The main goal for this project was to design, manufacture and evaluate a thermoelectric cooler, TEC, prototype. One of the biggest challenges with TECs is that they need to be very reliable and have a long lifetime. The two biggest contributing factors to degradation and breakdown stem from thermal expansion mismatch, resulting in cracks, and from material diffusion between the thermoelectric material and connecting materials. The thermoelectric material in this case is Bismuth telluride, Bi2Te3, obtained from two suppliers. The thermoelectric cooler prototype was successfully manufactured. The prototype, which consisted of 38 thermoelectric elements, showed a maximum temperature difference of 65.1 degrees Celsius. A commercial TEC of the same size had a maximum temperature difference of 68 degrees Celsius. The figure of merit and grain size of p- and n-doped Bismuth Telluride from two different suppliers have been measured as means of testing the thermoelectric material prior to manufacturing, and to compare the suppliers. In this report, the figure of merit is a measure of how well a material converts electrical current to a heat gradient. The figure of merit for bismuth telluride, Bi2Te3, from both suppliers was found to be between 0.4 and 0.8 through the Harman method. Since studies show that smaller grains for Bi2Te3 result in a more durable material, the morphology was investigated. However, no grains could be observed with light optical microscopy with an applied etchant, or scanning electron microscopy. A cohesion tape test showed that Bismuth telluride from one of the suppliers is more fragile than the other.

The object of this master’s thesis is design of a suitable hydrostatic travel drive for harvester. The first part dedicates of constructions of harvesters and actual different conceptions of travel drive. Next, there are design of hydrostatic circuit, calculation of general hydraulic parameters and design of hydraulic components in the second part. The last part deals with issue of combustion engine and cooler.

L'électronique de puissance est en pleine mutation matérielle, technologique et conceptuelle. Cette évolution bouscule l'approche traditionnelle de la conception et de la fabrication des convertisseurs statiques avec pour objectif de proposer des solutions plus performantes, plus fiables et plus compactes et tout cela dans un contexte technico économique de plus en plus exigeant. Cette thèse analyse et expérimente un concept innovant de terminaisons en tension verticales ouvrant la voie vers l'intégration en 3D des composants de puissance mais également l'intégration, au sein même de la zone active d'un échangeur thermique. En s'appuyant sur la technique de réalisation des tranchées profondes issue de la micro électronique, ce document présente une approche permettant la co-intégration de plusieurs composants de puissance indépendants partageant la même électrode et le même substrat en face arrière. L'autre volet de ce travail de thèse est focalisé sur le concept DRIM Cooler (Drift Region Integrated Microchannel Cooler), un réseau de microcanaux perpendiculaires au plan de jonction du composant de puissance permettant son refroidissement direct. Les analyses numériques sont complétées par de nombreuses réalisations, caractérisations et mises en œuvre des approches précitées. / The power electronics field is struggling for new material, technological and conceptual evolutions. These changes induce breakthrough in the conventional design and fabrication of static power converters with the aim to offer more efficient, reliable and compact solutions in an increasingly demanding techno economical context. This PhD thesis presents the results obtained by analyzing, realizing and characterizing an innovative concept based on vertical voltage terminations that opens the way towards the 3D integration of power devices. Moreover, the proposed concept authorizes the integration of a microchannel cooler directly into the drift region of the power device. Based on the realization of deep trench terminations, a technique initially developed for the microelectronics field, this PhD thesis presents an approach allowing the integration of multiple power devices in the same die, all sharing the same backside electrode. This document also focuses on the DRIM Cooler (Drift Region Integrated Microchannel Cooler) concept that allows the direct cooling of the device through multiple parallel microchannels integrated perpendicular to the plane of the device's PN junction. The analytical analysis is completed with numerous realizations, characterizations and practical implementations of the above mentioned concepts.

This diploma thesis deals with the issue of regrigerant cooling. The theoretical part describes laws of termodynamics, basic thermodynamic processes of ideal gas and cooling cycles. The dependence of the cooler bypass factor of air handling unit on its capacity is the main issue of the experimental part. The aim of practical part is to design the air-conditioning device using knowledge of experimental part and compare it with the proposal of air-conditiong device in my bachelor thesis.

