The Mars Helicopter will be a technology demonstration conducted during the Mars 2020 mission. The primary mission objective is to achieve several 90-second flights and capture visible light images via forward and nadir mounted cameras. These flights could possibly provide reconnaissance data for sampling site selection for other Mars surface missions. The helicopter is powered by a solar array, which stores energy in secondary batteries for flight operations, imaging, communications, and survival heating. The helicopter thermal design is driven by minimizing survival heater energy while maintaining compliance with allowable flight temperatures in a variable thermal environment. Due to the small size of the helicopter and its complex geometries, along with the fact that it operates with very low power and small margins, additional care had to be paid while planning thermal tests and designing the thermal system. A Thermal Desktop® model has been developed to predict the thermal system’s performance. A reduced-order model (ROM) created with the Veritrek software has been utilized to explore the sensitivities of the thermal system’s drivers, such as electronics dissipations, gas gaps, heat transfer coefficients, etc., as well as to assess and verify the final thermal design. This paper presents the performance of the Veritrek software products and the details of the ROM creation process. The results produced by Veritrek were utilized to study the effect of the major thermal design drivers and Mars environment on the Mars Helicopter in as little as 10 days, an effort that would have taken over 4 months using traditional thermal analysis techniques.

Publication: 2018-assessmentofthemarshelicopterthermaldesignsensitivitiesusingtheveritreksoftware.pdf

Source: TFAWS 2018

Author: Stefano Cappucci, Michael T. Pauken, Jacob A. Moulton, Derek W. Hengeveld

Year: 2018

Content Tags: third-party software, heater, emissivity, absortivity, conduction, heat loads, convection heat transfer, sweep, design space scanning, output, robust engineering, validation, design optimization

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.

Publication: optiOpt-ICES2002a.pdf

Source: Semi-Therm

Author: B. Cullimore, T. Panczak, J. Baumann, Dr. Victor Genberg, Mark Kahan

Year: 2002

Content Tags: finite element, finite elements, finite difference, parametric, conductance, contact conductance, design optimization, robust design, optical, registers, radiation, dynamic SINDA, dynamic mode

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 isothermality 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.

Publication: optiOpt-ICES2002b.pdf

Source: ICES

Author: B. Cullimore, T. Panczak, J. Baumann

Year: 2002

Content Tags: concurrent engineering, design optimization, parametric, robust design, design variables

Traditionally, the preliminary thermal design is behind the mechanical and electrical spacecraft design. Many factors contribute to this including a lack of detailed physical characteristics of the spacecraft and knowledge of the distribution of the thermal loads within the spacecraft. Therefore, the thermal design typically reacts to the mechanical and electrical designs. The thermal analyst gets a configuration and then tries to wrap an acceptable solution around it. The analyst relies on years of experience and trial and error to determine the appropriate design cases and create a thermal design. Depending on the experience level of the engineer, several iterations may be necessary to determine the worst-case design points and an acceptable thermal design.

Suppose analysis tools were available that would allow the thermal engineer to rapidly produce preliminary designs and weave the thermal design requirements such as thermal radiator size, preferred radiator location and heat load location into the overall spacecraft design. The result would be a more integrated spacecraft thermal design completed in less time using less of the spacecraft resources.

Advances in thermal analysis software provide the tools for the thermal engineer to perform preliminary analyses more quickly and accurately than ever before. The result is that the thermal engineer can have a greater influence on the spacecraft design process.

Publication: 2004-01-2273v001.pdf

Source: SAE Technical Paper Series

Author: D. Martin

Year: 2004

Content Tags: concurrent design, concurrent engineering, parametric, design-optimization, radiator

Loss in optical fiber coupling efficiency and transmission are computed for a telecommunication optical circulator. Optical performance degradation is due to thermally induced optical errors in the two beam splitter cubes. The computation of the optical errors is discussed for two materials and the effects illustrated. Bulk volumetric absorption of the incident laser radiation from the input optical fiber and surface absorption via the coatings on the beam splitter interface generate temperature gradients. Loss in optical fiber coupling efficiency is produced by wavefront error caused by thermal expansion effects, and refractive index changes with temperature and stress. Transmission loss in the optical circulator is caused by polarization errors generated by the effects of stress birefringence. The optical errors were computed using temperatures generated from a Thermal Desktop model and displacements and stresses generated by a MSC/Nastran finite element model. The optical errors were imposed upon a Code V optical model to compute loss in fiber coupling efficiency and transmission in the optical circulator.

