Effect Of Solar Heating Research Articles

Numerical study of transient heat and mass transfer and stability in a salt-gradient solar pond

In this work, the problem of the transient heat and mass transfer and stability within a salt-gradient solar pond has been numerically investigated by mean of a 3D-model with all properties variable as function of temperature and salt concentration. The pond has been subject to real external perturbations resulting from the variations of the local weather conditions. The initial conditions correspond to an ‘artificially stabilized’ pond with the linear temperature and salinity profiles in the gradient zone. Numerical results as obtained for a Tunisian experimental test-site have been satisfactorily compared and validated against measured temperature data. They have clearly shown that after a relatively short period of operation, say only a few days, the changes in the weather conditions have produced important effects not only on the internal temperature field of the pond, but also on its stability as well. In general, one may expect that some instability could develop and growth from within two critical zones: the first one beneath the water free surface and the second one in the region immediate to the bottom surface. The transient behaviours of the pond, in particular its stability, have also been investigated for a very short period of time, say 24 hours of operation. It has been clearly observed that the overnight cooling at the water free surface may rend unstable the immediate region beneath that surface. On the other hand, the solar heating effect during the daytime may have adverse effect on the stability near the bottom surface. Finally, results have also shown that the water transparency has an important effect on the pond stability itself. A pond with good transparency water has been found to be more susceptible to instabilities than a poor transparency one.

Analysis of sulfur–iodine thermochemical cycle for solar hydrogen production. Part I: decomposition of sulfuric acid

The sulfur–iodine (S–I) thermochemical water splitting cycle is one of the most studied cycles for hydrogen (H 2) production. S–I cycle consists of four sections: (I) acid production and separation and oxygen purification, (II) sulfuric acid concentration and decomposition, (III) hydroiodic acid (HI) concentration, and (IV) HI decomposition and H 2 purification. Section II of the cycle is an endothermic reaction driven by the heat input from a high temperature source. Analysis of the S–I cycle in the past thirty years have been focused mostly on the utilization of nuclear power as the high temperature heat source for the sulfuric acid decomposition step. Thermodynamic as well as kinetic considerations indicate that both the extent and rate of sulfuric acid decomposition can be improved at very high temperatures (in excess of 1000 °C) available only from solar concentrators. The beneficial effect of high temperature solar heat for decomposition of sulfuric acid in the S–I cycle is described in this paper. We used Aspen Technologies' HYSYS chemical process simulator (CPS) to develop flowsheets for sulfuric acid (H 2SO 4) decomposition that include all mass and heat balances. Based on the HYSYS analyses, two new process flowsheets were developed. These new sulfuric acid decomposition processes are simpler and more stable than previous processes and yield higher conversion efficiencies for the sulfuric acid decomposition and sulfur dioxide and oxygen formation.

Thermodynamic designing of a solar block of flats with a tromb's wall with ventuce holes

The paper examines the effects of passive solar heating of an individual residential object, located in Nis, that occur by the use of a combined passive system consisting of a Tromb's wall with ventuce holes and windows for direct insulation. The diagrams are included that show the inner air temperatures of a thermally insulated residential object with A Tromb's wall made of brick and concrete, 20cm and 45cm thick, with ventuce openings.

Discussion of "High temperature ampacity model for overhead conductors"

The author comments on the paper by S.L. Chen et al. (see ibid., vol.17, p.1136-41, 2002) on "High temperature amapacity model for overhead conductors." In particular the author comments on the solar heating and wind parameters effects.

Cosmic-ray exposure and gas retention ages of the Guangmingshan (H5) chondrite

Isotopic compositions of noble gases from the Guangmingshan chondrite were analyzed. Based on the analyses of cosmogenic nuclei, cosmic-ray exposure age of the meteorite is (65±10.0) Ma (3He), (80±12) Ma (21Ne) and (65±10.0) Ma (38Ar), with an average of 70 Ma. This is the highest exposure age of H-group ordinary chondrites. Gas retention ages of K-Ar and U, Th-4He are (4230±100) Ma and (3300±60) Ma, respectively. The smaller ages of3He than21Ne and4He than40Ar suggest that both3He and4He lost together. This is probably related to a solar heating effect of a meteorite with a small perihelion during the last exposure period.

