Publications
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Assessment of the Mars Helicopter Thermal Design Sensitivities Using the Veritrek Software
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
Thermoelastic Analysis in Design
This study explores the capability of Thermal Desktop to map temperatures from a thermal model to a Nastran model to evalautate thermal stress and distortion
Publication: bell_thermoelastic.pps
Source: Aerospace Thermal Control Workshop
Author: William Bell & Paul-W. Young
Year: 2005
Content Tags: chilldown, thermal stress, third-party software, convection heat transfer, walls, heat flux, convergence, temperature map, temperature mapping, finite element, finite elements, material properties, heat pipe, heatpipe, pipes
Modeling and Sizing a Thermoelectric Cooler Within a Thermal Analyzer
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
Implementation of STEP-TAS Thermal Model Exchange Standard in Thermal Desktop
Publication: TFAWS07-1011.pdf
Source: TFAWS
Author: Tim Panczak and Georg Siebes
Year: 2007
Content Tags: robust design, meshing, parametric, material properties, orbit, articulation, tracker, trackers, concurrent engineering, concurrent design, third-party software, optical properties, model correlation, thermocouples
Free Molecular Heat Transfer Programs for Setup and Dynamic Updating the Conductors in Thermal Desktop
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
Collaborative design and analysis of Electro-Optical sensors
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
Thermo-electrochemical analysis of lithium ion batteries for space applications using Thermal Desktop
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)
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.
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
Optimization, Data Correlation, and Parametric Analysis Features in SINDA/FLUINT Version 4.0
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
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:
Reliability Engineering and Robust Design: New Methods for Thermal/Fluid Engineering
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
Beyond Point Design Evaluation
Publication: NewOsummary.pdf
Source: ASME
Author: Brent A. Cullimore
Year: 2001
Content Tags: model calibration, CFD, parametric, design optimization, design synthesis, Phenomena
Dealing with Uncertainties and Variations in Thermal Design
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)
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
Automated Determination of Worst-case Design Scenarios
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
Customizable Multidiscipline Environments for Heat Transfer and Fluid Flow Modeling
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
Noncondensible Gas, Mass, and Adverse Tilt Effects on the Start-up of Loop Heat Pipes
In recent years, loop heat pipe (LHP) technology has transitioned from a developmental technology to one that is flight ready. The LHP is considered to be more robust than capillary pumped loops (CPL) because the LHP does not require any preconditioning of the system prior to application of the heat load, nor does its performance become unstable in the presence of two-phase fluid in the core of the evaporator. However, both devices have a lower limit on input power: below a certain power, the system may not start properly. The LHP becomes especially susceptible to these low power start-ups following diode operation, intentional shut-down, 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 start-up test data, this paper will describe how the minimum power required to start the loop is increased due to the presence of mass, noncondensible gas, and adverse tilt. The end-product is a methodology for predicting a “safe start” design envelope for a given system and loop design.
Publication: 1999-01-.pdf
Source: ICES
Author: Jane Baumann, Brent Cullimore, Boris Yendler, Eva Buchan
Year: 1999
Content Tags: Loop Heat Pipe, LHP, noncondensable gas, start-up, heat loads, compensation chamber, condenser, condensers, evaporator, evaporators, thermoelectrics, two-phase, two-phase flow, transient, bayonet, heat transfer coefficient, model correlation
A Methodology for Enveloping Reliable Start-up of LHPs
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
Novel Simulation Techniques for Design of Air-cooled Electronics
This paper describes a new means of analyzing the thermal response of air-cooled and liquid-cooled electronics that overcomes limitations in available tools and current design methods. It also shows how these new tools and methods can extend the reach of such thermal/fluid analyses by helping to size and locate components as well as dealing with both pre-test uncertainties and post-deployment variations in manufacturing, environment, and usage.
