Study of Different Parameters Affecting the Productivity of Solar Still for Seawater Desalination under Djiboutian Climate

Experimental studies were carried out to determine the influence of solar radiation, temperatures variations, basin water amount, wind speed, glass cover thickness and salinity on the daily production of the distillate output using solar desalination process, namely single slope solar still to produce fresh water from seawater in the context of Djibouti. The temperatures variations increase in relation to solar radiation. Consequently the hourly distillate output increases and reaches a maximum around noon when the solar still receives maximum intensity of solar radiation. An inverse relation is found between glass cover thickness, basin water amount and distillate output production. The variation wind speed has an effect on the daily production;which increases in relation to wind speed. In order to assess the effect of salinity on the daily production, the solar still is provided with brackish water to compare the daily production obtained from seawater. Experimental results show that the cumulative productivity decreases when there is an increase of salinity. In addition, the quality of the distillate output was tested by measuring TDS, EC, pH, hardness water and chlorides and was compared to WHO standards. The values obtained for these parameters were in accordance with the requirements of WHO and good removal efficiency for four parameters.

"Extended" shear bands in interior of Pd-based bulk metallic glasses

Shear bands in the interior of Pd（79）Cu6Si（10）P5,Pd（79）Cu3Ag3Si（10）P5, and Pd（79）Cu4Au2Si（10）P5 bulk metallic glasses were investigated by optical microscopy（OM） and scanning electron microscopy（SEM）. No shear bands can be observed in the samples before etching. By etching in aqua regia solution, shear bands are found to be susceptible to preferential etching, and multiple etched bands could be observed. The thickness of the etched bands is about 1-7 μm. Therefore, the preferentially etched shear bands found in the study are called the ＂extended＂ shear bands.The ＂extended＂ shear bands can be divided into three classes according to their features： early, developing, and well-developed ＂extended＂ shear bands with thickness of about 1, 5, and 7 μm, respectively. The interface between the well-developed ＂extended＂ shear bands and the matrix is clearer than that of the others.

Heat Leakage Numerical Investigation of a Compound Parabolic ConcentratorPulsating Heat Pipe Solar Collector

As a new type of equipment for solar medium temperature utilization, the compound parabolic concentrator-pulsating heat pipe solar collector(CPC-PHPSC) uses pulsating heat pipe(PHP) as an endotherm, which can realize efficient energy conversion. The design of proper concentration ratio of compound parabolic concentrator(CPC) ensures that the incident sunlight can be concentrated on the evaporator section surface of PHP without solar tracking system. The objective of the present work is to study the influence of solar radiation intensity, air speed, material thickness(glass and insulation board) and tilt angle on the thermal performance of the new collector, which is difficult to control in the experiment. The heat leakage process and characteristics of the CPC-PHPSC were numerically studied by establishing a 3D numerical model of the collector unit. The results show that the theoretical collector efficiency of CPC-PHPSC reaches 74.5%, which is consistent with the experimental results. During operation, the heat collection performance is the best when the tilt angle is 45° and the solar radiation intensity is 1000 W/m^(2), while the excessive air speed will increase the convective heat loss. Increasing the thickness of insulation board and glass has little effect on the collector efficiency.