scholarly journals Experimental Analysis of Height to Base Length Effect in Trapezoidal Prism Inclined Solar Chimney

2020 ◽  
Vol 65 (1) ◽  
pp. 47-55
Author(s):  
Omar Belhadj ◽  
Hamidou Benzenine ◽  
Rachid Saim
Keyword(s):  
Architectural Design ◽  
Base Length ◽  
Solar Chimney ◽  
Air Velocity ◽  
Length Effect ◽  
Active Systems ◽  
Living Space ◽  
Flow Rate Increase ◽  
Favorable Conditions ◽  
Good Agreement

The use of a solar chimney for ventilation has a very significant environmental and economic impact. The aim of this work is to found the optimum ratio between height and base length in trapezoidal prism-shaped solar chimney. The idea is to give more flexibility to the architectural design in buildings and offer the possibility of combination with other passive or active systems. Trapezoidal shape of solar chimney can be interesting not by increasing the efficiency comparing with other shapes like the rectangular. It may be more aesthetically pleasing, easily to be installed and retrofitted on trapezoidal roofs even on existing buildings. For this reason, three differents ratios of height to base length (h/l = 1), (h/l = 1.5) and (h/l = 2) have been experimentally studied. Two correlations to predict solar chimney exit air velocity and efficiency were developed and tested; good agreement with experimental results is proved. Results show that the flow rate increase by increasing (h/l) in a logarithmic tendency. The optimum thermal efficiency is given where h/l = 1.65. An approach using RETScreen4 software was also carried out and showed that 1 m² solar chimney installed in favorable conditions can cover 37 m² of living space in term of ventilation. For a 120 m² house, solar chimney system saves the equivalent of 23.9 liters of gasoline per year.

Experimental and Theoretical Investigation of Performance of a Solar Chimney Model, Part I: Experimental Investigation

2021 ◽  
Vol 3 (1) ◽  
Author(s):  
Essaied M Shuia ◽  
Bashir H Arebi ◽  
Ibrahim A abuashe
Keyword(s):  
Experimental Data ◽  
Wind Speed ◽  
Solar Radiation ◽  
Air Temperature ◽  
Solar Collector ◽  
Experimental Results ◽  
Internal Diameter ◽  
Solar Chimney ◽  
Air Velocity ◽  
Collector Temperature

This paper presents the experimental data that was collected from small pilot solar chimney. The experimental data together with ambient conditions are used to evaluate the performance and study the behavior of the solar chimney; this data will be used for comparison with theoretical models in another paper [part II). The solar chimney prototype was designed and constructed at the Subrata Faculty of Engineering-Libya. The data were collected over several days of June 2011. The solar chimney system contains two main components; the solar collector and the solar chimney. The solar collector root‘ has a circular area of126 m3, the solar chimney is a PVC tube with internal diameter of 0.2 m and the total height of chimney is 9.3 m. The measurements include the intensity of solar radiation inside/outside the collector, temperature and velocity of air at the entrance of the chimney, temperature and speed of wind outside the collector, temperature of the ground inside collector al1d temperature measurements of air at speci?c points at different levels throughout the collector. Solar irradiance was found to affect the chimney temperature and subsequently affects chimney air velocity. The experimental results showed that temperature differences of (30 - 45°C) were recorded between the ambient temperature and that of air inside the chimney in the middle of the day, where the highest air temperature of 73.4°C was recorded at the entrance of the solar chimney. The maximum air velocity of 3.6 m/s was recorded inside the solar chimney at noon on 9 June. Wind speed outside the collector had a small effect on the speed of the air inside the chimney and tends to change slightly, hence, can neglect influence of wind speed on the performance of the system. Also the experimental results indicate that such type of system can trap a suf?cient amount of solar radiation, which elevates the air temperature to a suf?cient value able to generate enough air ?ow to operate a wind turbine to produce electricity; this means the solar chimney system for electricity production can work in the north-western part of Libya in the summer time at least.

scholarly journals Experimental Investigation on The Effect of Divergent Tower Solar Chimney on The Theoretical Power Potential

2021 ◽  
Vol 81 (1) ◽  
pp. 140-149
Author(s):  
Ahmad Jawad ◽  
Mohd Suffian Misaran ◽  
Md. Mizanur Rahman ◽  
Mohd Azlan Ismail
Keyword(s):  
Power Plant ◽  
Cost Ratio ◽  
Main Body ◽  
Test Results ◽  
Solar Chimney ◽  
Air Velocity ◽  
Higher Temperature ◽  
Electric Heat ◽  
Solar Chimney Power Plant ◽  
Tall Structure

