Experimental Study of a Stationary Hot Air Solar Collector Built with Hemispherical Concentrators and Enhanced with Fresnel Lenses

Aims: This paper is about a solar collector made of hemispherical concentrators. This collector is sun tracking free, and used for natural convection. Lenses are used on top of each concentrator to improve its efficiency. Study Design: The Solar collector is made of hemispherical concentrators with Fresnel lenses axially-centered to those concentrators and placed on top of each one of them. Those concentrators are covered with a 4 mm glass for a greenhouse effect. The concentrators generate hot spots that heat the inside air. There is no need for receivers at the hot spots. Methodology: from Inlet to outlet, temperatures are measured as well as inlet air speed, which allow the efficiency evaluation. Results: Although those measurements were conducted in a cloudy period, temperature difference from the inlet to the outlet was around 55°C to 65°C. This result is superior to previous studies of the same system without lenses which gave temperature difference around 35°C to 45°C. It is sharply superior to that of usual black-painted convective system with fined plates that gives a temperature difference of around 20°C to 25°C. Conclusion and Perspectives: The global efficiency calculated using measurement values reaches 56%. This is far greater compared to previous black plate systems’ efficiency of 29%, giving an efficiency increase of 93%, but expected knowing that we are using a concentration system for convection.

Rotation of a Thin Heated Plate by Its Own Thermal Radiation

The results of the theoretical investigation of a heated solid plate rotation caused by its own thermal radiation are presented. The rotational moment of the plate with uniform temperature is due to the asymmetry of a recoil of photons of thermal radiation from different areas of its wide faces. The time dependences of the rotation angle of a rectangular plate with stable temperature and at radiative cooling are calculated. The rotation angle dependences on the plate geometric and optical parameters are studied. It is shown that the rotation angle depends nontrivially on the plate thickness because of the thickness-dependent plate emittance. The numerical calculations are performed for a silicon plate. The biggest rotation effect (rotation angle of 118.5∘ for 70 s) is obtained for a mirror black plate 0.1 mm thick at a preset plate temperature of 350 K and a background temperature of 300 K. The considered model can be useful to develop thermal motors, whose rotors consist of a set of heated plates with photon recoil asymmetry.

Effect of Black Plate on Growth Action and Corrosion Resistance of Sn-Fe Alloy Film

Effect of black plate on growth action and corrosion resistance of Sn-Fe alloy film was investigated by means of metallurgical microscope, scanning electron microscopy (SEM), salt spray corrosion test and electrochemistry methods. The results show that the different modes of annealing and rolling have a remarkably effects on the surface morphology and grain size of Sn-Fe alloys. Crystalline grain of Sn-Fe alloy film for T4-CA or T2.5-BA is relatively continues, homogeneous and denser, but that for DR materials exists obviously surface inhomogeneity sizes and even void space of interweave. Rust spot easily generate on discontinuous alloy films or void space of interweave growth and gradually cover on the surface of Sn-Fe alloy films without corrosion damage. Corrosion resistance of BA materials is better than that of CA materials. Under the same annealing mode, corrosion resistance of DR materials is worse.

Description and Control of Tin Plate Surface Visual Quality

This article suggests that divide the strip surface quality into the damage class, the adhesion class as well as the surface vision class. In order to improve the surface vision quality of the tin plate, the chromaticity of gloss and lightness are used to measure the tin plate surface vision quality. Predictive models of gloss and lightness are established to determine the influencing factors by stepwise regression in the article. The research indicats: the gloss and lightness of tin plate are closely related with tin coating weight and the roughness of tin mill black plate, including profile arithmetic average error and superficial peak density. By enhancing the roughness control accuracy of tin mill black plate, the surface visual quality of tin plate has been greatly improved and the chromatic aberration after printing is solved.