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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

Development of a contact heat exchanger for a constructable radiator system

A development program for a contact heat exchanger to be used to transfer heat from a spacecraft coolant loop to a heat pipe radiator is described. The contact heat exchanger provides for a connectable/disconnectable joint which allows for on-orbit assembly of the radiator system and replacement or exchange of radiator panels for repair and maintenance. The contact heat exchanger does not require the transfer of fluid across the joint; the spacecraft coolant loop remains contained in an all welded system with no static or dynamic fluid seals. The contact interface is also "dry' with no conductive grease or interstitial material required.

Howell, H. R.↗
DOE OSTI2020

High-Temperature Particle Heat Exchanger for sCO2 Power Cycles [Award 30342]

This report describes the design, development, and testing of a prototype 100 kWt particle-to-supercritical CO 2 (sCO2) heat exchanger. An analytic hierarchy process was implemented to compare and evaluate alternative heat-exchanger designs (fluidized bed, shell-and-plate moving packed bed, and shell-and-tube moving packed bed) that could meet the high pressure (≥ 20 MPa) and high temperature (≥ 700 °C) operational requirements associated with sCO2 power cycles. Cost, heat-transfer coefficient, structural reliability, manufacturability, parasitics and heat losses, scalability, compatibility, erosion and corrosion, transient operation, and inspection ease were considered in the evaluation. A 100 kWt shell-and-plate design was selected for construction and integration with Sandia’s falling particle receiver system that heats the particles using concentrated sunlight. Sandia worked with industry to design and construct the moving packed-bed shell-and-plate heat exchanger. Tests were performed to evaluate its performance using both electrical heating and concentrated sunlight to heat the particles. Overall heat transfer coefficients at off-design conditions (reduced operating temperatures and only three stainless steel banks in the counter-crossflow heat exchanger) were measured to be approximately ~25 - 70 W/m 2 -K, significantly lower than simulated values of >100 W/m 2 -K. Tests using the falling particle receiver to heat the particles with concentrated sunlight yielded overall heat transfer coefficients of ~35 – 80 W/m 2 -K with four banks (including a nickel-alloy bank above the three stainless steel banks). The overall heat transfer coefficient was observed to decrease with increasing particle inlet temperatures, which contrasted the results of simulations that showed an increase in heat transfer coefficient with temperature due to increased effective particle-bed thermal conductivity from radiation. The likely cause of the discrepancy was particle-flow maldistributions and funnel flow within the heat exchanger caused by internal ledges and cross-bracing, which could have been exacerbated by increased particle-wall friction at higher temperatures. Additional heat loss at higher temperatures may also contribute to a lower overall heat-transfer coefficient. Design challenges including pressure drop, particle and sCO2 flow maldistribution, and reduced heat transfer coefficient are discussed with approaches for mitigation in future designs. Lessons learned regarding instrumentation, performance characterization, and operation of particle components and sCO2 flow loops are also discussed. Finally, a 200 MWt commercial-scale shell-and-plate heat-exchanger design based on the concepts investigated in this report is proposed.

14 SOLAR ENERGY↗
DOE OSTI2021

Numerical Study and Validation of Melting and Solidification in PCM Embedded Heat Exchangers with Straight Tube

Latent heat thermal energy storage (LHTES) systems have shown great potential to enable reliable use of renewable energy and load shifting. LHTES offer high storage density and release energy at near constant temperature because of its use of phase change materials (PCMs). The cylindrical PCM heat exchangers (PCMHX) are one of the most used technologies due to their simplicity. Numerical models for such PCMHX enable engineers to estimate their performance for different design parameters and operating conditions without having to test them all. However, modeling the phase change phenomena can be challenging. To better understand the difficulties involving accurate modeling of PCMHX, a cylindrical latent storage unit filled with PCM and water as in-tube heat transfer fluid (HTF) is numerically investigated. This paper presents a study based on a 2D-axisymmetric model of a straight tube embedded in PCM in a cylindrical container. CFD is used to study the charging (melting) and discharging (solidification) phenomena. The models are validated against experimental and numerical data from the literature. The predicted local PCM temperature profile over time agrees within 2K compared to the experimental values. The paper also presents a simple method to estimate the melting and solidification phase change temperature range from limited data provided by PCM manufacturers.

