Publications related to Refrigerant

High-speed turbocompressors for natural fluid heat-pumps: from integrated design to digital-twin

Compressors for commercial and industrial heat-pumps in the 100kW-load range are currently dominated by positive displacementmachines. In the context of refrigerant phaseouts and changing regulations, natural refrigerants are seen as a compelling alternati ...

EPFL2023

Heat transfer of uncoated and nanostructure coated commercially micro-enhanced refrigeration tubes under pool boiling conditions

John Richard Thome

The heat transfer performance of commercially produced micro-enhanced tubes with and without a nanocoating was investigated under pool boiling of saturated refrigerant. These multiscale enhancements were on the outside of 19 mm horizontal copper tubes heat ...

Pergamon-Elsevier Science Ltd2023

Flow Boiling of Carbon Dioxide at Different Channel Orientations for the Thermal Management of Future Detector Technologies at the High-Luminosity Large Hadron Collider at CERN

David Schmid

The global warming potential (GWP) of working fluids in thermodynamic cycles and their environmental impact have been gaining considerable attention within the recent years. The global objectives on climate protection are becoming increasingly ambitious, w ...

EPFL2022

Novel pulsating heat pipe for high density power data centres: performance and flow regime analysis

John Richard Thome, Jackson Braz Marcinichen, Filippo Cataldo, Raffaele Luca Amalfi

With the advancement of technologies such as Artificial Intelligence and 5G telecommunications, where computational rate is constantly pushing its limits, highly efficient and reliable cooling devices are starting to become an overly critical factor. Not o ...

IEEE2021

The Indoor Chemical Human Emissions and Reactivity (ICHEAR) project: Overview of experimental methodology and preliminary results

Dusan Licina, Shen Yang

With the gradual reduction of emissions from building products, emissions from human occupants become more dominant indoors. The impact of human emissions on indoor air quality is inadequately understood. The aim of the Indoor Chemical Human Emissions and ...

WILEY2020

Experimental Performance of Completely Passive Single and Recirculating Loop Thermosyphon Cooling Systems using Low GWP R1234ze and R1234yf

John Richard Thome

This paper proposes a novel concept for a loop thermosyphon cooling system, designed for the transistor module of a transformer. The thermosyphon uses a free convection cooled condenser, making the system completely passive, i.e. no energy consumption is n ...

IEEE2019

Impact of large tip clearance ratios on the performance of a centrifugal compressor

Jürg Alexander Schiffmann, Markus Diehl

Ultra-compact and fast spinning turbomachinery is a key technology to increase performance of domestic heating applications and to address decentralization of power and heat as a consequence of the rise of renewable energy sources. Recently, a heat pump us ...

2019

Fifth generation district energy systems for low carbon cities

Raluca-Ancuta Suciu

The focus and challenge for energy engineering in the context of rapid climate change is summarised by the Europe 20-20-20 targets, committing to a reduction in energy consumption of 20%. The most logical approach to achieve these goals is to target the mo ...

EPFL2019

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

Pressure drop prediction in annular two-phase flow in macroscale tubes and channels

John Richard Thome, Andrea Cioncolini

A new prediction method for the frictional pressure drop in annular two-phase flow is presented. This new prediction method focuses on the aerodynamic interaction between the liquid film and the gas core in annular flows, and explicitly takes into account ...

Pergamon-Elsevier Science Ltd2017

Effect of O2 migration in Pt/HfO2/Ti/Pt structure

Giovanni De Micheli, Pierre-Emmanuel Julien Marc Gaillardon, Maxime Victor Thammasack

In this paper, we study the post-fabrication phenomenon of natural oxidation of the Ti layer observed in a Pt/HfO2/Ti/Pt Resistive Random Access Memory (OxRRAM) stack with no external influence. We identify that the resistance ratio decreases by ...

Springer Verlag2017

Critical heat flux: Performance of R1234yf, R1234ze and R134a in an aluminum multi-minichannel heat sink at high saturation temperatures

John Richard Thome

In this paper, new saturated critical heat flux (CHF) values at medium-to-high saturation temperatures are presented for an aluminum multi-minichannel test section. Among the possible working fluids, R134a and the low GWP refrigerants R1234yf and R1234ze h ...

Elsevier France-Editions Scientifiques Medicales Elsevier2016

Potential of refrigerant based district heating and cooling networks

Samuel Henchoz

Urban areas represent an ever increasing challenge in terms of energy use and environmental impact associated with it. Projections from the United Nation expect this number to reach 66% by 2050. In Europe 40% of the final energy consumption and 36% of the ...

EPFL2016

Key Energy and Technological Aspects of Three Innovative Concepts of District Energy Networks

François Maréchal, Daniel Favrat, Samuel Henchoz, Patrick Chatelan

Energy needs in urban areas are heterogeneous by their nature, spatial distribution and temperature level required. Three concepts of district energy networks that could provide the energy services efficiently to a city centre are compared. The focus is on ...

2016

Two-Phase Heat Transfer Mechanisms within Plate Heat Exchangers : Experiments, Modeling and Simulations

Raffaele Luca Amalfi

Plate heat exchangers are adopted in many domestic and industrial applications, such as ventilation, air conditioning, evaporation or condensation process, heat pumps and cooling of hydrodynamic circuits in engines. In the present thesis, an extensive expe ...

EPFL2016

Potential of Small-Scale Turbomachinery for Waste Heat Recovery on Automotive Internal Combustion Engines

Jürg Alexander Schiffmann, Eliott Philippe Guenat, Violette Mounier, Kévin Rosset

This paper investigates the waste heat recovery potential of internal combustion engines, using organic Rankine cycles running on small-scale radial turbomachinery. ORC are promising candidates for low-grade thermal sources and the use of dynamic expanders ...

2015

Dynamic flow control and performance comparison of different concepts of two-phase on-chip cooling cycles

John Richard Thome, Jackson Braz Marcinichen, Duan Wu, Bruno Michel

A hybrid on-chip two-phase cooling cycle specifically designed to cool server boards with chips of high performance computers was experimentally evaluated considering steady-state and transient operation of two parallel pseudo-chips and auxiliary electroni ...

Elsevier2014

Fine-resolution two-phase flow heat transfer coefficient measurements of refrigerants in multi-microchannel evaporators

John Richard Thome, Navid Borhani, Sylwia Szczukiewicz

The time-averaged two-phase flow heat transfer coefficients were determined with a very fine resolution based on infra-red (IR) temperature measurements conducted over a 1 cm(2) heated area of a multi-micro-, channel evaporator. This experimental investiga ...

Elsevier2013

Application of micro-channel cooling to the local thermal management of detectors electronics for particle physics

Philippe Renaud, Alessandro Mapelli, Andrea Francescon, Giulia Romagnoli

Micro-channel cooling is gaining considerable attention as an alternative technique for cooling of high energy physics detectors. This is of particular interest for future trackers, where large silicon surfaces are involved and the amount of material cross ...

Elsevier2013

Dynamic Modeling and Simulation of Two-stage Compression Heat Pumps with Flash Economizer

Daniel Favrat, Jean-Baptiste Carré, Samuel Henchoz, Simon Gailledrat

Multistage heat pumps are one of the most efficient technologies for delivering heat at temperatures below 100°C, Thanks to their fairly high exergy efficiency. In the recent years the development of radial compressors mounted on gas bearings have unlock t ...

2013