Matching Items (11)
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- All Subjects: Heat Transfer
- Creators: Mechanical and Aerospace Engineering Program
- Resource Type: Text
- Status: Published
Description
In this paper, the effectiveness and practical applications of cooling a computer's CPU using mineral oil is investigated. A computer processor or CPU may be immersed along with other electronics in mineral oil and still be operational. The mineral oil acts as a dielectric and prevents shorts in the electronics while also being thermally conductive and cooling the CPU. A simple comparison of a flat plate immersed in air versus mineral oil is considered using analytical natural convection correlations. The result of this comparison indicates that the plate cooled by natural convection in air would operate at 98.41[°C] while the plate cooled by mineral oil would operate at 32.20 [°C]. Next, CFD in ANSYS Fluent was used to conduct simulation with forced convection representing a CPU fan driving fluid flow to cool the CPU. A comparison is made between cooling done with air and mineral oil. The results of the CFD simulation results indicate that using mineral oil as a substitute to air as the cooling fluid reduced the CPU operating temperature by sixty degrees Celsius. The use of mineral oil as a cooling fluid for a consumer computer has valid thermal benefits, but the practical challenges of the method will likely prevent widespread adoption.
ContributorsTichacek, Louis Joseph (Author) / Huang, Huei-Ping (Thesis director) / Herrmann, Marcus (Committee member) / Middleton, James (Committee member) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
Many industries require workers in warehouse and stockroom environments to perform frequent lifting tasks. Over time these repeated tasks can lead to excess strain on the worker's body and reduced productivity. This project seeks to develop an exoskeletal wrist fixture to be used in conjunction with a powered exoskeleton arm to aid workers performing box lifting types of tasks. Existing products aimed at improving worker comfort and productivity typically employ either fully powered exoskeleton suits or utilize minimally powered spring arms and/or fixtures. These designs either reduce stress to the user's body through powered arms and grippers operated via handheld controls which have limited functionality, or they use a more minimal setup that reduces some load, but exposes the user's hands and wrists to injury by directing support to the forearm. The design proposed here seeks to strike a balance between size, weight, and power requirements and also proposes a novel wrist exoskeleton design which minimizes stress on the user's wrists by directly interfacing with the object to be picked up. The design of the wrist exoskeleton was approached through initially selecting degrees of freedom and a ROM (range of motion) to accommodate. Feel and functionality were improved through an iterative prototyping process which yielded two primary designs. A novel "clip-in" method was proposed to allow the user to easily attach and detach from the exoskeleton. Designs utilized a contact surface intended to be used with dry fibrillary adhesives to maximize exoskeleton grip. Two final designs, which used two pivots in opposite kinematic order, were constructed and tested to determine the best kinematic layout. The best design had two prototypes created to be worn with passive test arms that attached to the user though a specially designed belt.
ContributorsGreason, Kenneth Berend (Author) / Sugar, Thomas (Thesis director) / Holgate, Matthew (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This paper presents an experimental investigation into the effects of altering electrode surface area roughness on thermogalvanic cell performance. A temperature difference between two electrodes was induced and brought to steady state to achieve a difference of around 50 °C, which was maintained with a DC power generated hot wire and a pumped ice bath. The open-circuit voltage values at steady-state were measured by a programed multimeter and the temperatures were measured by a series of type K thermocouples. Electrode surface area roughness was altered using different grit values of sandpaper and measuring the values using a Zescope Optical Profilometer. Once three different surface area average values were achieved, 6 trials were performed with 2 trials per roughness value. The results were tabulated in Section 4 of this report.
It was predicted that increasing the surface area roughness would increase the number of electrons present in the reduction oxidation reaction and decrease the activation resistance of the thermogalvanic system. Decreasing the activation resistance, a component of total internal resistance, would therefore increase the power output of the cell by a small magnitude. The results showed that changing the surface area roughness of the Copper electrodes evidently had no effect on the outputs of the cell system. Additionally, the Seebeck coefficient was also unaffected by the presence of increased surface area roughness.
The work presented in the following paper is part of a continuing effort to better understand the performance of thermogalvanic cells and their heat to electrical energy transfer properties.
It was predicted that increasing the surface area roughness would increase the number of electrons present in the reduction oxidation reaction and decrease the activation resistance of the thermogalvanic system. Decreasing the activation resistance, a component of total internal resistance, would therefore increase the power output of the cell by a small magnitude. The results showed that changing the surface area roughness of the Copper electrodes evidently had no effect on the outputs of the cell system. Additionally, the Seebeck coefficient was also unaffected by the presence of increased surface area roughness.
The work presented in the following paper is part of a continuing effort to better understand the performance of thermogalvanic cells and their heat to electrical energy transfer properties.