Solar chimney power plant is a sustainable alternative for electricity generation using solar as the source of energy. In general, the main body of a solar chimney plant requires a tall structure which is costly and challenging to construct. Thus, it is important to increase the performance of the solar chimney power plant and have a better energy-cost ratio. This study aims to experimentally investigate the influence of divergent solar chimney as opposed to a cylindrical chimney on solar chimney performance. Three divergent scaled-down solar chimney model at 1-meter, 1.5-meter and 2-meter were fabricated and tested for its performance at various simulated heat loads. The test results were compared with similar heights cylindrical solar chimney. The experiments show that divergent solar chimney increases the theoretical power generation potential and improves the stalk effect and have higher outlet velocity compared to a cylindrical solar chimney. The power potential of the divergent chimney is increased up to 18 times with the maximum theoretical power obtain at 0.183W on the 2-meter divergent chimney. Higher temperature was recorded on the 2-meter divergent chimney outlet at 341.3k compared to 330.4k on the cylindrical chimney indicates better stack effect. The highest average velocities in the divergent and cylindrical chimneys were recorded under the electric heat load of 2 kW at 0.994 m/s and 0.820 m/s respectively in the 1-meter configuration. It is also observed that the air velocity in a shorter divergent chimney is higher than taller divergent chimney models while better compared to all cylindrical height. This study finds that a shorter divergent solar chimney produces greater energy compared to a higher cylindrical solar chimney. Therefore, it is possible to reduce the overall cost of solar chimney by reducing the height of the main structure without sacrificing the performance of the solar chimney.

Evaluation of Indoor Climate in Small University Lecture Hall

2016 ◽  
Vol 861 ◽  
pp. 369-375
Author(s):  
Mária Budiaková
Keyword(s):  
Thermal Comfort ◽  
Architectural Design ◽  
Winter Season ◽  
Lecture Hall ◽  
Experimental Measurements ◽  
Optimal Parameters ◽  
Indoor Climate ◽  
Air Velocity ◽  
Globe Temperature ◽  
The University

This paper is focuses on the evaluation of the indoor climate in the small university lecture hall. Providing the optimal parameters of thermal comfort in the interiors of a university is immensely important for the students of the university. Fulfilling these parameters is inevitable not only for the physiological needs of students but also for the required performance of students. Reconstruction took place in the small university lecture hall. The original windows were exchanged for the modern wood tight windows. Experimental measurements were carried out in the winter season in 2016 in this small university lecture hall in order to evaluate the thermal comfort after the reconstruction. The device Testo 480 was used for the measurements. Obtained values of air temperature, air relative humidity, air velocity, globe temperature and indexes PMV, PPD are presented in the graphs. Heating, operation and architectural design of the small university lecture hall were evaluated on the basis of the parameters of thermal comfort. In the conclusion of this paper, there are principles how to design new small university lecture halls. Furthermore, there are presented recommendations how to operate the existing small university lecture halls.

Experimental and Theoretical Investigation of Performance of a Solar Chimney Model Part II: Model Development and Validation

2021 ◽  
Vol 5 (2) ◽  
Author(s):  
Ibrahim A Abuashe ◽  
Bashir H Arebi ◽  
Essaied M Shuia
Keyword(s):  
Mathematical Model ◽  
Power Output ◽  
Model Development ◽  
Geometrical Parameters ◽  
Balance Equations ◽  
Solar Chimney ◽  
And Performance ◽  
Development And Validation ◽  
The Mathematical Model ◽  
Good Agreement

A mathematical model based on the momentum, continuity and energy balance equations was developed to simulate the behavior of the air flow inside the solar chimney system. The model can estimate the power output and performance of solar chimney systems. The developed mathematical model is validated by the experimental data that were collected from small pilot solar chimney; (experiment was presented in part I). Good agreement was obtained between the experimental results and that from the mathematical model. The model can be used to analyze the solar chimney systems and to determine the effect of geometrical parameters such as chimney height and collector diameter on the power output and the efficiency of the system

scholarly journals Modelling particle movement in conical guide of seeder pneumatic pipe

2020 ◽  
Vol 175 ◽  
pp. 12019
Author(s):  
Vladimir Zaitsev ◽  
Artem Kravtsov ◽  
Vladimir Konovalovi
Keyword(s):  
Mathematical Model ◽  
Finite Element ◽  
Air Flow ◽  
Force Analysis ◽  
Particle Movement ◽  
Air Velocity ◽  
Finite Element Calculations ◽  
Calculation Results ◽  
Case Part ◽  
Good Agreement

