Action Of Solar Radiation Research Articles

INVESTIGATION OF FLOW PATTERNS IN A GREENHOUSE WITH MECHANICALLY ASSISTED VENTILATION

In the present work, the effect of fan ventilation in an arc type tunnel greenhouse under the encumbering action of solar radiation is studied. Results are accrued for the air velocity, temperature, pressure, vapour and fresh air concentrations taking into account the plants’ drag force and the buoyancy effects caused by higher temperatures prevailing at the upper part of the greenhouse. The numerical results are compared to experimental data, providing the appropriate base for the validation of the developed numerical model. Inside the greenhouse there is a tomato crop 1.5 m tall. For the simulation a 3D grid is created to figure the geometry of a real experiment, and the finite volume method is taken in hand to treat the fully elliptic partial differential equations’ problem. Climatic data provided by the Centre of Research and Technology of Thessaly, Greece, were used in order to approach realistic conditions of experiment. Special items like the thermo-physical and optical properties of covering material or the aerodynamic behaviour of the tomato crop are also considered. The results show the influence of the forced convection air flow patterns resulted from the mechanical assisted ventilation. Flow recirculations are presented due to buoyancy effects in areas where forced convection is limited via to the topology showing how the temperature gradients affect the flow. The conclusions of the comparison will feature a valuable guideline assisting in the improvement of a computational tool for the estimation and prediction for the optimum selection of mechanical installation for fan ventilation in various structural greenhouse specifications.

Thermodynamic scale of the efficiency of chemical action of solar radiation

Thermodynamic scale of the efficiency of chemical action of solar radiation

Study of solar radiation stability of modern polymer materials on a large solar furnace

The testing of modern polymer insulators designed for transmission facilities for light stability under the action of solar radiation is considered. The technique of accelerated testing including irradiation of the samples with ultraviolet radiation using a large solar furnace has been proposed.

Features of dusty structures in the upper Earth’s atmosphere

The features of the Earth’s dusty ionosphere are considered using as an example the summer polar mesosphere. The effect of the optical properties of microparticles on their heating and photoelectron emission under the action of solar radiation is analyzed in detail. Certain photochemical consequences of the presence of dust in the upper atmosphere are studied. In particular, it is shown that microparticles can noticeably reduce the concentration of water vapor in the upper atmosphere and this decrease in turn limits the particle sizes. The influence of the effect under consideration on the behavior of the charged component of the upper atmosphere is discussed.

Construção e estudos de perfomance de um reator fotoquímico tipo CPC ("Compound Parabolic Concentrator")

A CPC (Compound Parabolic Concentrator) reactor was projected and constructed aiming to promote the degradation of the organic matter present in considerable volumes of aqueous effluents, under the action of solar radiation. The essays were done using a model effluent which consists of a mixture of fragments of a sodium salt of lignosulphonic acid possessing a mean molecular weigth of 52,000 Daltons, and a real effluent, from a chip board industry. The volume of effluent in each test was about 50 L. The tests involved heterogeneous (TiO2 P25 Degussa and formulations made from the association of TiO2 with a photosensitiser), and homogeneous (thermal and photochemical Fenton reactions) catalysis of the effluents. The results demonstrate the viability of application of this kind of reactor even when the load of organic pollutants is high.

Direct statistical simulation of the near-surface layers of the cometary atmosphere. I. A spherical nucleus

The key to the explanation of the variety of processes associated with the activity of comets lies in a more profound understanding of the events that occur in the near-surface layer of the cometary nucleus and in the inner part of the cometary atmosphere, which is formed under the action of solar radiation. A complete description of the mass- and energy-transfer processes inside and outside the cometary nucleus, which can be presented as a body with a complex morphology and high porosity and which is composed of mineral, organic, and volatile components, is an extremely complicated problem of space physics. The nucleus and the inner part of the coma are closely related to each other as physical subsystems, and physical processes in these regions are in close symbiosis because of the permanent exchange of both energy and mass. The thermophysical model of the circumnuclear coma cannot be confined only to the consideration of the processes in the nucleus—the entire system should be simulated as a whole. A consistent model of the inner part of a cometary atmosphere of this kind has been developed in this paper within the framework of the gas-kinetic approach. Based on direct statistical simulation with weights, we simulated the two-dimensional gas flow from the cometary nucleus. The nucleus was assumed to be spherical. We considered different models of the nucleus morphology that determined the effective gas production: the homogeneous nucleus, the “spotty” nucleus with its active area in the vicinity of the subsolar point, and the “spotty” nucleus with its active area in the form of a spherical segment. For the first time, the boundary conditions at the inner boundary of the simulation domain required for the kinetic modeling of the inner coma were found from a self-consistent model of the heat and mass transfer in a porous cometary nucleus. The model was earlier developed by the authors. The basic new features of the model included taking into account the volumetric character of the radiation absorption in a porous medium, the kinetic simulation of the transport of sublimation products in the pores, and the consideration of the backward fluxes from the coma due to the intermolecular collisions. The kinetic simulation was performed using the SMILE program package. The parallel computer implementation of the model made it possible to calculate the spatial fields of the basic macrocharacteristics of the gas flow. It was demonstrated that the structure of the inner coma is essentially dependent on variations in the effective gas production. In all the cases considered, the main part of the coma is far from thermodynamic equilibrium. This means that the entire structure of the inner cometary atmosphere can be accurately studied only within the framework of the kinetic approach. In a general case, it can result from the interaction of gas flows generated by different active subregions on the nucleus surface. Thus, fine structures are formed and local efficient gas recondensation from the coma occurs in the model for some regimes with “spotty” activity (where considerable variations in gas production take place on small spatial scales).

