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. Following the overview are descriptions and algorithm methodologies of the new capabilities added to the GSFC framework, including: a new PI heater/controller approach for improved steady state predictions, selective copying of symbol over-rides from one source CaseSet to destination CaseSet(s), comparison of submodel object counts between a source and destination model to verify model integration, comparison of thermo-optical and thermo-physical properties between models, and improved display of extracted thermo-optical and thermo-physical properties for documentation.

Publication: ICES-2022-396.pdf

Source: ICES

Author: Hume L. Peabody, Eric Yee

Year: 2022

Content Tags: third-party software, OpenTD, heater, surface properties, parametric, parameterize, optical properties, thermophysical properties, symbols, case set manager, submodels, pid controller, heat loads, API

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 discusses some of the utilities and capabilities developed using the OpenTD API at the NASA Goddard Space Flight Center. These include utilities to help with configuration control of models and case sets, addition of logic to better process heater performance, and a methodology implemented to allow for submodel level processing of radiation couplings to include smaller radks where needed in a cryogenic region without using the same criteria for the warmer portions of the model. This last utility is targeting a reduction in run time without sacrificing accuracy. Lastly, some lessons learned, work-arounds, and wishes for the next release of the OpenTD API are also presented.

Publication: ICES-2020-297.pdf

Source: ICES

Author: Hume L. Peabody

Year: 2020

Content Tags: third-party software, OpenTD, heater, Monte Carlo, ray tracing, orbital heating, surface properties, parametric, parameterize, optical properties, thermophysical properties, symbols, absorptivity, mli, multi-layer insulation, case set manager, API

Advancements in satellite technologies are increasing the power density of electronics and payloads. When the power consumption increases within a limited volume, waste heat generation also increases and this necessitates a proper and efficient thermal management system. Mostly, micro and nanosatellites use passive thermal control methods because of the low cost, no additional power requirement, ease of implementation, and better thermal performance. Passive methods lack the ability to meet certain thermal requirements on larger and smaller satellite platforms. This work numerically studies the performance of some of the passive thermal control techniques such as thermal straps, surface coatings, multi-layer insulation (MLI), and radiators for a 6U small satellite configuration carrying a mid-wave infrared (MWIR) payload whose temperature needs to be cooled down to 100K. Infrared (IR) imagers require low temperature, and the level of cooling is entirely dependent on the infrared wavelengths. These instruments are used for various applications including Earth observations, defence, and imaging at IR wavelengths. To achieve these low temperatures on such instruments, a micro-cryocooler is considered in this study. Most of the higher heat dissipating elements in the satellite are mounted to a heat exchanger plate, which is thermally coupled to an external radiator using thermal straps and heat pipes. The effects of the radiator size, orbital inclinations, space environments, satellite attitude with respect to the sun, and surface coatings are discussed elaborately for a 6U satellite configuration.

Publication: applsci-12-02858.pdf

Source: Applied Sciences, 2022, 12(6), 2858

Author: Shanmugasundaram Selvadurai, Amal Chandran, David Valentini, and Bret Lamprecht

Year: 2022

Content Tags: mli, multi-layer insulation, surface elements, surface coating a mesh, radiator, phase change material, thermocouples, finite element, finite elements, convergence, material properties, properties, CCHP

Understanding fluid behavior in microgravity is essential to further development of cryogenic storage in space environments. The Reduced Gravity Cryogenic Transfer project is designed to investigate tank chilldown in a microgravity environment onboard a parabolic flight. This work focused on examining the feasibility of chilling down different tank sizes using liquid nitrogen within the time constraints of the flight. Thermal models of four different tank geometries were made using Thermal Desktop and SINDA/FLUINT. The tank wall was modeled as a series of solid finite elements while the fluid inside the tank was represented by twinned liquid and vapor lumps. Fluid was injected into the bottom of the tank to simulate a dip tube and vented out of the top of the tank. The tank wall temperature as well as the state of the fluid inside the tank was tracked throughout the simulation. Several different cases were run with different chilldown operations for each tank model using a combination of charge, hold, and vent cycles. The average wall temperature, propellant mass savings and thermal efficiency of each of the four tanks were compared under seven different chilldown operations. A recommendation was made for the receiver tank size based on these parameters.