PCM, melting, solidification, CFD, heat exchanger↗
DOE OSTI2021

Two Dimensional Topology Optimization of Heat Exchangers with the Density and Level-Set Methods

We design heat exchangers using two topology optimization approaches: the density, i.e. volume fraction and level set methods. Our goal is to maximize the heat exchange between two fluids in separate channels while constraining the pressure drop across each channel. The heat exchanger is modeled with a coupled thermal-flow formulation. The flow is governed by an isothermal and incompressible Stokes-Brinkman equation and the heat transfer is governed by a convection-diffusion equation with high Peclet number. We solve one set of Stokes-Brinkman equations per fluid. Each Brinkman term in the flow equation serves to model the other phase as a solid, thereby preventing mixing. We first represent the solid and fluid phases using a volume fraction variable and apply a SIMP-like penalization in the Brinkman term to drive the optimization to a discrete design. The cost and constraint function derivatives are automatically calculated with the library pyadjoint and the optimization is performed by the Method of Moving Asymptotes. In a second optimization formulation, we use the level set approach to define the interface that separates the two fluids. Pyadjoint calculates the shape derivatives of the cost and constraint functions and the Hamilton-Jacobi advects the interface, allowing for topological changes. We present results in two dimensions and discuss the advantages and disadvantages of each approach.

42 ENGINEERING↗
DOE OSTI2023

Heat transfer model for moving packed-bed particle-to-sCO 2 heat exchangers integrated with metal foams

Particle-to-supercritical carbon dioxide (sCO 2 ) heat exchangers (HXs) play a vital role in coupling heat transfer fluid (HTF) from high-temperature thermal receivers to power cycle working fluids (WF). Heat transfer enhancement is essential for adopting particle-based moving packed-bed heat exchangers (MPBHXs) in next-generation thermal energy storage (TES) systems, as MPBHXs usually exhibit low particle bed-to-wall heat transfer coefficients. High-porosity metal foams have shown their effectiveness in heat transfer enhancement. Here, this work presents a continuum heat transfer model to demonstrate the heat transfer enhancement in MPBHXs when the particle bed channel is filled with high porosity metal foams compared to open channel MPBHXs. The presence of metal foams increases the effective thermal conductivity in the particle channel and enhances the interstitial heat transfer coefficient between the moving particle bed and the stationary metal foams. The present model considers coupled two-dimensional (2D) heat transfer in the particle channel with metal foams and 1D heat transfer in the sCO 2 channel and the dividing wall. The temperature profiles for the particle bed, metal foam, dividing wall, and sCO 2 stream, as well as the local heat flux profiles between those, are studied in detail for various foam porosities, from which the particle bed-to-wall heat transfer coefficient, overall heat transfer coefficient, and total heat transfer rate for the MPBHX are determined. The effects of major MPBHX design and operating parameters on the particle bed-to-wall heat transfer coefficient and overall heat exchange capacity are thoroughly examined; thus, the MPBHX performance improvement with metal foams is quantified for each case. The present heat transfer model can provide valuable insights into the metal-foam MPBHX design and optimization, scale-up, and operating parameters selection.

