Measurement of VIP Edge Conduction Using Vacuum Guarded Hot Plate
Abstract—Vacuum insulation panel (VIP) is a promising thermal insulator for buildings, refrigerator, LNG carrier and so on. In general, it has the thermal conductivity of 2~4 mW/m·K. However, this thermal conductivity is that measured at the center of VIP. The total effective thermal conductivity of VIP is larger than this value due to the edge conduction through the envelope. In this paper, the edge conduction of VIP is examined theoretically, numerically and experimentally. To confirm the existence of the edge conduction, numerical analysis is performed for simple two-dimensional VIP model and a theoretical model is proposed to calculate the edge conductivity. Also, the edge conductivity is measured using the vacuum guarded hot plate and the experiment is validated against numerical analysis. The results show that the edge conductivity is dependent on the width of panel and thickness of Al-foil. To reduce the edge conduction, it is recommended that the VIP should be made as big as possible or made of thin Al film envelope.
Analysis of the temperature distribution in a guarded hot plate apparatus for measuring thermal conductivity
Abstract A guarded hot plate apparatus (GHPA) is used to measure the thermal conductivity of insulating materials. This apparatus uses a circular heat source. It was studied the applications of such kind of heat sources. The particular problem for which the solution is developed here concerns with the use of a heater embedded in a central plate and guard ring to generate a heat flux. An elegant closed form analytical solution was obtained for this problem. The Green’s function formulation was used to compute the distribution of temperatures in the central plate and the guard. The analytic results were compared with measurements made on aluminum plates and it was found that they are in good agreement with experimental data with a standard deviation of 3%. These results can be used for obtaining the average temperature in the plates, which are used as the representative temperature. Likewise, the position of the main temperature zone was determined; this position is the one where the thermocouples should be placed on the plates of GHPA.
The Politics of Truth: Power in Nietzsche’s Epistemology
This article concerns first a curiosity found in Friedrich Nietzsche’s The Antichrist. In the midst of a heated attack on Christianity, Nietzsche detours into a discussion of epistemology. I argue that this turn indicates the importance of epistemology, and illustrates its political and moral character. The weak, who cannot tolerate uncertainty and shades of gray, seek to impose an epistemology of clarity and certainty. At the same time, the strong, who revel in ambiguity, seek to enjoy the richness and subtlety of a non-dichotomous view of the world. This is a political struggle because the weak cannot allow the strong’s epistemology to exist, let alone prevail. It is not surprising, then, that Nietzsche talks about epistemology in the midst of attacking Christianity: its view of truth is essential to its mission of taming the nobles. Here, I consider Nietzsche as a political thinker in a different light. Political battles are fought far beyond the halls of government. Nietzsche is a political thinker; one, however, who looks at politics in an uncommon way.