against a full Computational Fluid Dynamics (CFD)-based model for three different designs. The compact model shows good agreement with the CFD results and robustness on different designs, while requiring much less computational capability and time. Afterwards, the compact model is used for optimization of the geometry of the fractal cooling system to achieve maximum flow rate and uniform flow distribution among the channels for a fixed pressure drop.

Development of a Mini Liquid Cooling System for High Heat Flux Electronic Devices

2009 ◽  
Author(s):  
Chien-Yuh Yang ◽  
Chun-Ta Yeh ◽  
Kou-Chung Huang ◽  
Shao-Nong Tsai
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Maximum Flow ◽  
Maximum Pressure ◽  
High Heat Flux ◽  
Cold Plate ◽  
Liquid Cooling ◽  
Commercial Products ◽  
Micro Pump ◽  
Liquid Cooling System

The size of the most of the current commercialized liquid cooling systems is apparently too large to be easily adapted in a notebook or a mini size desk top computer. This study incorporated the authors’ previous micro heat exchanger design with an extra slim pump concept proposed by a local manufacturer to develop a high performance miniature liquid cooling system. An integrated pump and cold plate assembly was also developed for further reducing the overall size of the system. In comparing to the commercial products, the test results show that the micro pump provides a higher maximum pressure head and maximum flow rate performance. The cold plate has the lowest thermal resistance at moderate and high flow rate region. And the performed of the entire liquid system is similar to that of the recently announced product. It is emphasized that the size of the present developed cold plate, pump and liquid cooling system is much smaller than that of all commercial products.

scholarly journals A large opening and high flow rate  piezoelectric pump with straight arm wheeled check valve

2020 ◽  
Author(s):  
Lipeng He ◽  
Xiaoqiang Wu ◽  
Zhe Wang ◽  
Da Zhao ◽  
Jianming Wen ◽  
...  
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Check Valve ◽  
Maximum Flow ◽  
Low Flow ◽  
Piezoelectric Pump ◽  
Cooling Systems ◽  
Microelectronic Devices ◽  
Valve Opening ◽  
Large Opening

Abstract Piezoelectric pumps are applied in cooling systems of microelectronic devices because of their small size. However, cooling efficiency is limited by low flow rate. A Straight arm wheeled check valve made of silica gel was proposed, which can improve flow rate of piezoelectric pump, solve the influence of glue aging on the sealing ability of a wheeled check valve and reduce the size of piezoelectric pump. This paper discusses the influence of valve arm number (N=2, 3 and 4), valve arm width (W=1.0, 1.2 and 1.4mm) and valve thickness (T=0.6, 0.8 and 1.0mm) on flow rate characteristics of piezoelectric pumps. When valve opening rises, the flow rate increases. The simulation results show that valves with 2 valve arms, 0.6mm valve thickness and 1.0mm valve arm width have maximum valve opening. Experimental results show that piezoelectric pumps with different valve parameters have different optimal frequencies. In addition, maximum flow rate is 431.6mL/min at 220V and 70Hz. This paper provides a reference for the application of piezoelectric pump in cooling system.

Review and Projections of Integrated Cooling Systems for Three-Dimensional Integrated Circuits

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Satish G. Kandlikar
Keyword(s):  
Hot Spots ◽  
Heat Dissipation ◽  
Cooling System ◽  
Mechanical Design ◽  
Heat Fluxes ◽  
Electrical Performance ◽  
Channel Height ◽  
Cooling Systems ◽  
3D Ic ◽  
Pressure Drops