Synergistic effect of solar radiation and solar heating to disinfect drinking water sources

Waterborne diseases are still common in developing countries as drinking water sources are contaminated and feasible means to reliably treat and disinfect these waters are not available. Many of these developing countries are in the tropical regions of the world where sunlight is plentiful. The objective of this study was to evaluate the effectiveness of combining solar radiation and solar heating to disinfect contaminated water using a modified Family Sol*Saver System (FSP). The non-UV transmittable cover sheet of the former FSP system was replaced with an UV transmittable plastic cover sheet to enable more wavelengths of sunlight to treat the water. Disinfection efficiency of both systems was evaluated based on reduction of the natural populations of faecal coliform, E. coli, enterococci, C. perfringens, total heterotrophic bacteria, hydrogen sulphide producing bacteria and FRNA virus. The results showed that under sunny and partly sunny conditions, water was heated to critical temperature (60 degrees C) in both the FSP systems inactivating more than 3 log (99.9%) of the concentrations of faecal coliform and E. coli to undetectable levels of < 1 CFU/100 mL within 2-5 h exposure to sunlight. However, under cloudy conditions, the two FSP systems did not reduce the concentrations of faecal indicator bacteria to levels of < 1 CFU/100 mL. Nonetheless, sufficient evidence was obtained to show that UV radiation of sunlight plus heat worked synergistically to enhance the inactivation of faecal indicator bacteria. The relative log removal of indicator microorganism in the FSP treated water was total heterotrophic bacteria < C. perfringens < F RNA virus < enterococci < E. coli < faecal coliform. In summary, time of exposure to heat and radiation effects of sunlight were important in disinfecting water by solar units. The data indicated that direct radiation of sunlight worked synergistically with solar heating of the water to disinfect the water. Thus, effective disinfection was observed even when the water temperature did not reach 60 degrees C. Finally, the hydrogen sulphide test is a simple and reliable test that householders can use to determine whether their water had been sufficiently disinfected.

Dating Collisional Events: 36Cl– 36Ar Exposure Ages of H-Chondritic Metals

A large fraction of the H chondrites (∼45%) have exposure ages around 7 Ma, presumably the time at which a large collision produced numerous fragments that were subsequently placed in Earth-crossing orbits. Although this exposure age peak is observed for all petrographic types, the maxima observed among subtypes H3–H6 differ. The fall time ratios of H5 chondrites do not show the excess of afternoon falls relative to morning falls that is typical for all other ordinary chondrites, indicating that a subgroup of the H5's experienced a distinct orbital evolution. We report results of 36Cl– 36Ar exposure ages obtained for metal separates of 6 H4 and 10 H5 chondrites with reported bulk exposure ages between 4 and 10 Ma; all the H4's selected are afternoon falls, while the H5's are morning falls. If there is structure in the ∼7-Ma event, this selection was expected to give a maximum resolution. 36Cl– 36Ar exposure ages of H4 p.m. falls show a cluster at ∼7.6 Ma, while a wider cluster at ∼7.1 Ma is found for the H5 a.m. falls. However, when we increase the database by including recent precise Ne ages, the H4 p.m. falls define a peak at 7.6±0.2 Ma, while a shifted peak for the H5 a.m. falls is observed at 7.0±0.2 Ma. The distribution of cosmic-ray-produced 3He/ 38Ar ratios is bimodal with two clusters at ∼15 and ∼9, the latter apparently due to solar heating effects and a quasi-continuous 3H diffusion loss from metal. 3H loss is significantly more frequent among H5 a.m. falls, consistent with the interpretation that a subgroup of H5 chondrites experienced a distinct orbital evolution. The “anomalous” H5 group may represent a small surviving tail of fragments that were directly injected into a resonance after a collision 7.0 Ma ago.

