Design And Numerical Simulation of One-Phase Liquid Immersion Cooling System For Small-Scale Cryptocurrency Mining Rigs
Design And Numerical Simulation of One-Phase Liquid Immersion Cooling System For Small-Scale Cryptocurrency Mining Rigs

Author: Faris Almutairi

Publisher:

Published: 2023

Total Pages: 0

ISBN-13:

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As the world is rapidly transitioning into a digital era, blockchain technology has high potential deployments in many organizations' digital transformation plans. Blockchain technology, which is the main driver of cryptocurrency as many other digital technologies, requires sophisticated computing hardware to run it, mainly Application specific Integrated Circuit (ASIC). One of the challenges that faces cryptocurrency miners, who are an integral pillar of the network, is efficiency of their hardware. Efficiency is crucial to miners since it dictates how fast and cost-effective they can run their rigs to generate reasonable profit. With high computing scenarios (or what is known as hash rates in the cryptocurrency community) the hardware capability, despite the existence of air-cooling fans, could be limited due to high temperatures. Computing hardware in a datacenter, cryptocurrency mining rig or even in a gaming console produces a tremendous amount of heat that is essentially cooled by forced air through fans. The excessive heat in the ASIC especially in a high hash rate scenario can affect performance and potentially develop micro cracks in the hash boards and lead to failure and disruptive service. Air cooling by fans is energy consuming, noisy and requires air conditioning to remove heat from the ambient. Moreover, air is considered a good insulator and poor thermal conductor. Alternatively, recent developments in dielectric fluids that have superior thermal characteristics over air show a promising future for cooling computing hardware more efficiently. In this thesis, the thermal performance of a dielectric liquid named Bitcool-888 is explored via numerical simulation to study its effectiveness in cooling ASIC miners. This method is known as one-phase liquid immersion cooling. The ASIC miner is one of four immersed in the dielectric fluid that is being circulated in a system of tank, piping, pumps and a heat exchanger. The objective of the simulation is to find the optimum flow rate and inlet temperature that ensures adequate cooling of the ASIC miners at their peak computing power and to compare the performance of air and dielectric liquid. 32 simulations were conducted via ANSYS Icepak to study the dielectric liquid cooling capability for various power densities (1000 W and 1250 W per hash board), inlet temperatures (30 °C, 35 °C, 40 °C and 45 °C) and inlet flow rates (4 lpm, 10 lpm, 15 lpm and 20 lpm). Air performance was examined for one power density (1000 W per hash board), various inlet velocities (2 m/s, 3 m/s, 4 m/s and 5 m/s) and at 30 °C and 35 °C inlet temperatures. The results show that the dielectric liquid is better than air in cooling the ASIC miner, even at high power density, low flow rates and high inlet temperatures. The maximum hash board temperatures particularly were lower in the dielectric liquid case. Air showed higher maximum hash board temperatures in both 30 °C and 35 °C inlet temperatures cases with low to medium velocities.

Investing Thermo-fluidic Performance of Si-based Embedded Microchannels-3D Manifold Cooling System for High Power Density Electronic Applications
Investing Thermo-fluidic Performance of Si-based Embedded Microchannels-3D Manifold Cooling System for High Power Density Electronic Applications

Author: Ki Wook Jung

Publisher:

Published: 2020

Total Pages:

ISBN-13:

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High performance and economically viable cooling solutions must be developed to reduce weight and volume, allowing for a wide-spread utilization of hybrid electric vehicles. However, the continued drive for higher device and packaging densities has led to extreme heat fluxes on the order of 1 kW/cm2 that requires aggressive microchannel cooling strategies in order to maintain the device junction temperature ~ 200 C. The traditional embedded microchannel cooling heat sinks suffer from high pressure drop due to small channel dimensions and long flow paths in 2D-plane. Utilizing direct "embedded cooling" strategy in combination with top access 3D-manifold strategy reduces the pressure drop by nearly an order of magnitude. In addition, it provides more temperature uniformity across large area chips and it is less prone to flow instability in two-phase boiling heat transfer. This dissertation presents a series of studies to develop an effective microchannel-based heat exchanger with a fluid router system, the Embedded Microchannels-3D Manifold Cooler (or EMMC). The overall microfabrication efforts for the EMMCs are presented. The configuration of the target EMMC design is introduced and two major fabrication challenges are discussed. For single-phase flow, thermo-fluidic behavior of the EMMC is experimentally examined and validated by a conjugate numerical simulation model. DI water and R-245fa are used as working fluids and the maximum heat transfer rate of 100 kW/m2-K was measured with DI water. Furthermore, the conjugate numerical simulation modeling is heavily used to predict the geometric effect on the thermo-fluidic performance of different EMMCs and used to develop correlations to predict friction factor and Nusselt number of the system. For two-phase flow, forced-convective subcooled boiling is confirmed by the experiments and a systematic trial to calculate exit vapor quality has been made based on a few assumptions. The highly pressurized subcooled boiling delays onset-of-nucleate boiling in the microchannels and this strong condensation effect allows the EMMC to remove higher heat fluxes with low void fraction inside of the channels. The present research motivates further study into flow visualization and different types of boiling heat transfer. The better understanding to the underlying physics of the EMMC will be a key to develop more effective heat exchanger design for high-power density applications.

