3.2.2. Thermal Solvers

The basic principle for all thermal solvers in V-HAB is the equation:

With the transfer heatflow between two capacities (which is the thermal representation of phases) $//<![CDATA[ \begin{array}{l}\dot Q\end{array} //]]>$ and the temperature difference between two capacities $//<![CDATA[ \begin{array}{l}\Delta T\end{array} //]]>$ as well as the overall thermal resistance of the branch connecting the two capacities $//<![CDATA[ \begin{array}{l}R\end{array} //]]>$. For information regarding thermal resistance calculations and modelling, please view the available literature (e.g. "Wärmeübertragung" by W. Polifke and J. Kopitz ISBN-13: 9783863266707). The thermal resistance $//<![CDATA[ \begin{array}{l}R\end{array} //]]>$ is represented in V-HAB through conductors inside the thermal branches. The available standard conductors are

• conductive
• convective
• fluidic (mass bound thermal energy transfer)
• radiative

For example, the following figure may show a V-HAB model with four capacities $//<![CDATA[ \begin{array}{l}C_{cap,i}\end{array} //]]>$ which each have the temperature $//<![CDATA[ \begin{array}{l}T_i\end{array} //]]>$. This model could for example be a rod a in space, where the capacities $//<![CDATA[ \begin{array}{l}C_{cap,1}\end{array} //]]>$ to $//<![CDATA[ \begin{array}{l}C_{cap,3}\end{array} //]]>$ represent the rod and $//<![CDATA[ \begin{array}{l}C_{cap,4}\end{array} //]]>$ represents space. Therefore, conductive resistances ($//<![CDATA[ \begin{array}{l}R_{c,i}\end{array} //]]>$) connect the different capacities of the rod while radiative resistances ($//<![CDATA[ \begin{array}{l}R_{r,i}\end{array} //]]>$) connect each capacity of the rod to space. This is a common approach to thermal modelling which is also called a lumped parameter model (see e.g. ESATAN).

The thermal capacity of each "lump" is calculated based on the mass in the corresponding phase. The thermal resistances are calculated based on the implemented conductors which the user has to define to perform the correct calculations.