Normalization of Landsat thermal imagery for the effects of solar heating and topography

This paper is an investigation of three simple normalization procedures for suppressing the effects of solar heating and topography in daytime thermal data. The first method is the hyperspherical direction cosine (HSDC) transformation, which separates the pixel vector into an illumination/albedo component and a spectral component. The second method, a model correction, is based on the assumption that, once an elevation correction using the normal lapse rate has been applied, temperatures are proportional to the instantaneous solar heating as measured by the cosine of the solar illumination incidence angle. The third method is a statistic-empirical correction. These three normalization methods were applied to a test site in the Humboldt Range, Pershing County, Nevada, using Landsat Thematic Mapper data. It was found that geological patterns were much clearer in the normalized data than in the original temperature information. The HSDC correction brought out lithological differences, helped discriminate between gravels and spectrally similar sedimentary rocks and resulted in a significant increase in classification accuracy. The model correction appeared to inadequately compensate for the cool temperatures found at high elevations, and therefore underestimates the actual decline in temperature with elevation. Nevertheless, the rock contacts are relatively clear, and the classification produced the second highest overall accuracy. The statistic-empirical classification resulted in improved elevation correction, but it over-corrected north-facing slopes and produced only intermediate improvements in accuracy.

Modeling of Ship Effluent Transport and Its Sensitivity to Boundary Layer Structure

The LES model is applied for studying ship track formation under various boundary layer conditions observed during the Monterey Area Ship Track experiment. Simulations in well-mixed and decoupled boundary layers show that ship effluents are easily advected into the cloud layer in the well-mixed convective boundary layer, whereas their transport may be suppressed by the subcloud transitional layer in the decoupled case. The clear difference between the well-mixed and decoupled cases suggests the important role of diurnal variation of solar radiation and consequent changes in the boundary layer stability for ship track formation. The authors hypothesize that, all other conditions equal, ship track formation may be facilitated during the morning and evening hours when the effects of solar heating are minimal. In a series of experiments, the authors also studied the effects of additional buoyancy caused by the heat from the ship engine exhaust, the strength of the subcloud transitional layer, and the subcloud layer saturation conditions. The authors conclude that additional heat from ship engine and the increase in ship plume buoyancy may indeed increase the amount of the ship effluent penetrating into the cloud layer. The result, however, depends on the strength of the stable subcloud transitional layer. Another factor in the ship effluent transport is the temperature of the subcloud layer. Its decrease will result in lowering the lifting condensation level and increased ship plume buoyancy. However, the more buoyant plumes in this case have to overcome a larger potential barrier. The relation between all these parameters may be behind the fact that ship tracks sometimes do, and sometimes do not, form in seemingly similar boundary layer conditions.

Effects of Natural Ventilation and Solar Radiation on the Performance of Pyrgeometers

Abstract In this work the authors present the results of field experiments carried out in Almeria (36.83°N, 2.42°W), a seashore location in southeastern Spain, in order to evaluate the performance of Eppley precision infrared radiometer (PIR) pyrgeometers. The authors estimate the systematic errors in the measurements of downward longwave radiation caused by solar heating of the pyrgeometer’s dome. Pyrgeometer measurements have been obtained in a series of experiments in which the dome of the pyrgeometer has been, alternately, exposed to the solar beam and shaded by a disk. These measurements have been completed with solar direct irradiance and wind velocity measurements. This study confirms previous assessments about the magnitude of this effect and its possible estimation in terms of global horizontal solar irradiance. Additionally, the authors have quantified the influence of natural ventilation on the solar heating effect. The experiments have confirmed the reduction of the solar heating effect with a...

Preliminary studies on the effect of solar heat on oviposition, development and adult mortality of the cowpea bruchidCallosobruchus maculatus(F.) in the Nigerian savanna

The effect of solarization on oviposition, adult mortality and emergence of the cowpea bruchidCallosobruchus maculatus(F.) was investigated in the Nigerian savanna during the hot season (March–May). Oviposition was significantly reduced as time of exposure to the sun increased, especially in bruchids that were exposed for 3 h, but adult mortality increased with increased exposure time. Adult emergence from eggs that were exposed to the sun 5 days after oviposition (DAV) began was significantly lower than from eggs that were exposed 10 or 15 DAV. Adult emergence was also significantly lower from eggs that were exposed to the sun for 3 h than from those that were exposed for only 1 h.