Publication: WFE_Polarization_Errors_SPIE00.pdf

Source:

Author: K. Doyle and B. Bell

Year: 2005

Content Tags: optical, optical properties, material properties, expansion, thermophysical properties, Monte Carlo, radiation analysis groups, emissivity, finite element, finite elements

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.

Publication: TFAWS07-1013.pdf

Source: TFAWS

Author: Eric T. Malroy

Year: 2007

Content Tags: transient, third-party software, user-defined Fortran array, radiation analysis groups, surface elements, radiation, radiation calculations, case set manager, user-defined Fortran arrays (UDFAs), submodels, radks

Complex products are best developed in a collaborative design environment where engineering data and CAD/CAE results can be shared across engineering discipline boundaries within a common software interface. A new software tool that allows Electro-Optical (EO) sensors to be developed in this manner has been used to conduct an integrated Structural/Thermal/Optical (STOP) analysis of a critical lens subassembly in a flight payload. This paper provides a description of the software environment and a summary of the technical results that were produced with it.

Publication: SPIE_August2009_Collaborative_Design_of_EO_Sensors_final.pdf

Source: The Aerospace Corporation

Author: Jason Geis, Jeff Lang, Leslie Peterson, Francisco Roybal, David Thomas

Year: 2009

Content Tags: concurrent engineering, concurrent design, third-party software, mesh, finite element, mashing, parametric, material properties, optical properties, boundary conditions, conductance, structural, thermocouples, transient

The United States Air Force and commercial aerospace industry recognize the importance of moving towards smaller, better, and cheaper spacecraft to support the nation’s increasing dependence on space-based technologies. Whether large or small, all spacecraft will require the same basic bus systems and environmental protection, simply scaled to fit the mission. The varying thermal environment in space is particularly important to spacecraft design and operation because of its affect on hardware performance and survivability. The Adaptive Thermal Modeling Architecture (ATMA) discussed in this thesis is meant to bridge the gap between the commercially available thermal modeling tools used for larger, more expensive satellites, and the low-fidelity algorithms and techniques used for simple first order analysis.

The ATMA consists of the MATLAB based Adaptive Thermal Modeling Tool (ATMT) and its user’s manual, as well as the process by which an inexperienced engineer can quickly and accurately perform on-orbit thermal trades studies for a range of space applications. The ATMA tools and techniques have been validated with an industry standard thermal modeling program (Thermal Desktop) and correlated to thermal test data taken from MIT’s CASTOR nanosatellite. The concepts derived and evaluated within ATMA can be extended to a variety of aerospace modeling applications. The ATMT program and modeling architecture are currently being utilized by members of MIT’s Space Engineering Academy (SEA) and undergraduate satellite team as well as the U.S. Air Force Academy’s FalconSAT-6 program.

Publication: SM-2010-RichmondJohn.pdf

Source:

Author: 2Lt. John Anger Richmond, USAF, Colonel John Keesee, USAF Retired

Year: 2010

Content Tags: model correlation, orbit, third-party software, radiation, material properties, surface, meshing, validation, conductance

This paper summarizes the thermal math model correlation effort for the Fast Affordable Science and Technology SATellite (FASTSAT-HSV01), which was designed, built and tested by NASA's Marshall Space Flight Center (MSFC) and multiple partners. The satellite launched in November 2010 on a Minotaur IV rocket from the Kodiak Launch Complex in Kodiak, Alaska. It carried three Earth science experiments and two technology demonstrations into a low Earth circular orbit with an inclination of 72° and an altitude of 650 kilometers. The mission has been successful to date with science experiment activities still taking place daily. The thermal control system on this spacecraft was a passive design relying on thermo-optical properties and six heaters placed on specific components. Flight temperature data is being recorded every minute from the 48 Resistance Temperature Devices (RTDs) onboard the satellite structure and many of its avionics boxes. An effort has been made to correlate the thermal math model to the flight temperature data using Cullimore and Ring's Thermal Desktop and by obtaining Earth and Sun vector data from the Attitude Control System (ACS) team to create an “as-flown” orbit. Several model parameters were studied during this task to understand the spacecraft's sensitivity to these changes. Many “lessons learned” have been noted from this activity that will be directly applicable to future small satellite programs.

Publication: TFAWS2011-PT-008.pdf

Source: TFAWS

Author: Callie McKelvey

Year: 2011

Content Tags: orbit, model correlation, optical properties, thermophysical properties, radiator, emissivity, material properties, steady state, transient, resistive heating, albedo, conductance, convergence, parametric

SINDA/FLUINT (Ref 1-7) is the NASA-standard heat transfer and fluid flow analyzer for thermal control systems. Because of its general formulation, it is also used in other aerospace specialties such as environmental control (ECLSS) and liquid propulsion, and in terrestrial industries such as electronics packaging, refrigeration, power generation, and transportation industries.

