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In our work, we focused on measuring the performance characteristics of a test hydrogen fuel cell with an open cathode. The aim of the work was to verify the effect of the mass flow through the fuel cell on the power output as a function of the current density and voltage on the fuel cell. A test bench capable of testing fuel cells up to 2000 W was used to measure the power characteristics. The test fuel cell was composed of three cells and its total membrane area was 100 cm2. A PIV measurement system was used to measure the mass flow. The mass flow measurement was performed at the inlet of the fuel cell. The measurements included the determination of the inlet temperature distribution using a thermal imaging camera. The presented measurements were performed for two configurations with original and optimized diffuser at the inlet of the fans. Finally, the effect of mass flow and overall thermal management on the fuel cell performance is discussed, including the effect of the newly designed diffuser.

The aim of present work is focused on determining accuracy of the measurement using the Particle Image Velocimetry based on an analysis of synthetic Uniform flow test and Couette flow test. We focused on testing the Standard Cross Correlation algorithm and interdependence between the several metrics based on the ratio signal and noise peak and the measurement accuracy at each point. This work is describing the influence of the new corrected metric that is corrected by a displacement measured in the last iteration, detected mean density of the particles and the velocity gradient. Newly proposed method of calculating the metric, Lost of Particle Ratio, is based on the determination of the magnitudes of two correlation peaks. In this work there is defined and compared another metric based on the result of synthetics data test which is based on determination of main parameters as number of particles, gradient in interrogation area and displacement of particles calculated in the last step of correlation. For all presented metrics the relationship is between the metrics and the accuracy.

This paper deals with flow around a bluff body of hyperboloid shape. It consists of results gathered in the course of research by means of Particle Image Velocimetry (PIV). The experiments were carried out by means of low-frequency 2D PIV in a range of Reynolds numbers from 40000 to 50000. A hyperboloid-shaped model was measured in a wind tunnel with a modelled atmospheric boundary layer (and additionally, in a low-speed wind tunnel with low turbulence). The model was tested in a subcritical range of Reynolds numbers and various planes in a wake of the model were captured with the intention of getting an estimation of 3D flow structures. The tunnel with the modelled atmospheric boundary layer has a high rate of turbulence, so the influence of the turbulence of incoming flow on the wake could be outlined. The ratio of the height of the model to a thickness of the modelled boundary layer in the tunnel was 1/3, meaning the turbulence in the boundary layer strongly influenced the flow around the model; it suppresses the wake which leads to a lot shorter area of recirculation than low turbulence incoming flow would cause.

This paper deals with flow around a bluff body of hyperboloid shape. It combines results gathered in the course of research by means of Particle Image Velocimetry (PIV). The experiments were carried out by means of low-frequency 2D PIV and the Reynolds number was 43 000.

This paper deals with setting of the acquisition equipment used to visualize and measure the concentration of intermediate species chemiluminescence combustion and laser-induced fluorescence. Observed intermediates such as OH, NO, CH and others have an emitted UV spectrum and their signal is very weak. For this reason, it is necessary to use a suitable image intensifier, and its proper setting and synchronization with the camera is also very important. In view of this problem, the following text deals with the appropriate setting of selected optical amplifiers with P46 and P43. Because the recording equipment can be used for both LIF and chemiluminescence, the experimentally determined setting will be performed using the OH-chemiluminescence method. This is reported by a weaker signal and creates a more stringent setup criterion. As a qualitative factor, a gradient of the image function has been selected, which plays a significant role in edge detection and therefore also in flame front position detection.

This paper deals with the flow in data racks. The aim of this work is to find a new arrangement of elements regulating the flow in the data rack so that the aerodynamic losses and the recirculation zones were minimized. The main reason for solving this problem is to reduce the costs of data racks cooling. Another problem to be solved is a reverse flow in the servers, thus not cooled, occuring due to the underpressure in the recirculation zones. In order to solve the problem, the experimental and numerical model of 27U data rack fitted with 10 pieces of server models with a total input of 10 kW was created. Different configurations of layout of elements affecting the flow in the inlet area of the data rack were compared. Depending on the results achieved, design solutions for the improvement of existing solutions were adopted and verified by numerical simulations. 1 Aim/Motivation The aim of the work was to reduce overall cooling costs in data centers. There are many studies and ways of deal- ing with the problem at the level of the whole data centers, or the elements constituting data centers. This paper fo- cuses on the level of data racks (27U) and servers (1U), specifically on the suction area of servers in the data rack. This include modification of the current state or equipment in the direction to reduce the effects of undesirable in- crease of energy consumption necessary for effective cool- ing of fitted components - the servers, in this particular case. The above mentioned undesirable effects can be de- scribed e.g. as recirculation zones, under-pressure areas or areas of flow separation.

This paper is aimed at modification of calculation algorithm used in data processing from PIV (Particle Image Velocimetry) method. The modification of standard Multi-step correlation algorithm is based on imaging the centre of mass of the interrogation area to define the initial point of the respective vector, instead of the geometrical centre. This paper describes the principle of initial point-vector assignment, the corresponding data processing methodology including the test track analysis. Both approaches are compared within the framework of accuracy in the conclusion. The accuracy test is performed using synthetic and real data.