Publication: TFAWS2021-CT-01.pdf

Source: TFAWS 2021

Author: Erin M. Tesny, Daniel M. Hauser, Jason W. Hartwig

Year: 2021

Content Tags: two-phase, twinned tanks, chilldown, solid finite elements, finite elements, finite element, parametric analysis, parametric, material properties

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

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

A method for determining margins in conceptual-level design via probabilistic methods is described. The goal of this research is to develop a rigorous foundation for determining design margins in complex multidisciplinary systems. As an example application, the investigated method is applied to conceptual-level design of the Mars Exploration Rover (MER) cruise stage thermal control system. The method begins with identifying a set oftradable system-level parameters. Models that determine each of these tradable parameters are then created. The variables of the design are classified and assigned appropriate probability density functions. To characterize the resulting system, a Monte Carlo simulation is used. Probabilistic methods can then be used to represent uncertainties in the relevant models. Lastly, results of this simulation are combined with the risk tolerance of thermal engineers to guide in the determination of margin levels. The method is repeated until the thermal engineers are satisfied with the balance of system-level parameter values. For the thermal control example presented, margins for maximum component temperatures, dry mass, power required, schedule, and cost form the set of tradable system-level parameters. Use of this approach for the example presented yielded significant differences between the calculated design margins and the values assumed in the conceptual design of the MER cruise stage thermal control system.

Publication: 04ICES-239_v3.pdf

Source: ICES

Author: D. Thunnissen, G. Tsuyuki

Year: 2004

Content Tags: system-level modeling, uncertainty, uncertainty analysis, parametric, Monte Carlo, 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

Thermoelectric couples are solid-state devices capable of generating electrical power from a temperature gradient (known as the Seebeck effect) or converting electrical energy into a temperature gradient (known as the Peltier effect). Thermoelectric coolers, being solid state devices, have no moving parts which makes them inherently reliable and ideal for cooling components in a system sensitive to mechanical vibration. The ability to use TECs to heat as well as cool makes them suitable for applications requiring temperature stabilization of a device over a specified temperature range. Although these devices have been around for years, they are gaining popularity in the aerospace industry for providing temperature control within optical systems and for loop heat pipes.

Historically, modeling and sizing of thermoelectric coolers was left to the analyst to work off-line from the modeling task. The analyst would then need to create his own logic in SINDA for simulating the cooler. This presenation will demonstrate how thermoelectric coolers are now easily modeled using off-the-shelf simulation routines and 3D user interfaces. The analytical demonstration includes sizing of a cooler for a specific application based on area, temperature requirements and heat load through a series of parametric analyses. Cooler performance will also be characterized at the device and system level.

Publication: ModelingAndSizingTECs.pps

Source: Aerospace Thermal Control Workshop

Author: Jane Baumann

Year: 2006

Content Tags: cooler, TEC, thermoelectrics, thermoelectric, LHP, Loop Heat Pipe, optical, user logic, parametric, thermostatic, convection heat transfer, expression editor, parameterize, steady state, transient, proportional, design opimization, system-level modeling

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

Publication: TFAWS-08-1018_presentation.pdf

Source: TFAWS

Author: Ruth M. Amundsen, Joe Del Corso

Year: 2008

Content Tags: third-party software, thermal stress, material properties, optical properties, conduction, convection heat transfer, radiation, submodels, radiation analysis groups, expression editor, symbol, symbols, symbol manager, logic manager, logic, user logic, boundary conditions, CFD

The Crew Exploration Vehicle (CEV) is the next generation space vehicle to follow the Space Shuttle. A design with the inclusion of a Composite Pressure Vessel (CPV) has been assessed for its thermal response. The temperature distribution on the CPV that results from the heat produced by internal spacecraft systems and external space environments was calculated as part of a project-level assessment to understand thermomechanical stresses. A finite element translation of the crew module CPV was integrated into an existing CEV Thermal Math Model (TMM) based on the 605 baseline configuration and analyzed for four orbital cases. Steady state temperature profiles were generated based on orbit average heating. Preliminary thermal analysis results suggest that the CPV requires less make-up energy when compared to the baseline aluminum pressure vessel. It is emphasized that only local make-up energy was considered in the study. The make-up energy did not include the zoning configuration that occurs with heaters. This document presents the approach and assumptions used for this thermal assessment.

