Shigenao Maruyama

Thermal radiation from two-dimensionally confined modes in microcavities

A two-dimensional array of a microcavity with a high aspect ratio is made on a Cr-coated Si surface using the micromachining technology. The thermal emission spectra whose wavelength is close to the dimension of cavity aperture (5 μm) are measured on samples with a different aspect ratio. The clear selective emission bands corresponding to the two-dimensionally confined electromagnetic modes are demonstrated experimentally. It is found that the low emissivity of the base material is essential to obtain the high spectral selectivity of thermal radiation. The direction and polarization properties are also examined. The dominant peaks of the emission spectra can be explained by a simple cavity resonator model.

Radiation heat transfer of arbitrary three-dimensional absorbing, emitting and scattering media and specular and diffuse surfaces

Analysis of radiation heat transfer using the Radiation Element Method by Ray Emission Model, REM 2 , is described. The REM 2 is a generalized numerical method for calculating radiation heat transfer between absorbing, emitting and scattering media and specular surfaces with arbitrary three-dimensional configurations. The ray emission model for various radiation elements is expressed by polyhedrons and polygons. Arbitrary thermal conditions can be specified for each radiation element, and generalized radiation transfer can be achieved for both of surface and volume elements by introducing a new definition of view factors. The accuracy of the present method is verified using simple configurations. A cubic participating medium with a spherical cavity covered with specular and diffuse surfaces is analyzed as an example of an arbitrary configuration.

Free convective/radiative heat transfer from pin-fin arrays with a vertical base plate (general representation of heat transfer performance)

Abstract An experiment was carried out on free convective and radiative heat transfer from dense pin-fin arrays with a vertical isothermal base plate. Data analyses are made in consideration of the temperature distribution in the pin-fins, and of the radiative heat transfer. The free convective heat transfer characteristics of the pin-fin arrays are correlated fairly well with the Nusselt number and Rayleigh number, based on the horizontal spacing of the vertical pin arrays as a characteristic length. The generalized characteristics are similar to those of rectangular fin arrays. An experimental formula for the average heat transfer coefficient is derived.

Dimensionless solutions and general characteristics of bioheat transfer during thermal therapy

Abstract The derivation and application of the general characteristics of bioheat transfer for medical applications are shown in this paper. Two general bioheat transfer characteristics are derived from solutions of one-dimensional Pennes’ bioheat transfer equation: steady-state thermal penetration depth, which is the deepest depth where the heat effect reaches; and time to reach steady-state, which represents the amount of time necessary for temperature distribution to converge to a steady-state. All results are described by dimensionless form; therefore, these results provide information on temperature distribution in biological tissue for various thermal therapies by transforming to dimension form.

Radiative heat transfer in anisotropic scattering media with specular boundary subjected to collimated irradiation

Abstract Generalized numerical method, radiation element method by ray emission model, REM 2 , is applied to plane-parallel and anisotropic scattering participating media using the delta function approximation. The boundary can be specular and/or diffuse, and both collimated and diffuse incident irradiation can be specified on the boundary. REM 2 can be applied to various thermal conditions in the medium and boundaries. Good agreement is obtained between the present numerical solutions using the delta function approximation and existing exact solutions, even for strong forward and back scattering media. The proposed method is applied to an anisotropic scattering participating medium with a specular surface. The effect of specular reflectivity of scattering layers subjected to obliquely collimated flux was investigated.

Radiative heat transfer in inhomogeneous, nongray, and anisotropically scattering media

Abstract Radiative heat transfer in three-dimensional inhomogeneous, nongray and anisotropically scattering participating media was investigated by using REM2 method. The accuracy of the method was verified by benchmark comparisons against the solutions of Monte Carlo and YIX methods in the case of three-dimensional inhomogeneous media and in the case of three-dimensional media composed of nongray CO2 gas and carbon particles with strong anisotropically scattering. The ray effect and the influences of radiation element division and spectral discretization were examined. The present predictions of heat flux, flux divergence and emissive power were found to be in good agreement with those by Monte Carlo and YIX methods. As an example of an application of engineering interest, radiative heat transfer in a boiler model with non-isothermal, nongray, and anisotropically scattering media is numerically studied. The distributions of radiative heat flux and flux divergences in the boiler furnace are obtained. It is found that larger heat fluxes appear at the wall near the flame and larger heat flux divergences exist around the boundary of the flame. The effect of particle radiation is small in the region downstream the flame.

