Abdelhafid Brima

Experimental study of new solar air heater design

ABSTRACT The suitable design is the most important key to a cost-effective solar air heater. Although there are many techniques that have been proposed to improve the solar air heaters’ performance by means of different turbulence promoters, they cannot ensure a compromise between the cost and the effectiveness. The aim of this study is to find simple and tolerable solution to get rid of the inconvenience resulting from the widely adopted heat-transfer-enhancement techniques by providing an optimized solar air heater design. The proposed design consists of a slightly curved smooth flow channel with an absorber plate of convex shape. A prototype of a curved solar air heater of 1.28 m2 collector area was built and tested under summer outdoor conditions in Biskra (Algeria). The performance was evaluated in terms of thermal and effective efficiency for mass flow rates of 0.0172, 0.029, and 0.0472 kg/sm2. It is observed that the overall efficiency of this solar air heater is considerably higher in comparison with the efficiency range of the conventional smooth flat plate heaters reported in the literature for similar operating conditions.

The rate sensitivity of the aerodynamic paramaters of the wind tubine blades to the flow losses for NACA profiles

The blade constitutes the critical element for the wind turbine performance. Its shape and size are of capital importance. The blade design requires the use of specific equations that allow the calculation of their aerodynamic parameters. To establish these relations in the context of the momentum of element blade MEB, we use the general theory of Betz, to which is associated the equations regarding the aerodynamic action of the wind. This leads to the values of the aerodynamics parameters required for the blade design. We can proceed with simplifications of equations to remain in the context of the simplified theory [1,2], or one can consider a loss causing a decrease in power wind capture crossing the blades rotation plane. The purpose of this work is to take into consideration a wind loss. Two profiles are considered the NACA 2415 and the NACA 23015. The parameters checked are: the chord and the pitch angle of the blade, the induction factors and the rotor efficiency coefficient.

An experimental and a numerical study of horizontal earth-air heat exchanger in a hot climate

Abstract Earth-air heat exchangers (EAHE) are devices used in the geothermal technique in order to reduce energy consumption in buildings. In this study, a simulation was conducted through the computational fluid dynamics platform FLUENT 6.3 for the prediction of thermal performance of the EAHE that describes the variation of the air temperature inside the tube. For this, it was necessary to design the heat exchanger while respecting the design and the actual dimensions of the experimental set-up, and stating that the temperature of the wall of the horizontal tube of the exchanger is equal to that of ground at 3 m depth. It should be noted that in assessing the temperature along the two sections vertical (input and output) of the exchanger, opting for a function (UDF) the user define function. Finally, noting a good agreement between both experimental and numerical study, and showing that a significant reduction in temperature at the outlet of the exchanger to a difference of 20 °C, confirming the effectiveness of the heat exchanger.