Abstract
By placing a sample between a heated and a cooled rod, a thermal conductivity of the sample can be evaluated easily with the assumption of a one-dimensional heat flow. However, a three-dimensional constriction/spreading heat flow may occur inside the rods when the sample is a composite having different thermal conductivities. In order to investigate the thermal resistance due to the constriction/spreading heat flow, the three-dimensional numerical analyses were conducted on the heat transfer characteristics of the rods. In the present analyses, a polymer-based composite board having thermal vias was sandwiched between the rods. From the numerical results, it was confirmed that the constriction/spreading resistance of the rods was strongly affected by the thermal conductivity of the rods as well as the number and size of the thermal vias. A simple equation was also proposed to evaluate the constriction/spreading resistance of the rods. Fairly good agreements were obtained between the numerical results and the calculated ones by the simple equation. Moreover, the discussion was also made on an effective thermal conductivity of the composite board evaluated with the heated and the cooled rod.
Highlights
IntroductionFrom a steady-state temperature distribution inside the rods, the thermal conductivity of the sample is obtained by using Fourier’s law
It was confirmed that the constriction/spreading resistance of the rods was strongly affected by the thermal conductivity of the rods as well as the number and size of the thermal vias
Numerical analyses were conducted on the heat transfer characteristics of the heated and the cooled rod having the composite board in between
Summary
From a steady-state temperature distribution inside the rods, the thermal conductivity of the sample is obtained by using Fourier’s law. In this method, a one-dimensional heat flow from the heated to the cooled section of the rod is assumed. An attention is required when this method is applied for the measurement of an effective thermal conductivity of a composite sample This is because a difference in thermal conductivity between components of the composite sample may cause a constriction/spreading heat flow inside the rods. To the authors’ knowledge, sufficient information has not been published on the constriction/ spreading heat flow inside the rods caused by the composite sample like a polymer board having thermal vias
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