Onset of double-diffusive convection in a saturated porous layer with time-periodic surface heating

The stability of a fluid saturated, horizontal porous layer in the presence of a solute concentration gradient and time-periodic thermal gradient is examined. The modulated gradient is the result of a sinusoidal upper surface temperature which models the effect of variable solar radiation heating of the layer. Darcy's law and the Boussinesq approximation are employed, and we assume an equation of state linear in temperature and concentration. A linear stability analysis is carried out to obtain predictions for the onset of convection and critical wavenumbers for the system. The critical conditions are obtained via the Galerkin method and Floquet theory. The effects of variable concentration gradient, temperature modulation amplitude and frequency are examined, and compared with the results obtained analytically from the corresponding unmodulated problem. It is shown that instabilities can occur as convective motions which are synchronous or subharmonic with the surface heating, or can be identified via complex conjugate Floquet exponents. The neutral stability curves at the transitions between instabilities are found to be bimodal when the temperature is time-periodic, and are characterized by jumps in the critical wavenumbers.

The effect of solar heating of soil on natural and inoculated agrobacteria

Solarization trials were carried out over 3 years and in two countries to control crown gall disease on fruit trees and eliminate Agrobacterium. In 1992, agrobacteria in naturally infested soils of two Italian nurseries were monitored before and after solarization. Agrobacteria populations decreased by 99% and 92% after the treatment; however, crown gall incidence did not decrease. In 1993 and 1994 solarization was tested in Oregon in fields artificially infested with two marked strains of A. tumefaciens. In sandy loam soil, the target bacteria were eliminated in 4 weeks, while in silty clay soil the populations were markedly reduced after 2 months of treatment. Crown gall incidence on cherry rootstocks transplanted to the field at the end of 1993 was 3.7% in the sandy loam soil control plots, while no tumours were observed on plants from solarized plots. The use of solarization in combination with reduced doses of metham‐sodium was also evaluated.

Estimations of Probable Maximum Precipitation (PMP) for the Evinos catchment in Greece using a Storm Model approach

AbstractA Storm Model is used to estimate Probable Maximum Precipitation (PMP) for the Evinos catchment in Greece. The model determines the maximum dew‐point temperature from the effects of solar heating, orographic lifting and convergence, in terms of the change in temperature of a rising parcel of air. From this the model estimates the maximum precipitable water over the catchment and together with storm efficiency calculates PMP. For the Evinos catchment the 12‐hour PMP is estimated to be 478 mm and the 24‐hour PMP is 494 mm, occurring in late July. Further, the total water from a maximum rainfall event taken together with a rare snowmelt is unlikely to exceed the amount of water produced by a maximum rainfall in late July; hence, the latter is taken as the catchment PMP.

New laboratory measurements of mid‐IR emission spectra of simulated planetary surfaces

We present emission spectra of particulate quartz measured in an environment chamber designed to simulate the conditions on actual planetary surfaces. The goal was to investigate near‐surface thermal gradients and their effects on emission spectra for other planetary environments. Our experiment parallels that of Logan et al. [1973] but is different, in that our samples were heated at the base by a temperature‐controlled hot plate rather than from above by a solar lamp in order to separate infrared surface cooling from solar heating effects. Our spectra show prominent emission peaks which are attributed to the presence of near‐surface thermal gradients created by infrared cooling of the uppermost layer of the material. The contrast of the emission peak is maximized under vacuum conditions, for which it is estimated that a temperature difference of at least 40 K existed within the top emission skin depth. The wavelength location of the emission peak occurs near the Christiansen wavelength at 7.35 μm but has been shifted by approximately 0.2 μm to shorter wavelengths. This result is in agreement with the earlier results of Logan et al. [1973] and points out that the existence of a thermal gradient violates the conditions required by Kirchoff's law, and therefore care should be taken when spectra of surfaces on airless bodies are interpreted using emissivity spectra converted from reflectance data. Increasing the atmospheric pressure in the chamber increased the conductivity of the soil, mitigating the thermal gradient and decreasing the contrast of the emission maxima. Although thermal gradients complicate the interpretation of emission spectra of airless bodies, they tend to enhance certain spectral features, and therefore emission spectroscopy should be useful for remote sensing of the surfaces of the Moon and Mercury.