ContributorsLopez, Maggie Marie (Author) / Phelan, Patrick (Thesis director) / Miner, Mark (Committee member) / School of Sustainability (Contributor) / School of Music (Contributor) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
For the past two decades, advanced Limb Gait Simulators and Exoskeletons have been developed to improve walking rehabilitation. A Limb Gait Simulator is used to analyze the human step cycle and/or assist a user walking on a treadmill. Most modern limb gait simulators, such as ALEX, have proven themselves effective and reliable through their usage of motors, springs, cables, elastics, pneumatics and reaction loads. These mechanisms apply internal forces and reaction loads to the body. On the other hand, external forces are those caused by an external agent outside the system such as air, water, or magnets. A design for an exoskeleton using external forces has seldom been attempted by researchers. This thesis project focuses on the development of a Limb Gait Simulator based on a Pure External Force and has proven its effectiveness in generating torque on the human leg. The external force is generated through air propulsion using an Electric Ducted Fan (EDF) motor. Such a motor is typically used for remote control airplanes, but their applications can go beyond this. The objective of this research is to generate torque on the human leg through the control of the EDF engines thrust and the opening/closing of the reverse thruster flaps. This device qualifies as "assist as needed"; the user is entirely in control of how much assistance he or she may want. Static thrust values for the EDF engine are recorded using a thrust test stand. The product of the thrust (N) and the distance on the thigh (m) is the resulting torque. With the motor running at maximum RPM, the highest torque value reached was that of 3.93 (Nm). The motor EDF motor is powered by a 6S 5000 mAh LiPo battery. This torque value could be increased with the usage of a second battery connected in series, but this comes at a price. The designed limb gait simulator demonstrates that external forces, such as air, could have potential in the development of future rehabilitation devices.
ContributorsToulouse, Tanguy Nathan (Author) / Sugar, Thomas (Thesis director) / Artemiadis, Panagiotis (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2016-12
Description
This work summarizes the development of a dynamic measurement platform in a cryostat to measure sample temperature response to space-like conditions and the creation a MATLAB theoretical model to predict sample temperature responses in the platform itself. An interesting variable-emittance sample called a Fabry-Perot emitter was studied for its thermal homeostasis behavior using the two developments. Using the measurement platform, it was shown that there was no thermal homeostatic behavior demonstrated by the sample at steady state temperatures. Theoretical calculations show other ways to demonstrate the cooling homeostasis behavior through time-varying heat inputs. Factors within the system such as heat loss and thermal mass contributed to an inhibited sample performance in the platform. Future work will have to be conducted, not only to verify the findings of the initial experiments but also to improve the measurement platform and the theoretical model.
ContributorsBoman, Neal D (Author) / Wang, Liping (Thesis director) / Taylor, Syndey (Committee member) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2021-05
Description
This paper explores to mitigate the issue of Formula SAE brakes vaporizing by creating a computational model to determine when the fluid may boil given a velocity profile and brake geometry. The paper explores various parameters and assumptions and how they may lead to error determining when the brake fluid will vaporize. Common assumptions such as a constant convection coefficient are questioned throughout the paper and compared to methods requiring higher computational power. Throughout this model, a significant dependence on the heat partition factor is found on the final steady state temperature of the brake fluid is found, and a sensitivity analysis is performed to determine the effect of its variation.
ContributorsWesterhoff, Andrew (Author) / Kwon, Beomjin (Thesis director) / Milcarek, Ryan (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2023-05
Description
Thermophotovoltaic energy conversion is seen as a viable option for efficiently converting heat to electricity. There are three key components to a thermophotovoltaic (TPV) system: a heat source, a heat emitter and a photovoltaic (PV) cell. A heat source heats up the emitter which causes the emitter to release thermal radiation. The photons are absorbed by a PV cell when they are acting above the bandgap energy. The PV cell then generates electricity from this thermal radiation. In theory, efficiency of a TPV system can be well above 50%. In order for TPV to reach large-scale adaptation, an efficiency at or above 20% is needed. In this project, a high-temperature heater capable of reaching 1000K was developed. The heater involved a copper block machined to hold two cartridge heaters, as well as two thermocouples. It has an accompanying copper lid that can be screwed tight to the main block, with an emitter in between. There is an aperture to allow radiation through the casing towards the PV cell. Preliminary thermal analysis showed that the heater provides uniform temperature distribution across the emitter, which is necessary for proper radiation. A mounting system was also designed to implement the heater into the overall TPV system. Current work is being done to lower the radiation loss from the heater and mounting system, as well as implementation of all auxiliary components to begin testing. The maximum temperature of the heater, radiation heat flux received by the cell, and overall power output and efficiency of the system will be tested.
