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Tank Sizing Analysis for Reduced Gravity Cryogenic Transfer Receiver Tank
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.
Source: TFAWS 2021
Author: Erin M. Tesny, Daniel M. Hauser, Jason W. Hartwig
JWST Testing Issues – Thermal & Structural
This study explores JWST thermal and structural testing issues and possible solutions, as presented to NASA in June 2004
Source: Aerospace Thermal Control Workshop 2005
Author: William Bell, Frank Kudirka, & Paul-W. Young
Modeling Transient Operation of Loop Heat Pipes using Thermal Desktop
Loop heat pipes (LHPs) are used in multiple terrestrial and space applications. Transient analysis of conventional and advanced loop heat pipes with complex radiators under varying conditions where the heat load and the effective sink temperature change in time can be best accomplished using Thermal Desktop™.
This paper presents a transient model of a LHP developed using Thermal Desktop™ (Sinda/Fluint). It includes the evaporator connected to the reservoir and condenser with fluid transport lines with bends, flow balancers, and connectors. The condenser is bonded to a honeycomb panel with two face-sheets spreading thermal energy across the radiating surfaces. The model was correlated to the thermal-vacuum test data.
The modeling provided better understanding of the critical transient fluid-flow mechanisms encountered in the LHP under transient operational conditions. Analysis of the numerical results shows that the secondary wick should be transporting liquid from the reservoir to the primary wick during transient operation where the sink temperature is decreasing or the evaporator heat load is being reduced.
Author: Dmitry Khrustalev
Content Tags: LHP, Loop Heat Pipe, sink temperature, transient, evaporator, condenser, model correlation, wicks, heat loads, conduction, wall, two-phase flow, convection heat transfer, radiation, phase change material, CAPPMP, iface, heat sink
Thermal Analysis on Plume Heating of the Main Engine on the Crew Exploration Vehicle Service Module
The crew exploration vehicle (CEV) service module (SM) main engine plume heating is analyzed using multiple numerical tools. The chemical equilibrium compositions and applications (CEA) code is used to compute the flow field inside the engine nozzle. The plume expansion into ambient atmosphere is simulated using an axisymmetric space-time conservation element and solution element (CE/SE) Euler code, a computational fluid dynamics (CFD) software. The thermal analysis including both convection and radiation heat transfers from the hot gas inside the engine nozzle and gas radiation from the plume is performed using Thermal Desktop. Three SM configurations, Lockheed Martin (LM) designed 604, 605, and 606 configurations, are considered. Design of multilayer insulation (MLI) for the stowed solar arrays, which is subject to plume heating from the main engine, among the passive thermal control system (PTCS), are proposed and validated.
Author: Xiao-Yen J. Wang and James R.Yuko
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.
Author: Brent A. Cullimore
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
Source: ICES 1998
Author: Brent A. Cullimore
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.
Source: IECEC 1998
Author: Brent A. Cullimore
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.
Source: CRTech White Paper
Author: Brent A. Cullimore
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
Development of Cryogenic Capillary Pumped Loop
A cryogenic capillary pumped loop (CPL) has been developed, designed, fabricated and successfully demonstrated by test. Using no moving parts, the novel device is able to start from a supercritical state and cool a remote dissipation source to 80-90K. Design studies were conducted for integration requirements and component design optimization and prototype units were designed, fabricated and successfully tested with excellent results. The development included the miniaturization of CPL technology to allow heat acquisition from sources with a small footprint and direct integration to a cryocooler cold finger. Applications include the cooling of cryogenic electronics, sensors, and fuels. The technology possesses many advantages over cryogenic heat pipes including ground testability and mechanical isolation. Because of the CPLs ability to transport loads over a distance, cryocoolers can be located remotely from the detector (up to a meter away or across a gimbaled joint). In addition, it passively seeks the coldest rejection environment, allowing a single cryogenic CPL to enable switching between multiple passive cryogenic radiators. This work was performed under funding from NASA Goddard Space Flight Center.
Author: Jane Baumann, Brent Cullimore
Content Tags: capillary pumped loop, CPL, CCPL, cryogenic, cooling loop, supercritical, start-up, design optimization, two-phase, heat loads, working fluids, evaporator, condenser, robust design, capillary systems, wicks, heat pipe, heatpipe
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.
