The Influence of Through-Metal on the Heat Loss From Insulated Walls

Abstract

The heat flow through insulation containing “through-metal,” or “thermal short-circuits” has been investigated. The heat flow through such a structure (occurring, for example, in the insulation of ship hulls) can be considerably larger than would be found from adding to the heat flow through the insulation that contributed by the “through-metal,” as if the two were independent. Thus the apparent effectiveness of an insulation can be very much smaller than would be calculated from the thermal conductivity alone. From the many different forms of thermal short-circuits, one specific type has been selected for investigation, i.e., that of metal strips or fins extending through insulation which is covered on its surfaces by sheet metal. General curves are developed and their application explained, from which an “increase factor” for any condition (conductivity and thickness of the insulation, conductivity and thickness of the strips, outside film conductance) can be read. The “increase factor” is defined as the ratio of the heat flow through an actual structure, compared with the flow that would occur if the insulation and heat flow through metal strips were independent of each other. The method of developing these general curves and the basis of the experimental technique used are explained in two Appendixes.

On Mechanical and Chaotic Problem Modeling and Numerical Simulation Using Electric Networks

“…Kirchhoff [1] 1845 Electrolytic tank Electrical currents on conductive surfaces Paschkis and Heisler [4] 1944 Resistors and capacitors (laboratory) Heat transfer sentences, which allows for implementing any type of physical problem in the models, particularly the so-called controlled generators, which allow for implementing any nonlinear or coupled term that is part of the governing equations; (iii) the computer algorithms developed in these programs being perhaps the most up-to-date, optimized, and computationally powerful, which results in the reliability of the numerical solutions and the reduction of computation time [24]; and (iv) the programming rules for preparing the text files of the models being relatively few and established on the basic theory of electric circuits, i.e., on the constitutive laws of their elements and on the theorems of uniqueness of the electric potential and conservation of electric charge (Kirchhoff's theorems) [22]. In fact, the researcher only has to worry about the correct design of the network model-or equivalent circuit-which has to collect the boundary and initial conditions of the problem, forgetting about the algorithms for numerical computation.…”

“…More recently, Arvinti et al [3] implemented a laboratory electrical model to solve the Laplace equation in the whole domain, approaching the solutions using Lagrange polynomials. During the decades between 1940 and 1970, large analog equipment consisting of resistors and capacitors were developed that allowed the simulation of heat and mass flow processes both linear, with the 'heat and mass analyzer' of Paschkis and Heisler [4], and nonlinear, by means of the 'differential analyzer' of Karplus and Soroka [5]. After the development of computers, these physical models were replaced by numerical computational techniques that directly address the solution to governing equations using a variety of precise methods, such as finite elements, finite differences, and variational techniques.…”