Goddard Space Flight Center (GSFC) has been developing a framework of additional analysis capabilities to aid in the verification, development, and execution of thermal models using the OpenTD Application Programming Interface (API). This paper provides a brief overview of the data structures, properties, methods, and relationships between the objects accessible through the current API and describes some of the algorithms necessary to implement the desired functions at GSFC. Some example code snippets are also provided to aid potential users in the development of their own utilities.
With the release of Thermal Desktop 6.0, users now had the ability to interface with some of the many elements and constructs of a Thermal Desktop model through external applications developed using the TD API (Application Programming Interface). This file allows applications to be developed in the .NET framework and interface to a number of object types within a Thermal Desktop model. The release of 6.1 expands the subset of objects able to be manipulated and now includes the raw geometrical information of surfaces. With the release of 6.1, the API was now referred to as OpenTD.
This paper provides an overview of the non-grey radiation modeling capabilities of Cullimore and Ring’s Thermal Desktop® Version 4.8 SindaWorks software. The non-grey radiation analysis theory implemented by Sindaworks and the methodology used by the software are outlined.
Thermal Desktop has the capability of modeling free molecular heat transfer (FMHT), but limitations are observed when working with large models during transient operation. To overcome this limitation, a MatLab program was developed that processes the Thermal Desktop free molecular conductors. It sets up the logic and arrays for the Thermal Desktop GUI used by SINDA/FLUINT. The theory of free molecular heating is presented along with the process required to setup the conductors, arrays, logic and Fortran subroutines for FMHT modeling in Thermal Desktop.
Thermal analysis is typically executed with multiple tools in a series of separate steps for performing radiation analysis, generating conduction and capacitance data, and for solving temperatures. This multitude of programs often leads to many user files that become unmanageable with their multitude, and the user often looses track as to which files go with which cases.
Thermal analysis is typically performed using a point design approach, where a single model is analyzed one analysis case at a time. Changes to the system design are analyzed by updating the thermal radiation and conduction models by hand, which can become a bottleneck when attempting to adopt a concurrent engineering approach. This paper presents the parametric modeling features that have been added to Thermal DesktopTM to support concurrent engineering. The thermal model may now be characterized by a set of design variables that are easily modified to reflect system level design changes.
Most radiation analysis tools in use in the aerospace industry assume that grey conditions hold. That is, over the range of temperatures considered, optical properties are assumed to have a constant value with respect to wavelength. This reasonable approximation for systems that are near room temperature may show significant error at temperature extremes, particulary for conductive materials at cryogenic temperatures. Other areas where non-grey analysis may be appropriate is in furnace and lamp design, and in systems with specialized optical filters such as thermalphotovoltaics.