Publication: TFAWS-08-1007_presentation.pdf

Source: TFAWS

Author: Laurie Y. Carrillo, Ángel R. Álvarez-Hernández, Steven L. Rickman

Year: 2008

Content Tags: finite element, finite elements, orbit, steady state, surface, optical properties, boundary conditions, temperature map, temperature mapping

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

Publication: TFAWS2011-PT-006.pps

Source: TFAWS

Author: Stephen W. Miller, William Q. Walker

Year: 2011

Content Tags: statistical methods, radiator, CAD geometry, radiation, orbit, parameterize, ray tracing, radks, steady state, dynamic mode, dynamic SINDA

Maintaining low temperature payloads through atmospheric reentry and ground recovery is becoming a larger focus in the space program as work in biology, cryogenic and other temperature dependent sciences becomes a higher goal on the International Space Station (ISS) and extraterrestrial surfaces. Paragon analyzes reentry system thermal control, particularly technology regarding small thermally controlled payloads anticipated for use in sample return from the International Space Station.

To minimize system mass and utilize the powerful insulative properties of a hard space vacuum the internal cavity of a small reentry vehicle can be left open. Thermally this causes concern during reentry, as even at very high altitudes there is enough pressure to cause a significant impact on insulation stratagems, such as MLI that rely on a high vacuum. At lower altitudes the vehicle is moving much slower, so the intense heat load of reentry is finished but soak-back from outer heated surfaces to the payload is a significant issue when air is present to facilitate heat transfer between layers. Initial assumptions that the cold temperatures of the upper atmosphere would cause a net cooling affect in the post-reentry times were overturned by a simple analysis set done in Thermal Desktop involving worst and best case scenarios as air starts to enter the vehicle. Additionally, CFD low pressure zones were shown to exist behind the vehicle where it is open to the atmosphere when the vehicle is travelling at extreme reentry speeds. These pressures are not so low however to prevent air from entering the vehicle. The impacts of this now apparent soak back, during the last phases of an atmospheric reentry were investigated leading to the conclusion that analyses of lower atmospheric portions of a reentry are critical to reentry studies and significantly changed the results.

An updated design is theorized using the knowledge gained from the preliminary studies called the Cryogenic Extended Duration and Reentry Thermal Control System (CEDR TCS) and the design is fully passive making it a low-complexity, zero-power system that does not necessitate the use of any consumables. The CEDR TCS uses a two-way pressure relief valve or “breather valve” that would allow the pressures inside and outside the vehicle to equilibrate once a great enough pressure differential is applied. This will allow air to leave while the unit is in space vacuum and prevent air from coming in until much later in the re-entry after much of the reentry heat has had a chance to convect to the upper atmosphere. Through further analysis CEDR is hoped to display a capability of near cryogenic temperatures through an atmospheric reentry and long durations on the ground.

Publication: TFAWS2011-AE-005.pdf

Source: TFAWS

Author: Erika T. Bannon, Jared Leidich, Alex Walker

Year: 2011

Content Tags: mli, multi-layer insulation, heat loads, design optimization, CFD, transient, insulation, model correlation, phase change material, PCM, radiation, sink temperature, heat flux, radks, radiation analysis group, material properties

Advances in computer technologies and manufacturing processes allow creation of highly sophisticated components in compact platform. For example, a small scale satellite, such as the CubeSat, can now be used for scientific research in space rather than big scale project like the International Space Station (ISS). Recently a team of undergraduate and graduate students at SJSU has the opportunity to collaborate on designing and building a miniature size CubeSat with the dimension of 10x10x10 cm. Although the integration of compact electronics allows sophisticated scientific experiments and missions to be carried out in space, the thermal control options for such small spacecraft are limited. For example, because of its small size there is no room for dedicated radiator or insulation panels. To minimize mass of the thermal control system while keeping the electronics at safe operating conditions, this thesis aims at studying the external orbital radiation heat flux the CubeSat is expected to expose to and the steady state heat conduction of the internal electronics. If the operating temperature from these heating conditions causes issue, appropriate thermal control solutions will be presented.

