Optical imaging of MHD bubble flow in Hele-Shaw liquid metal cells

As a simple and affordable alternative to often prohibitively expensive or unavailable X-ray and neutron imaging, an improved optical imaging method for bubble flow in Hele-Shaw liquid metal cells is presented, enabling measurements with a significantly greater liquid metal layer thickness than previously reported. This enables studying bubble dynamics with varying degrees of geometric confinement, without or with applied magnetic field. The main principles and the experiment setup, as well as the necessary image/data processing pipeline are described, and preliminary results show that the proposed methods can be used to quantify the effects of varying gas flow rate and magnetic field configuration on bubble chain flow in a Hele-Shaw cell

Numerical Model and System for Prediction and Reduction of Indoor COVID-19 Infection Risk

Airborne aerosol transmission is a significant route of SARS-CoV-2 and other viruses in indoor environments. The developed numerical model assesses the risk of a COVID-19 infection in a room based on the measurements of temperature, relative humidity, CO2 and particle concentration, as well as the number of people and occurrences of speech, coughing, and sneezing obtained through a dedicated low-cost sensor system [1]. As the model operates faster than real-time, it can dynamically feed this information back to the measurement system or building management system, and it can activate an air purifier with filtration and UV-C disinfection when the predicted infection risk is high. This solution enhances energy efficiency as (1) lower ventilation intensity is necessary in the cold season to reach the same safety level and (2) the purifier is activated only if the predicted infection risk is above a certain threshold.The model is integral and takes into account the average values of simulated variables. However, it considers the inhomogeneous vertical distribution of concentration of droplets and aerosol particles. The droplets expelled by a potentially infectious person at a certain height through breathing, speaking, coughing, and sneezing are characterized by the total amount of expelled liquid, droplet size distribution and virus particle concentration. The rate of droplet evaporation depends on the temperature and relative humidity. Droplets are redistributed within the room vertically through turbulent diffusion and gravitational force. If the final droplet diameter is less than 5 mm, these particles are considered airborne and can leave the room only by ventilation, filtration, or by sedimentation on surfaces through Brownian diffusion. As a person in the room inhales these droplets and aerosols, the risk of infection increases as the number of absorbed virions grows, with the probability of infection being 50% when 300 virions have been inhaled.The parameter studies using the model indicate that the coughing and sneezing events greatly increase the probability of infection in the room, therefore the identification of these events is crucial for the applied measurement system. A method for determining the unknown ventilation intensity by measuring the number of people and the CO2 concentration is proposed and tested

Analysis of Thermal Comfort Conditions and Actual Energy Efficiency for Different Heating Systems in Test Buildings

The aim of this study is detailed analysis of long-term monitoring data on thermal comfort conditions and energy efficiency in small test buildings equipped with different heating systems. Calculations of PPD index and local thermal discomfort factors, as well as actual energy efficiency ratios for different heat pump systems are provided for the test buildings during three weeks of the heating season. It is shown that the type of heating system has an influence not only on heating energy needs, but also on thermal comfort conditions in the room

Modelling of EM glass convection

Purpose – To develop the mathematical model, which allows predicting the temperature and flow distribution of an opaque glass melt with the temperature-dependent properties in case it is generated by electromagnetic and thermal convection. Analysis has been done for geometry of the model crucible with the immersed rod electrodes. Numerical analysis is used as a tool for finding out the parameters of the system, which allow getting desiderated homogeneity of temperature field by EM action. Design/methodology/approach – ANSYS CFX software is implemented for coupling of EM, thermal and HD processes in the modelled system. Usability of non-inductive approximation is shown using a full harmonic analysis in ANSYS. Findings – External magnetic field can impact the temperature distribution in the whole volume of the melt significantly, it relocates the hottest zones and changes the maximal temperature in the melt. Qualitative agreement between the numerical and experimental results has been obtained. Dependence of the potential difference between the electrodes on the velocity and temperature range has been examined. Impact of different thermal boundary conditions has been analysed. Research limitations/implications – Effects analysed in the publication occur in each conducting media subjected to the impact of simultaneous electrical and magnetical field. The main limitation is non-transparency of the melt. Practical implications – The purpose is to develop a mathematical tool for parameter optimisation of real glass melting furnace. Originality/value – In the present model temperature dependent properties of the melt have been taken into account, which has been neglected in previous models

Distributed Multi-Sensor Real-Time Building Environmental Parameters Monitoring System with Remote Data Access

In this paper the advanced monitoring system of multiple environmental parameters is presented. The purpose of the system is a long-term estimation of energy efficiency and sustainability for the research test stands which are made of different building materials. Construction of test stands, and placement of main sensors are presented in the first chapter. The structure of data acquisition system includes a real-time interface with sensors and a data logger that allows to acquire and log data from all sensors with fixed rate. The data logging system provides a remote access to the processing of the acquired data and carries out periodical saving at a remote FTP server using an Internet connection. The system architecture and the usage of sensors are explained in the second chapter. In the third chapter implementation of the system, different interfaces of sensors and energy measuring devices are discussed and several examples of data logger program are presented. Each data logger is reading data from analog and digital channels. Measurements can be displayed directly on a screen using WEB access or using data from FTP server. Measurements and acquired data graphical results are presented in the fourth chapter in the selected diagrams. The benefits of the developed system are presented in the conclusion