The stability of the radiative regime in Bucharest during 2017-2018

The paper presents an analysis of the solar irradiation and the stability of the solar radiative regime, available for Bucharest and the southern area of Romania. The study is based on meteorological data measured at 3.6 seconds, on several consecutive days of each season, in the years 2017 and 2018. Data acquisition was performed at Technical University of Civil Engineering Bucharest. The daily mean values for sunshine number and sunshine stability number are computed and analysed. The analyses carried out in this research are useful for applications of solar energy and conversion to thermal energy in hot air solar collectors to estimate the temperature variation at the collector air outlet as well as for photovoltaic panels to estimate the resulting electrical energy

Experimental and numerical study of the air distribution inside a car cabin

The main declared goal of all car manufacturers is to ensure high comfort inside the cabin and to reduce the fossil fuel. It is well-known that the time spent by the people indoor has raised in the last decade. The distance between the home and the workplace increased due to diversity of activities and hence job diversity. The thermal comfort during the travel must to be ensured to reduce the occupant’s thermal stress. The present study is investigating a comparison between the measured data and the numerical simulation results in the case when the ventilation system is functioning. It was evaluated the effect of the boundary conditions air flow and air velocity distribution in a passenger compartment in two cases: first is the general used constant inlet flow and the second is a new approach of importing the measured data obtained during the experimental measurement session as a boundary condition.CFD simulations were made taking as input the measured data obtained during experimental session. We have observed differences between initial simulation results and the measured data, therefore, for more accurate results, a new approach is needed, to impose as boundary conditions the measured data

Preliminary numerical studies conducted for the numerical model of a real transpired solar collector with integrated phase changing materials

Solar energy has a great potential to reduce the worldwide energy consumptions thus mitigating the impact of building systems on the global warming. Transpired solar collectors (TSC) are cost-effective solutions and phase changing materials (PCM) implemented within them could store the energy during the periods when solar radiation is available. The current paper is part of comprehensive numerical studies and analyses the mesh independency studies conducted in ANSYS Fluent with SST k-Ω viscous model and the numerical model preliminary results (3.3ºC rise in temperature). The results emphasise that the 5 million cells mesh is the feasible option for the studied case

Local exhaust ventilation solutions for an industrial hall – Part 1 CFD analysis of the local exhaust systems

Industrial hygiene is an important aspect of any workplace environment, especially for the industrial domain. A previous study has shown that high ammonia levels were present in a wastewater treatment facility in Romania. The initial ventilation strategy was not efficient in maintaining pollutant concentrations within standard safety limits. An optimization of the initial ventilation system was realized, but CFD results and on-site measurements have shown that high local concentrations were still present. Two local exhaust methods have been proposed and analysed in order to improve the quality of the air inside the hall. A CFD approach has been used for the preliminary design process. The results indicate that both local exhaust solutions offer great improvements over the general dilution-based system, but only one can be applied

Real scale experimental study for performance evaluation of unidirectional air diffuser perforated panels

Nowadays, there is an increasing emphasis on indoor air quality due to technological evolution and the fact that people spend most of the time in enclosed spaces. Also, energy efficiency is another related factor that gains more and more attention. Improving air distribution in an enclosure can lead to achieve these goals. This improvement can be done by adjustingthe air terminals position, theredimensions or the air diffuser perforations. The paper presents the study of 8 types of panels with different perforations shapes. The systems were characterized by flow, pressure loss and noise. Usualand special geometries were chosen, all having the same flowsurface. The perforated panels were mounted in a unidirectional air flow (UAF)diffuser, also called a laminar air flow (LAF)diffuser, that is placed in a real scale operating room (OR) in our laboratory.The purpose of this study is to determine whether changing the shape in the perforated panels can improve the technical parameters of the diffuser

