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.
Corporations and the Market for Law
The state competition for corporate law has long been studied as a distinct phenomenon. Under the traditional view, corporations are subject to a unique choice-of-law rule, the internal affairs doctrine (IAD). This rule is explained as a historical accident, or by the special logistics of the corporate contract. The resulting market for corporate law appears to have special characteristics, particularly including the dominance by the single state of Delaware. This paper challenges the traditional view. It shows that the corporate law market is best understood as a special application of the general market for law. Any differences are matters of degree rather than kind, and are explained by considerations underlying enforcement of all choice-of-law contracts rather than by factors unique to corporations. It follows that theories of corporate competition that ignore the broader law market context are incomplete, and that the competition for corporate law carries lessons for the law market generally. Moreover, the connection between the corporate and other law markets has implications for the nature of corporate law, the constitutional status of the IAD, the scope of the IAD, and for the relationship between state and federal law.