In an effort to increase processor speeds, 3D IC architecture is being aggressively pursued by researchers and chip manufacturers. This architecture allows extremely high level of integration with enhanced electrical performance and expanded functionality, and facilitates realization of VLSI and ULSI technologies. However, utilizing the third dimension to provide additional device layers poses thermal challenges due to the increased heat dissipation and complex electrical interconnects among different layers. The conflicting needs of the cooling system requiring larger flow passage dimensions to limit the pressure drop, and the IC architecture necessitating short interconnect distances to reduce signal latency warrant paradigm shifts in both of their design approach. Additional considerations include the effects due to temperature nonuniformity, localized hot spots, complex fluidic connections, and mechanical design. This paper reviews the advances in 3D IC cooling in the last decade and provides a vision for codesigning 3D IC architecture and integrated cooling systems. For heat fluxes of 50–100 W/cm2 on each side of a chip in a 3D IC package, the current single-phase cooling technology is projected to provide adequate cooling, albeit with high pressure drops. For future applications with coolant surface heat fluxes from 100 to 500 W/cm2, significant changes need to be made in both electrical and cooling technologies through a new level of codesign. Effectively mitigating the high temperatures surrounding local hot spots remains a challenging issue. The codesign approach with circuit, software and thermal designers working together is seen as essential. The through silicon vias (TSVs) in the current designs place a stringent limit on the channel height in the cooling layer. It is projected that integration of wireless network on chip architecture could alleviate these height restrictions since the data bandwidth is independent of the communication lengths. Microchannels that are 200 μm or larger in depth are expected to allow dissipation of large heat fluxes with significantly lower pressure drops.

Performance Analysis With Future Predictions of Different Solar Cooling Systems in Guayaquil, Ecuador

2014 ◽  
Author(s):  
Carlos Naranjo-Mendoza ◽  
Jesús López-Villada ◽  
Gabriel Gaona ◽  
Jerko Labus
Keyword(s):  
Flow Rate ◽  
Cooling System ◽  
Meteorological Data ◽  
Cooling Systems ◽  
Great Opportunity ◽  
Constant Flow Rate ◽  
Solar Cooling ◽  
Average Annual Temperature ◽  
System Configurations

This paper presents a comparative analysis of three different solar cooling system configurations developed for a case study building in Guayaquil, Ecuador. Guayaquil is a city located at the Ecuadorian coast with an average annual temperature of 25°C. The city’s need for air conditioning throughout the year and the relatively intense solar radiation provide a great opportunity for implementation of solar cooling systems. The first cooling system includes a 175 kWc single-effect absorption chiller powered by evacuated tubes solar thermal collectors. This system was compared with two 140 kWc compression chiller systems (air-cooled (AC) and water-cooled (WC)) powered by grid-connected photovoltaics. Both constant flow rate (CFR) and variable flow rate (VFR) of chilled water were analyzed. The three systems have to satisfy a cooling demand of the top floor in one governmental building (app. 1296 m2) which was selected as case study. Additionally, two 140 kWc conventional compression chiller systems (AC and WC) were included in the comparison as reference systems. Cooling demand of the building was simulated in EnergyPlus and coupled with the appropriate system configurations developed in TRNSYS. The weather file (TMY) was developed based on real meteorological data collected in the last decade. The present analysis was extended with the prediction scenarios for the years 2020, 2050 and 2080 using climate change adapted weather files.

Relative Cooling With Liquid for Gas Turbines: Part I — A Solution for Exceeding 2000 K at Turbine Inlet

2001 ◽  
Author(s):  
Sandu Constantin ◽  
Dan Brasoveanu
Keyword(s):  
Thermal Efficiency ◽  
Gas Turbines ◽  
Cooling System ◽  
Turbine Blades ◽  
Air Cooling ◽  
Liquid Cooling ◽  
Cooling Systems ◽  
Turbine Inlet ◽  
Cooling Methods ◽  
Current Operating