Economical and environmental factors together with energy policies towards more efficient systemsare the driving force for the development of the vehicle industry. Significant changes have beenmade to fulfill new emissions legislation but the basic internal combustion vehicle architecture hasbeen kept. New emission treatment systems that increase the thermal loading of the cooling systemhad been added within the same package envelope as before, which means less space to place coolingfans and a greater need for airflow. Changes in the cooling system, namely the replacement of thehydraulic fan drive system by electrical fans is one of the energy efficient alternatives for severalcity buses under certain environments, like the ”typical red city buses”, well-known in the UnitedKingdom. In this thesis study, hydraulic fans are compared with electrical fans and a road-mapof the benefits and drawbacks of the two systems is developed, based on real traffic performanceperformance data and the results of existing simulations and tests. In addition, new simulations arepresented in order to find the most efficient design for the cooling system as well as a comparisonof these results with previous ones. This road map will be used later by Volvo-Buses Group as atool to better understand in which circumstances electrical fans can be beneficial, in terms of fuelconsumption, noise production, cooling performance, control of the fans and associated costs.

A novel hybrid cooling scheme is proposed to remove non-uniform heat flux in real time from the microprocessor. It consists of a liquid cooled microchannel heat sink to remove the lower background heat flux and superlattice coolers to dissipate the high heat flux present at the hotspots. Superlattice coolers (SLC) are solid-state devices, which work on thermoelectric effect, and provide localized cooling for hotspots. SLCs offer some unique advantage over conventional cooling solutions. They are CMOS compatible and can be easily fabricated in any shape or size. They are more reliable as they don't contain any moving parts. They can remove high heat flux from localized regions and provide faster time response. Experimental devices are fabricated to characterize the steady-state, as well as transient performance, of the hybrid cooling scheme. Performance of the hybrid cooling scheme has been examined under various operating conditions. Effects of various geometric parameters have also been thoroughly studied. Heat flux in excess of 300 W/cm² has been successfully dissipated from localized hotspots. Maximum cooling at the hotspot is observed to be more than 6 K. Parasitic heat transfer to the superlattice cooler drastically affects its performance. Thermal resistance between ground electrode and heat sink, as well as thermal resistance between ground electrode and superlattice cooler, affect the parasitic heat transfer from to the superlattice cooler. Two different test devices are fabricated specifically to examine the effect of both thermal resistances. An electro-thermal model is developed to study the thermal coupling between two superlattice coolers. Thermal coupling significantly affects the performance of an array of superlattice coolers. Several operating parameters (activation current, location of ground electrode, choice of working fluid) affect thermal coupling between superlattice coolers, which has been computationally as well as experimentally studied. Transient response of the superlattice cooler has also been examined through experiments and computational modeling. Response time of the superlattice cooler has been reported to be less than 35 µs.

The state of the art in artificial micro self assembly concepts are reviewed. The history of assembly is presented with a comparison to macro assembly, which has been widely studied, and micro self assembly. Criteria were developed and tested to show that macro assembly is more complex in ways that micro self assembly is not. Self assembly requirements for successful and complex self assembly, which evolved from the macro and micro comparison, are also established and tested. A method to assemble complex structures in the micro scale is proposed and demonstrated at the meso scale. The basic concepts of self assembly and a novel approach to complex multi layer self assembly is analyzed.

Modern high frequency electronic devices are continually becoming smaller in area but capable of generating higher RF power, thereby increasing the dissipated power density. For many microwave devices, for example the planar Gunn diode, standard thermal management may no longer be sufficient to effectively remove the increasing dissipated power. The work has looked at the design and development of an active micro-cooler, which could be fully integrated with the planar Gunn diode at wafer level as a monolithic microwave integrated circuit (MMIC). The work also resulted in the further development of novel thermal measurement techniques, using micro-particle sensors with infra-red (IR) thermal microscopy and for the first time to measure thermal profiles along the channel of the planar Gunn diode. To integrate the gallium arsenide (GaAs) based planar Gunn diode and micro-cooler, it was first necessary to design and fabricate individual GaAs based planar Gunn diodes and micro-coolers for thermal and electrical characterisation. To obtain very small area micro-coolers, superlattice structures were investigated to improve the ratio between the electrical and thermal conductivities of the micro-cooler. To measure the specific contact resistivity of the superlattice based micro-cooler contacts, the Reeves & Harrison TLM (transmission line method) was used as it included both horizontal and vertical components of the contact resistance. It was found, for the GaAs based micro-cooler, only small amounts of cooling (< 0.4 °C) could be obtained, therefore the novel temperature measurement method using micro-particle sensors placed on both the anode and cathode contacts was utilised. The bias probes used to supply DC power to the micro-coolers were found to thermally load these very small structures, which led to anomalously high measured cooling temperatures of > 1°C. A novel approach of determining if the measured cooling temperature was due to cooling or probe loading was developed. A 1D model for the integrated micro-cooler was developed and the results indicated that when the micro-cooler was used as a cooling element in a monolithic microwave integrated circuit, the supporting substrate thickness was very important. Simulation showed to obtain cooling the substrate thickness had to be very thin (< 50 μm), which may preclude the use of GaAs micro-coolers as part of a monolithic microwave integrated circuit.

