Ahmed Ayadi

A computational and an experimental study on the effect of the chimney height on the thermal characteristics of a solar chimney power plant

The aim of this paper is to highlight the impact of the chimney height on the local characteristics of the air flow within a solar chimney power plant. The solar chimney power plant prototype was numerically and experimentally investigated. The experimental prototype of the solar chimney power plant was built in the National School of Engineers of Sfax, University of Sfax, Tunisia in the North Africa. The prototype is characterized by a collector diameter equal to D = 2750 mm, a collector height equal to h = 50 mm, a chimney height equal to H = 3000 mm, and a chimney diameter equal to d = 160 mm. The air flow has been simulated using the commercial software Ansys Fluent 17.0 and the computational findings have been validated using our experimental results. Computational fluid dynamics findings confirm that the chimney height is very influential on the local characteristics of the solar chimney power plant.

Analysis of the technological features of regional public transport companies: the Tunisian case

The purpose of this paper is to assess the cost-structure of the public transport industry in Tunisia. Thus, we use a translog variable cost function to identify the firms’ technological features. In this analysis, we work on a sample of 12 Tunisian regional transport companies (RTC) over the 2000/2010 period. The main results show the critical productive situation of the urban public transport system in Tunisia. This can be exemplified by the presence of a short and long term diseconomy of scale, given that the overall factor productivity is low and almost zero.

Efficiency of public transport system in Tunisia: DEA-SFA approach

The purpose of this paper is to study the cost efficiency of the Tunisian public transport industry, using the deterministic and stochastic method to compare the parametric approach and the non-parametric one. This analysis is conducted on the basis of 12 regional transport companies (RTC) sample over the period 2000 to 2010. The main results showed that the RTCs are economically inefficient having almost a similar magnitude whatever the estimated frontier is, considering that the classification has not significantly changed. This means that the cost efficiency of RTCs is not considerably affected by factors beyond their control.

Effect of the number of turbine blades on the air flow within a solar chimney power plant

Solar chimney power plants generate thermal heat and electrical power using the radiation from sun. These systems are characterized by their high costs. In fact, it is required to optimize the components of the solar system such as the collector, the chimney, the absorber, and the turbine. This paper focuses on the effect of the number of turbine blades on the air flow within a small prototype of a solar chimney power plant. Four configurations with different turbine blades are proposed to study the effect of the turbine blades number on the thermal characteristics of a solar chimney power plant. For each configuration, the distribution of the magnitude velocity, the air temperature, the pressure, the turbulent kinetic energy, and the turbulent viscosity are presented and discussed. This paper is identified to be of interest for engineers and designers for increasing the power output of a solar chimney power plant.

Study of the Collector Diameter Effect on the Characteristics of the Solar Chimney Power Plant

This chapter aimed to optimize the geometry of the collector in a solar chimney power plant (SCPP). Particularly, we were interested in the study of the collector diameter effect on the SCPP output. A two-dimensional steady model with the standard k-e turbulence model has been developed using the commercial computational fluid dynamics (CFD) code “ANSYS Fluent 17.0.” A numerical simulation was achieved to study the local characteristics of the air flow inside the SCPP. Four collector diameters, equal to D = 100 cm, D = 200 cm, D = 300 cm, and D = 400 cm, were considered in this study. The local flow characteristics were presented and discussed for each case. The comparison shows that the collector diameter is an important parameter for the optimization of the solar setup.

Study of the Turbulence Model Effect on the Airflow Characteristics Inside a Solar Chimney Power Plant

A numerical simulation was developed to study the behavior of the airflow characteristics inside the solar chimney power plant (SCPP). A two-dimensional (2D) steady model has been carried out using the commercial computational fluid dynamics (CFD) code ANSYS Fluent 17.0. In this chapter, five turbulence models were tested to present the airflow characteristics distribution such as the magnitude velocity, temperature, pressure, and turbulence characteristics. The above work showed that the turbulence model types have a direct effect on the numerical results. Computational results were compared to the experimental data found by Kasaeian et al. (2014) to choose the adequate model.