Design Considerations and Thermodynamic Feasibility Study of a Meso-scale Refrigerator

Recent advances in micro-fabrication technology have ushered a new era in miniaturization of chemical, environmental and energy systems. This foreseeable trend towards miniaturization in chemical, environmental and mechanical systems is expected to revolutionize the ways the human life is being perceived today. The high volume and mass reproducibility is seen as the striking aspect of micro-fabrication based miniature systems, offering economies far exceeding than the economies of scale obtained in large plants. The focus of this thesis work is directed at the thermodynamic feasibility and preliminary prototype design for a meso-scale refrigerator. Miniaturization to sub-centimeter domain will enable configuring these refrigerator units as sheet architectures integrated in layers, facilitating efficient local control of temperature. In the design abstraction, the entire refrigeration unit, comprising motor-compressor, evaporator, condenser, valves and fluidic control, is to be fabricated from several layers of bonded silicon wafers. The material treated in this thesis provides a perspective on the actuation mechanism of the integrated rotor-compressor through an axial-drive high-throughput variable capacitance electrostatic disk motor and underlying stator assembly. The design optimization of the motor actuation dynamics to extract optimal set of design parameters is provided to yield reasonably good output power of the compressor

A Review of Thermoelectric MEMS Devices for Micro-power Generation, Heating and Cooling Applications

Thermoelectric technology can be used to generate a small amount of electrical power, typically in the µW or mW range, if a temperature difference is maintained between two terminals of a thermoelectric module. Alternatively, a thermoelectric module can operate as a heat pump, providing heating or cooling of an object connected to one side of a thermoelectric module if a DC current is applied to the module’s input terminals. This chapter reviews the development of microelectromechanical systems (MEMS) based thermoelectric devices suitable for micro-power generation, heating and cooling applications. The chapter begins with a brief overview of thermoelectric technology, macro-thermoelectric module construction and operation. Micro-thermoelectric modules are introduced, and a review of recent developments in research, commercial development, and typical application of MEMS based micro-thermoelectric devices is made. The chapter draws conclusions on the development and potential application of MEMS based thermoelectric devices suitable for thermoelectric cooling, heating and micro-power generation

A Review of Thermoelectric MEMS Devices for Micro-power Generation, Heating and Cooling Applications

Thermoelectric technology can be used to generate a small amount of electrical power, typically in the µW or mW range, if a temperature difference is maintained between two terminals of a thermoelectric module. Alternatively, a thermoelectric module can operate as a heat pump, providing heating or cooling of an object connected to one side of a thermoelectric module if a DC current is applied to the module’s input terminals. This chapter reviews the development of microelectromechanical systems (MEMS) based thermoelectric devices suitable for micro-power generation, heating and cooling applications. The chapter begins with a brief overview of thermoelectric technology, macro-thermoelectric module construction and operation. Micro-thermoelectric modules are introduced, and a review of recent developments in research, commercial development, and typical application of MEMS based micro-thermoelectric devices is made. The chapter draws conclusions on the development and potential application of MEMS based thermoelectric devices suitable for thermoelectric cooling, heating and micro-power generation

Quikchill : thermoelectric water cooler

Motivated by the increasing residential energy utilization projections and the fact that water and ice dispensers consume 20% of total refrigerator energy, a thermoelectric water chiller was designed to provide a more energy efficient alternative. Implementing the chiller under the sink provides a convenient means to source cold, filtered water, thereby eliminating the need for water and nice dispensers as well as filtering pitchers. The cooling chamber design integrates thermoelectric modules (TEMs), which operate on the Peltier effect to cool filtered water down to 14 [degrees] C. The implementation of TEMs reduced current dispenser energy consumption by 82.4%, from 91 W to 16 W

Design Strategy of a Thermoelectric Evaporative Refrigerator for Safe Food Storage

Lack of safe food storage can lead to sickness, cancer, and even death. This has effects on developing communities where over a billion people live without access to electricity. This lack of electrical power limits families in developing communities’ ability to utilize modern refrigeration systems, forcing them to instead rely on ice boxes to keep their food cold. Ice boxes are a time consuming refrigeration system that can be highly inconsistent and unsafe, if not constantly monitored. Simply, poor food storage can lead to illness and systemic problems caused by poor diet. In order to combat this problem, we are developing an off-grid, low power, compact refrigeration system with a user interface to allow for greater individual control. By optimizing thermoelectric modules with regards to the refrigerator size and heat dissipation system, it is possible to achieve a temperature difference suitable for storing food at power levels lower than that of a standard light bulb. The cooling system is further enhanced using an evaporative cooling solution that is rigorously designed to provide the greatest cooling effect with minimal user interaction. When used in conjunction with the main thermoelectric heat pump, lower internal temperatures can be achieved at reduced power. This system performance is monitored and controlled using a micro-controller that measures environmental conditions as well as fridge performance. It can inform the user and allow them a greater amount of control over the performance of their refrigeration system. In summary, we seek to effectively design a product that will enhance the quality and safety of life for those without access to reliable refrigeration