Author: Jane Baumann, Brent Cullimore, Boris Yendler, Eva Buchan
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.
Source: AIAA Thermophysics
Author: Jane Baumann, Brent Cullimore, Jay Ambrose, Eva Buchan, Brois Yendler
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
Propulsion Applications of the NASA Standard General Purpose Thermohydraulic Analyzer
The NASA standard tool for thermohydraulic analysis, SINDA/FLUINT, includes thermodynamic and hydrodynamic solutions specifically targeted at the growing demand for design and analysis of liquid propulsion systems. Applications in this field have included:
- Helium pressurization system design
- Cryogenic line chill-down transients
- Regenerative nozzle cooling
- Cryogenic turbomachinery chill-down transients
- Hydrazine line filling
- Feedline transients, including pogo suppression
- Feedline anti-geyser design
- Cryogenic tank pressurization and discharge, including thermal stratification, dissolved pressurant, and capillary liquid acquisition devices
Many organizations have previously used separate in-house tools specialized for each of the above applications. However, these organizations typically do not have the resources nor infrastructure to maintain these codes when cognizant engineers are lost, nor to modify and validate them for new vehicles or applications, nor to train new engineers on their use.
The use of a single general-purpose tool to encompass all such analyses offers not only solutions to the above problems, but also enables integrated analyses and the ability to communicate with vendors and customers.
Source: CRTech White Paper
Author: Brent A. Cullimore, Cynthia M. Beer, David A. Johnson
Content Tags: chilldown, cryogenics, turbomachinery, register, registers, oxidizer tank, two-phase flow, cryogenic storage, nonequilibrium, valves, parametric, model correlation, solver, supercritical, mixtures, pressurant gas, orifices, compressors, user logic, choking, choked, nozzles, slip flow, liquid surface, interface, capillary systems, thermal stratification, stratified tanks, stratification
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.
Author: Jane Baumann, Suraj Rawal
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.
Source: Aerospace Thermal Control Workshop
Author: Jane Baumann
FDM/FEM System-level Analysis of Heat Pipes and LHPs in Modern CAD Environments
Source: Aerospace Thermal Control Workshop
Author: Brent Cullimore, Jane Baumann
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
Analysis and Test Verification of Transitional Flow in a Dewar Vent
The pressure of the cryogen within a Dewar determines the operating temperature since the cryogen is typically in a saturated state. Thus, the operating temperature of a Dewar is directly related to the ambient pressure external to the Dewar and the flow losses associated with venting cryogen. Given the low vapor pressures of some cryogens, such as solid hydrogen, the vent flow from Dewars used in space can enter the transitional and molecular flow regimes. In order to accurately predict the operating temperature within such Dewars, the analysis tool used to model the cryostat must account for free molecular and mixed flow losses as well as those for continuum flow.
As part of our analysis of Dewar designs for the James Webb Space Telescope Mid-Infrared Instrument (MIRI), we modified the continuum flow modeling capability of SINDA/FLUINT to accurately predict the pressure drop due to transitional and molecular flow in the MIRI Dewar vent line. This paper describes the modifications made to the flow loss computations within the analyzer and the testing conducted to verify these modifications.
Source: Topsfield Engineering Service, Inc.
Author: Russell B. Schweickart and Gary Mills
Upper Stage Tank Thermodynamic Modeling Using SINDA/FLUINT
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.
Author: P. Schallhorn, D. Michael Campbell, Sukhdeep Chase, Jorge Piquero, Cindy Fortenberry, Xiaoyi Li, Lisa Grob
Content Tags: Optimization, parametric, radiation, radiation analysis groups, conduction, evaporation, CFD, convergence, structural, heat flux, thermal stratification, register, two-phase, slosh, wall, splash
Upper Stage Tank Thermodynamic Modeling Using SINDA/FLUINT (Presentation)
Source: TFAWS Short Course
Author: Paul Schallhorn, D. Michael Campbell, Sukhdeep Chase, Jorge Piquero, Cindy Fortenberry, Xiaoyi Li, Lisa Grob