42 ENGINEERING↗
DOE OSTI2022

An autonomous robot for shell and tube heat exchanger inspection

Shell and tube heat exchangers (STHEs) are critical to energy conversion efficiency of power plants. Eddy current examination is a way to evaluate working conditions of these tubes. However, the current testing apparatus requires human to manually insert an eddy current testing (ECT) probe into and extract it out of individual tubes, and meanwhile monitor measurement results for diagnosis. It is a time-consuming and labor-intensive procedure even for an experienced technician. To tackle this challenge, in this study, we developed a robot enabled ECT system for autonomous inspection of STHEs. The robotic platform employs Mecanum wheeled chassis for high mobility, machine vision to locate tube bundle and tube inlets, a rotational Cartesian mechanism to operate at planes with all possible inclinations, and a task-specific mechanism for ECT probe delivery. Machine vision locates tube bundle and tube inlets by an April tag detection algorithm and a Circle Hough Transform algorithm, respectively. Assisted by a guiding cone, the ECT probe is continuously fed into the tubes with a fill factor of 0.819. In conclusion, during this process, the eddy current data are automatically collected and real-time analyzed by convolutional neural networks, showing accuracy of nearly 100% for identifying defective and nondefective tubes and 85% for four types of defective tubes and nondefective tubes.

42 ENGINEERING↗
DOE OSTI2022

An Autonomous Robot for Shell and Tube Heat Exchanger Inspection

Shell and tube heat exchangers (STHEs) are critical to energy conversion efficiency of power plants. Eddy current examination is a way to evaluate working conditions of these tubes. However, the current testing apparatus requires human to manually insert an eddy current testing (ECT) probe into and extract it out of individual tubes, and meanwhile monitor measurement results for diagnosis. It is a time-consuming and labor-intensive procedure even for an experienced technician. To tackle this challenge, in this work, we developed a robot enabled ECT system for autonomous inspection of STHEs. The robotic platform employs Mecanum wheeled chassis for high mobility, machine vision to locate tube bundle and tube inlets, a rotational Cartesian mechanism to operate at planes with all possible inclinations, and a task-specific mechanism for ECT probe delivery. Machine vision locates tube bundle and tube inlets by an April tag detection algorithm and a Circle Hough Transform (CHT) algorithm, respectively. Assisted by a guidance cone, the ECT probe is continuously fed into the tubes with a fill factor of 0.819. During this process, the eddy current data are automatically collected and real-time analyzed by convolutional neural networks (CNN), showing accuracy of nearly 100% for identifying defective and non-defective tubes and 85% for four types of defective tubes and non-defective tubes.

autonomy, deep learning, eddy current testing, hea↗
NASA NTRS1975

Wall mounted heat exchanger characterization

Analytical models are presented for describing the heat and mass transfer and the energy distribution in the contents of a cryogenic propellant tank, under varying gravity levels. These models are used to analytically evaluate the effectiveness of a wall heat exchanger as a means of controlling the pressure in the tank during flight and during fill operations. Pressure and temperature histories are presented for tanks varying in size from 4 to 22.5 feet in diameter and gravity levels from 0-1. Results from the subscale test program, utilizing both non-cryogenic and cryogenic fluid, designed to evaluate a tank wall heat exchanger are described and compared with the analytical models. Both the model and test results indicate that a passive tank wall heat exchanger can effectively control tank pressure. However, the weight of such a system is considerably higher than that of an active mixer system.

Bullard, B. R.↗
DOE OSTI2023

Experimental Investigation of a Phase Change Material Charged Serpentine Heat Exchanger with Louvered Fins

Phase change material heat exchangers (PCM-HX) can be used as a latent heat thermal energy storage (LHTES) component in heat pump applications to further enhance the efficiency of a heat pump as well as to yield financial savings by peak-load shifting. In this paper, a low-cost commercially available aluminum serpentine heat exchanger with louvered fins was experimentally investigated to check its thermal performance as a PCM-HX. A transparent rectangular box fabricated from acrylic plates served as a PCM container. Two cameras were used to capture the phase change process of the PCM on the front and top sides of the container during the experiment. A total of 88 installed temperature sensors throughout the test setup and a mass flow meter enabled a quantitative analysis of the PCM-HX as well. The energy balance deviation between the estimated theoretical and experimentally calculated PCM storage was ±14% considering the often-neglected heat loss and thermal mass of the PCM-HX. PCM temperature profiles, charge and discharge rates, and energy densities under different test conditions were also investigated.

