<div>As space exploration continues to accelerate, various cooling applications follow suit. Refrigeration and freezing of biological samples, astronaut food as well as electronics cooling and air-conditioning are necessary and demand increased capacity. In the past, these demands have been met by thermoelectric cooling or cryogenic cycles, which are easily adapted to a microgravity environment but have a relatively low efficiency in the refrigeration and freezing temperature range. A number of studies have investigated the development of higher efficiency vapor compression cycles for spacecraft, which would have the benefit of a smaller mass penalty due to the reduced power consumption. Despite notable research efforts during the 1990s, the number of vapor compression coolers that have operated in microgravity until today is small and their performance was insufficient to provide confidence into the technology for microgravity applications. Related experimental research has decreased since the 2000s.<br></div><div><br></div><div>For this dissertation, all vapor compression cycles (VCC) that have operated in microgravity according to the open literature were reviewed with their applications, compressor types and reported issues. Suggested design tools were summarized with a focus on gravity independence criteria for two-phase flow. For the most effective increase of the technology readiness level, simple but systematic experiments regarding the stability of VCCs against orientation and gravity changes were prioritized in this dissertation. An important goal of the research was the continuous operation and start-up of vapor compression cycles on parabolic flights, experiments that have not been reported in the open literature. Two separate test stands were built and flown on four parabolic flights, totaling 122 parabolas for each experiment.<br></div><div><br></div><div>The parabolic flight experiments were prepared with extensive ground-based testing. Multiple anomalies were encountered during the pursuit of continuous vapor compression cycle operation through a rotation of 360 degrees, including liquid flooding of the compressor. Systematic inclination testing was conducted with two different cycle configurations and a wide range of operating conditions. A strong correlation was found between the relative stability of the heat source heat transfer rate and the refrigerant mass flux for an inclination procedure with angle changes once every 2 minutes.<br></div><div><br></div><div>The parabolic flights exposed the test stand to quickly alternating hyper and microgravity. The evaporation temperature reacted to the different gravity levels with fluctuations that stretched on average 2.2 K from the maximum to minimum temperature measured during one set of parabolas. Changes of the evaporator inlet flow regime as a function of gravity were observed visually and the low-side pressure and mass flow rate sometimes oscillated in microgravity. The cycle responses induced by ground-based inclination testing were typically stronger than changes caused by the parabolic flight maneuvers for relatively low mass flow rates. Overall, the parabolic flight maneuvers were not detrimental to the cycle operation. <br></div><div><br></div><div>The second test stand was dedicated to liquid flooding observations at cycle start-up. Different flow regimes were observed in microgravity during testing with a transparent evaporator but the absence of gravity did not significantly alter the general time-based flooding quantifiers.<br></div><div><br></div><div>Design recommendations are drawn from the research where possible and summarized at the end of the dissertation. Selected data, code, pictures and videos were released together with this dissertation(Brendel, 2021)<br></div>

The subject of this master´s thesis is the design of a single-purpose assembly device for pressing round seats into the cylinders of an air conditioning compressor. The whole thesis leads to a complete 3D model of the machine, including drawings. The 3D model and drawings were created in SOLIDWORKS.

The diploma thesis consists of a theoretical part, which deals with the description of reversing turbocharger and its components. The following part is devoted to calculating the radial-axial compressor and turbine. It also performs a calculation of gear box and characteristics of the turbine.

This diploma thesis deals about the combustion turbine, design, processing and utilization. This work can be divided into three parts. The first part focuses on the theoretical knowledge gained in the field of gas turbines and their applications. The second part addresses the design of combustion turbine and its integral part. The third section describes the expected characteristics of combustion turbines. The work also includes the annex, which includes the technical documentation.

The Diploma thesis deals with the testing of turbochargers. Aim of this work is to perform a search on a teststands. Further suggest the teststand's construction. Part of the work is the creation of software for utility measurements available. The program will serve as a basis for checking the measurement data of the turbocharger.

