- Author
- Gardon, R.
- Title
- Temperatures Attained in Wood Exposed to High Intensity Thermal Radiation.
- Coporate
- University of London, England
- Report
- Thesis, March 1959, 247 p.
- Keywords
- thermal radiation | high intensity | temperature | wood | ignition | temperature distribution | physical properties | irradiation | solar radiation
- Identifiers
- theoretical study of temperature distributions in irradiated solids; temperature distributions in opaque materials; temperature distributions in diathermanous materials
- Abstract
- The development of atomic weapons has brought interest to bear on the behavior of materials exposed to thermal radiation of much higher intensities than have hitherto been obtained on a large scale. That these high intensities can cause the attainment of critically high temperatures in very short times has prompted the present study of the transient energy transfer phenomena involved. In the theoretical part of this investigation it was shown that temperatures near irradiated surfaces are lower in diathermanous materials than in opaque materials having otherwise identical properties, and that the difference between the two diminishes at progressively longer exposures. More generally, the significance of diathermancy was shown to decrease as the parameter [see report] increases. Allowance for scattering could be made by combining the coefficients of absorption and scattering in an "effective absorption coefficient [see report]. For the experimental part of the study a solar furnace was built and instruments were devised for the measurement of very intense thermal radiation. Temperatures were measured in wooden samples exposed to radiant intensities up to 5.5 cal/cm² sec. Masonite and blackened wood were found to behave as opaque materials, and temperature distributions in them could be well correlated on the basis of independently measured thermal diffusivities. Natural-colored wood was found to be partially diathermanous to solar radiation. The experiments confirmed the theoretical finding that the significance of diathermancy diminishes with increasing time of irradiation. Thus, if the irradiation is not so intense as to char the exposed wooden surface in less time, temperatures near the surface are noticeably affected by diathermancy for periods of irradiation up to about two seconds. Some measurements of the relevant physical properties of wood, notably its reflectivity and coefficients of absorption and scatter, are reported in the appendix.