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Jürg Alexander Schiffmann

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Publications associées (112)

Effects of humid air on aerodynamic journal bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat

The development of aerodynamic bearings applications where ambient conditions cannot be controlled (e.g., for automotive fuel cell compressor) raises the question of the effects of condensation in the humid air on perfor-mance. A modified Reynolds equation ...

2018

Small, High-Speed, Oil-Free Radial Turbo-compressors for Cooling Applications: Refrigerant Selection

Jürg Alexander Schiffmann

Emerging energy-efficient, oil-free radial centrifugal compressors seem promising for small to mid-capacity air conditioning and refrigeration applications. Compressor design must balance trade-offs among impeller diameter, bearing type, and refrigerant se ...

2018

A co-rotational scroll machine

Jürg Alexander Schiffmann, Luis Carlos Mendoza Toledo

A co-rotating scroll machine operable as compressor or expander, comprises a transmission and guidance mechanism (9,10) for first and second scroll plates (7,8), having three transmission and guidance units (9,10) uniformly distributed around the scroll pl ...

2018

Real-gas effects on aerodynamic bearings

Jürg Alexander Schiffmann, Eliott Philippe Guenat

Motivated by the use of aerodynamic bearings lubricated with high-pressure gases in energy conversion cycles, the Reynolds equation is adapted in order to include effects of real-gas and turbulence. Three geometries (Rayleigh-step slider, plain and herring ...

2018

Dimensionless correlations and performance maps of scroll expanders for micro-scale Organic Rankine Cycles

Jürg Alexander Schiffmann, Luis Eric Olmedo Ocampo, Violette Mounier, Luis Carlos Mendoza Toledo

In the endeavor towards distributed power systems, not seasonal-dependent micro-power generation technologies are expected to integrate the energy scenario in the years to come. In this context, the Organic Rankine Cycle (ORC) in the (1e10) KWe scale has c ...

2018

Data-Driven Predesign Tool for Small-Scale Centrifugal Compressor in Refrigeration

Jürg Alexander Schiffmann, Cyril Picard, Violette Mounier

Domestic scale heat pumps and air conditioners are mainly driven by volumetric com-pressors. Yet the use of reduced scale centrifugal compressors is reconsidered due to their high efficiency and power density. The design procedure of centrifugal compressor ...

2018

Testing and modelling of a novel oil-free co-rotating scroll machine with water injection

Jürg Alexander Schiffmann, Luis Carlos Mendoza Toledo

Efficient compressed air energy storage requires reversible isothermal compression and expansion devices. The isothermal compression and expansion processes can either be approached by several stages with intercooling or by the more convenient injection of ...

Elsevier2017

Theoretical analysis of steam generation methods - Energy, CO 2 emission, and cost analysis

Jürg Alexander Schiffmann

A theoretical case study on steam generation has been performed. Different methods of producing steam by vapour compression, direct electrical heating, gas heating, heat pumping, use of waste heat, and a mixture thereof, were theoretically analysed. The fi ...

Elsevier2017

Heat Pump driven by a Small-Scale Oil-Free Turbocompressor – System Design and Simulation

Jürg Alexander Schiffmann, Adeel Javed

Small-scale oil-free turbocompressors driven by high-speed electric motors and supported on refrigerant vapor bearings represent a promising technology to increase the performance of domestic heat pumps. Gas bearings enable high rotational speeds with low ...

2017

Modeling and Designing of a Radial Anode Off-Gas Recirculation Fan for Solid Oxide Fuel Cell Systems

Stefan Diethelm, Jürg Alexander Schiffmann, Jan Van Herle, Zacharie Wuillemin, Patrick Hubert Wagner

To improve the industry benchmark of solid oxide fuel cell (SOFC) systems, we consider anode off-gas recirculation (AOR) using a small-scale fan. Evolutionary algorithms compare different system design alternatives with hot or cold recirculation. The syste ...

