Inst. Energietechnik

106 Items

Recent Submissions
Exergy-based analysis of aircraft environmental control systems and its integration into model-based design

Bender, Daniel (2019)

Aircraft environmental control systems are complex energy intensive systems and the most important non-propellant consumer of energy among all aircraft systems. The intense pressure on airlines to remain competitive on the global market demands more efficient aircraft greater than ever. Meaningful analysis methods for the evaluation of architectural designs and effective modeling and simulation...

Comparative evaluation of methanol production processes using natural gas

Blumberg, Timo Dominik (2018)

In the work, different processes for the production of methanol from natural gas are analysed from a thermodynamic and an economic point of view. Commercially available processes and promising future alternatives for increased thermodynamic efficiency, improved economics and reduced greenhouse gas emissions are assessed and compared. The analysed processes are based on the indirect synthesis ro...

Experimentelle und modellgestützte Charakterisierung von Adsorptionswärmeübertragern

Wittstadt, Ursula (2018)

Adsorptionsprozesse können zur Wärme- oder Kälteerzeugung genutzt werden. Dafür kommen thermisch angetriebene Wärmepumpen oder Kältemaschinen zum Einsatz. Zentrale Komponenten dieser Anlagen sind Wärmeübertrager, die mit einem Adsorptionsmaterial befüllt oder beschichtet sind. Da Wärme – und Stofftransport in solchen Adsorptionswärmeübertragern stark gekoppelt sind, ist die gezielte Entwicklung...

Theoretische Untersuchung des Wärme- und Stoffübergangs am laminaren Fallfilm

Mittermaier, Martin (2018)

In this thesis a model is presented describing a laminar film flow over a vertical isothermal plate while heat and mass transfer is occurring. Most common assumptions, such as constant property data and constant film thickness, have been cancelled. The hydrodynamic model results in longitudinal and transversal velocity components and their evolution in the entrance region. Heat and mass transfe...

Analytische und numerische Modellbildung zur Vermeidung von Rückströmungen aufgrund von Störgrößen in Reinräumen

Brandt, Stefan (2018)

In der vorliegenden Arbeit werden Funktionen und Berechnungen von Rückströmungen aufgrund von Zustandsänderungen der Volumenstromstellglieder in Reinräumen dargestellt. Die Zustandsänderungen werden in aktive und passive Störgrößen unterteilt. Ausgehend von den Ergebnissen der Untersuchungen werden Berechnungsvorschriften zum Auftreten von Rückströmungen aufgrund von Störgrößen in Reinräumen be...

The PSS quality framework for solar home systems

Kebir, Noara Zohra ; Philipp, Daniel (2016-08)

In September 2015, the United Nations General Assembly has adopted the Sustainable Development Goals; they include SDG 7 targeting universal access to electricity by 2030. Reaching this goal implies huge investments in generation capacity, grid extension and densification. However, according to the International Energy Agency, 70% of the world's population currently excluded from electricity se...

Dampferzeugeroptimierung zur Abwärmenutzung mittels Dampfkraftprozess an mobilen Verbrennungsmotoren

Stinner, Karl (2018)

Die im Kraftstoff gespeicherte Energie wird auch bei modernsten Verbrennungsmotoren nur zu ungefähr 30% in mechanische Antriebsleistung umgewandelt. Der größere Teil geht als Abwärme an die Umgebung verloren. Der daraus resultierende mittlere Wirkungsgrad des Pkw-Verbrennungsmotors kann jedoch durch teilweise Umwandlung der thermischen Energie erhöht werden. Hierzu kann die im Abgas verbleiben...

Evaluation of an energy- and exergy-based generic modeling approach of combined heat and power plants

Mollenhauer, Eike ; Christidis, Andreas ; Tsatsaronis, George (2016-02-29)

Reduced models of combined heat and power plants are required for different applications. Among other usages, they are implemented as mixed integer linear programs (MILP) in energy market models or price-based unit commitment problems to study the economic feasibility and optimal operation strategies of different units. Generic models are particularly useful when limited information is availabl...

Advanced exergoeconomic analysis of a power plant with CO2 capture

Petrakopoulou, Fontina ; Tsatsaronis, George ; Morosuka, Tatiana (2015)

Conventional exergy-based analyses reveal options for improving energy conversion systems, but they suffer from some limitations that are addressed by advanced exergy-based analyses. Advanced exergy-based methods are capable of (1) identifying interdependencies among plant components (endogenous / exogenous values), and (2) revealing the potential for improvement (avoidable / unavoidable values...