The stability of the radiative regime in Bucharest during 2017-2018

The paper presents an analysis of the solar irradiation and the stability of the solar radiative regime, available for Bucharest and the southern area of Romania. The study is based on meteorological data measured at 3.6 seconds, on several consecutive days of each season, in the years 2017 and 2018. Data acquisition was performed at Technical University of Civil Engineering Bucharest. The daily mean values for sunshine number and sunshine stability number are computed and analysed. The analyses carried out in this research are useful for applications of solar energy and conversion to thermal energy in hot air solar collectors to estimate the temperature variation at the collector air outlet as well as for photovoltaic panels to estimate the resulting electrical energy

Real scale experimental study for performance evaluation of unidirectional air diffuser perforated panels

Nowadays, there is an increasing emphasis on indoor air quality due to technological evolution and the fact that people spend most of the time in enclosed spaces. Also, energy efficiency is another related factor that gains more and more attention. Improving air distribution in an enclosure can lead to achieve these goals. This improvement can be done by adjustingthe air terminals position, theredimensions or the air diffuser perforations. The paper presents the study of 8 types of panels with different perforations shapes. The systems were characterized by flow, pressure loss and noise. Usualand special geometries were chosen, all having the same flowsurface. The perforated panels were mounted in a unidirectional air flow (UAF)diffuser, also called a laminar air flow (LAF)diffuser, that is placed in a real scale operating room (OR) in our laboratory.The purpose of this study is to determine whether changing the shape in the perforated panels can improve the technical parameters of the diffuser

A Numerical Analysis of the Air Distribution System for the Ventilation of the Crew Quarters on board of the International Space Station

Quality of life on the International Space Station (ISS) has become more and more important, since the time spent by astronauts outside the terrestrial atmosphere has increased in the last years. The actual concept for the Crew Quarters (CQ) have demonstrated the possibility of a personal space for sleep and free time activities in which the noise levels are lower, but not enough, compared to the noisy ISS isle way. However, there are several issues that needs to be improved to increase the performance of CQ. Our project QUEST is intended to propose a new concept of CQ in which we will correct these issues, like the noise levels will be lower, more space for astronaut, increased thermal comfort, reduce the CQ total weight, higher efficiency for the air distribution, personalized ventilation system in CQ for the crew members in order to remove CO2 from the breathing zone. This paper presents a CFD study in which we are comparing the actual and a proposed ventilation solution for introducing the air in CQ. A preliminary numerical model of the present configuration of the air distribution system of the Crew Quarters on board of the ISS, shows the need for an improved air distribution inside these enclosures. Lower velocity values at the inlet diffuser, distributed over a larger surface, as well as diffusers with improved induction would appear to be a better choice. This was confirmed through the development of a new model including linear diffusers with a larger discharge surface. In this new configuration, the regions of possible draught are dramatically reduced. The overall distributions of the velocity magnitudes displaying more uniform, lower values, in the same time with more uniform temperatures. All these observations allow us to consider a better mixing of the air inside the enclosure

Experimental and numerical study of the air distribution inside a car cabin

International audienc

Numerical model of a solar ventilated facade element: experimental validation, final parameters and results

The present paper analyses the airflow through the lobed orifices of a transpired solar collector which acts as a solar ventilated facade element through numerical simulation. This study is part of a complex research project which analyses the implementation of phase changing materials within air solar collectors. We decided to study an elementary part of the collectors' absorbent plate with four equivalent orifices in order to obtain the velocity and temperature field at the outlet of the computing domain since the numerical simulation of the entire solar collector (more than 5000 orifices) is not feasible due to the big amount of computational resources and time needed. This paper presents the experimental validation of the numerical model, its final parameters and preliminary results. The numerical simulation was conducted using Ansys Fluent CFD software and the results were processed via Tecplot. The boundary conditions imposed were emphasised and k-ε RNG turbulence model was used according to the literature. After comparing the velocity profiles and temperature fields obtained with both experimental and numerical approaches we concluded that the numerical model reproduces real flow phenomena within acceptable limits. The numerical model thus obtained will be used in further studies in order to optimise the collectors' geometry and characteristics by means of parametrical analyses