Geometrical scale dependency of thin film solid oxide fuel cells

To study the geometrical scale dependency of thin film solid oxide fuel cells (SOFCs), we fabricated three thin films SOFCs which have the same cross-sectional structure but different electrode areas of 1 mm2, 4 mm2 and 9 mm2. Since the activation and ohmic losses of SOFCs depend on their active region, we examined the variations of the power density of the cells with a Pt/YSZ/Pt structure and simulated the power density variations using the COMSOL software package.

Performance Assessment of a Hybrid Wave Energy Converter Integrated into a Harbor Breakwater

Seaports are highly energy demanding infrastructures and are exposed to wave energy, which is an abundant resource and largely unexploited. As a result, there has been a rising interest in integrating wave energy converters (WEC) into the breakwaters of seaports. The present work analyzes the performance of an innovative hybrid WEC module combining an oscillating water column (OWC) and an overtopping device (OWEC) integrated into a rubble mound breakwater, based on results of a physical model study carried out at a geometrical scale of 1:50. Before the experimental tests, the device’s performance was numerically optimized using ANSYS Fluent and WOPSim v3.11. The wave power captured by the hybrid WEC was calculated and the performance of the two harvesting principles discussed. It was demonstrated that hybridization could lead to systems with higher efficiencies than its individual components, for a broader range of wave conditions. The chosen concepts were found to complement each other: the OWEC was more efficient for the lower wave periods tested and the OWC for the higher. Consequently, the power production of the hybrid WEC was found to be less dependent on the wave’s characteristics.

Simulation of the Scale-up Process of a Venturi Jet Pyrolysis Reactor

Micro- and nano-sized cerium oxide particles can be prepared through pyrolyzing cerium chloride solution directly in the venturi jet pyrolysis reactor. Micro- and nano-sized cerium oxide particles have better performance and higher application value. To increase the production of micro-and nano-sized cerium oxide, it is necessary to scale up the venturi jet pyrolysis reactor. According to the geometric similarity principle, the scale-up of the venturi jet pyrolysis reactors utilize dimensional analysis methods, with FLUENT13.0 and user-defined functions, following the mathematical simulation of the resulting enlarged reactors. After the dimensional analysis, the empirical formula obtained between the reactants and all the parameters is Q = 2.240727 × 10−4P0.004568ρ0.26223d−0.24801V1.25714n0.076479μ−0.26628, and the geometrical scale-up of the reactors needs to follow V = 0.0209d0.196. The results in this study can provide data support for the future optimization and amplification of reactors.

FIRTEZ-dz

We present a numerical code that solves the forward and inverse problem of the polarized radiative transfer equation in geometrical scale under the Zeeman regime. The code is fully parallelized, making it able to easily handle large observational and simulated datasets. We checked the reliability of the forward and inverse modules through different examples. In particular, we show that even when properly inferring various physical parameters (temperature, magnetic field components, and line-of-sight velocity) in optical depth, their reliability in height-scale depends on the accuracy with which the gas-pressure or density are known. The code is made publicly available as a tool to solve the radiative transfer equation and perform the inverse solution treating each pixel independently. An important feature of this code, that will be exploited in the future, is that working in geometrical-scale allows for the direct calculation of spatial derivatives, which are usually required in order to estimate the gas pressure and/or density via the momentum equation in a three-dimensional volume, in particular the three-dimensional Lorenz force.

Smoke Obscuration Measurements in Reduced-Scale Fire Modelling Based on Froude Number Similarity

A common method for investigating various fire- and smoke-related phenoma is a reduced-scale fire modelling that uses the conservation concept of Froude number as its primary similarity criterion. Smoke obscuration measurements were not commonly used in this approach. In this paper, we propose a new type of optical densitometer that allows for smoke obscuration density measurements on a reduced-scale. This device uses a set of mirrors to increase the optical path length, so that the device may follow the geometrical scale of the model, but that still measures smoke obscuration as if it were in full scale. The principle of operation is based on the Bougher-Lambert-Beer law, with modifications related to the Froude number-based scaling principles, to streamline the measurements. The proposed low-budget (< $1000) device was built, calibrated with a set of the reference optical filters, and used in a series of full- (1:1) and reduced-scale (1:4) experiments with n-Heptane fires in a small compartment. The main limitation of this study is the assumption that there is similar soot production in full- and reduced-scale fires, which may not be true for many Froude-number scaling applications. Therefore, it must be investigated in a case-by-case basis. In our case, the results are promising. The measured obscuration in the reduced-scale had a 10% error versus averaged measurements in full-scale measurements. Moreover, there were well represented transient changes of the smoke layer optical density during the combustion and after the smoke layer settled.

Reprogrammable Braille on an elastic shell

We describe a minimal realization of reversibly programmable matter in the form of a featureless smooth elastic plate that has the capacity to store information in a Braille-like format as a sequence of stable discrete dimples. Simple experiments with cylindrical and spherical shells show that we can control the number, location, and the temporal order of these dimples, which can be written and erased at will. Theoretical analysis of the governing equations in a specialized setting and numerical simulations of the complete equations allow us to characterize the phase diagram for the formation of these localized elastic states, elastic bits (e-bits), consistent with our observations. Given that the inherent bistability and hysteresis in these low-dimensional systems arise exclusively due to the geometrical-scale separation, independent of material properties or absolute scale, our results might serve as alternate approaches to small-scale mechanical memories.

Preliminary Study on a Reduced Scaled Model Regarding the Air Diffusion inside a Crew Quarter on Board of the ISS

The paper focus on the air quality inside the Crew Quarters on board of the International Space Station. Several issues to improve were recorded by NASA and ESA and most important of them are the following: noise level reduction, CO2 accumulation reduction and dust accumulation reduction. The study in this paper is centred on a reduced scaled model used to provide simulations related to the air diffusion inside the CQ. It is obvious that a new ventilation system is required to achieve the three issues mentioned above, and the solutions obtained by means of numerical simulation need to be validated by experimental approach. First of all we have built a reduced scaled physical model to simulate the flow pattern inside the CQ and the equipment inside the CQ has been reproduced using a geometrical scale ratio. The flow pattern was considered isothermal and incompressible. The similarity criteria used was the Reynolds number to characterize the flow pattern and the length scale was set at value 1/4. Water has been used inside the model to simulate air. Velocity magnitude vectors have been obtained using PIV measurement techniques.

The Study of Mengkuang Dam`s Chute Spillway by Physical Modeling

This paper presents a case study of water flow over the chute spillway type for the Mengkuang Dam expansion project. It governs the surplus water from the dam to the downstream area. However, flows were driven by gravity along the curvature and vertical direction which cause unpredictable flow direction along the chute. Its cause’s thickening of turbulence, changing the velocity, pressure and depth of the water along the spillway. This study was simulated using a physical model with geometrical scale of 1:20. After some test conducted on the spillway, eleven locations on the spillway were selected for the test based on observation for the study. For each location, there were five points in a line with equal distance. Manometers were installed on six locations of the spillway. The water level, velocity and pressure were measured at every point for 100, 1000, 10000 years and PMF design discharge of the spillway. Several critical occurrences on the spillway such as turbulent and cross-wave were presented in this paper.