SINDA/FLUINT is used to design and simulate thermal/fluid systems that can be represented in networks corresponding to finite difference, finite element, and/or lumped parameter equations. In addition to conduction, convection, and radiation heat transfer, the program can model steady or unsteady single- and two-phase flow networks.

C&R’s SinapsPlus® is a complete graphical user interface (preand postprocessor) and interactive model debugging environment for SINDA/FLUINT (Ref 8, 9). SinapsPlus also supports the C language in addition to the traditional choice of Fortran for concurrently executed user logic.

This paper describes revolutionary advances in SINDA/FLUINT, the NASA-standard heat transfer and fluid flow analyzer, changing it from a traditional point-design simulator into a tool that can help shape preliminary designs, rapidly perform parametrics and sensitivity studies, and even correlate modeling uncertainties using available test data.

Innovations include the incorporation of a complete spreadsheet-like module that allows users to centralize and automate model changes, even while thermal/fluid solutions are in progress. This feature reduces training time by eliminating many archaic options, and encourages the performance of parametrics and other what-if analyses that help engineers develop an intuitive understanding of their designs and how they are modeled.

The more revolutionary enhancement, though, is the complete integration of a nonlinear programming module that enables users to perform formal design optimization tasks such as weight minimization or performance maximization. The user can select any number of design variables and may apply any number of arbitrarily complex constraints to the optimization. This capability also can be used to find the best fit to available test data, automating a laborious but important task: the correlation of modeling uncertainties such as optical properties, contact conductances, as-built insulation performance, natural convection coefficients, etc.

Finally, this paper presents an overview of related developments that, coupled with the optimization capabilities, further enhance the power of the whole package.

Publication: sfpaper.pdf

Source: IECEC

Author: Brent A. Cullimore

Year: 1998

Content Tags: design optimization, model correlation, parameterize, parametric, two-phase flow, two-phase, optical properties, submodels, registers, expression editor, user logic, concurrent engineering, concurrent design, dynamic mode, dynamic SINDA, specific heat, solver, constraint, slip flow, Phenomena, capillary systems, mixtures, working fluids, nonequilibrium, vapor compression, uncertainty, uncertainty analysis

This paper describes revolutionary advances in SINDA/FLUINT, the NASA-standard heat transfer and fluid flow analyzer, changing it from a traditional point-design simulator into a tool that can help shape preliminary designs, rapidly perform parametrics and sensitivity studies, and even correlate modeling uncertainties using available test data.

Innovations include the incorporation of a complete spreadsheet-like module that allows users to centralize and automate model changes, even while thermal/fluid solutions are in progress. This feature reduces training time by eliminating many archaic options, and encourages the performance of parametrics and other what-if analyses that help engineers develop an intuitive understanding of their designs and how they are modeled.

The more revolutionary enhancement, though, is the complete integration of a nonlinear programming module that enables users to perform formal design optimization tasks such as weight minimization or performance maximization. The user can select any number of design variables and may apply any number of arbitrarily complex constraints to the optimization. This capability also can be used to find the best fit to available test data, automating a laborious but important task: the correlation of modeling uncertainties such as optical properties, contact conductances, as-built insulation performance, natural convection coefficients, etc.

Finally, this paper presents an overview of related developments that, coupled with the optimization capabilities, further enhance the power of the whole package.

Publication: sf981574.pdf

Source: ICES 1998

Author: Brent A. Cullimore

Year: 1998

Content Tags: design optimization, model correlation, parameterize, parametric, two-phase flow, two-phase, optical properties, submodels, registers, expression editor, user logic, concurrent engineering, concurrent design, dynamic mode, dynamic SINDA, specific heat, solver, constraint, slip flow, Phenomena, capillary systems, mixtures, working fluids, nonequilibrium, vapor compression, uncertainty, uncertainty analysis

Optimization and Automated Data Correlation in the NASA Standard Thermal/Fluid System Analyzer