The annual temperature cycle in shelf seas

A generalized theory is developed to describe the annual temperature cycle in shelf seas. A sinusoidal approximation to the annual solar heating component, S, is assumed and the surface loss term is expressed as a constant k times the air-sea temperature difference ( T a − T s ). In well-mixed seas, analytical solutions show that in shallow water the sea temperature follows closely that of the ambient air temperature with limited separate effect of solar heating. Conversely in deep water, the sea surface temperature variations will be reduced relative to that of the ambient air. Providing such deep water remains mixed vertically, the annual variation will be inversely proportional to depth and maximum temperatures will occur up to 3 months after the maximum of solar heating. Generally, the magnitude of the inter-annual variability of sea surface temperatures will be less than corresponding variability in either the effective solar heating, S, (reduced by cloud cover) or the surface loss coefficient, k, (increased by stronger winds). The annual-mean sea temperature will exceed the annual mean air temperature by the annual mean of S divided by k. The above results can be extended to partially-stratified waters so long as autumnal overturning does not occur. For such conditions, an analytical expression is derived for the annual cycle of depth-varying temperatures for mixing associated with a vertical eddy dispersion coefficient E (constant in depth and time). The time taken for solar heating to be equalized throughout the water depth, D, is given by Tv = D 2/E , for a tidal current amplitude of 20 cm s −1. Tv ranges from 3.6 days for D = 50m to231days forD = 400m. To simulate the effect of gravitational instability that produces autumnal overturning, a numerical model is used that represents the effect of daily surface heat exchanges by a series expansion. Results from this model are used to indicate the effects of stratification over a range of values of both depth and Tv. Stratification will have a significant influence on the annual cycle and will be accompanied by autumnal overturning for values of Tv > 40days. Overall, stratification insulates the sea, (especially at greater depths) from atmospheric influences (in more complex models where E is reduced by vertical density gradients this effect would be further enhanced). In combination with autumnal overturning the effect is to lower both the variability and mean of the temperature in deeper water. The above model is used to simulate the annual temperature cycle for an off-shore cross section of constant slope (increasing in the example chosen from 25 to 250 m). The results indicate that horizontal gradients in temperature at the sea surface may be significantly smaller than those at lower depths. Sensitivity tests of the effects of both horizontal dispersion and advection showed that the “localized-equilibrium” for thermal exchanges assumed throughout the above analyses will be valid in many seas where bathymetry changes gradually. The dynamic response to the horizontal density gradients associated with these modelled cross-shore temperature structures are calculated. These responses are generally small with (steady) currents much less than 1 cm s −1 and changes in elevation less than 1 mm (except in fully enclosed seas where volume changes associated with thermal expansion cannot be balanced by oceanic exchanges).

Dynamical and radiative forcing of the summer mesopause circulation and thermal structure: 1. Mean solstice conditions

We present here a simple eigenvalue model which illustrates the sensitivity of the mean circulation and thermal structure near the high‐latitude summer mesopause to dynamical and radiative processes under solstice conditions. Dynamical forcing is provided by gravity wave energy and momentum fluxes and their divergence which contribute both a zonal body force and implied turbulent heating and transport in the mesopause region. These profiles are chosen to be consistent with measurements of gravity wave fluxes and energy densities at high latitudes. Radiative forcing represents the effects of solar heating, non‐LTE CO2 cooling, and LTE O3 cooling below 70 km and is parameterized as a height‐dependent relaxation toward an equilibrium temperature profile accounting for both radiative and chemical influences. Gravity wave momentum flux divergence forces a mean vertical motion related to the meridional gradient of the density‐weighted momentum flux through the “downward control principle” and a mean meridional circulation required to balance the zonal body force. The model exhibits strong sensitivity to dynamical forcing and implies significant constraints on wave influences at mesopause altitudes. For plausible wave fluxes and energy densities, the model yields a mean vertical motion of ∼0.05 m s−1, a mean meridional jet of ∼10 to 15 m s−1, and a mesopause temperature of ∼130 K at Arctic latitudes, all of which are in good agreement with observations. The eigenvalue solution also yields estimates of the induced turbulent heating and vertical diffusion that may pose useful guidelines in modeling studies. Seasonal variations in the mesopause structure are the subject of a companion paper.