ContributorsDeffigos, Nikolas (Author) / Wang, Liping (Thesis director) / Milcarek, Ryan (Committee member) / Ni, Qing (Committee member) / Barrett, The Honors College (Contributor) / Mechanical and Aerospace Engineering Program (Contributor)
Created2021-12
Description
This thesis project explains what thermal interface materials (TIMs) are, what they are used for, and how to measure their properties. Thermal interface materials are typically either a grease like paste or a soft polymer pad that is placed between two solids to increase the heat transfer rate. Solids in contact with each other experience a very large thermal contact resistance, this creates a thermal bottleneck which severely decreases the heat transfer from one solid to another. To solve this, particles with a high thermal conductivity are used as filler material in either a grease or polymer. A common application for TIMs is in computer components, where a TIM is used to remove the heat generated from computer chips. These materials allow for computer chips to run faster without overheating or throttling performance. However, further improvements to TIMs are still desired, which are needed for more powerful computer chips. In this work, a Stepped Bar Apparatus (SBA) is used to evaluate the thermal properties of TIMs. The SBA is based on Fourier’s Law of one-dimensional heat transfer. This work explains the fundamentals of the SBA measurement, and develops a reliable way to confirm the SBA’s measurement consistency through the use of reference samples. Furthermore, this work evaluates the effects of volume fraction and magnetic alignment on the performance of nickel flakes mixed into a polymer to create a soft TIM composite pad. Magnets are used to align the nickel flakes into a column like arrangement in the direction that heat will travel. Magnetic alignment increases the thermal conductivity of the composite pads, and has peak performance at low compression.
ContributorsHart, Matthew (Author) / Rykaczewski, Konrad (Thesis director) / Wang, Robert (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2019-12
Description
The ASU Compact X-ray Free Electron Laser (CXFEL) is a first of its kind instrument that will illuminate the processes of life and allow scientists to create more effective treatments for disease. The dimensions of the linear accelerator (LINAC) cavities must remain stable during operation, for a change in the geometry alters the standing wave microwave energy resonance within the cavities and leads to reflected rather than coupled and useful microwave energy to electric field coupling. This disturbs the electron bunch acceleration dynamics critical to the ultimate generation of x-ray pulses. Cooling water must be supplied to the electron generating RF-GUN, and linear accelerator (LINAC) structures at unique flowrate and temperature setpoints that are specific to the operating mode of the CXFEL. Design specifications for the water supply to the RF-GUN and three LINACs and were made for the nominal operating mode, which adds a 3 kW heat load to the water. To maintain steady cavity dimensions, water must be supplied to each device under test at 30.0 ºC ± 0.06 ºC. The flowrate of water must be 3.5 GPM to the RF-GUN and 2.5 GPM to each of the three LINACs with ± 0.01 GPM flowrate resolution. The primary function of the Dedicated-Precision Thermal Trim Unit (D-PTTU) is to control the flowrate and temperature of water supply to each device under test. A simplified model of the system was developed to select valves that would meet our design specifications for flowrate and temperature control. After using this model for valve selection, a detailed system model was created to simulate relevant coupled-domain physics of the integrated system. The detailed system model was used to determine the critical sensitivities of the system and will be used to optimize the performance of the system in the future. Before the detailed system model can be verified and tuned with experiments, the sensors were calibrated in an ice-bath to ensure the sensors measure accurate and precise values. During initial testing, the D-PTTU was able to achieve ± 0.02 ºC temperature resolution, which exceeds the design specification by a factor of three.
ContributorsGardeck, Alex John (Author) / Holl, Mark (Thesis director) / Smith, Dean (Committee member) / Department of Physics (Contributor) / Mechanical and Aerospace Engineering Program (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05
Description
The temperature of exhaust pipes can be dangerous in dry areas where there is a lot of brush. The temperatures of exhaust pipes can reach a high enough temperature to start a fire if touching the dry brush, which ignites around 300°C. The goal of this project was to explore different techniques to limit the possibility of these brush fires. Specifically, different methods were explored to reduce the temperature of the pipe that would be contacting the brush. Fires can begin within seconds of contacting the hot exhaust pipes [10]. This experiment found that of the three options tested: exhaust wrap, heat sink with thermoelectric devices, and high temperature paint, adding a heat shield/sink is the best way to limit the high temperatures from igniting the brush. There was a cooling difference of nearly 100°C when a heat shield/sink was added to the bare pipe. The additional thermal mass as well as the finned heat sinks attached to the heat sink helped dissipate the heat from the pipe and release the waste heat into the surroundings. The increase in surface area in correspondence with forced convection from the surrounding air lowered the temperature of the metal in contact with the dry brush.
ContributorsHodges, Andrew (Author) / Benson, David (Thesis director) / Bocanegra, Luis (Committee member) / Mechanical and Aerospace Engineering Program (Contributor) / Barrett, The Honors College (Contributor)
Created2020-05