Absorptance, Solar

Thermal characteristics of material layers for each type of wall must be specified, including thickness, conductivity, density, and specific heat. Moreover, the features of internal and external surfaces of each wall must be specified, including solar absorptance and roughness, which affect surface heat transfer coefficients. 

The case of water is particularly convenient because the required high Ka states may be detected in the solar absorption spectrum. However, it is difficult to observe the necessary high vibrational angular momentum states in molecules, which can only be probed by dispersed fluorescence or stimulated emission techniques. On the other hand, it is now possible to perform converged variational calculations on accurate potential energy surfaces, from which one could hope to verify the quantum monodromy and assess the extent to which it is disturbed by perturbations with other modes. Examples of such computed monodromy are seen for H2O in Fig. 2 and LiCN in Fig. 12. 

Kinne, S O. B. Toon, G. C. Toon, C. B. Farmer, E. V. Browell, and M. P. McCormick, Measurements of Size and Composition of Particles in Polar Stratospheric Clouds from Infrared Solar Absorption Spectra, J. Geophys. Res., 94, 16481-16491 (1989). 

Conant, W. C., V. Ramanathan, F. P. J. Valero, and J. Meywerk, An Examination of the Clear-Sky Solar Absorption over the Central Equatorial Pacific Observations versus Models, J. Clim., 10, 1874-1884 (1997). 

Li, Z., and L. Moreau, Alteration of Atmospheric Solar Absorption by Clouds Simulation and Observation, J. Appl. Meteorol., 35, 653-670 (1996). 

Pilewskie, P., and F. P. J. Valero, Direct Observations of Excess Solar Absorption by Clouds, Science, 267, 1626-1629 (1995). 

Podgorny, I. A., A. M. Vogelmann, and V. Ramanathan, Effects of Cloud Shape and Water Vapor Distribution on Solar Absorption in the Near Infrared, Geophys. Res. Lett, 25, 1899-1902 (1998). 

Ramanathan, V., and A. M. Vogelmann, Atmospheric Greenhouse Effect, Excess Solar Absorption and the Radiation Budget From the Arrhenius/Langley Era to the 1990s, Ambio, 26, 38-46 (1997). 

Ramaswamy, V., and V. Ramanathan, Solar Absorption by Cirrus Clouds and the Maintenance of the Tropical Upper Troposphere Thermal Structure, J. Atmos. Sci., 46, 2293-2310 (1989). 

Considine, D.M. Solar Absorption Coaling and Heat-Pipe System, in Energy Technology Handbook (DM Considine, editor). The McGraw-Hill Companies, Inc., New York, NY, 1977. 

One of the first examples of the modem application of remote sensing of the composition of the atmosphere was the assertion by Hartley in 1880 that the UV absorption in the solar absorption spectrum was attributable to ozone. In this manner the earth s stratospheric ozone layer was discovered. Since this pioneering work and especially in die past 30 years, there has been rapid progress in the development of atmospheric remote sensing techniques. 

Cover temperature is another variable which controls distillation rate and efficiency. All of the heat transferred to the underside of the cover from the basin, plus the small solar absorption in it, must be dissipated by convection to the surrounding air and by radiation to the sky. Ambient temperature, wind velocity, and atmospheric clarity all influence the temperature driving force necessary to attain the equilibrium heat transfer rate. Cover temperature, in turn, affects basin temperature, so that an over-all equality in heat flows prevails. The primary variable remains, of course, the solar energy input rate, its most important effect being the temperature level in the salt water basin. 

Oji Shunsako, Fujimoto, Masanori Furata, Thermally insulating synthetic fibres with selective solar absorpting , JK1-132816. 

The plate of Example 5-4 is 30 cm by 30 cm square and is sprayed with a white paint having a solar absorptivity of 0.16 and a low-temperature absorptivity of 0.09. The plate is exposed to a solar radiation flux of 1100 W/m2 and allowed to reach equilibrium with the convection surroundings. Assuming that the underside of the plate is insulated, calculate the equilibrium temperature of the plate. 

Calculate the solar-heat input to the tank. Since the sun, although an extremely powerful emitter, subtends a very small solid angle, it has an only minute radiant interchange factor with objects on earth. The earth s orbital distance from the sun is nearly constant throughout the year. Therefore, it is a valid simplification to consider solar radiation simply as a heat source independent of the radiation environment and governed solely by the solar absorptance of each surface and the angular relationship of the surface to the solar vector. 

Finally, take the solar absorptance of the paint as into account. Thus, the solar heat absorbed qs equals as(G, + Gs ). The calculations can be summarized as follows ... 

It was during the same time that astronomers began to extract quantitative information about elemental abundances in the Sun by solar absorption spectroscopy and it was soon realized that the compositions of the Sun and the whole Earth are similar, except for hydrogen and other extremely volatile elements (see Russell, 1941). 

The inner and outer surfaces of a 25-cm-thick wall in summer are at 27"C and 44 C, respectively. The outer surface of the wall exchanges heal by radiation with surrounding surfaces at 40°C, and convection svith ambient air also at 40 C with a convection heat transfer coefficient of 8 W/m - °C. Solar radiation is incident on the surface at a rate of 150 W/m If both the emissivity and the solar absorptivity of the outer surface are 0.8, determine the effective thermal conductivity of the wall. 

Consider a large plane wall of thickness L = 0.06 m and thermal conductivity k = 1.2 W/m C in space. The wall is covered with white porcelain tiles that have an emissivity of e = 0.85 and a solar absorptivity of a = 0.26, as shown in Fig. 2-48. The inner surface of the v/all is maintained at Ti = 300 K at all times, while the outer surface Is exposed to solar radiation that is incident at a rate of 800 W/m. The outer surface is also losing heal by radiation to deep space at 0 K. Determine the temperature of the outer surface of the wall and the rate of heat transfer through the wall when steady operating conditions are reached. What would your response be if no solar radiation was incident on the surface ... 

A solar heat flux q, is incident on a sidewalk whose thermal conductivity is k, solar absorptivity is a and convective heat transfer coefficient is h. TaWng the positive x direction to be towards the sky and disregarding radiation exchange with the surroundings surfaces, the correct boundary condition for this sidewalk surface is... 

I Reconsider Prob. 7-24. Using HHS (or other) software, investigate the effects of the train velocity and the rate of ab.sorplion of solar radiation on the equilibrium temperature of the top surface of the car. Let the train velocity vary from 10 ktn/h to 120 km/h and the nite of solar absorption from 100 V/in to 500 W/m". Plot the equilibrium temperature as functions of train velocity and. solar radiation absorption rale, and discuss the results. 

What would your answer be if the absorber plate is made of ordinary aiuminum plate that has a solar absorptivity of 0.28 and an emissivity of 0.07 ... 

Repeat Prob. 9-29 for an aiuminum plate painted flat black (solar absorptivity 0.98 and emissivity 0.98) and also for a plate painted white (solar absorptivity 0.26 and emissivity 0.90),... 

SOLUTION A surface is exposed to solar and sky radiation. The net rate of radiation heat transfer is to be determined for four different combinations of emissivities and solar absorptivities. 

Comparison of the solar absorptivity o, of some surfaces v/ith their emissivity e at room temperature... 

Dcscriotion/composition Solar Absorptivity, Emissivity, e, at 300 K Ratio, otje Solar Transmissivity,... 

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