Experimental investigation of a liquid desiccant system for air dehumidification working with ionic liquids

Zegenhagen, Mark T. ; Ricart, Cristina ; Meyer, Thomas ; Kühn, Roland ; Ziegler, Felix (2015)

Electrically-driven compression chillers are the commonly used technology for cooling and dehumidifying air. Open sorption systems driven by solar heat are an alternative to conventional air dehumidification technology and may reduce primary energy consumption. For air dehumidification, liquid desiccant systems may exhibit some process engineering and thermodynamic advantages in comparison to s...

Applicability of Drag Reducing Agents in Domestic Heating Systems

Brandt, Daniel ; Tawackolian, Karsten ; Kriegel, Martin (2017-04-05)

A special test rig was built to investigate the applicability of drag reducing agents, especially in domestic heating systems, detect problems inside the technical implementation and describe the difference between ideal characterization and application.

Additives Shear-Thinning and Turbulence Damping Influence on the Fitting Loss Coefficient of Bends

Tawackolian, Karsten ; Brandt, Daniel ; Kriegel, Martin (2017-04-05)

The flow of a drag-reducing surfactant solution in a bend with a curvature radius of 1.5 is considered, where 20 mm is the pipe inside diameter.

Transient lattice contraction in the solid-to-plasma transition

Ferguson, K. R. ; Bucher, M. ; Gorkhover, Tais ; Boutet, S. ; Fukuzawa, H. ; Koglin, J. E. ; Kumagai, Y. ; Lutman, A. ; Marinelli, A. ; Messerschmidt, M. ; Nagaya, K. ; Turner, J. ; Ueda, K. ; Williams, G. J. ; Bucksbaum, P. H. ; Bostedt, C. (2016)

In condensed matter systems, strong optical excitations can induce phonon-driven processes that alter their mechanical properties. We report on a new phenomenon where a massive electronic excitation induces a collective change in the bond character that leads to transient lattice contraction. Single large van der Waals clusters were isochorically heated to a nanoplasma state with an intense 10-...

Against the Odds: The Potential of Swarm Electrification for Small Island Development States

Koepke, Mathias ; Groh, Sebastian (2016)

The paper builds on earlier observations using system complexity theory to explain the characteristics of a swarm electrification approach using existing small, distributed renewable energy generation infrastructure integrated into a grid. The concept is based on swarm intelligence where information and electricity flow between neighbors to achieve a compounding network effect, in that they are...

Towards biochar and hydrochar engineering

Dieguez-Alonso, Alba ; Funke, Axel ; Anca-Couce, Andrés ; Rombolà, Alessandro Girolamo ; Ojeda, Gerardo ; Bachmann, Jörg ; Behrendt, Frank (2018-02-27)

The impact of conversion process parameters in pyrolysis (maximum temperature, inert gas flow rate) and hydrothermal carbonization (maximum temperature, residence time and post-washing) on biochar and hydrochar properties is investigated. Pine wood (PW) and corn digestate (CD), with low and high inorganic species content respectively, are used as feedstock. CD biochars show lower H/C ratios, th...

Formation and properties of ultrathin silicon dioxide films on Ru(0001)

Klemm, Hagen William (2018)

This work presents the results of a systematic study of the preparation conditions of silica mono- and bilayers on a single crystal ruthenium (0001) surface. Each preparation step was analysed in detail with different methods. Starting with the clean Ru(0001) surface and the different oxygen terminations on it, the deposition of silicon in a low oxygen atmosphere onto an oxygen-pre-covered ruth...

Messdaten zur Absorptionskälteanlage FA2

Kühn, Annett (2018-02-09)

This contribution provides measured data of a single stage H2O/LiBr absorption chiller under partload conditions.

Präzisierungen zur Methode der charakteristischen Gleichungen

Albers, Jan (2017-11-24)

The method of characteristic equations tries to describe the part load behaviour of sorption heat converters (e.g. ab- and adsorption chillers, heat pumps and transformers) in a simple but precise manner. Nevertheless, during the application of the established method some disagreements and inaccuracies occur. For example, the analytically determined parameters of the characteristic equation do ...

Renewable electricity and backup capacities: an (un-) resolvable problem?

Praktiknjo, Aaron J. ; Erdmann, Georg (2016)

Public support for renewables has led to an unexpected investment momentum in Germany. A consequence is reduced wholesale electricity prices, the so-called merit order effect of renewables.We estimate this reduction using an econometric approach and give a quantitative overview of the financial situation of conventional generators. Our results indicate that investments in new conventional capac...

CE_Method. A MATLAB function for calculating the part load behaviour of absorption chillers and heat pumps based on (C)haracteristic (E)quations

Albers, Jan (2017-09-26)

The algorithm CE_METHOD calculates the part load behaviour of single stage absorption chillers and heat pumps explicitly as function of inlet temperatures and flow rates. For the characterisation of the chiller or heat pump the heat transfer capabilities (i.e. the UA-values) of five heat exchangers (Desorber, Evaporator, Condenser, Absorber and Solution heat exchanger) have to be known.