Related to an evaluation for heat-shielding properties of functionally gradient materials (FGMs), an attempt has been made to estimate a profile of the thermal diffusivity from the temperature response on the rear surface of the FGM when the FGM is subjected to the transient heating. In order to solve the so-called “Inverse Problem”, a focus is put on distribution parameters which give the profiles of the thermophysical properties when there exists an exact analytical solution for the temperature response in the FGM. An explicit relation between the distribution parameters and thermophysical properties on the rear surface is successfully obtained. This explicit expression can fairly represent the dependence of the temperature response on the thermophysical properties within 3%. It is expected that this identification can provide useful insight into the estimation of thermophysical properties in FGMs. Usefulness of this relation is also examined by comparing the given and the estimated profiles for the thermal diffusivity. Fair agreement is demonstrated, as far as the trend and the approximate magnitude are concerned.
A simplified measurement method for thermal conductivity of low conductive materials such as polymers and ceramics has been developed. Plate-shaped (2-8×25×25mm3) samples and reference samples are adhered on a heated copper base plate in a vacuum chamber. Temperature differences between the sample surfaces and the base plate caused by radiative heat exchange are measured by differential thermocouples. Thermal conductivities of the samples are calculated using the reference data on the reference samples. As a result of test measurements at 30-70°C, uncertainties of the measured values were estimated to be ±15% in a standard deviation.
Clathrate hydrates are a class of crystalline solids which have increasing relations to energy technology and environmental sciences. Fluorocarbon hydrates as cool storage media for residential air conditioning, CO2 hydrate to be formed by disposing fossil-fuel-originated CO2 into deep oceans, and methane hydrate as a potential energy resource and/or a source of increasing global warming are among principal examples of such clathrate hydrates. This article gives a historical survey of clathrate-hydrate research, introductory descriptions of molecular structures and phase equilibria of clathrate hydrates, and the status of our current knowledge on the behavior of clathrate-hydrate formation at liquid-liquid or liquid-vapor interfaces.
The temperature response in a functionally gradient material (FGM), subjected to pulsewise heating at the front surface, is evaluated. The approximate solution for the temperature response is investigated by comparing it with an exact analytical solution for the FGM in which the thermophysical properties have logarithmic profiles. By using these solutions the thermophysical properties are evaluated as the total properties for the FGM.
Thermosensitive liquid crystal and image processor are applied to measure temperature distribution. The article focuses on regression method to correlate color and temperature. The effectiveness is presented by the heat transfer of impinging jet and around a spacer and the natural convection in a vessel.