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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 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Performance Characterization of a Microchannel Liquid/Liquid Heat Exchanger Throughout an Extended Duration Life Test

Liquid/Liquid Heat Exchangers (L/L HX) are an integral portion of any spacecraft active thermal control system. For this study the X-38 L/L HX was used as a baseline. As detailed in a previous ICES manuscript, NASA paired with Pacific Northwest National Laboratory to develop a Microchannel L/L HX (MHX). This microchannel HX was designed to meet the same performance characteristics as the aforementioned X-38 HX. The as designed Microchannel HX has a 26% and 60% reduction in mass and volume, respectively. Due to the inherently smaller flow passages the design team was concerned about fouling affecting performance during extended missions. To address this concern, NASA has developed a test stand and is currently performing an 18 month life test on the MHX. This report will detail the up-to-date performance of the MHX during life testing.

Sheth, Rubik B.↗
DOE OSTI2022

Header for high-pressure heat exchanger

A header for a high-pressure heat exchanger includes a first high-pressure transition section with inlets for multiple first high-pressure flow channels that are spaced from one another in a radial direction and collectively arranged in a substantially circular shape. The inlets for the multiple first high-pressure flow channels on a radially outer edge of the first high-pressure transition section are spaced further apart in a circumferential direction from adjacent inlets of the multiple first high-pressure flow channels than radially inward inlets are spaced from adjacent radially inward inlets of the multiple first high-pressure flow channels. The header also includes multiple first high-pressure flow channels extending from the first high-pressure transition section to a second-high pressure transition section that is configured to divide each of the multiple first high-pressure flow channels into at least two first high-pressure sub-flow channels. Each flow channel of the multiple first high-pressure flow channels and each sub-flow channel of the first high-pressure sub-flow channels have a round cross-sectional shape.

Kirsch, Kathryn L.↗
DOE OSTI2024

UHTC-TPMS Heat Exchangers for Concentrating Solar Power Applications with Thermal Energy Storage in Molten Chlorides

Concentrating solar power (CSP) plants convert energy from sunlight into electricity. Generally, a heliostat field is used to reflect sunlight and concentrate it onto a receiver, which heats the receiver and/or the media flowing through it. A flow loop transports the media through the system to a heat exchanger before returning the media back to the receiver to be reheated. The heat extracted by the heat exchanger is then converted into electricity using a conventional heat engine.

14 SOLAR ENERGY↗
DOE OSTI2026

Evaluating Microchannel Heat Exchanger Lifetime for Concentrating Solar Power Applications

This report presents thework and results of a SolarEnergyTechnologyOffice (SETO) funded project to evaluate the lifetime of advanced microchannel etched and diffusion bonded heat exchangers for use in Generation 3 concentrated solar power (CSP) plants. Such plants transfer heat from a high temperature solid media to supercritical carbon dioxide (sCO2) via a primary heat exchanger in order to drive advanced Brayton cycles with turbine inlet temperatures greater than 700 °C.

Sandlin, Matthew James [Sandia National Laboratori↗
NASA NTRS1969

Cryogenic fluid flow instabilities in heat exchangers

Analytical and experimental investigation determines the nature of oscillations and instabilities that occur in the flow of two-phase cryogenic fluids at both subcritical and supercritical pressures in heat exchangers. Test results with varying system parameters suggest certain design approaches with regard to heat exchanger geometry.

Fleming, R. B.↗
DOE OSTI2022

Multi-scale and multi-physics analysis, design optimization, and experimental validation of heat exchangers utilizing high performance, non-round tubes

Air-to-refrigerant heat exchangers (HXs) are fundamental components in HVAC&R systems, and considerable research has been dedicated designing continually smaller, lighter, and more efficient HX designs. In recent years, researchers have leveraged advancements in Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA), and optimization algorithms to consider primary tube shape and topology optimization to design highly compact, high performance HXs for a multitude of applications. In this research, we present a computationally efficient, comprehensive, multi-scale, and multi-physics analysis and optimization method for air-to-refrigerant HXs featuring automated CFD and FEA simulations and approximation-assisted optimization. This methodology was utilized to design HXs with shape-optimized, non-round tubes which outperform current state-of-the-art tube-fin HXs without compromising structural integrity. The optimal HXs were shown to deliver similar thermal performance to the baseline HXs while also achieving more than 20% reductions in airside pressure drop and core envelope volume and more than 30% reduction in internal volume. Comprehensive experimental validation of the optimization methodology was conducted through the testing of two prototypes in a standardized wind tunnel facility under multiple operating conditions. For prototype #1 under dry evaporator conditions, the predicted heat load agreed within ± 10% of measured values and the predicted airside pressure drop agreed within ± 30%, while for dehumidifying conditions, the predicted sensible and latent heat loads agreed within ± 10% and ± 20% of the measured values, respectively. For prototype #2, the predicted condenser heat load agreed within ± 3.0% of measured values, and the predicted airside pressure drop agreed within ± 27%. The acceptable agreement between simulation and experimental results for the present application highlights the flexibility of the novel optimization methodology to design next generation HXs with improved performance and reduced volume, weight, and environmental impact.