42 ENGINEERING↗
NASA NTRS2017

Design and testing of high-performance mini-channel graphite heat exchangers in thermoelectric energy recovery systems

Recent national energy usage studies by Lawrence Livermore National Laboratory in 2015 [1] show that there is approximately 59 Quads (1015 Btu’s) of waste thermal energy throughout various industrial, residential, power generation, and transportation sectors of the U.S. economy. Thermoelectric energy recovery is one important technology for recovering this waste thermal energy in high-temperature industrial, transportation and military energy systems. Thermoelectric generator (TEG) systems in these applications require high performance hot-side and cold-side heat exchangers to provide the critical temperature differential and transfer the required thermal energy. High performance hot-side heat exchangers in these systems are often metal-based due to requirements for high-temperature operation, strength at temperature, corrosion resistance, and chemical stability. However, the generally selected metal-based hot-side heat exchangers (i.e., Inconels, Stainless Steels) suffer from low thermal conductivity, high thermal expansion, and high density, which degrades their thermal performance, leads to high thermal-expansion-driven stresses, and creates relatively high mass/high volume (i.e., low power density) TEG systems that are then difficult to fabricate and integrate into viable energy recovery systems. This paper describes the design and testing of a new, high-temperature minichannel graphite heat exchanger designed for operation up to 500C that is a critical element of a high-power-density TEG power system for aircraft energy recovery. This high-performance graphite heat exchanger represents a new state-of-the-art standard in high-temperature heat exchangers for TEG systems, which provides higher thermal transport, less thermal expansion at operation, lower system level stresses on TE components, and a lighter weight TEG system. This new heat exchanger creates a new design paradigm in TEG system design for terrestrial energy recovery and potential NASA technology infusion into terrestrial energy system applications. This paper will present and discuss the key heat transfer, pressure drop, pumping power analyses and design tradeoffs that created this unique design. Heat transfer and pressure drop modeling was performed with both empirical models based on known heat transfer and friction factor correlations and COMSOL thermal/fluid dynamic modeling of the graphite heat exchanger structure. We will also discuss resulting thermal transport and heat fluxes predicted at the TEG interface level. Heat exchanger performance testing was performed under simulated operating conditions and correlation with test data at the anticipated operating temperature conditions will be presented and discussed.

Shevade, Abhijit↗
NASA NTRSDate not supplied

Design of a Radioisotope Heat Exchanger Rocket

The state of planetary exploration vehicle technology has become increasingly more advanced over its long history. Better technologies enable more detailed scientific research to be conducted during the vehicle’s life, while advanced manufacturing strategies allow the vehicles to operate for greater lengths of time. However, one aspect of these vehicles has remained constant: the means of exploration. Previous vehicles have all relied on wheels to traverse the surface of the explored planet, limiting their range. The Mars Opportunity Rover, the longest operating rover, only traveled 45.15 km over its life. The radioisotope heat exchanger rocket is a new vehicle concept, designed to use heated gas as a means of propellant. The vehicle collects gas from the surface of a body, stores it in a heated tank, and passes it through a heat exchanger. This process significantly increases the temperature of the collected gas, allowing it to exit through a nozzle with high velocity and efficiency. This process will enable the vehicle to hop across the surface of the body and repeatedly refuel, with the potential of travelling thousands of kilometers during its lifetime. A computer model was constructed to simulate the heat exchanger and nozzle of this proposed system. This simulation allowed the heat exchanger and propellant tank properties to be optimized for the current mission parameters: the exploration of Triton. The nitrogen flows through a 25 kg lithium heat exchanger, consisting of 540, 1.5-mm diameter, 40-cm long Titanium Zirconium Molybdenum pipes, to three operating nozzles. Once landed, the vehicle will conduct science and refueling operations for six days before hopping again. With the optimized design determined from the simulations conducted in this paper, 235.26 kg of nitrogen is collected and stored in a 300 K, 3000 psia tank. With these parameters, a potential hop distance of 39 km with an average specific impulse of 127.5 s is attained. A previous iteration of this vehicle did not include a heat exchanger, instead heating 100 kg of nitrogen to 300 K, only allowing the vehicle to hop 5 km and with a low specific impulse of 60 s. Thus, the addition of the heat exchanger component of the vehicle is shown to potentially double the specific impulse and quadruple the hop distance compared to the previous design.