Centrifugal compressors with high pressure ratio are widely used in small aircraft turbine engines and turbocharges. At high rotational speeds they have narrow stable operating region and commonly used impellers with back swept blades are not able to ensure requested stability. In order to achieve wider stable operating region, some other anti-surge measures can be used, such as an Internal Recirculation Channel (IRC) located in compressor impeller inlet. This thesis deals with an investigation of IRC influence on centrifugal compressor operational parameters. As a first, the various recirculation channel geometry was studied by using of CFD analysis on simplified computational models. Those geometry, which indicated best results in terms of mass flow and looses in channel were used for testing on a model test device. Subsequently the same geometry was tested on real centrifugal compressor in experimental turbine engine to verify influence of IRC on compressor performance map – pressure ratio and efficiency. Simultaneously the CFD analyses of IRC with a 3D model of compressor impeller were performed and results compared with those, gained from measurement on model and compressor. In addition the measurement of flow field downstream the recirculation channel outlet slot with using of 3-hole pressure probe was performed and compared with flow velocity profiles evaluated from numerical simulations.

Nach offiziellen Schätzungen sind weltweit derzeit rund drei Milliarden Geräte im Bereich der Kälte- und Klimatechnik im Einsatz. In diesen kommen vornehmlich Hubkolbenverdichter zum Einsatz. Entsprechend bergen die Auswirkungen selbst kleinster, energetischer Verbesserungen in der Summe ein enormes Einsparungspotential. Als essentieller und eng mit dem Gütegrad verknüpfter Bestandteil eines Verdichters nehmen die Ventile eine zentrale Rolle ein. Zu diesen kann dem Stand der Technik bereits eine Vielzahl numerischer und experimenteller Untersuchungen entnommen werden. Eine Literaturrecherche zeigte, dass im Laufe der analysierten 68 Jahre, zwar ein breites Spektrum an Messmethoden angewandt wurde, diese aber fast ausschließlich einen punktuellen Charakter besaßen. Hinsichtlich der im Bereich der Kälte- und Klimatechnik hauptsächlich eingesetzten Lamellenventile, deren Öffnungs- bzw. Schließvorgang keiner linearen Bewegungsfunktion entspricht, können daraus nur eingeschränkte Erkenntnisse gewonnen werden. Der Bedarf an einer experimentellen Validierung existierender Berechnungsmethoden bestand. Aus diesem Grund wird im Rahmen dieser Arbeit erstmals, unter Anwendung des Messverfahrens der Laserlinientriangulation, die Erfassung einer Reihe aufeinanderfolgender Abstandsinformationen durchgeführt. Die eingesetzte, optische Methode beeinflusst den Bewegungsvorgang der Lamelle demnach nicht. Hierzu ist an der Technische Universität Dresden ein Versuchsstand eingerichtet worden, der die Analyse der Bewegungsprofile einer Sauglamelle sowohl entlang als auch senkrecht zur neutralen Faser erlaubt. Dabei stellte sich heraus, dass die parallel mit einem marktseitig verfügbaren Simulationsprogramm durchgeführten Berechnungen, das Biegeverhalten bereits sehr gut abbilden. Bedingung hierfür ist jedoch die rechenintensive, zweiseitige Kopplung der Strukturmechanik von z. B. ANSYS Mechanical mit der Fluiddynamik von z. B. ANSYS CFX sowie der zielgerichteten Beeinflussung der Netzverformung. Doch weitere, gewinnbringende Erkenntnisse sind ableitbar. Insbesondere die Torsionsbewegung der Lamelle, deren messtechnische Untersuchung aufgrund ihrer Größenordnung herausfordernd ist, und deren Entstehung konnte somit untersucht werden. Weiterhin sind Versuche an einem Verdichterleistungsprüfstand mit dem Kältemittel R449A durchgeführt worden. Die hierfür notwendige Bewertung der Einflussgrößen zeigte eine Verwendbarkeit der Messmethode für sämtliche, in einer Kälteanlage auftretenden Zustände. Ferner konnte, als Parameter mit dem größten Einfluss auf die Messwerterfassung, das Öl identifiziert und quantifiziert werden. Solange das Laserlicht eine Schichtdicke von weniger als 1 mm durchdringen muss, ist das Verfahren verwendbar. Werte, die darüber liegen, erfordern eine zusätzliche Korrektur. Die abschließenden Vergleiche mit der numerischen Simulation zeigen eine gute Übereinstimmung und ermöglichen Einblicke auf die Belastung der Lamelle vom Hineindrücken in die Bohrung bis zum Anschlag an den Hubfänger.