42 ENGINEERING↗
NASA NTRS1978

Passive heat exchanger - installation package

Package covers installation, operation, and maintenance of heat exchanger which has auxiliary heaters that provide backup heat in inclement weather. Drawings, including schematics, complement text material, which is organized as step-by-step instructions. Trouble-shooting section discusses probable causes and repairs for most common difficulties.

Source record↗
NASA NTRS1987

Heat transfer and flow studies of the liquid droplet heat exchanger

This paper describes a lightweight, highly effective liquid droplet heat exchanger (LDHX) concept for thermal management in space. Heat is transferred by direct contact between fine droplets (100 to 300 micron diameter) of a low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the microgravity environment is accomplished by configuring the LDHX as a vortex chamber. A quasi-one-dimensional, two-phase heat transfer model of the LDHX is developed and used to investigate the potential use of the LDHX for both heating and cooling the working gas in a 100-k W(e) Braytoan cycle. Experimental studies on a small scale LDHX chamber, using air and water as the two media, show excellent agreement with the theoretical model.

Bruckner, A. P.↗
NASA NTRS1990

Oscillating flow loss test results in Stirling engine heat exchangers

The results are presented for a test program designed to generate a database of oscillating flow loss information that is applicable to Stirling engine heat exchangers. The tests were performed on heater/cooler tubes of various lengths and entrance/exit configurations, on stacked and sintered screen regenerators of various wire diameters and on Brunswick and Metex random fiber regenerators. The test results were performed over a range of oscillating flow parameters consistent with Stirling engine heat exchanger experience. The tests were performed on the Sunpower oscillating flow loss rig which is based on a variable stroke and variable frequency linear drive motor. In general, the results are presented by comparing the measured oscillating flow losses to the calculated flow losses. The calculated losses are based on the cycle integration of steady flow friction factors and entrance/exit loss coefficients.

Koester, G.↗
DOE OSTI2020

Systems with multi-circuited, phase-change composite heat exchangers

A system comprising a first plurality of microchannels, a second plurality of microchannels in thermal communication with the first plurality of microchannels such that the first plurality of microchannels and second plurality of microchannels form a heat exchanger, and a phase change composite in thermal communication with the heat exchanger and methods of operating are disclosed herein.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2023

Systems with multi-circuited, phase-change composite heat exchangers

A system comprising a first plurality of microchannels, a second plurality of microchannels in thermal communication with the first plurality of microchannels such that the first plurality of microchannels and second plurality of microchannels form a heat exchanger, and a phase change composite in thermal communication with the heat exchanger and methods of operating are disclosed herein.

Kozubal, Eric↗
DOE OSTI2024

Machine Learning Based Prediction of Airflow Maldistribution in A-Type Heat Exchangers

Airflow maldistribution is one of the primary causes of performance degradation in air-to refrigerant heat exchangers (HX) and has been shown to decrease heat transfer by as much as 35%. As a result, many units are oversized to meet the target capacity, resulting in increased system cost and refrigerant charge. Several studies have explored how characteristics like package type and HX geometry impact the flow profile, but results are restricted to a limited range of parameters and cannot be extrapolated to new designs. In this work, a machine learning (ML) model is trained to predict the inlet flow profile of dry air entering A-type HXs across a broad range of geometries and conditions. Flow profiles are generated using a porous media CFD model and used to train an Artificial Neural Network (ANN) which exhibits maximum and average relative L2 norm errors of 0.48 and 0.05. Additionally, these predictions take less than a second to generate resulting in a speed up factor of 2.42E5 compared to CFD. Component-level simulations are conducted to determine the performance degradation resulting from the predicted airflow maldistribution profiles. The new ML model will enable rapid and accurate prediction of performance degradation resulting from airflow maldistribution in A-type HXs, allowing for more accurate and cost-effective HX design.

