Search Results

This paper describes readily available techniques for automating the search for worst-case (e.g., “hot case”, “cold case”) design scenarios using only modest computational resources. These methods not only streamline a repetitive yet crucial task, they usually produce better results. The problems with prior approaches are summarized, then the improvements are demonstrated via a simplified example that is analyzed using various approaches. Finally, areas for further automation are outlined, including attacking the entire design problem at a higher-level.

Active cooling technologies such as heat pipes, loop heat pipes (LHPs), thermosyphons, loop thermosyphons (LTSs), and pumped single- or two-phase coolant loops require specialized modeling treatment. However, these 1D ducted systems are largely overlooked in 3D thermal modeling tools. The increasing popularity of CFD and FEM models and generation of analysis data from 3D CAD data are strong trends in the thermal analysis community, but most software answering such demands has not provided linear modeling elements appropriate for the simulation of heat pipes and coolant loops. This paper describes techniques whereby CAD line-drawing methods can be used to quickly generate 1D fluid models of heat pipes and coolant loops within a 3D thermal model.

Automated design space exploration was implemented and demonstrated in the form of the multidisciplinary optimization of the design of a space-based telescope. Off-the-shelf software representing the industry standards for thermal, structural, and optical analysis were employed. The integrated thermal/structural/optical models were collected and tasked with finding an optimum design using yet another off-the-shelf program. Using this integrated tool, the minimum mass thermal/structural design was found that directly satisfied optical performance requirements without relying on derived requirements such as isother-mality and mechanical stability. Overdesign was therefore avoided, and engineering productivity was greatly improved. This ambitious project was intended to be a pathfinder for integrated design activities. Therefore, difficulties and lessons learned are presented, along with recommendations for future investigations.

Thankfully, the age of stand-alone fixed-input simulation tools is fading away in favor of more flexible and integrated solutions. “Concurrent engineering” once meant automating data translations between monolithic codes, but sophisticated users have demanded more native integration and more automated tools for designing, and not just evaluating point designs. Improvements in both interprocess communications technology and numerical solutions have gone a long way towards meeting those demands. This paper describes a small slice of a larger on-going effort to satisfy current and future demands for integrated multidisciplinary tools that can be highly customized by end-users or by third parties. Specifically, the ability to integrate fully featured thermal/fluid simulations into Microsoft’s Excel™ and other software is detailed. Users are now able not only to prepare custom user interfaces, they can use these codes as portals that allow integration activities at a larger scale.

The NASA-standard thermohydraulic analyzer, SINDA/FLUINT (Ref 1), has been used to model various aspects of loop heat pipe* (LHP) operation for more than 12 years. Indeed, this code has many features that were specifically designed for just such specialized tasks, and is unique in this respect. Furthermore, SINDA is commonly used at the vehicle (integration) level; has a large user base both inside and outside the aerospace industry; has several graphical user interfaces, preprocessors, postprocessors; has strong links to CAD and structural tools; and has built-in optimization, data correlation, parametric analysis, reliability estimation, and robust design tools. Nonetheless, the LHP community tends to ignore these capabilities, yearning instead for “simpler” methods.

Structural and thermal engineers currently work independently of each other using unrelated tools, models, and methods. Without the ability to rapidly exchange design data and predicted performance, the achievement of the ideals of concurrent engineering is not possible. Thermal codes have been unable to exploit the geometric information in structural models and the CAD design database, and do not facilitate transfer of temperature data to other discipline’s analysis models. This paper discusses the key features in Thermal Desktop for supporting integrated thermal/structural analysis. Approaches to thermal modeling in an integrated analysis environment are discussed along with Thermal Desktop’s data mapping algorithm for exporting temperature data on to structural model grid points.

Productivity bottlenecks for integrated thermal, structural, and optical design activities were identified and systematically eliminated, making possible automated exchange of design information between different engineering specialties. The problems with prior approaches are summarized, then the implementation of the corresponding solutions is documented. Although the goal of this project was the automated evaluation of coupled thermal/optical/structural designs, significant process improvements were achieved for subset activities such as stand-alone thermal, thermal/ structural, and structural/optical design analysis.