In the course of the study, methods for ensuring the centeringof particlesofbulkmaterialintheairflowmovinginthepneumaticductofthe seeder were investigated. To solve this problem, it is proposed to use a conical confusor. The aim of the study was to obtain the functional dependences of the movement of particles in a conical airflow guide (confusor) for the conditions of transportation of the sown particles on the basis of force analysis and to identify the nature of the movement of the sownparticlesinataperingairflow.Duringthestudy,todescribethemotion of particles in a vertical tapering pipe, a system of expressions was substantiated. The developed mathematical model of particle motion in a conical air flow, implemented in the MathCAD mathematical package, allowscalculatingboththeparticletrajectoryandthevelocityparametersof the air flow and the particles to be sown. The digital calculation results in the MathCAD program are in good agreement with the finite element calculations. The magnitude of the error in air velocity is less than 1%. The differences in the velocities of the transported particles in the calculation options do not exceed 7%. The installation of a conical guide helps tofocus the flow of particles in the central part of the narrowed air line. In this case, part of the particles in the central part of the guide will retain the initial longitudinaltrajectory.Theangleattheapexoftheconeandtheparameters of the particles affect the speed and angle of the tangent contact of the particle with theguide.

scholarly journals Period Doubling Bifurcations in a Forced Cell-Free Genetic Oscillator

2021 ◽  
Author(s):  
Lukas Aufinger ◽  
Johann Brenner ◽  
Friedrich C Simmel
Keyword(s):  
Gene Networks ◽  
Computational Models ◽  
Expression System ◽  
Period Doubling ◽  
Genetic Oscillator ◽  
A Cell ◽  
Free Gene ◽  
Favorable Conditions ◽  
Period Doubling Bifurcations ◽  
Good Agreement

Complex non-linear dynamics such as period doubling and chaos have been previously found in computational models of the oscillatory gene networks of biological circadian clocks, but their experimental study is difficult. Here, we present experimental evidence of period doubling in a forced synthetic genetic oscillator operated in a cell-free gene expression system. To this end, an oscillatory negative feedback gene circuit is established in a microfluidic reactor, which allows continuous operation of the system over extended periods of time. We first thoroughly characterize the unperturbed oscillator and find good agreement with a four-species ODE model of the system. Guided by simulations, microfluidics is then used to periodically perturb the system by modulating the concentration of one of the oscillator components with a given amplitude and frequency. When the ratio of the external `zeitgeber' period and the intrinisic period is close to 1, we experimentally find period doubling and quadrupling in the oscillator dynamics, whereas for longer zeitgeber periods, we find stable entrainment. Our theoretical model suggests favorable conditions for which the oscillator can be utilized as an externally synchronized clock, but also demonstrates that related systems could, in principle, display chaotic dynamics.

Performance of a Solar Chimney With a Modified Collector Geometry: A Case Study From Erbil to the North of Iraq

2019 ◽  
Vol 142 (1) ◽  
Author(s):  
Dara Khalid Khidhir ◽  
Soorkeu A. Atrooshi
Keyword(s):  
Solar Radiation ◽  
Ambient Temperature ◽  
Temperature Difference ◽  
Mechanical Energy ◽  
Maximum Temperature ◽  
Geometrical Shape ◽  
Solar Chimney ◽  
Air Velocity ◽  
Temperature Loss ◽  
Solar Intensity

Abstract The principle of solar chimney power plant (SCPP) is based on harvesting the thermal spectrum of solar radiation and converting it to mechanical energy by the means of a collector, a wind turbine, and a chimney. In this work, a number of experiments were performed on a modified model made up of one-third of the circular collector area. Field data from selected clear, sunny days were recorded and studied. The analysis focused on time-temperature relations for ambient, near chimney entry point and the collector periphery, in addition to hourly solar radiation intensity and air velocity inside the chimney. The results show that for this geometry arrangement, the maximum temperature of the air entering the chimney is achieved before the ambient temperature reaches its peak value. Air velocity inside the chimney depends on the intensity of solar radiation and the temperature difference between the air temperature entering the chimney and the ambient temperature. Solar intensity directly affects the temperature of air beneath the collector, and a part of this energy is stored in the ground. Later, when the solar radiation is impaired, the stored energy can be utilized. Air velocity of 2.1 m/s is obtained after the solar noon, when the solar intensity is 737 W/m2 and the maximum temperature difference is 11.2 °C. Due to the unique geometrical shape of the rig, a minor temperature loss of up to 1.3 °C occurs for the air near the center of the chimney.

