Enclosure Size Research Articles

Influence of the size of enclosure of the development of myopathy in the captive Rottnest quokka.

Influence of the Size of Enclosure on the Development of Myopathy in the Captive Rottnest Quokka

Radiation Heat Transfer in a Spherical Enclosure Containing a Participating, Heat-Generating Gas

An analysis is made of the thermal radiation in an absorbing-emitting nonisothermal gas confined in a hollow spherical enclosure or in the space between two concentric spheres. The gas is gray and contains a volume heat source, while the bounding walls are black and isothermal. The conservation of energy principle yields an integral equation which has been solved for a wide range of geometric and radiative conditions. It is found that as the absorption coefficient increases in a fixed geometry, the gas temperature decreases and becomes more nonuniform. On the other hand, as the enclosure size increases, the gas temperature increases and becomes more nonuniform. An approximate analysis using a conduction-type transfer law has been carried out, and the results are compared with the integral equation solutions.

Noise Reduction by Partial Enclosures

Noise exposure in factories is often a serious problem only for workers close to noisy machines. Partial enclosure of a machine will often provide a reduction of 10 to 20 db in the near field and, with good design, a significant reduction can also be obtained in the far field. These reductions are, of course, for frequencies having wavelengths considerably smaller than the enclosure dimensions. Enclosure design parameters were obtained by measurements of noise reduction in the model factory described in the previous paper. Enclosures with 2, 3, and 4 sides were tested to obtain noise reduction in octave bands as a function of enclosure size. For practical sizes, reductions in the near field were 6 to 10 db for enclosures without a top and up to 25 db with a top. Acoustical lining of the ceiling above an enclosure increased the reduction and was particularly effective in the far field, where 12 db could be obtained even with fairly “open” enclosures. [This work was supported in part by the National Gypsum Company.]