2017

Thermo-economic optimization of an ORC driven heat pump based on small scale turbomachinery and comparison with absorption heat pumps

Jürg Alexander Schiffmann, Violette Mounier, Luis Carlos Mendoza Toledo

The current paper presents the thermo-economic optimization and comparison, through a multi-objective algorithm, between HP-ORC and the competing single effect absorption heat pump (SEAHP), with the aim to find the best trade-off between investment cost an ...

Elsevier2017

Turbocompressors for Domestic Heat Pumps – A Critical Review

Jürg Alexander Schiffmann, Jean-Baptiste Carré

Small-scale, oil-free radial compressors on gas lubricated bearings represent a promising alternative to state-of-the-art compressor technology for driving domestic sized heat pumps. The inherent characteristics of turbocompressors manage to fit the heat p ...

2017

Comparative Evaluation of Foil Bearings with Different Compliant Structures for Improved Manufacturability

Jürg Alexander Schiffmann, Karim Magdi Zakaria Abdelrahman Shalash

Potential geometrical deviations in bump foil bearings due to manufacturing uncertainty can have significant effects on both the local stiffness and clearance, and hence, affecting the overall bearing performance. The manufacturing uncertainty of bump type ...

Amer Soc Mechanical Engineers2017

The Role of Impeller Outflow Conditions on the Performance of Vaned Diffusers

Jürg Alexander Schiffmann

Highly loaded impellers, typically used in turbocharger and gas turbine applications, exhaust an unsteady, transonic flow that is nonuniform across the span and pitch and swirling at angles approaching tangential. With the exception of the flow angle, conf ...

American Society of Mechanical Engineers2017

ORC Driven Heat Pump Running on Gas Bearings for Domestic Applications: Proof of Concept and Thermo-Economic Improvement Potential

Jürg Alexander Schiffmann, Violette Mounier

ORC driven Heat Pumps (HP-ORC) offer a promising technology of thermally driven heat pumps (TDHPs) for domestic applications. Recently, a 40 kW HP-ORC unit based on gas supported turbomachinery has been investigated in which the ORC radial turbine drives t ...

2017

Multi-temperature heat pumps: A literature review

Jürg Alexander Schiffmann

This review highlights the major advantages and challenges of mechanically driven heat pumps and refrigeration systems with focus on multi-temperature applications. Different design strategies are presented, including cycles with multi-stage compressors, e ...

Elsevier2016

Small-scale turbocompressors for wide-range operation with large tip-clearances for a two-stage heat pump concept

Jürg Alexander Schiffmann, Adeel Javed

Two mechanically driven small-scale turbocompressors running on gas lubricated bear-ings have been theoretically designed for a 6.5 kW two-stage heat pump functioning under variable operating conditions. The novelty in the heat pump system lies in the appl ...

Elsevier2016

Theoretical Study of a Novel Oil-Free Co-Rotating Scroll Compressor Integrated into a Hybrid Absorption Heat Pumps

Jürg Alexander Schiffmann, Luis Carlos Mendoza Toledo

Hybrid absorption heat pumps (Osenbrück cycle and Hybrid wet compression cycle) are known for high temperature lifts, low-pressure ratios and wide capacity control. They are well suited for processes with the occurrence of significant heat sink and heat so ...

2016

Experimental investigation of a two-stage oil-free domestic Air/Water heat pump prototype powered by an oil-free high-speed twin-stage radial compressor rotating on gas bearings

Jürg Alexander Schiffmann, Daniel Favrat, Jean-Baptiste Carré

Domestic heat pumps have been identified as a key-technology to decrease the energy consumption of the domestic sector, which represents 29% of the world final energy consumption. Space & water heating represent more than two third of the domestic sector e ...

2016

Design of Oil-Free Turbocompressors for a Two-Stage Industrial Heat Pump under Variable Operating Conditions

Jürg Alexander Schiffmann, Adeel Javed

A pair of mechanically driven small-scale turbocompressors running on gas lubricated bearings have been designed for a two-stage heat pump application functioning under variable operating conditions. Novelty in the present two-stage heat pump system lies i ...

2016

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