As the time lag from design to market diminishes, the pressure to abandon “build and test” approaches to electronics thermal cooling has created a wide variety of design analysis methods ranging from simple hand calculations of energy balances to detailed three-dimensional CFD (Computational Fluid Dynamics) approaches. Surprisingly few options are available between these two extremes, leaving most designers feeling that they face an “all or nothing” choice. Hand calculations and other simple software approaches, while contributing to an engineer’s intuition, cannot be relied upon for the entire design cycle, especially with the reduced emphasis on hardware prototyping that is necessary to speed up product development time. Fluid network modeling (FNM) approaches offer more analytic power but lack strong connectivity to geometric thermal models, and are therefore cumbersome to use. CFD approaches include limited geometric thermal modeling, but are relatively inflexible because they focus on detailed point design evaluations, and therefore contribute little to design knowledge.
This paper will describe a new approach using multidimensional heat transfer modeling in combination with ducted or quasi-multidimensional flow solutions for fast and easily modifiable models of electronics packaging that lends itself to high-level operations such as sizing and reliability estimation.
Publication: IPACK2001-15523.pdf
Source: InterPack
Author: David A. Johnson, Mark J. Welch, Brent A. Cullimore
Year: 2001
Content Tags: CFD, convection heat transfer, natural convection, parametric, finite elements, finite difference
Viability of Loop Heat Pipes for Space Solar Power Applications
The primary thermal management issue associated with Space Solar Power (SSP) is the need to acquire, transport and reject waste heat loads, on the order of 3.8 GW, from the transmitter to remote radiator locations. Previous conceptual studies have focused on transporting these loads to large remote radiators. These concepts assumed the ability to transport the heat either passively or mechanical over large transport distances of 100 meters or more.
A recent study, Innovative Deployable Radiators (IDR) for Space Solar Power, focused directly on the thermal control issues. This study has produced new concepts which break the system into small clusters of radiators which have more reasonable transport lengths of 1-2 meters. This study considers a system based on the klystron conversion technologies with a system architecture based on cluster radiators located near the waste heat source. The study evaluated various fluids for use between 50 and 500°C to determine their viability for use in LHPs. The evaluation considered fluid properties in addition to material compatibility with traditional LHP wick and containment materials.
The results of this study have provided new insight regarding the feasibility and limitations of LHPs for Space Solar Power applications. New technology development areas have been identified for both traditional LHPs and liquid metal LHPs.
Publication: AIAA2001-3078.pdf
Source: AIAA
Author: Jane Baumann, Suraj Rawal
Year: 2001
Content Tags: radiator, LHP, Loop Heat Pipe, capillary pumped loop, CPL, noncondensable gas, evaporator, evaporators, condenser, condensers, working fluids, pressure drops
Guidelines for Modeling Capillary Two Phase Loops At the System Level
LHPs and CPLs are increasingly accepted as thermal control solutions for spacecraft, and they are being investigated for various terrestrial applications as well. For a potential user of these technologies, modeling at the system level has been difficult, to say the least, and concurrent engineering methods were non-existent. New methods are now available to address these needs and concurrent CAD methods result in fast and accurate model generation. These same tools can be used for system level modeling of heat pipes, both fixed conductance with or without noncondensible gas or variable conductance.
Historically the thermal/hydraulic modeling of LHP has been approached with either oversimplified, design specific spreadsheets, or detailed thermal hydraulic models developed by the advanced user or LHP developer. To model these devices properly, and consequently gain confidence in the technology, the user needs to be able to model the LHP at the system level without becoming “caught up” in detail. This does not imply that the intricacies of two-phase flow and heat transfer within the evaporator core and secondary wicks of LHPs and CPLs aren’t important; but they should be left to the developers and the effects of these details can easily be enveloped through a series of steady state analyses. The potential user of the technology should focus on developing quasi-steady analyses to perform worst-case enveloping estimates, statistical treatment of the uncertainties, and post-test calibrations for use in extrapolation to untestable conditions. In a nutshell: if they are going to fly them, they’re first going to have to analyze them, integrated into their own vehicle model.