The human body has a unique mechanism for perceiving surrounding temperatures. When an object is in contact with the skin, we do not feel its temperature. Instead, we feel the temperature change that is caused on our skin by that object. The faster the heat is transferred, the more intense the thermal sensation is. In this dissertation, a new dynamic thermal display method, where different rates of warm and cold are applied on the skin to generate a unique sensation, is presented. The new method can be related in a wide range of applications including thermal haptics and virtual reality. To understand the perception of temperature and the general thermal state of the human body, the first aspect of this dissertation focuses on investigating the interaction between temperature change and perception on a large scale. Three field surveys were conducted inside airconditioned buildings to investigate the change in the thermal state and temperature perception of occupants when the room temperature changes. The results showed that the participants’ prediction of constant operating temperature was poor, however, their prediction was significantly improved when temperature changes were presented. In order to more accurately investigate the perception of temperature on the skin, a new thermal display method using multiple-channel thermal actuators was developed. The principle of this method is to apply slow and fast rates of temperature change simultaneously on the skin. The slowly changing temperatures are below the perceptual threshold of the thermal receptors, therefore will not be detected whereas the quickly changing temperatures are above the perceptual threshold, hence, will be detected. The idea here is to keep the average surface temperature of the skin constant, however a person will perceive a sensation of continuous cooling. This method was tested through a series of experiments, and the results showed that it is capable of generating a continuous cooling sensation without changing the average temperature of the stimulation area. Multiple variations of this method were tested including different heating and cooling rates of change, different skin locations and patterns of stimuli. Also, a continuous warming was generated using similar concept. To further investigate the temperature distribution that is caused by this method and its effect on the skin, a computational simulation was conducted. An approximate model of the skin was used to monitor its surface temperature and record the temperatures in the stimulation area when the continuous cooling method is applied. The results of the simulation showed that the temperature under the surface of the stimulation area was affected by the continuous cooling method that was applied on the skin model, however this method did not affect the average surface temperature of the skin. These findings may later determine the efficiency and intensity of the method of continuous cooling, and allow us to investigate different technically challenging variations of this method.

Today many processes generate a lot of waste heat, for example industries or cars. One way to make this thermal energy useful is to transform it into electrical energy with a thermoelectric generator (TEG) or thermoelectric cooler (TEC). This technology is not used in any large scale today, but a lot of research is being done on the subject. The technology is based on the Seebeck effect and uses a temperature difference between two sides of an element to generate an electrical current. The reason that the research has gained more attention in recent years is because of the increasing electricity prices and the diminishing natural resources. Other benefits are that they run quietly and do not demand much maintenance.Another area where this technology could be useful is in off-grid cabins where it is easy to generate a lot of thermal energy by burning wood, but electrical energy is in high demand.In this thesis two different types of TEGs and one type of TEC are tested to investigate how much power they generate at different temperature differences, how well they meet the specified values in their respective data sheet and what their power per euro value is. For this, an experimental setup was made with:- An induction plate to increase the temperature on the hot side.- A CPU-fan, to reduce the temperature on the cold side.- Two temperature sensors (one for measuring the hot temperature and one for the cold one).- An electric circuit featuring a voltmeter, an amperemeter and an adjustable resistor (rheostat).The results show that, for this experiment the highest received power (6,38 W) comes from the medium-priced element but the highest power per euro comes from the lowest priced element (1,16 W/€). A quality problem for the lowest priced element was that parts of the solder melted when the temperature exceeded 225 °C. Another problem was that the induction plate was unable to provide enough heat for the most expensive of the elements to reach the temperature for which the retailer supplies their measured data.