Abstract The increasing demand for high-performance computing in applications such as the Internet of Things, Deep Learning, Big data for crypto-mining, virtual reality, healthcare research on genomic sequencing, cancer treatment, etc. have led to the growth of hyperscale data centers. To meet the cooling energy demands of HPC datacenters efficient cooling technologies must be adopted. Traditional air cooling, direct-to-chip liquid cooling, and immersion are some of those methods. Among all, Liquid cooling is superior compared to various air-cooling methods in terms of energy consumption. Direct on-chip cooling using cold plate technology is one such method used in removing heat from high-power electronic components such as CPUs and GPUs in a broader sense. Over the years Thermal Design Power (TDP) is rapidly increasing and will continue to increase in the coming years for not only CPUs and GPUs but also associated electronic components like DRAMs, Platform Control Hub (PCH), and other I/O chipsets on a typical server board. Therefore, unlike air hybrid cooling which uses liquid for cold plates and air as the secondary medium of cooling the associated electronics, we foresee using immersion-based fluids to cool the rest of the electronics in the server. The broader focus of this research is to study the effects of adopting immersion cooling, with integrated cold plates for high-performance systems. Although there are several other factors involved in the study, the focus of this paper will be the optimization of cold plate microchannels for immersion-based fluids in an immersion-cooled environment. Since immersion fluids are dielectric and the fluids used in cold plates are conductive, it exposes us to a major risk of leakage into the tank and short-circuiting the electronics. Therefore, we propose using the immersed fluid to pump into the cold plate. However, it leads to a suspicion of poor thermal performance and associated pumping power due to the difference in viscosity and other fluid properties. To address the thermal and flow performance, the objective is to optimize the cold plate microchannel fin parameters based on thermal and flow performance by evaluating thermal resistance and pressure drop across the cold plate. The detailed CFD model and optimization of the cold plate were done using Ansys Icepak and Ansys OptiSLang respectively.
more »
« less
Numerical Analysis of Oil Immersion Cooling of a Server Using Mineral Oil and Al2O3 Nanofluid
Abstract Increased demand for computer applications has manifested a rise in data generation, resulting in high Power Density and Heat Generation of servers and their components, requiring efficient thermal management. Due to the low heat carrying capacity of air, air cooling is not an efficient method of data center cooling. Hence, the liquid immersion cooling method has emerged as a prominent method, where the server is directly immersed in a dielectric liquid. The thermal conductivity of the dielectric liquids is drastically increased with the introduction of non-metallic nanoparticles of size between 1 to 150 nm, which has proven to be the best method. To maintain the dielectric feature of the liquid, non-metallic nanoparticles can be added. Alumina nanoparticles with a mean size of 80 nm and a mass concentration of 0 to 5% with mineral oil are used in the present study. The properties of the mixture were calculated based on the theoretical formula and it was a function of temperature. Heat transfer and effect of the nanoparticle concentration on the junction temperature of the processors using CFD techniques were simulated on an open commute server with two processors in a row. The junction temperature was studied for different flow rates of 0.5, 1, 2, and 3 LPM, at inlet temperatures of 25, 35, and 45 degrees Celsius. The chosen heatsink geometries were: Parallel plate, Pin fin, and Plate fin heatsinks.
more »
« less
- Award ID(s):
- 1738811
- PAR ID:
- 10276621
- Date Published:
- Journal Name:
- ASME 2020 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Miniaturization and high heat flux of power electronic devices have posed a colossal challenge for adequate thermal management. Conventional air-cooling solutions are inadequate for high-performance electronics. Liquid cooling is an alternative solution thanks to the higher specific heat and latent heat associated with the coolants. Liquid-cooled cold plates are typically manufactured by different approaches such as: skived, forged, extrusion, electrical discharge machining. When researchers are facing challenges at creating complex geometries in small spaces, 3D-printing can be a solution. In this paper, a 3D-printed cold plate was designed and characterized with water coolant. The printed metal fin structures were strong enough to undergo pressure from the fluid flow even at high flow rates and small fin structures. A copper block with top surface area of 1 inch by 1 inch was used to mimic a computer chip. Experimental data has good match with a simulation model which was built using commercial software 6SigmaET. Effects of geometry parameters and operating parameters were investigated. Fin diameter was varied from 0.3 mm to 0.5 mm and fin height was maintained at 2 mm. A special manifold was designed to maximize the surface contact area between coolant and metal surface and therefore minimize thermal resistance. The flow rate was varied from 0.75 L/min to 2 L/min and coolant inlet temperature was varied from 25 to 48 oC. It was observed that for the coolant inlet temperature 25 oC and aluminum cold plate, the junction temperature was kept below 63.2 oC at input power 350 W and pressure drop did not exceed 23 Kpa. Effects of metal materials used in 3D-printing on the thermal performance of the cold plate were also studied in detail.more » « less
-