This presentation will identify important LHP and CPL design parameters and how they should be modeled in addition to outlining the criteria for developing a system level model using new concurrent CAD-based methods.
Publication: LHPmodelGuide.pps
Source: Aerospace Thermal Control Workshop
Author: Jane Baumann
Year: 2003
Content Tags: LHP, Loop Heat Pipe, compensation chamber, evaporator, evaporators, condenser, condensers, iface, capillary systems
Adding Heat Pipes and Coolant Loop Models to Finite Element and/or Finite difference Thermal/Structural Models
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. These arcs and lines can be attached intimately or via linear contact or saddle resistances to plates and other surfaces, whether those surfaces are modeled using thermal finite difference methods (FDM), or finite element methods (FEM), or combinations of both. The fluid lines can also be manifolded and customized as needed to represent complex heat exchangers and plumbing arrangements. Furthermore, the assumption of 1D flow can be combined with 2D/3D models of walls, including advanced methods of extruding a complex 2D cross-section along a curved or mitered centerline.
To demonstrate these concepts, several distinct examples are developed and discussed.
Publication: FloCAD3-ICES.pdf
Source: ICES
Author: B. Cullimore, D. A. Johnson
Year: 2003
Content Tags: finite difference, heat pipe, Loop Heat Pipe, finite element, structural mesh, duct, noncondensible gas, condenser, wall
The Design and Performance of a Water Cooling System for a Prototype Coupled Cavity linear Particle Accelerator for the Spallation Neutron Source
The Spallation Neutron Source (SNS) is a facility being designed for scientific and industrial research and development. The SNS will generate and employ neutrons as a research tool in a variety of disciplines including biology, material science, superconductivity, chemistry, etc. The neutrons will be produced by bombarding a heavy metal target with a high-energy beam of protons, generated and accelerated with a linear particle accelerator, or linac. The low energy end of the linac consists of, in part, a multi-cell copper structure termed a coupled cavity linac (CCL). The CCL is responsible for accelerating the protons from an energy of 87 MeV, to 185 MeV.
Acceleration of the charged protons is achieved by the use of large electrical field gradients established within specially designed contoured cavities of the CCL. While a large amount of the electrical energy is used to accelerate the protons, approximately 60-80% of this electrical energy is dissipated in the CCL’s copper structure. To maintain an acceptable operating temperature, as well as minimize thermal stresses and maintain desired contours of the accelerator cavities, the electrical waste heat must be removed from the CCL structure. This is done using specially designed water cooling passages within the linac’s copper structure. Cooling water is supplied to these cooling passages by a complex water cooling and temperature control system.
This paper discusses the design, analysis, and testing of a water cooling system for a prototype CCL. First, the design concept and method of water temperature control is discussed. Second, the layout of the prototype water cooling system, including the selection of plumbing components, instrumentation, as well as controller hardware and software is presented. Next, the development of a numerical network model used to size the pump, heat exchanger, and plumbing equipment, is discussed. Finally, empirical pressure, flow rate, and temperature data from the prototype CCL water cooling tests are used to assess water cooling system performance and numerical modeling accuracy.
Publication: TED-AJ03-537.pdf
Source: ASME-JSME
Author: John D. Bernardin, Curtt Ammerman, Steve Hopkins
Year: 2003
Content Tags: expansion, contraction, pump, valve, heat exchangers, cooler, heat loads
FDM/FEM System-level Analysis of Heat Pipes and LHPs in Modern CAD Environments
Publication: aerospace2005heatpipes.pps
Source: Aerospace Thermal Control Workshop
Author: Brent Cullimore, Jane Baumann
Year: 2005
Content Tags: LHP, Loop Heat Pipe, radiation analysis groups, concurrent engineering, heat pipe, system-level modeling, noncondensable gas, VCHP, CCHP, wall, two-phase heat transfer, two-phase flow, condenser, condensers, evaporator, evaporators
Integrating Thermal And Structural Analysis with Thermal Desktop
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.