SINDA/FLUINT (Ref 1-7) is the NASA-standard heat transfer and fluid flow analyzer for thermal control systems. Because of its general formulation, it is also used in other aerospace specialties such as environmental control (ECLSS) and liquid propulsion, and in terrestrial industries such as electronics packaging, refrigeration, power generation, and transportation industries. SINDA/FLUINT is used to design and simulate thermal/fluid systems that can be represented in networks corresponding to finite difference, finite element, and/or lumped parameter equations. In addition to conduction, convection, and radiation heat transfer, the program can model steady or unsteady single- and two-phase flow networks. CRTech's SinapsPlus® is a complete graphical user interface (preand postprocessor) and interactive model debugging environment for SINDA/FLUINT (Ref 8, 9). SinapsPlus also supports the C language in addition to the traditional choice of Fortran for concurrently executed user logic. This paper describes revolutionary advances in SINDA/FLUINT, the NASA-standard heat transfer and fluid flow analyzer, changing it from a traditional point-design simulator into a tool that can help shape preliminary designs, rapidly perform parametrics and sensitivity studies, and even correlate modeling uncertainties using available test data. Innovations include the incorporation of a complete spreadsheet-like module that allows users to centralize and automate model changes, even while thermal/fluid solutions are in progress. This feature reduces training time by eliminating many archaic options, and encourages the performance of parametrics and other what-if analyses that help engineers develop an intuitive understanding of their designs and how they are modeled. The more revolutionary enhancement, though, is the complete integration of a nonlinear programming module that enables users to perform formal design optimization tasks such as weight minimization or performance maximization. The user can select any number of design variables and may apply any number of arbitrarily complex constraints to the optimization. This capability also can be used to find the best fit to available test data, automating a laborious but important task: the correlation of modeling uncertainties such as optical properties, contact conductances, as-built insulation performance, natural convection coefficients, etc. Finally, this paper presents an overview of related developments that, coupled with the optimization capabilities, further enhance the power of the whole package.

Publication: sfpaper.pdf

Source: IECEC 1998

Author: Brent A. Cullimore

Year: 1998

Content Tags:

Recent years have witnessed more improvement to the SINDA/FLUINT thermohydraulic analyzer than at any other time in its long history. These improvements have included not only expansions in analytic power, but also the additions of high-level modules that offer revolutions in thermal/ fluid engineering itself.

One such high-level module, “Reliability Engineering,” is described in this paper. Reliability Engineering means considering tolerances in design parameters, uncertainties in environments, uncertainties in application (e.g. usage scenarios), and variations in manufacturing as the stochastic phenomena that they are. Using this approach, the probability that a design will achieve its required performance (i.e., the reliability) is calculated, providing an assessment of risk or confidence in the design, and quantifying the amount of over- or under-design present.

The design to be evaluated for reliability will likely have been produced using traditional methods. Possibly, the design was generated using the Solver optimizer, another high-level module available in SINDA/FLUINT. Using design optimization, the user quantifies the goals that make one design better than another (mass, efficiency, etc.), and specifies the thresholds or requirements which render a given design viable or useless (exceeding a performance limit, etc.). SINDA/FLUINT then automatically searches for an optimal design.

Robust Design means factoring reliability into the development of the design itself: designing for a target reliability and thereby avoiding either costly over-design or dangerous under-design in the first place. Such an approach eliminates a deterministic stack-up of tolerances, worst-case scenarios, safety factors, and margins that have been the traditional approaches for treating uncertainties.

In any real system or product, heat transfer and fluid flow play a limited role: there are many other aspects to a successful design than the realm of thermal/fluids that is encompassed by SINDA/FLUINT. Therefore, this paper concludes with brief descriptions of methods for performing interdisciplinary design tasks.

Publication: releng1.pdf

Source: CRTech White Paper

Author: Brent A. Cullimore

Year: 2000

Content Tags: design optimization, reliability engineering, robust design, constraints, boundary conditions, concurrent design, concurrent engineering, batteries, flow control, orifices, radiator, registers, two-phase flow, solver, model correlation, dynamic SINDA, dynamic mode, variables, Monte Carlo, material properties, third-party software, uncertainty analysis, uncertainty

Publication: NewOsummary.pdf

Source: ASME

Author: Brent A. Cullimore

Year: 2001

Content Tags: model calibration, CFD, parametric, design optimization, design synthesis, Phenomena

Nonlinear Programming Applied to Calibrating Thermal and Fluid Models to Test Data (Semi-Therm 2002)

Publication: calibrating.pdf

Source: Semi-Therm

Author: Jane Baumann, Brent Cullimore

Year: 2002

Content Tags: model calibration, model correlation, condenser, condensers, validation, design optimization, parametric

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. Previous enabling technologies are first described, then examples and repercussions of current capabilities are presented, and finally in-progress and future technologies are listed.