Thomas E. O'Brien↗
DOE OSTI2024

High Power Density Thermal Energy Storage With Phase Change Material in Enhanced Compact Heat Exchangers

Abstract Performance of a novel ultracompact thermal energy storage (TES) heat exchanger, designed as a microchannel finned-tube exchanger is presented. With water as the heating–cooling fluid in the microchannels, a salt hydrate phase change material (PCM), lithium nitrate trihydrate (LiNO3 · 3H2O), was encased on the fin side. To establish the hypothesis that small-length-scale encasement (<3 mm) of PCM substantially enhances heat transfer to yield very high power-density energy storage, heat exchanger designs with 10 and 24 fins/inch were considered. They were subjected to thermal cycling, or repeated heating (melting) and cooling (freezing), with inlet fluid flow mimicking diurnal variation between 42 °C and 25 °C (representing typical arid-region conditions) over an accelerated time period. By employing salt self-seeding to obviate subcooling during cooling or recrystallization, the TES was found to exhibit stable long-term (100 heating–cooling cycles) operation with very high PCM-side heat transfer coefficients (∼100–500 W/m2 K) and storage power density (∼160–175 kW/m3). In fact, with optimization of heating–cooling fluid flowrate for given charging–discharging time period and exchanger size, power density >300 kW/m3 can be achieved. The results clearly establish that highly compact heat exchangers used as TES units can provide very high-performance alternatives to conventional ones.

Engineering↗
NASA NTRS1976

Joule-Thomson expander and heat exchanger

The Joule-Thomson Expander and Heat Exchanger Program was initiated to develop an assembly (JTX) which consists of an inlet filter, counterflow heat exchanger, Joule-Thomson expansion device, and a low pressure jacket. The program objective was to develop a JTX which, when coupled to an open cycle supercritical helium refrigerating system (storage vessel), would supply superfluid helium (He II) at 2 K or less for cooling infrared detectors.

Norman, R. H.↗
NASA NTRS2015

Design and Test of a Liquid Oxygen / Liquid Methane Thruster with Cold Helium Pressurization Heat Exchanger

A liquid oxygen / liquid methane 2,000 lbf thruster was designed and tested in conjuction with a nozzle heat exchanger for cold helium pressurization. Cold helium pressurization systems offer significant spacecraft vehicle dry mass savings since the pressurant tank size can be reduced as the pressurant density is increased. A heat exchanger can be incorporated into the main engine design to provide expansion of the pressurant supply to the propellant tanks. In order to study the systems integration of a cold-helium pressurization system, a 2,000 lbf thruster with a nozzle heat exchanger was designed for integration into the Project Morpheus vehicle at NASA Johnson Space Center. The testing goals were to demonstrate helium loading and initial conditioning to low temperatures, high-pressure/low temperature storage, expansion through the main engine heat exchanger, and propellant tank injection/pressurization. The helium pressurant tank was an existing 19 inch diameter composite-overwrap tank, and the targert conditions were 4500 psi and -250 F, providing a 2:1 density advantage compared to room tempatrue storage. The thruster design uses like-on-like doublets in the injector pattern largely based on Project Morpheus main engine hertiage data, and the combustion chamber was designed for an ablative chamber. The heat exchanger was installed at the ablative nozzle exit plane. Stand-alone engine testing was conducted at NASA Stennis Space Center, including copper heat-sink chambers and highly-instrumented spoolpieces in order to study engine performance, stability, and wall heat flux. A one-dimensional thermal model of the integrated system was completed. System integration into the Project Morpheus vehicle is complete, and systems demonstrations will follow.