Simulation-based Micro-scale System Modeling and Design Optimization of a Portable Absorption Cycle Cooling System (tactical Energy System) Under Uncertainty
Simulation-based Micro-scale System Modeling and Design Optimization of a Portable Absorption Cycle Cooling System (tactical Energy System) Under Uncertainty

Author: David Shielee

Publisher:

Published: 2007

Total Pages: 158

ISBN-13:

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Product design is often driven by customer needs and desires. In this case the customer is the US military, and the desire is to have a cooling unit small enough and light enough to incorporate into hazard suits for use in desert combat. The Micro technology-based Energy and Chemical Systems (MECS) being developed at Oregon State University (OSU) and other institutions can generate an extraordinary rate of heat and mass transfer capabilities. As this MECS technology is progressing into the application stages, simulation-based design optimization models will provide invaluable information; saving time and money by guiding the direction of prototype creation and validation. This project studies a 2 kW cooling load based on an absorption cycle ammonia-water cooling system. The absorption cycle was chosen because it requires much less work input in the compression phase than the standard compression cycle systems, making it more suitable for portable applications. Using basic principles of robust design methodology to reduce the sensitivity of the system performance to changes in input conditions, a more robust system is implemented throughout the research. Specifically for the cooling system that means that varying ambient conditions and thermal configurations will have less of an impact on overall system performance and system weight. The thermodynamic system modeling is done using Engineering Equation Solver. A tradeoff study is conducted to determine an appropriate design space, and then a D-Optimal fractional factorial design is selected using Matlab to define a manageable sized data sample within the design space with the eight design variables with five levels each. Based on the EES-based thermodynamics model and sizing results, S-PLUS is the statistical analysis program used to develop the surrogate models of the system performance and weight. Microsoft Excel0́9s 0́−solver0́+ function was used to optimize and do a sensitivity analysis of the objective function that was created. The results of this process are a range of potential optimal configurations for the system that can be evaluated and selected by a user depending on conditions and the importance of certain factors. The optimization process generated optimal values for the thermal properties of each component based on a range of starting points. Each of these sets of optimal points had a variance of less than 20% when the input parameters were varied in a range of 10%. The resulting data supplies potential users with a good range of reasonable configurations for a 2 kW system that operate within acceptable parameters.

Development of a Prototype Thermoelectric Space Cooling System Using Phase Change Material to Improve the Performance
Development of a Prototype Thermoelectric Space Cooling System Using Phase Change Material to Improve the Performance

Author: Dongliang Zhao

Publisher:

Published: 2014

Total Pages: 152

ISBN-13: 9781321175059

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The thermoelectric cooling system has advantages over conventional vapor compression cooling devices, including compact in size, light in weight, high reliability, no mechanical moving parts, no refrigerant, being powered by direct current, and easily switching between cooling and heating modes. However, it has been long suffering from its relatively high cost and low energy efficiency, which has restricted its usage to niche applications, such as space missions, portable cooling devices, scientific and medical equipment, where coefficient of performance (COP) is not as important as reliability, energy availability, and quiet operation environment. Enhancement of thermoelectric cooling system performance generally relies on two methods: improving thermoelectric material efficiency and through thermoelectric cooling system thermal design. This research has been focused on the latter one. A prototype thermoelectric cooling system integrated with phase change material (PCM) thermal energy storage unit for space cooling has been developed. The PCM thermal storage unit used for cold storage at night, functions as the thermoelectric cooling system's heat sink during daytime's cooling period and provides relatively lower hot side temperature for the thermoelectric cooling system. The experimental test of the prototype system in a reduced-scale chamber has realized an average cooling COP of 0.87, with the maximum value of 1.22. Another comparison test for efficacy of PCM thermal storage unit shows that 35.3% electrical energy has been saved from using PCM for the thermoelectric cooling system. In general, PCM faces difficulty of poor thermal conductivity at both solid and liquid phases. This system implemented a finned inner tube to increase heat transfer during PCM charging (melting) process that directly impacts thermoelectric system's performance. A simulation tool for the entire system has been developed including mathematical models for a single thermoelectric module, for the thermoelectric cooling unit, for the PCM thermal storage unit, and for the outdoor air-water heat exchanger. When modeling PCM thermal storage unit, the enthalpy method has been adopted. Since natural convection has been observed in experiments playing a key effect on heat transfer in PCM, a staged effective thermal conductivity ( k[subscript] e ) concept and modified Rayleigh (Ra ) number formula have been developed to better capture natural convection's variable effects during the PCM charging process. Therefore, a modeling-based design procedure for thermoelectric cooling system integrating with PCM has been proposed. A case study has been completed for a model office room to demonstrate the qualitative and quantitative evaluations to the major system components. Results of this research can be extended to other applications in relevant areas. For instance, the proposed PCM thermal storage unit can be applied to integration with water-cooled conventional air-conditioning devices. Instead of using water cooling, a case study of using the proposed PCM unit for a water-cooled air-conditioner shows a COP increase of more than 25.6%.