2020 NASA Technology Taxonomy

This document is an update (new photos used) of the PDF version of the 2020 NASA Technology Taxonomy that will be available to download on the OCT Public Website. The updated 2020 NASA Technology Taxonomy, or "technology dictionary", uses a technology discipline based approach that realigns like-technologies independent of their application within the NASA mission portfolio. This tool is meant to serve as a common technology discipline-based communication tool across the agency and with its partners in other government agencies, academia, industry, and across the world

High-frequency operation and miniaturization aspects of pulse-tube cryocoolers

Cryocoolers are small refrigerators capable of achieving useful refrigeration below 120 K. Recent developments in the field of high Tc superconductors spawned a wide range of applications such as terahertz sensors, SQUIDS, low noise amplifiers, filters for microwave applications and many more. These devices are typically, nondissipating and require a cryocooler delivering refrigeration power of about 10 mW operating at 80 K. The existing commercial closed loop cryocoolers are huge, less reliable and expensive. Several research groups have been investigating development of cryocoolers using microsystems technologies for on-chip cryocooling. Gas cycles which, can be broadly divided into recuperative (steady flow) and regenerative (oscillating flow) cycles are the only current means of reaching cryogenic temperature in a single stage. The aim of this thesis is to investigate miniaturization of regenerative cycles. Pulse-tube cryocoolers, a variation of the Stirling cycle (regenerative type), are a fairly recent development in cryocooler technology. The principal advantage of a pulse-tube refrigerator is that it has no cold moving parts in the refrigerator

Cooling for Microsystems: Miniaturization Prospects for Pulse Tube Cryocooler

Regenerative Kryokühler wie Stirling-, Gifford-McMahon- und Pulsrohr-Kryokühler besitzen große Vorzüge wie geringe Größe, niedrige Kosten, hohe Zuverlässigkeit und gute Kühlleistung. Diese Vorzüge führten dazu, dass sie viele Anforderungen von IR- und supraleitenden Anwendungen erfüllen. Unter diesen Kryokühlern gibt es eine Maschine, die als Pulsröhren-Kryokühler (PTC) bezeichnet wird, die ausgezeichnete Vorzüge aufweist und das Potenzial hat, für On-Chip- und Mikrosystem-Anwendungen miniaturisiert zu werden. In dieser Arbeit werden die Miniaturisierungsaspekte dieser Maschine anhand verschiedener numerischer Analysen und computergestützter fluiddynamischer (CFD) Simulationsmodelle untersucht. In dieser Arbeit wird eine Analyse des komplexen Betriebs für das Röhrenelement für einen Orifice Pulse Tube Cryocooler (OPTC) vorgeschlagen. Dies wird durch eine Phasenanalyse unter Verwendung fundamentaler thermodynamischer Beziehungen erreicht, um die mit dieser Maschine verbundene Kühlleistung näherungsweise abzuschätzen. Darüber hinaus wird der Effekt des Phasenverschiebungswinkels veranschaulicht, indem eine Analogie zwischen dem Phasenverschiebungsmechanismus und einem Serien-RLC-Schaltungsmodell gebildet wird. Anschließend wird ein eindimensionales Modell vorgestellt, das auf Massen- und Energieerhaltungsgleichungen basiert; das reduzierte Modell wird numerisch für die Temperatur und Geschwindigkeit des Gases entlang des Rohrs gelöst, um den Massenstrom und die zeitlich gemittelten Enthalpieströme am kalten und heißen Ende des Rohrs zu bestimmen. Die Erkenntnisse aus der eindimensionalen Analyse werden mit den bisherigen Ergebnissen der Phasoranalyse verglichen. Der Regenerator ist eine kritische Komponente in diesen Kryokühlern mit geschlossenem Kreislauf. Die Arbeit präsentiert eine eindimensionale numerische Analyse der idealisierten thermischen Gleichungen der Matrix und des Arbeitsgases innerhalb des Regenerators. Der Algorithmus prognostiziert die Temperaturprofile des Gases während des Aufheizens und Abkühlens sowie die Matrix-Knotentemperaturen. Es wird untersucht, wie die Länge und der Durchmesser des Regenerators, die geometrischen Parameter der Matrix, die Anzahl der Wärmeübertragungseinheiten und der Volumenstrom die Leistung eines idealen Regenerators beeinflussen. Es wird auch ein achsensymmetrisches 2D-CFD-Modell vorgeschlagen, um das Modell des idealen Regenerators zu bewerten und zu validieren. Darüber hinaus wird ein analytisches Verfahren entwickelt, um die im Regenerator vorhandenen Verluste abzuschätzen. Die Ergebnisse werden mit denen einer anderen Software, genannt REGEN, die vom NIST entwickelt wurde, verglichen. Danach wird über eine achsensymmetrische numerische CFD-Simulation berichtet, die die oszillierenden Strömungs- und Wärmeübertragungsprozesse in einem Inertanz-Pulsrohr-Kryokühler aufzeigt. Die Auswirkungen der Betriebsfrequenz werden untersucht, und die Auswirkungen der reduzierten Größe des Systems bei Betrieb mit hoher Frequenz auf die Kühlleistung des Systems werden untersucht. Darüber hinaus wird eine spezielle Software namens Sage und CFD-Modellierung verwendet, um Ultra-Miniatur-PTC-Modelle zu entwickeln. Ihre Leistungsparameter werden untersucht und ihre Eignung für On-Chip- und Mikrosystemanwendungen wird bestimmt