Abstract The thermal efficiency of gas turbines is critically dependent on the temperature of burnt gases at turbine inlet, the higher this temperature the higher the efficiency. Stochiometric combustion would provide maximum efficiency, but in the absence of an internal cooling system, turbine blades cannot tolerate gas temperatures that exceed 1300 K. Therefore, for this temperature, the thermal efficiency of turbine engine is 40% less than theoretical maximum. Conventional air-cooling techniques of turbine blades allow inlet temperatures of about 1500 K on current operating engines yielding thermal efficiency gains of about 6%. New designs, that incorporate advanced air-cooling methods allows inlet temperatures of 1750–1800 K, with a thermal efficiency gain of about 6% relative to current operating engines. This temperature is near the limit allowed by air-cooling systems. Turbine blades can be cooled with air taken from the compressor or with liquid. Cooling systems with air are easier to design but have a relatively low heat transfer capacity and reduce the efficiency of the engine. Some cooling systems with liquid rely on thermal gradients to promote re-circulation from the tip to the root of turbine blades. In this case, the flow and cooling of liquid are restricted. For best results, cooling systems with liquid should use a pump to re-circulate the coolant. In the past, designers tried to place this pump on the engine stator and therefore were unable to avoid high coolant losses because it is impossible to reliably seal the stator-rotor interface. Therefore it was assumed that cooling systems with liquid could not incorporate pumps. This is an unwarranted assumption as shown studying the system in a moving frame of reference that is linked to the rotor. Here is the crucial fact overlooked by previous designers. The relative motion of engine stator with respect to the rotor is sufficient to motivate a cooling pump. Both the pump and heat exchange system that is required to provide rapid cooling of liquid with cold ambient air, could be located within the rotor. Therefore, the entire cooling system can be encapsulated within the rotor and the sealing problem is circumvented. Compared to recent designs that use advanced air-cooling methods, such a liquid cooling system would increase the thermal efficiency by 8%–11% because the temperatures at turbine inlet can reach stoichiometric levels and most of the heat extracted from turbine during cooling is recuperated. The appreciated high reliability of the system will permit a large applicability in aerospace propulsion.

Temporal Response of Porous Glass Electroosmotic Pumps

2002 ◽  
Author(s):  
Shuhuai Yao ◽  
Shulin Zeng ◽  
Juan G. Santiago
Keyword(s):  
Flow Rate ◽  
Maximum Flow ◽  
Ion Concentration ◽  
Temporal Response ◽  
Short Term ◽  
Cooling Systems ◽  
Sintered Glass ◽  
Rate Capacity ◽  
Bioanalytical Applications ◽  
Electroosmotic Pumps

Sintered glass electroosmotic pumps have been fabricated that provide maximum flow rates and pressure capacities exceeding 14 ml/min and 1.4 atm, respectively, at 150 V, with an active pumping volume of less than 2 cm3. These compact devices with no moving parts have the potential to impact a variety of applications including microelectronics cooling systems and bioanalytical applications. We present here a preliminary a study of the response of the pumps to changes in fluidic load, including their short-term transient performance. A 0.5 mM borate buffer (pH = 9.2) is used to stabilize pump performance, with nearly optimal flow rate capacity. The experiments are conducted for working electrolytes of varying ion concentration. These performance characteristics are critical to applications that aim to use feedback control of flow rate and pressure over varying conditions.

On Development of a Semi-Mechanistic Wall Boiling Model

2013 ◽  
Author(s):  
Saurish Das ◽  
Hemant Punekar
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Stresses ◽  
Cooling System ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Working Fluid ◽  
Wall Heat Transfer ◽  
Cooling Systems ◽  
Transfer Phenomenon