This thesis deals with the design of a stretcher and compressor systems used for the chirped pulse amplification method for the L4 beamline. The L4 beamline is being developed for the ELI Beamlines project and aims to deliver pulses with peak power of 10 petawatt, central wavelength of 1060 nanometers, pulse duration of 150 femtoseconds and energy of 1500 Joules. Since the laser induced damage threshold and aperture of commercial diffraction gratings is currently a limiting factor in reaching higher peak powers, it was necessary to increase the effective aperture of the compressor using either tiled grating or object-image-grating self tiling methods. These two methods are compared for two compressor configurations using either 1740 ln/mm or 1136 ln/mm diffraction gratings, methods for their alignment are discussed and the selected alignment method is experimentally tested. Moreover, an analytical theory connecting the Seidel aberrations of the stretcher imaging system with the spectral phase deviation of the stretched pulse is presented. This theory is applied to commonly used Banks and Offner stretcher designs and it is demonstrated how it can be employed for the suppression of residual spectral phase of compressed pulses. Next, the design of the stretcher for the L4 beamline based on this theory is...

This thesis presents the experimental work on testing the seasonal performance of a 40 kW air-to-water propane heat pump, as a part of the research project Next Heat Pump Generation working with Natural fluids (NxtHPG) that has been carried out in ‘Applied thermodynamics and refrigeration Division’ in the department of Energy Technology, KTH. The thesis work involves three parts: preparation of the HP unit test rigs, experimental campaign and the evaluation of test results. In the first part, the set-up of the measurement device and necessary modifications to the heat pump unit as well as the test rigs have been completed to create an accurate measuring environmental for the experimental campaign. During the second stage, two series of experimental campaign have been done in the heating mode of the heat pump unit, and satisfactory results have been obtained in parts of the test conditions. Finally, the evaluation on the system performance as well as the behaviors of the components is discussed. The variation between experimental results and the simulation conducted by IMST-ART model is within reasonable range, proving that the heat pump unit has been working in good conditions. The compressor is proved to have been performing as manufacturer expected. However, some further investigations on the behaviors of the heat exchangers and expansion valve, such as superheat oscillation, are recommended be carried out in the future work. The completion of the rest of tests in which minus air temperature should be maintained and the ones with the desuperheater working should be done as well. / Next generation heat pump working with natural fluids

Gas supplying process for consumers needs sufficient share of energy for upstream, midstream and downstream purposes. In spite of a huge amount of great investments into the industry it is still available to improve the efficiency of energy usage inside the industry. The biggest share of energy consumption is within transportation sector. Optimization of operating conditions of gas pipeline is a one of the cheapest ways for reducing energy consumption. Optimization doesn’t need any investments into the industry. It works only within operating parameters. Adjustable operating parameters of a gas pipeline are operative pressure, rotation speed of compressors, amount of operating units, gas temperature after a compressor station and others. The energy consumption depends on the combination of the parameters which determine an appropriate operation mode to provide the particular gas flow through a pipeline, the maximum capacity, the minimum energy consumption and others. From energy saving point of view it is possible to reduce energy demand in the gas industry due to optimization of the operation mode. A few approaches to achieving energy reduction through optimization are investigated in this work and presented in this article, such as saving energy through changing of loading between compressor stations, varying the depth of gas cooling and changing the loading of gas pumping units. The results of analyzing inside the study model reflect the possibility for improving efficiency of gas trunk pipelines.