Publication: 99es-40.pdf
Source: ICES
Author: Tim Panczak, Mark J. Welch
Year: 1999
Content Tags: structural, finite elements, finite difference, structural mesh, temperature mapping, temperature map, concurrent engineering, concurrent design, radiation calculations, CAD geometry, postprocessing, orbit, orbital heating, radiation analysis groups, Monte Carlo, ray tracing, data mapper, solver
Automating Thermal Analysis with 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. 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
Parametric Thermal Analysis and Optimization Using Thermal Desktop
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
Nonlinear Programming Applied to Thermal and Fluid Design Optimization
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
CAD-based Methods for Thermal Modeling of Coolant Loops and Heat Pipes
As air cooling of electronics reaches the limits of its applicability, the next generation of cooling technology is likely to involve heat pipes and single- or two-phase coolant loops (including perhaps loop thermosyphons, spray cooling, vapor compression refrigeration cycles, and loop heat pipes). These technologies are not suitable for analysis using 2D/3D computational fluid dynamics (CFD) software, and yet the geometric complexities of the thermal/structural models make network-style schematic modeling methods cumbersome.
This paper describes techniques whereby CAD linedrawing methods can be used to quickly generate 1D fluid models of heat pipes and coolant loops within a 3D thermal model. These arcs and lines can be attached intimately or via lineal contact or saddle resistances to plates and other surfaces, whether those surfaces are modeled using thermal finite difference methods (FDM) or finite element methods (FEM) or combinations of both. The fluid lines can also be manifolded and customized as needed to represent complex heat exchangers and plumbing arrangements.
To demonstrate these concepts, two distinct examples are developed: a copper-water heat pipe, and an aluminumammonia loop heat pipe (LHP) with a serpentined condenser. A summary of the numerical requirements for system-level modeling of these devices is also provided.
Publication: cadloopmodelingrevised.pdf
Source: ICES
Author: David A. Johnson, Jane Baumann, Brent Cullimore
Year: 2002
Content Tags: CFD, LHP, Loop Heat Pipe, evaporator, evaporators, condensers, noncondensable gas, design optimization, parametric, two-phase flow, two-phase
Highlights in thermal engineering at Carlo Gavazzi Space
Publication: 17th_EWTES_MOLINA_FREQUENCYDOMAIN.pdf
Source: 17th Workshop on Thermal and ECLS Software-ESTEC
Author: Marco Molina, Christian Vettore
Year: 2003
Content Tags: third-party software, radks, heating rates
A CAD-based Tool for FDM and FEM Radiation and Conduction Modeling
Thermal engineering has long been left out of the concurrent engineering environment dominated by CAD (computer aided design) and FEM (finite element method) software. Current tools attempt to force the thermal design process into an environment primarily created to support structural analysis, which results in inappropriate thermal models. As a result, many thermal engineers either build models “by hand” or use geometric user interfaces that are separate from and have little useful connection, if any, to CAD and FEM systems.
This paper describes the development of a new thermal design environment called the Thermal Desktop. This system, while fully integrated into a neutral, low-cost CAD system, and which utilizes both FEM and FD methods, does not compromise the needs of the thermal engineer. Rather, the features needed for concurrent thermal analysis are specifically addressed by combining traditional parametric surface-based radiation and FD based conduction modeling with CAD and FEM methods. The use of flexible and familiar temperature solvers such as SINDA/FLUINT is retained.
Publication: ices-98es-51.pdf
Source: ASME
Author: Tim Panczak, Steve Ring, Mark Welch
Year: 1997
Content Tags: finite element, finite difference, concurrent engineering, heater, heatpipe, heat pipe, radiation analysis groups, optical properties, Phenomena, refraction, scaffolding, CAD geometry, layers, expression editor, solver, mesh, mesher, structural mesh, ray tracing, boundary conditions, thermal stress, radiator, conductance, batteries, orbital heating, mli, multi-layer insulation, radks, articulation, articulating