In modern cooling systems the requirement of higher performance demands highest possible heat transfer rates, which can be achieved by controlled nucleate boiling. Boiling based cooling systems are gaining attention in several engineering applications as a potential replacement of conventional single-phase cooling system. Although the controlled nucleate boiling enhances the heat transfer, uncontrolled boiling may lead to Dry Out situation, adversely affecting the cooling performance and may also cause mechanical damage due to high thermal stresses. Designing boiling based cooling systems requires a modeling approach based on detailed fundamental understanding of this complex two-phase heat and mass transfer phenomenon. Such models can help analyze different cooling systems, detect potential design flaws and carry out design optimization. In the present work a new semi-mechanistic wall boiling model is developed within commercial CFD solver ANSYS FLUENT. A phase change mechanism and wall heat transfer augmentation due to nucleate boiling are implemented in mixture multiphase flow framework. The phase change phenomenon is modeled using mechanistic evaporation-condensation model. Enhancement of wall heat transfer due to nucleate boiling is captured using 1D empirical correlation, modified for 3D CFD environment. A new method is proposed to calculate the local suppression of nucleate boiling based on the flow velocity, and hence this model can be applied to any complex shaped coolant passage. For different wall superheat, the wall heat fluxes predicted by the present model are validated against experimental data, in which 50-50 volume mixture of aqueous ethylene glycol (a typical anti-freeze coolant mixture) is used as working fluid. The validation study is performed in ducts of different sizes and shapes with different inlet velocities, inlet sub-cooling and operating pressures. The results are in good agreement with the experiments. This model is applied to a typical automobile Exhaust Gas Recirculation (EGR) system to study boiling heat transfer phenomenon and the results are presented.

Analysis and Design of Liquid-Cooling Systems Using Flow Network Modeling (FNM)

2003 ◽  
Author(s):  
Kanchan M. Kelkar ◽  
Suhas V. Patankar
Keyword(s):  
Cooling System ◽  
Network Modeling ◽  
Thermal Characteristics ◽  
Flow Distribution ◽  
Computer Applications ◽  
Liquid Cooling ◽  
Cooling Systems ◽  
Flow Network ◽  
Analysis And Design ◽  
Liquid Cooling System

Liquid cooling is used for thermal management of electronics in defense, power, medical, and computer applications due to the increasing power density and the desire for compact packaging. The objectives in the design of these systems are to create a sufficient amount of total flow and to appropriately distribute the flow so as to maintain the electronic component temperatures at the desired level. The technique of Flow Network Modeling (FNM) is ideally suited for the analysis of flow distribution and heat transfer in liquid-cooling systems. The FNM technique uses overall flow and thermal characteristics to represent the behavior of individual components. Therefore, solution of conservation equations over the network enables efficient prediction of the flow rates, pressures, and temperatures in a complete liquid-cooling system. This article describes the technical basis of the FNM technique and illustrates its application in the design of a distributed-flow cold plate and of a complete water-cooled system. The study demonstrates the utility of the FNM technique for rapid and accurate evaluation of different design options and the ensuing productivity benefits in the design of liquid cooling systems.

scholarly journals Controlling the Distribution of Cold Water in Air Cooling Systems of Underground Mines

2016 ◽  
Vol 61 (4) ◽  
pp. 793-807 ◽  
Author(s):  
Nikodem Szlązak ◽  
Dariusz Obracaj ◽  
Justyna Swolkień ◽  
Kazimierz Piergies
Keyword(s):  
Automatic Control ◽  
Water Flow ◽  
Flow Rate ◽  
Cold Water ◽  
Cooling System ◽  
Water Flow Rate ◽  
Underground Mines ◽  
Air Cooling ◽  
Cooling Systems ◽  
Pipeline Network

Abstract In Polish underground mines in which excavations are subjected to high heat load, central and group cooling systems based on indirect cooling units are implemented. Chilled water, referred to as cold water and produced in chillers, is distributed through a pipeline network to air coolers located in mining and development districts. The coolers are often moved to other locations and the pipeline network undergoes constant modification. In such a system, parameters of cold water in different branches of the pipeline network need to be controlled. The article presents the principles for controlling the cooling capacity of air coolers installed in an underground mine. Also, the authors propose automatic control of water flow rate in underground pipeline network and in particular coolers, depending on the temporary cooling load in the system. The principles of such a system, controlling cold water distribution, and the functions of its individual components are described. Finally, an example of an automatic control of water flow rate in a central cooling system currently implemented in a mine is presented.

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