Design and Modeling of the Navy Integrated Power and Energy Corridor Cooling System
Design and Modeling of the Navy Integrated Power and Energy Corridor Cooling System

Author: Ivan Andres Reyes

Publisher:

Published: 2022

Total Pages: 0

ISBN-13:

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This thesis used numerical analysis and modeling to design an indirect liquid-cooling system aboard U.S. Navy Surface Vessels. Guided by Department of Defense and industry requirements, a new cooling paradigm was developed, promoting human- and intra-system operations, a comprehensive component design, and a robust cooling system architecture within the NiPEC compartment footprint. Documented are the initial investigation, equipment analysis, concept selection, and proof-of-concept testing that set the foundation for future prototyping and NiPEC cooling system development.

Tradeoffs of Electronics Liquid Cooling Design Features
Tradeoffs of Electronics Liquid Cooling Design Features

Author: Joshua Morse

Publisher:

Published: 2021

Total Pages:

ISBN-13:

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As consumer electronics get more complex, the need for innovation in the field of thermal management increases. Products are getting smaller, smarter, faster, and more computationally demanding. These trends cause the products' electronics to get hotter, as well. Hot temperatures trigger electronics overheating, which causes most instances of electronics failure. Thus, cooling the electronics is essential because products which require electronics to function range across all industries, such as automotive, medical, military, electronics, and tech industries. Some specific product examples include data server racks, electric car batteries, jet engines, and heart rate monitoring equipment. All of these electronics require cooling to avoid failure. Liquid cooling is one common method of cooling electronics. This thesis details liquid cooling heat sink design choices and their effects on heat transfer, fluid flow and fabrication cost. This work also explores the design of liquid cooling for a specific electronics industry application: cooling a circuit board designed and manufactured by the electronics company Keysight Technologies. The approach used was to examine the effect on performance and price of three common design features of liquid cooling heat sinks: the header angle, pin fin geometry, and mini channel geometry. Specifically, the effect of diameter and spacing of the pin fin geometry and the effect of length of the mini channel geometry were examined. The methods used were that of numerical CFD simulation using the Ansys Fluent 19.2 software package. The system's geometry was modeled using 3D modeling software and set up for simulation in Ansys Fluent using the appropriate boundary conditions of the physical system. The simulations yielded raw pressure and temperature data, which were processed into a combined heat transfer and hydraulic performance parameter PPTC. Since this was a real-world application to be used for purchasing prototypes, manufacturing cost was considered as well. The manufacturing price was combined with the PPTC parameter to implement a PPTC/$ parameter, using which can allow comparison between each heat sink design. This examination of manufacturing price is unique because many studies focus solely on technical performance parameters and neglect the price of fabrication. It was found that the cases with the top three PPTC/$ values, in order from highest to lowest, are MCSF-AL (mini channel short fin-aluminum), MCSF (mini channel short fin-copper), and PF1-2 (Pin fin, 1mm diameter, 1mm spacing-copper).

Crimes Committed by Terrorist Groups
Crimes Committed by Terrorist Groups

Author: Mark S. Hamm

Publisher: DIANE Publishing

Published: 2011

Total Pages: 258

ISBN-13: 1437929591

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This is a print on demand edition of a hard to find publication. Examines terrorists¿ involvement in a variety of crimes ranging from motor vehicle violations, immigration fraud, and mfg. illegal firearms to counterfeiting, armed bank robbery, and smuggling weapons of mass destruction. There are 3 parts: (1) Compares the criminality of internat. jihad groups with domestic right-wing groups. (2) Six case studies of crimes includes trial transcripts, official reports, previous scholarship, and interviews with law enforce. officials and former terrorists are used to explore skills that made crimes possible; or events and lack of skill that the prevented crimes. Includes brief bio. of the terrorists along with descriptions of their org., strategies, and plots. (3) Analysis of the themes in closing arguments of the transcripts in Part 2. Illus.

Out Of Control
Out Of Control

Author: Kevin Kelly

Publisher: Basic Books

Published: 2009-04-30

Total Pages: 528

ISBN-13: 078674703X

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Out of Control chronicles the dawn of a new era in which the machines and systems that drive our economy are so complex and autonomous as to be indistinguishable from living things.