Formation of ordered structures and collective phenomena in dusty plasmas

Dust particle ordering is discussed in various types of low-temperature plasma, such as dc glow discharges, UV- and radioactivity induced plasmas. Nuclear induced plasma was formed in the rare gases by alpha-particles and fission fragments of 252Cf. The ordered liquid-type structures of dust particles levitating in the interelectrode space have been observed. To remove charged particles from a volume an electrostatic probe has been designed and used. The dynamics of the formation of ordered structures of macroparticles charged by photoemission under the action of solar radiation under microgravitational conditions is studied experimentally and theoretically. An analysis and comparison of tile results of the experimental and theoretical investigations permit drawing a conclusion regarding the possibility of the existence of extended ordered formations of macroparticles charged by photoemission under microgravitational conditions.

Dusty plasma induced by solar radiation under microgravitational conditions: An experiment on board the Mir orbiting space station

The dynamics of the formation of ordered structures of macroparticles charged by photoemission under the action of solar radiation under microgravitational conditions without the use of electrostatic traps to confine the particles is studied experimentally and theoretically. The working conditions needed for the formation of structures of charged macroparticles are chosen as a result of a numerical solution of the problem posed, the particle charges and the interparticle interaction parameter are determined, and the characteristic times specifying the dynamics of the formation of an ordered system of macroparticles are calculated. The behavior of an ensemble of macroparticles under the effect of solar radiation is observed experimentally on board the Mir space station. An analysis and comparison of the results of the experimental and theoretical investigations permit drawing a conclusion regarding the possibility of the existences of extended ordered formations of macroparticles charged by photoemission under microgravitational conditions.

Production, in a stationary state, of solid material in a coma of cometary nuclei under the action of solar radiation

A stationary state of production of solid material in the coma of a comet is sought by assuming a production and dynamics of solid grains liberated during the vaporization of cometary nuclei under the action of solar radiation.

Reactions in the ionosphere

Abstract The ion chemistry of the E and F layers depends on a few ion-neutral reactions, with NO+ as the terminating ion, and on dissociative recombination. In the topside ionosphere the main source and sink of the H+ ions is the reversible charge transfer process H+ O+ ⇆ H+ + O; the He+ ions are formed by the action of solar radiation and are neutralized in dissociative charge transfer collisions with nitrogen molecules. The metallic positive ions present in sporadic E and in the D region result from photoionization and charge transfer. It is not certain how they recombine. Positive ions in the middle and lower part of the D region take part in a sequence leeding to the hydrated protons H3O+(H2O)n observed. Negative ions are here important but little can be said with asurance about their nature.

Effect of Some White Pigments on the Actinic Degradation of Cotton

THE action of solar radiation in reducing the strength of cotton is well known. In our experience, 12-oz. grey cotton duck exposed to weather in a non-industrial atmosphere near Melbourne, Victoria, loses about 25 per cent of its strength in twelve months, due solely to the action of light. Although fungal growth is commonly observed on exposed cotton fabrics, the species isolated have always been non-cellulolytie; fibres from exposed fabrics when examined microscopically by the modified congo red test1 show actinic damage but no fungal damage.

The Movements of Jupiter's Atmosphere

IN NATURE, vol. xxv. p. 213, Mr. Darwin describes the bands on Jupiter as “due to the trades and anti-trades” set in motion by the action of solar radiation on the solid body of the planet as are the trade-winds of the earth. Many other eminent astronomers still appear to accept this time-honoured explanation of the phenomena.