More than ever before, data centers must deploy robust thermal solutions to adequately host the high-density and high-performance computing that is in high demand. The newer generation of central processing units (CPUs) and graphics processing units (GPUs) has substantially higher thermal power densities than previous generations. In recent years, more data centers rely on liquid cooling for the high-heat processors inside the servers and air cooling for the remaining low-heat information technology equipment. This hybrid cooling approach creates a smaller and more efficient data center. The deployment of direct-to-chip cold plate liquid cooling is one of the mainstream approaches to providing concentrated cooling to targeted processors. In this study, a processor-level experimental setup was developed to evaluate the cooling performance of a novel computer numerical control (CNC) machined nickel-plated impinging cold plate on a 1 in. 1 in. mock heater that represents a functional processing unit. The pressure drop and thermal resistance performance curves of the electroless nickel-plated cold plate are compared to those of a pure copper cold plate. A temperature uniformity analysis is done using compuational fluid dynamics and compared to the actual test data. Finally, the CNC machined pure copper one is compared to other reported cold plates to demonstrate its superiority of the design with respect to the cooling performance.more » « less
-
Abstract Data centers have started to adopt immersion cooling for more than just mainframes and supercomputers. Due to the inability of air cooling to cool down recent high-configured servers with higher Thermal Design Power, current thermal requirements in machine learning, AI, blockchain, 5G, edge computing, and high-frequency trading have resulted in a larger deployment of immersion cooling. Dielectric fluids are far more efficient at transferring heat than air. Immersion cooling promises to help address many of the challenges that come with air cooling systems, especially as computing densities increase. Immersion-cooled data centers are more expandable, quicker installation, more energy-efficient, allows for the cooling of almost all server components, save more money for enterprises, and are more robust overall. By eliminating active cooling components such as fans, immersion cooling enables a significantly higher density of computing capabilities. When utilizing immersion cooling for server hardware that is intended to be air-cooled, immersion-specific optimized heat sinks should be used. A heat sink is an important component for server cooling efficacy. This research conducts an optimization of heatsink for immersion-cooled servers to achieve the minimum case temperature possible utilizing multi-objective and multidesign variable optimization with pumping power as the constraint. A high-density server of 3.76 kW was modeled on Ansys Icepak that consists of 2 CPUs and 8 GPUs with heatsink assemblies at their Thermal Design Power along with 32 Dual In-line Memory Modules. The optimization is conducted for Aluminum heat sinks by minimizing the pressure drop and thermal resistance as the objective functions whereas fin count, fin thickness, and heat sink height are chosen as the design variables in all CPUs, and GPUs heatsink assemblies. Optimization for the CPU and the GPU heatsink was done separately and then the optimized heatsinks were tested in an actual test setup of the server in ANSYS Icepak. The dielectric fluid for this numerical study is EC-110 and the cooling is carried out using forced convection. A Design of Experiment (DOE) is created based on the input range of design variables using a full-factorial approach to generate multiple design points. The effect of the design variables is analyzed on the objective functions to establish the parameters that have a greater impact on the performance of the optimized heatsink. The optimization study is done using Ansys OptiSLang where AMOP (Adaptive Metamodel of Optimal Prognosis) as the sampling method for design exploration. The results show total effect values of heat sinks geometric parameters to choose the best design point with the help of a Response Surface 2D and 3D plot for the individual heat sink assembly.more » « less
-
Abstract This paper proposes a computational fluid dynamics (CFD) simulation methodology for the multi-design variable optimization of heat sinks for natural convection single-phase immersion cooling of high power-density Data Center server electronics. Immersion cooling provides the capability to cool higher power-densities than air cooling. Due to this, retrofitting Data Center servers initially designed for air-cooling for immersion cooling is of interest. A common area of improvement is in optimizing the air-cooled component heat sinks for the fluid and thermal properties of liquid cooling dielectric fluids. Current heat sink optimization methodologies for immersion cooling demonstrated within the literature rely on a server-level optimization approach. This paper proposes a server-agnostic approach to immersion cooling heat sink optimization by developing a heat sink-level CFD to generate a dataset of optimized heat sinks for a range of variable input parameters: inlet fluid temperature, power dissipation, fin thickness, and number of fins. The objective function of optimization is minimizing heat sink thermal resistance. This research demonstrates an effective modeling and optimization approach for heat sinks. The optimized heat sink designs exhibit improved cooling performance and reduced pressure drop compared to traditional heat sink designs. This study also shows the importance of considering multiple design variables in the heat sink optimization process and extends immersion heat sink optimization beyond server-dependent solutions. The proposed approach can also be extended to other cooling techniques and applications, where optimizing the design variables of heat sinks can improve cooling performance and reduce energy consumption.more » « less
An official website of the United States government