A Numerical Model of Nonmigrating Diurnal Tides between the Surface and 65 km

Observations of surface pressure and middle atmosphere temperatures and winds indicate that a substantial nonmigrating component is present in the diurnal tide. The nonmigrating tides, which propagate with a zonal phase speed that is different from the earth's rotation, are attributed to the diurnal heating of geographically fixed sources. In this study we utilize a classical tidal model to examine the propagation characteristics of diurnal tides. The global fields of tropospheric sensible, radiative, and latent heating used to drive the model are supplied from summer and winter diurnal climatologies of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM2). A novel aspect of this study is the focus on the relative importance of the nonmigrating components. The classical model successfully reproduces many observed features of the low-latitude diurnal surface pressure tides. In the middle atmosphere, the simulated migrating (or sun-synchronous) tide shows qualitative agreement with November-March Limb Infrared Monitor of the Stratosphere (LIMS) observations. Tropospheric solar heating is clearly the dominant driving force for the migrating tide, with secondary contributions from boundary-layer sensible heating and tropospheric latent heat release. The leading modes of the zonal mean tide are also driven chiefly by tropospheric solar heating. The higher-order modes of the zonal mean and eastward propagating tides may be attributed to the joint effects of tropospheric solar heating, sensible heating, and latent heat release. The LIMS and other data reveal features that cannot be explained or examined within the context of the classical model used in the present study. These include upward phase propagation, vertical attenuation, and temporal variations in the migrating diurnal tide.

Stability of the annual temperature cycle in shelf seas

1. 1. In shallow well-mixed seas the sea temperature follows closely that of the ambient air temperature with limited separate effect of solar heating. Conversely in deep water, the annual variation in sea surface temperature variations will be less than that of the ambient air. In such deep water the annual variation will decrease with increasing depth and maximum temperatures will occur up to 3 months after the maximum of solar heating. Generally, inter-annual variability of sea surface temperatures will be less than corresponding variability in either the effective solar heating, QI, (reduced by cloud cover) or the surface loss coefficient, k, (increased by stronger winds). The annual-mean sea temperature will exceed the annual mean air temperature by the annual mean of QI divided by k. 2. 2. The time taken for solar heating to be equalised throughout the water depth, D, is given by T v = D 2 K z ( K z a vertical eddy dispersion coefficient). T v ranges from a day or less when D ≈ 10 m to in excess of 1 year when D > 500 m. 3. 3. The effects of stratification on the annual cycle generally become increasingly apparent for values of T v > 20 days. Overall, stratification insulates the sea, (especially at greater depths) from atmospheric influences. In combination with autumnal overturning, the effect is to lower both the variability and mean of the temperature in deeper water. 4. 4. The relative influence of variability in adjacent oceanic conditions depends on the ratio D : F T where F T is the flushing time of the shelf sea relating to oceanic exchanges.

Design and field operation of an in-situ environmental enclosure for tree branches

In order to examine the effects of airborne chemicals and other atmospheric components on mature trees in natural ecosystems, branch-sized environmental chambers were developed. These were designed to withstand the rigors of season-long exposure in montane environments while effectively controlling the conditions within. Field testing of the chambers demonstrated a reasonable, although not exact semblance of ambient conditions. Solar heating effects were difficult to control, although a configuration was developed that allowed the chambers to operate within standard specifications for similar devices. Overall, performance was good, and it is felt that this technique is a valuable tool for the evaluation of the effects of atmospheric chemicals on trees, as long as attention is paid to the environmental alterations caused by the chambers, and comparisons are made against control chambers.