Radiation heat transfer between arbitrary three-dimensional bodies with specular and diffuse surfaces

A numerical method is presented for predicting radiation heat transfer from arbitrary bodies composed of numerous polygons. Each polygon is gray and has the comined characteristics of specular and diffuse surfaces. Both heat flux and temperature can be specified arbitrarily on the surfaces. A new concept of view factors was introduced for analyzing radiation heat transfer between specular and diffuse surfaces. A radiation ray tracing method was adopted for estimating the view factors, and efficient vector operation and parallel processing were achieved for a supercomputer. The accuracy of the method was checked in comparison with analytical solutions for a simple configuration, and the effect of specular reflectivity was investigated. As a numerical example, radiation heat transfer of a machine element and healer panels composed of 4388 polygons was demonstrated.

Measurement of diffusion fields of solutions using real-time phase-shift interferometer and rapid heat-transfer control system

Abstract A new measurement system for investigation of transient diffusion fields using an accurate interferometer system was developed. This system was composed of a rapid heat-transfer control system and a real-time phase-shift interferometer. The heat-transfer control system had a small test-cell in which the liquid temperature was controlled by non-equilibrium thermoelectric device. In order to investigate pure diffusion fields without double diffusive convection, micorgravity experiments using an airplane were carried out. Thermal and mass diffusion fields of aqueous solutions of NaClO 3 and Ba(NO 3 ) 2 were measured by the system. Thermal and mass diffusion fields were investigated with various temperature conditions. The effect of double diffusive convection on the measurement of diffusion fields was observed. Mass diffusion of NaClO 3 solution in various temperature gradients was measured in normal and micro-gravity conditions. The relation between crystal growth and super cooling was investigated, and no crystal growth was observed at small supersaturation ratio. The result agreed with that obtained using a small rocket experiment.

Scaling anisotropic scattering in radiative transfer in three-dimensional nonhomogeneous media

Abstract Radiative heat transfer in three-dimensional nonhomogeneous participating medium was investigated by using REM 2 method. The anisotropic scattering phase function was dealt with the scaling technique based on delta function approximation. The three-dimensional scaled isotropic results were compared with the published anisotropic scattering computations. A good agreement between the scaled isotropic approaches and the anisotropic solutions was found. The effects of scattering albedo, forward fraction of phase function, and wall emissivity were discussed. It was found that, with the increase of the scattering albedo, the radiative heat flux increases for forward scattering media, but decreases for backward scattering media. The radiative heat flux is increased with the increases of forward fraction of phase function and wall emissivity. The emissive power at the center of a cubical nonhomogeneous medium in radiative equilibrium with gray diffuse walls equals to the averaged blackbody emissive power of the six walls.

Photothermal therapy of tumors in lymph nodes using gold nanorods and near-infrared laser light

Lymph node dissection for regional nodal metastasis is a primary option, but is invasive and associated with adverse effects. The development of non-invasive therapeutic methods in preclinical experiments using mice has been restricted by the small lymph node size and the limited techniques available for non-invasive monitoring of lymph node metastasis. Here, we show that photothermal therapy (PTT) using gold nanorods (GNRs) and near-infrared (NIR) laser light shows potential as a non-invasive treatment for tumors in the proper axillary lymph nodes (proper-ALNs) of MXH10/Mo-lpr/lpr mice, which develop systemic swelling of lymph nodes (up to 13mm in diameter, similar in size to human lymph nodes). Tumor cells were inoculated into the proper-ALNs to develop a model of metastatic lesions, and any anti-tumor effects of therapy were assessed. We found that GNRs accumulated in the tumor in the proper-ALNs 24h after tail vein injection, and that irradiation with NIR laser light elevated tumor temperature. Furthermore, combining local or systemic delivery of GNRs with NIR irradiation suppressed tumor growth more than irradiation alone. We propose that PTT with GNRs and NIR laser light can serve as a new therapeutic method for lymph node metastasis, as an alternative to lymph node dissection.