Publication: COMAPI-ICES.pdf

Source: ICES

Author: B. Cullimore, S. G. Ring, J. Baumann

Year: 2004

Content Tags: parametric, parameterize, dynamic mode, dynamic SINDA, third-party software

The loop heat pipe (LHP) is known to have a lower limit on input power. Below this limit the system may not start properly creating the potential for critical payload components to overheat. The LHP becomes especially susceptible to these low power start-up failures following diode operation, intentional shut-down of the device, or very cold conditions. These limits are affected by the presence of adverse tilt, mass on the evaporator, and noncondensible gas in the working fluid. Based on analytical modeling correlated to startup test data, this paper will describe the key parameters driving this low power limit and provide an overview of the methodology for predicting a “safe start” design envelope for a given system and loop design. The amount of incipient superheat was found to be key to the enveloping procedure. Superheat levels have been observed to vary significantly based on evaporator design and even from unit to unit of identical designs. Statistical studies of superheat levels and active measures for limiting superheat should be addressed by both the hardware vendors and the system integrators.

Publication: AIAA2000-2285.PDF

Source: AIAA Thermophysics

Author: Jane Baumann, Brent Cullimore, Jay Ambrose, Eva Buchan, Brois Yendler

Year: 2000

Content Tags: Loop Heat Pipe, LHP, noncondensable gas, start-up, evaporator, wicks, parametric, Phenomena, working fluid, model correlation, parameter, heat loads, compensation chamber, transient, capillary systems

Modeling to predict the condition of cryogenic propellants in an upper stage of a launch vehicle is necessary for mission planning and successful execution. Traditionally, this effort was performed using custom, in-house proprietary codes, limiting accessibility and application. Phenomena responsible for influencing the thermodynamic state of the propellant have been characterized as distinct events whose sequence defines a mission. These events include thermal stratification, passive thermal control roll (rotation), slosh, and engine firing. This paper demonstrates the use of an off the shelf, commercially available, thermal/fluid-network code to predict the thermodynamic state of propellant during the coast phase between engine firings, i.e. the first three of the above identified events. Results of this effort will also be presented.

Publication: AIAA-2006-50513.pdf

Source: AIAA

Author: P. Schallhorn, D. Michael Campbell, Sukhdeep Chase, Jorge Piquero, Cindy Fortenberry, Xiaoyi Li, Lisa Grob

Year: 2006

Content Tags: Optimization, parametric, radiation, radiation analysis groups, conduction, evaporation, CFD, convergence, structural, heat flux, thermal stratification, register, two-phase, slosh, wall, splash

Publication: TFAWS-08-1009_presentation.pdf

Source: TFAWS Short Course

Author: Paul Schallhorn, D. Michael Campbell, Sukhdeep Chase, Jorge Piquero, Cindy Fortenberry, Xiaoyi Li, Lisa Grob

Year: 2008

Content Tags: CFD, two-phase, slosh, thermal stratification, diffusion, boundary layer, twinned tanks, boiling

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. In addition to combining the output from multiple programs, current processes often involve the user inputting various hand calculations into the math model to account for MLI/Insulation and contact conductance between entities. These calculations are not only tedious to make, but users often forget to update them when the geometry is changed.

Several new features of Thermal Desktop are designed to automate some of the tedious tasks that thermal engineers now practice. To start with, Thermal Desktop is a single program that does radiation analysis, generates conduction/capacitance data and automates the building of a SINDA/FLUINT model to solve for temperatures. Some of these new features of Thermal Desktop are Radiation Analysis Groups, Property Aliases, MLI/Insulation Objects, Contact Conductance Objects, Model Browser, and the Case Set Manager.

This paper describes the application and benefits of Thermal Desktop along with other unique features used to automate the thermal analysis process.

Publication: tDesktop99.pdf

Source: ICES

Author: Mark J. Welch, Tim Panczak

Year: 1999

Content Tags: radiation analysis groups, property, alias, multi-layer insulation, mli, insulation, contact conductance, model browser, case set manager

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. Geometric features, optical and material properties, and orbital elements may all be specified using user-defined variables and expressions. Furthermore, these variables may be automatically modified by Thermal Desktop’s optimization capabilities in order to satisfy user-defined design goals, or for correlating thermal models to test data. By sharing the set of design variables among analysis models spanning multiple disciplines, further integrated analysis and design may be accomplished. The framework into which Thermal Desktop is embedded in order to support an integrated Thermal/Structural/Optical design, analysis, and optimization system is also presented.

Publication: 00ICES-266.pdf

Source: ICES

Author: Timothy D. Panczak, Brent A. Cullimore

Year: 2000

Content Tags: concurrent engineering, parametric, parameterize, register, registers, dynamic mode, dynamic SINDA, symbol manager, expression editor, expressions, design optimization, orbital heating, model correlation, solver, optical properties, heat pipes, symbol, variables, case set manager, properties, structural