Thermal radiation

About: Thermal radiation is a research topic. Over the lifetime, 12290 publications have been published within this topic receiving 197186 citations. The topic is also known as: heat radiation.

Role of Radiative Transport in the Propagation of Laser Supported Combustion Waves

Abstract: We report results of an investigation into the roles played by thermal and radiative transport in the propagation of Laser Supported Combustion (LSC) waves We replace the volume radiation losses assumed by Raizer with detailed treatment of radiation in 19 frequency groups, the flux of each being calculated from the temperature in discrete cells along the LSC wave axis and allowed to deposit in other cells according to temperature dependent absorption coefficients for air Calculations of LSC wave structure and propagation velocity as a function of laser intensity are compatible with available experimental data a = c = CP = f = h = h = hi(a) = K = k = KV =

Measurement of thermal diffusion in thin films using a modulated laser technique: Application to chemical‐vapor‐deposited diamond films

Abstract: A method to determine the thermal diffusivity in thin films, based on the measurement and analysis of thermal waves induced by a modulated infrared laser, is demonstrated. A nearly exact mathematical description, independent of the film geometry and including surface heat losses, is presented. It is shown that the in‐plane thermal diffusivity and the heat loss through the surface can be determined independently by analysis of both the phase and the amplitude of the thermal waves. The validity of the method has been verified using high‐purity copper sheets of varying thickness, for different modulation frequencies. Several polycrystalline, chemical‐vapor‐deposited (CVD) diamond films have been investigated. The measurements were performed both on free‐standing films and on two‐layer systems of CVD diamond and copper. Thermal diffusivities for polycrystalline diamond up to 6.2 cm2 s−1 were recorded.

Unsteady hydromagnetic free convection flow of a dissipative and radiating fluid past a vertical plate with constant heat flux

Abstract: The effect of thermal radiation absorption on an unsteady free convective flow past a vertical plate is studied in the presence of a magnetic field and constant wall heat flux. Boundary layer equations are derived, and the resulting approximate nonlinear ordinary differential equations are solved analytically using asymptotic technique. A parametric study of all parameters involved is conducted, and a representative set of numerical results for the velocity and temperature profiles as well as the skin-friction parameter are illustrated graphically to show typical trends of the solutions.

Thermal Noise in Biomagnetic Measurements

Abstract: Studies of weak magnetic fields are generally influenced by magnetic noise emanating from thermal agitation of electric charge (Johnson noise) in electrically conducting materials surrounding the magnetic‐field sensor. In this article, the thermal magnetic noise fields generated by slabs with high electric conductivity (copper, aluminum) or high magnetic permeability (mu metal) are studied. The analysis is based both on a previously published phenomenological model and on measurements with an ultrasensitive superconducting magnetometer. Both the spectral densities and spatial correlations of the magnetic field fluctuations are evaluated. The computed correlation coefficients are utilized to develop a practical method for estimating the thermal noise due to thin conducting foils, such as thermal radiation shields in a cryogenic measurement Dewar. Also experiments to reduce the Dewar noise are reported. Finally, estimations are presented for the thermal noise fields arising in the walls of a magnetically shielded room. In practice, thermal magnetic noise, particularly due to the superinsulation in cryogenic Dewars, can be the limiting factor of sensitivity in measurements of weak biomagnetic signals arising in the human heart and brain. The results are useful in the estimation and minimization of the contribution of thermal noise.