Melcher, John C.↗
DOE OSTI2023

Reducing the Flow Maldistribution in Heat Exchangers through a Novel Polymer Manifold: Numerical Evaluation

The maldistribution of working fluid is one of the issues in heat exchangers that causes a reduction in performance of not only the heat exchanger but also the entire HVAC system. One of the methods to reduce such maldistribution is to improve manifold design to evenly distribute the flow. In the present work, an advanced maldistribution reduction manifold, which was based on a preliminary maldistribution reduction manifold, was designed to further improve the flow distribution in the heat exchanger. In the design, spiral baffles are used to create vortices in the tubes to regulate the flow in each tube. The design also keeps the tubes away from the manifold inlet to avoid direct flow from the inlet. Due to the complexity, the design of the advanced maldistribution reduction manifold is for AM only, which cannot be fabricated by traditional manufacturing. To evaluate the design, a computational fluid dynamic model is developed to study flow distribution in heat exchanger manifolds. The simulation results reveal that the relative standard deviation of the tubes in the advanced maldistribution reduction design is half of the preliminary maldistribution reduction design and about 1/20 of the reference design.

42 ENGINEERING↗
NASA NTRSDate not supplied

Computational Evaluation of an OML-based Heat Exchanger Concept for HEATheR

Feasibility of outer mold line (OML) heat exchangers for electrified aircraft is computationally explored for three different aircraft concepts within The High-efficiency Electrified Aircraft Thermal Research (HEATheR) project. OML surface temperature limits were selected based on aluminum-alloy and carbon-fiber composite materials commonly used in transport aircraft. Heat flux distribution over the aircraft OML at the surface temperature limit was evaluated with computational fluid dynamics (CFD) analysis. The candidate OML locations and the size for the implementation of the OML-based heat exchanger is down-selected using this initial analysis and other considerations including the concern for structural integrity and proximity to heat-generating electrical components. The sensitivity of the heat transfer analysis to the computational grid, aircraft angle of attack, surface temperature, and the interaction of individual OML heat exchanger patches were investigated.

CAS↗
DOE OSTI2023

Additively manufactured polymer composites for heat exchanger applications: evaluation of critical thermophysical properties

Polymeric heat exchangers (PHXs) have been used in applications involving weight restrictions, chemical compatibility, and fouling issues. Additive manufacturing (AM) or 3D printing provide new solutions to previously inaccessible combinations of properties and geometries. There are some advancements in the PHXs by AM; however, the process and the properties of materials still need further investigation to improve the overall performance. In this study, additively manufactured polyethylene terephthalate glycol (PETG) composites reinforced with graphite and pitch-based carbon fibers were evaluated for their potential application as PHXs. The thermal conductivity, volumetric heat capacity, coefficient of thermal expansion, creep behavior, and long-term performance were studied in detail. Our results reveal that the composites have an anisotropic thermal conductivity. The thermal conductivity along the printing direction is higher than the layer building direction due to the shear-induced alignment of the fillers. The printed composites achieve good thermal stability with 80% lower CTE at room temperature than neat PETG. Creep tests suggest the creep and creep recovery were highly temperature-dependent, and the deformation can be recovered when the temperature is below glass transition. These results suggest additive manufactured composites be potentially used for heat exchanger applications at low temperatures.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Fuel delivery system including heat exchanger means

A fuel delivery system is presented wherein first and second heat exchanger means are each adapted to provide the transfer of heat between the fuel and a second fluid such as lubricating oil associated with the gas turbine engine. Valve means are included which are operative in a first mode to provide for flow of the second fluid through both first and second heat exchange means and further operative in a second mode for bypassing the second fluid around the second heat exchanger means.

Coffinberry, G. A.↗