42 ENGINEERING↗
DOE OSTI2020

An Enhanced Vertical Ground Heat Exchanger Model for Whole-Building Energy Simulation

This paper presents an enhanced vertical ground heat exchanger (GHE) model for whole-building energy simulation (WBES). WBES programs generally have computational constraints that affect the development and implementation of component simulation sub-models. WBES programs require models that execute quickly and efficiently due to how the programs are utilized by design engineers. WBES programs also require models to be formulated so their performance can be determined from boundary conditions set by upstream components and environmental conditions. The GHE model developed during this work utilizes an existing response factor model and extends its capabilities to accurately and robustly simulate at timesteps that are shorter than the GHE transit time. This was accomplished by developing a simplified dynamic borehole model and then exercising that model to generate exiting fluid temperature response factors. This approach blends numerical and analytical modeling methods. The existing response factor models are then extended to incorporate the exiting fluid temperature response factor to provide a better estimate of the GHE exiting fluid temperature at short simulation timesteps.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Design and Implementation of a 1-3 MW th sCO 2 Support Loop for Gen3 CSP Primary Heat Exchangers

The generation 3 concentrating solar power, or Gen3CSP, campaign seeks to de-risk and deploy a CSP pilot plant through three parallel project tracks focused on solid, liquid, and gas-phase primary heat transfer fluids. Although the components between the sun and the primary heat exchanger from the thermal storage system differ with each track, the supercritical carbon dioxide (sCO 2 ) coolant system required to cool the primary heat exchanger in place of a complete power conversion system has very similar requirements regardless of the primary heat transfer fluid. In order to avoid duplicative efforts, this project will design, assemble, perform acceptance testing, and deploy a single sCO 2 coolant system design meeting the needs of any Gen3CSP topic 1 pathway pilot plant design.

14 SOLAR ENERGY↗
DOE OSTI2024

Heat exchanger(s) for recovering water and/or heat energy from turbine engine combustion products

A turbine engine is provided that includes a fan section, a turbine engine core and a recovery system. The turbine engine core is configured to power the fan section. The turbine engine core includes a core compressor section, a core combustor section and a core turbine section. A centerline axis of the turbine engine core is offset from a centerline axis of the turbine engine. The recovery system includes an evaporator module and a condenser module. A core flowpath extends sequentially through the core compressor section, the core combustor section, the core turbine section, the evaporator module and the condenser module from an inlet into the core flowpath to an exhaust from the core flowpath.

Sobanski, Jon E.↗
DOE OSTI2021

A novel lung-inspired 3D-printed desiccant-coated heat exchanger for high-performance humidity management in buildings

Offering an independent humidity management method for buildings, desiccant-coated heat exchangers (DCHXs) are deemed a promising approach to improve the overall energy efficiency of air conditioning (AC) systems. State-of-the-art DCHXs, however, are bound with conventional HX topologies either providing limited desiccant-air interfacial areas or introducing excessive pressure drop penalties. In this paper a novel 3D-printed DCHX concept inspired by the bronchi arrangement of a human lung is introduced to address the shortcomings inherent in existing DCHX designs. The proposed lung-inspired DCHX utilizes two intertwined bicontinuous flow networks enabling highly efficient heat and mass transfer characteristics for augmented adsorption and regeneration processes at low pressure drop penalties. While the first network evenly distributes an incoming air stream through the entire volume of the lung-inspired DCHX, the second network volumetrically splits a cooling water stream within and through the first network. Effects of various parameters including air flow rate, outdoor air humidity ratio, and regeneration temperature on dehumidification performance and energy efficiency of the proposed lung-inspired DCHX were investigated. Experimental results indicated the proposed lung-inspired 3D-printed DCHX outperforms existing DCHX systems by demonstrating an excellent balance between a high volumetric adsorption rate and a low pressure drop penalty. The volumetric adsorption rate of the proposed lung-inspired DCHX technology is 54.8 g/m 3 -s, a more than two-fold improvement compared with state-of-the-art DCHX systems. Additionally, the lung-inspired DCHX offers high thermal energy efficiency of 56% at a low regeneration temperature of 40 °C. Therefore, the proposed lung-inspired 3D-printed DCHX offers a new solid-desiccant-based air dehumidification pathway for next-generation high-performance AC systems.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