Publications de Alexandros Terzis

Celebration of Professor Bernhard Weigand on his 60th birthday

PERGAMON-ELSEVIER SCIENCE LTD2022

Transient Liquid Crystal Thermography Using a Time Varying Surface Heat Flux

Peter Ott, Michele Gaffuri, Alexandros Terzis

Heat transfer measurements are required in a wide range of fields, for example to validate new cooling concepts in turbomachinery, to assess the performances of heat exchangers, and to provide data for numerical simulations. Thereby transient methods are o ...

2021

Narrow Impingement Channels: Recent Advancements and Future Directions

Peter Ott, Michele Gaffuri, Alexandros Terzis

This paper summarizes the state-of-the-art related to the heat transfer characteristics of narrow impingement cooling channels, which can nowadays be integrated within the external wall of turbine airfoils. Particular emphasis is given to the experimental ...

European Turbomachinery Society2019

Evaluation of Heat Transfer Coefficients for an Impingement Cooling Cascade: Experimental Challenges and Preliminary Results

Peter Ott, Michele Gaffuri, Alexandros Terzis

In this paper, a modification of the widely used transient liquid crystal heat transfer measurement technique for impingement cooling is presented, in which a constant heat flux at the surface is used to drive the experiment, instead of a step change in th ...

2018

On the Effects of Coating Thickness in Transient Heat Transfer Experiments Using Thermochromic Liquid Crystals

Peter Ott, Alexandros Terzis, Sebastian Schulz

Transient heat transfer experiments typically employ thermochromic liquid crystals to temporally map surface temperatures. The desired heat transfer coefficient is then calculated from the solution of Fourier’s 1D transient heat conduction equation which i ...

Elsevier2016

Effect of Varying Jet Diameter on the Heat Transfer Distributions of Narrow Impingement Channels

Peter Ott, Bernhard Weigand, Alexandros Terzis

The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities ...

Asme2015

Impact of ns-DBD Plasma Actuation on the Boundary Layer Transition Using Convective Heat Transfer Measurements

Peter Ott, Bernhard Weigand, Philip Peschke, Alexandros Terzis, Dirk Ullmer

This paper demonstrates that the impact of nanosecond pulsed dielectric barrier discharge (ns-DBD) actuators on the structure of the boundary layer can be investigated using quantitative convective heat transfer measurements. For the experiments, the flow ...

Iop Publishing Ltd2015

A method to visualise near wall fluid flow patterns using locally resolved convective heat transfer experiments

Peter Ott, Bernhard Weigand, Alexandros Terzis

The present study demonstrates an alternative approach for describing ﬂuid ﬂow characteristics very close to the wall, using locally resolved convective heat transfer experiments. Heat transfer coefﬁcients on the base surface and around a surface mounted v ...

Elsevier2015

High-Resolution Heat Transfer Measurements and Crossflow Regulation in Narrow Impingement Cooling Channels with Divergent Geometries

Peter Ott, Alexandros Terzis, Stavros Bontitsopoulos

The present study describes an experimental investigation into narrow impingement cooling channels with divergent geometries. The following analysis aims to clarify the influence that this particular form factor exerts on the heat transfer distribution, as ...

2015

Heat Transfer Characteristics of High Crossflow Impingement Channels: Effect of Number of Holes

Peter Ott, Alexandros Terzis, Santiago Llucià

In modern turbine airfoils, narrow impingement cooling channels can be formed in a double-wall configuration. In these wall-integrated cooling cavities, the generated crossflow is one of the most important design factors, and hence, the number of impingeme ...

2015

Heat Transfer Characteristics of High Crossflow Impingement Channels: Effect of Number of Holes

Peter Ott, Alexandros Terzis, Santiago Llucià

In modern turbine airfoils, narrow impingement cooling channels can be formed in a double-wall configuration. In these wall-integrated cooling cavities, the generated crossflow is one of the most important design factors, and hence, the number of impingeme ...

Sage Publications Ltd2015

Detailed heat transfer distributions of narrow impingement channels for integrally cast turbine airfoils

Alexandros Terzis

EPFL2014

Detailed Heat Transfer Distributions of Narrow Impingement Channels with Varying Jet Diameter

Peter Ott, Bernhard Weigand, Alexandros Terzis

The development of integrally cast turbine airfoils allows the production of narrow impingement channels in a double-wall configuration, where the coolant is practically injected within the wall of the airfoil providing increased heat transfer capabilities ...

ASME2014

Detailed Heat Transfer Distributions of Narrow Impingement Channels for Cast-In Turbine Airfoils

Peter Ott, Bernhard Weigand, Alexandros Terzis

The current capabilities of the foundry industry allow the production of integrally cast turbine airfoils. Impingement cooling effectiveness can be then further increased due to the manufacturing feasibility of narrow impingement cavities in a double-wall ...

American Society of Mechanical Engineers2014

A Comparative Study of the Local Heat Transfer Distributions Around Various Surface Mounted Obstacles

Peter Ott, Robert Wyssmann, Alexandros Terzis, Dirk Ullmer

In many engineering applications, heat transfer enhancement techniques are of vital importance in order to ensure reliable thermal designs of convective heat transfer applications. This study examines experimentally the heat transfer characteristics on the ...

Science Press2014

Detailed heat transfer distributions of narrow impingement channels for cast-in turbine airfoils

Alexandros Terzis

Gas turbine operation at elevated temperatures ensures increased thermal efficiency and useful power output. However, the industrial tendency to push further firing temperatures is limited by the capabilities of the current turbine blade cooling technologi ...

2014

Hole Staggering Effect on the Cooling Performance of Narrow Impingement Channels Using the Transient Liquid Crystal Technique

Peter Ott, Guillaume Wagner, Bernhard Weigand, Alexandros Terzis

This study examines experimentally the cooling performance of narrow impingement channels as could be cast-in in modern turbine airfoils. Full surface heat transfer coefficients are evaluated for the target plate and the sidewalls of the channels using the ...

American Society of Mechanical Engineers2014

Experimental and Numerical Investigation of a Fully Confined Impingement Round Jet

Peter Ott, Gwenael Hannema, Gabriel Charles Gnaegi, Alexandros Terzis, Oriana Caggese

The heat transfer characteristics of a fully confined impingement jet are experimentally and numerically evaluated. Full surface heat transfer coefficient distributions are obtained for the target and impingement plate of the model using the transient liqu ...

Pergamon-Elsevier Science Ltd2013

Experimental and numerical investigation of narrow impingement cooling channels

Peter Ott, Bernhard Weigand, Alexandros Terzis

Impingement cooling effectiveness of gas turbine vanes and blades can be further increased due to the manufacturing feasibility of integrally cast airfoils which can provide narrow impingement cooling cavities. This study examines experimentally using the ...

Elsevier2013

Thermocouple Thermal Inertia Effects on Impingement Heat Transfer Experiments Using the Transient Liquid Crystal Technique

Peter Ott, Bernhard Weigand, Alexandros Terzis

The transient liquid crystal technique is widely used for impingement heat transfer experiments. Additionally, due to the difficulty of producing pure temperature steps in the flow, many authors assumed the fluid temperature evolution as a series of step c ...

Institute of Physics2012