Chain processes in cognitive dynamics

10.12737/3399 ◽  
2014 ◽  
Vol 3 (1) ◽  
pp. 70-78
Author(s):  
Комиссаров ◽  
G. Komissarov ◽  
Рубцова ◽  
N. Rubtsova
Keyword(s):  
Present Model ◽  
Average Length ◽  
Random Access ◽  
Long Term Memory ◽  
Cognitive Dynamics ◽  
Chain Explosion ◽  
Favorable Conditions ◽  
Good Agreement ◽  
Reaction Chain

The article discusses the construction of circuits only within random-access memory, additionally limited by attention. We propose a model explaining the features of the dynamics of solving problems on insight using N.N. Semenov’s theory of chain branching chemical reactions. When referring to long-term memory (and return from it with the result on the construction of a representation) the real average length of generalized mental chains can only increase, since it is known that the concepts and objects in it branched and associated with others. In circuit theory, the condition when values of average length chains go to infinity means nonstationary mode of reaction (chain explosion). Thus, in the present model this mode of sharp increase in the average length of the chains is the most favorable conditions for the building the representation – any circuit (with a length of no longer than d) we take to build from existing units operated with all its branches - it is taken in our attention and has no time to break off. These conditions are most favorable for the building and restructuring the representations, and there is the insight moment in our model. Well-known literature data on the experimental investigation of insight and creativity are in good agreement with the requirements of this model towards insight parameters.

scholarly journals Nanoparticle formation in the exhaust of vehicles running on ultra-low sulfur fuel

2008 ◽  
Vol 8 (16) ◽  
pp. 4729-4739 ◽  
Author(s):  
H. Du ◽  
F. Yu
Keyword(s):  
Formation Rate ◽  
Particle Mass ◽  
Nanoparticle Formation ◽  
Model Predictions ◽  
Detailed Composition ◽  
Formation And Evolution ◽  
Favorable Conditions ◽  
Low Sulfur ◽  
Exhaust After Treatment ◽  
Good Agreement

Abstract. The concern of adverse health impacts from exposure to vehicle-emitted nanoparticles has been escalating over the past few years. In order to meet more stringent EPA emission standards for particle mass emissions, advanced exhaust after-treatment systems such as continuously regenerating diesel particle filters (CRDPFs) have to be employed on vehicles and fuel with ultra-low sulfur is to be used. Although CRDPFs were found to be effective in reducing particle mass emissions, they were revealed to increase the potential of volatile nanoparticle formation. Significant nanoparticle concentrations have also been detected for vehicles running on ultra-low sulfur fuel but without CRDPFs. The main focus of this paper is the formation and evolution of nanoparticles in an exhaust plume under ultra-low sulfur conditions. Such a study is necessary to project future nanoparticle emissions as fuel compositions and after-treatment systems change. We have carried out a comprehensive quantitative assessment of the effects of enhanced sulfur conversion efficiency, sulfur storage/release, and presence of non-volatile cores on nanoparticle formation using a detailed composition resolved aerosol microphysical model with a recently improved H2SO4-H2O homogeneous nucleation (BHN) module. Two well-controlled case studies show good agreement between model predictions and measurements in terms of particle size distribution and temperature dependence of particle formation rate, which leads us to conclude that BHN is the main source of nanoparticles for vehicles equipped with CRDPFs. We found that the employment of CRDPFs may lead to the higher number concentration of nanoparticles (but smaller size) in the exhaust of vehicles running on ultra-low sulfur fuel compared to those emitted from vehicles running on high sulfur fuel. We have also shown that the sulfate storage and release effect can lead to significant enhancement in nanoparticle production under favorable conditions. For vehicles running on ultra-low sulfur fuel but without CRDPFs, the BHN is negligible; however, the condensation of low volatile organic compounds on nanometer-sized non-volatile cores may explain the observed nucleation mode particles.

A Compressible Transient Model of the Solar Chimney and Heat Collector

2013 ◽  
Vol 283 ◽  
pp. 15-21 ◽  
Author(s):  
Gang Li ◽  
Hui Lan Huang ◽  
Hua Zhang ◽  
Jian Bin Liu ◽  
Xiang Chen
Keyword(s):  
Fluid Pressure ◽  
State Equation ◽  
Ideal Gas ◽  
Solar Chimney ◽  
Transient Model ◽  
Heat Collector ◽  
Solar Chimney Power Plant ◽  
Improved Model ◽  
The Given ◽  
Good Agreement

The compressible transient model of solar chimney power plant system was proposed. It was added to the pressure equation and the ideal gas state equation basis on the heat balance equation for the solar collector model. The air flow station can be easily calculated with the improved model. The results of dynamic changes of the total pressure difference calculated in the model were in good agreement with the given actual measured values in references. The solar chimney model was considered the influence of fluid pressure on the density. The influence of the structural chimney on the chimney efficiency was analyzed with the established model. It was shown that the chimney efficiency changes significantly with the chimney height and its diameter. The chimney efficiency was decreased with a convergent chimney shape while increased with the divergent one. When the tilt angle of chimney reached a peak and then further increased, the chimney efficiency was the constant. These results will provide the important reference to improving the system efficiency.

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