Thermal Bridge Heat Transfer & Vapour Diffusion Simulation Program AnTherm Version 6.115 - 10.137 [ ← ] [ ↑ ] [ → ] [ToC]

# Basics and Some Theory of AnTherm

## Calculation Model

Using the concept of a conductance, Lij (between the spaces i and j), the heat which flows out of space i is a sum depending on the temperatures of space i and of all other spaces, j: Since Lij can be proven to be symmetrical (= Lji), this equation corresponds formally to Kirchhoff's law of electrical networks. The analogy that this allows is quite significant: the spaces of a building construction (model) can be thought of as nodes in a heat conducting network.

 equation model Thus the heat conduction model, otherwise only describable with partial differential equations, can be mathematically defined as a relatively simple, linear system of equations with a given conductance matrix. Furthermore, only the thermal coupling between spaces which interchange heat directly through the building component ("neighbouring spaces") is of practical effect; coupling between indirectly connected spaces is generally negligible. boundary conditions As the equation above shows, in addition to the appropriate value in the conductance matrix, either air temperature or heating load must be defined for each space of the model (evaluation boundary conditions) in order to attain a complete description of a particular heat flow situation.

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