Publication: Dihn.S12.pdf

Source: San José State University

Author: Dai Q. Dinh

Year: 2012

Content Tags: heat flux, orbital heating, steady state, conduction, wall, boundary condition, third-party software, radiation, albedo, material properties, optical properties, parametric

Lithium-ion batteries (LIBs) are replacing the Nickel–Hydrogen batteries used on the International Space Station (ISS). Knowing that LIB efficiency and survivability are greatly influenced by temperature, this study focuses on the thermo-electrochemical analysis of LIBs in space orbit. Current finite element modeling software allows for advanced simulation of the thermo-electrochemical processes; however the heat transfer simulation capabilities of said software suites do not allow for the extreme complexities of orbital-space environments like those experienced by the ISS. In this study, we have coupled the existing thermo-electrochemical models representing heat generation in LIBs during discharge cycles with specialized orbital-thermal software, Thermal Desktop (TD). Our model's parameters were obtained from a previous thermo-electrochemical model of a 185 Amp-Hour (Ah) LIB with 1–3 C (C) discharge cycles for both forced and natural convection environments at 300 K. Our TD model successfully simulates the temperature vs. depth-of-discharge (DOD) profiles and temperature ranges for all discharge and convection variations with minimal deviation through the programming of FORTRAN logic representing each variable as a function of relationship to DOD. Multiple parametrics were considered in a second and third set of cases whose results display vital data in advancing our understanding of accurate thermal modeling of LIBs.

Publication: TD_Application.pdf

Source: Science Direct (Journal of Power Sources)

Author: W. Walker, H. Ardebili

Year: 2014

Content Tags: batteries, orbital heating, orbit, finite element, parametric, thermoelectric, convection heat transfer, variable, user-defined Fortran array, user-defined Fortran arrays (UDFAs)

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:

Publication: NewOsummary.pdf

Source: ASME

Author: Brent A. Cullimore

Year: 2001

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

The major influence on the reliability of electronics is temperature, yet thermal/fluid modeling is plagued with uncertainties and unknowns. Nonetheless, if appropriate values of these unknown parameters are available for any specific electronics package, then its temperature response can be accurately predicted using modern thermal/fluid analysis tools.

Traditionally, uncertainties are dealt with by a combination of testing, safety factors or margins, and worst-case design scenarios. Analyses are performed iteratively in a repetitive “point design evaluation” mode. Computer-based design simulation tools have emphasized increasing detail and fidelity to physical phenomena, seemingly ignoring the fact that the inputs to these simulations are highly uncertain.

This paper describes both current and future methods of dealing with uncertainties in thermal engineering. It introduces advanced tools and alternative methodologies that can automate not only the quantification of reliability, but can also help synthesize designs on the basis of reliability. It advocates using rapid gains in computer speed not to increase the degree of detail in a model, but to help the engineer find a robust design by automating high-level design tasks.

Publication: IPACK2001-15516.pdf

Source: InterPack

Author: Brent A. Cullimore

Year: 2001

Content Tags: parameterize, parametric, contact conductance, design synthesis, Phenomena, robust design, design optimization, design variables, reliability engineering

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

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.

Publication: WorstCase-ICES.pdf

Source: ICES

Author: B. Cullimore

Year: 2003

Content Tags: parametric, model correlation, design optimization, convergence

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 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

Historically, thermal/fluid modeling began as a means of validating and sometimes correcting passively cooled designs that had been proposed by nonspecialists in heat transfer and fluid flow. As dissipation fluxes have risen, and as air cooling reaches the limits of its usefulness, involvement of thermal engineers is required earlier in the design process. Thermal engineers are now commonly responsible for sizing and selecting active cooling components such as fans and heat sinks, and increasingly single and two-phase coolant loops.

Meanwhile, heat transfer and fluid flow design analysis software has matured, growing both in ease of use and in phenomenological modeling prowess. Unfortunately, most software retains a focus on point-design simulations and needs to do a better job of helping thermal engineers not only evaluate designs, but also investigate alternatives and even automate the search for optimal designs.

This paper shows how readily available nonlinear programming (NLP) techniques can be successfully applied to automating design synthesis activities, allowing the thermal engineer to approach the problem from a higher level of automation. This paper briefly introduces NLP concepts, and then demonstrates their application both to a simplified fin (extended surface) as well as a more realistic case: a finned heat sink.

Publication: Optimizing.pdf

Source: ITherm

Author: Brent A. Cullimore

Year: 2002

Content Tags: design optimization, parametric, design synthesis, design variables, variables, sink temperature