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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 703 records · Page 39
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Bundled multi-tube nozzle for a turbomachine

A turbomachine includes a compressor, a combustor operatively connected to the compressor, an end cover mounted to the combustor, and an injection nozzle assembly operatively connected to the combustor. The injection nozzle assembly includes a cap member having a first surface that extends to a second surface. The cap member further includes a plurality of openings. A plurality of bundled mini-tube assemblies are detachably mounted in the plurality of openings in the cap member. Each of the plurality of bundled mini-tube assemblies includes a main body section having a first end section and a second end section. A fluid plenum is arranged within the main body section. A plurality of tubes extend between the first and second end sections. Each of the plurality of tubes is fluidly connected to the fluid plenum.

42 ENGINEERING↗
DOE OSTI2016

System for supporting a bundled tube fuel injector within a combustor

A combustor includes an end cover having an outer side and an inner side, an outer barrel having a forward end that is adjacent to the inner side of the end cover and an aft end that is axially spaced from the forward end. An inner barrel is at least partially disposed concentrically within the outer barrel and is fixedly connected to the outer barrel. A fluid conduit extends downstream from the end cover. A first bundled tube fuel injector segment is disposed concentrically within the inner barrel. The bundled tube fuel injector segment includes a fuel plenum that is in fluid communication with the fluid conduit and a plurality of parallel tubes that extend axially through the fuel plenum. The bundled tube fuel injector segment is fixedly connected to the inner barrel.

42 ENGINEERING↗
DOE OSTI2017

Fuel nozzle tube retention

A system for retaining a fuel nozzle premix tube includes a retention plate and a premix tube which extends downstream from an outlet of a premix passage defined along an aft side of a fuel plenum body. The premix tube includes an inlet end and a spring support feature which is disposed proximate to the inlet end. The premix tube extends through the retention plate. The spring retention feature is disposed between an aft side of the fuel plenum and the retention plate. The system further includes a spring which extends between the spring retention feature and the retention plate.

42 ENGINEERING↗
DOE OSTI2020

Steam generator with inclined tube sheet

A steam generation system may include a plurality of heat transfer tubes configured to circulate a secondary coolant of the steam generation system. The steam generation system may be thermally coupled to a reactor vessel, and the reactor vessel may be configured to house a primary coolant. Heat generated from within the reactor vessel may be transferred from the primary coolant to the secondary coolant. The steam generation system may further include an inclined tube sheet fluidly coupled to the plurality of heat transfer tubes. The inclined tube sheet may be attached to a wall of the reactor vessel in a non-horizontal orientation.

42 ENGINEERING↗
DOE OSTI2021

Design Optimization of A-Type Heat Exchangers based on High Performance, Non-Round Tubes

Air-to-refrigerant heat exchangers (HXs) have been the topic of considerable research as they are the fundamental heat transfer components of HVAC&R systems. For residential and commercial applications, indoor heat exchangers are often in A-type configurations to reduce air-conditioner system footprint while still delivering the required cooling or heating. Classical HX design practices typically assume a uniform frontal air velocity profile to facilitate the use of conventional tube-fin airside heat transfer and pressure drop correlations for performance prediction. However, it is well-reported throughout the literature that A-type HXs experience significant airflow maldistribution which can severely degrade HX performance. Additionally, recent advancements in simulation software such as Computational Fluid Dynamics (CFD), Finite Element Analysis (FEA) and optimization algorithms have led researchers to consider primary heat transfer surface optimization to achieve highly compact HXs which do not require fins. In this paper, an A-type HX which utilizes shape-optimized non-round tubes is optimized for minimum duct size and airside pressure drop. This is achieved through coupling of an experimentally validated finite volume HX model with automated 2D CFD simulations of airflow through the HX for airside thermal-hydraulic performance evaluation. Preliminary results show that the optimal designs deliver similar capacity while achieving 20% reductions in airside pressure drop and duct cross-section area. Additionally, the optimal design apex angles in this study were similar to those from previous A-Type HX optimization studies for conventional tube-fin HX geometries, suggesting that the apex angle for optimal A-Type configuration performance may be independent of tube geometry.

42 ENGINEERING↗
DOE OSTI2021

Heat Transfer and Pressure Drop Characteristics of Water Flow Boiling in Internally Enhanced Tubes

Flow boiling is a critical process for many thermal conversion processes such as HVAC&R, water heating, power generation and desalination applications. The major goal of this paper is to enhance the in-tube heat transfer for flow boiling of water and further improve the efficiency of the boiler. This paper presents an experimental investigation of the heat transfer and pressure drop characteristics for water under forced convection and boiling conditions inside both smooth and enhanced tubes. The results in the smooth copper tube are compared with several correlations and used as a baseline. The two-phase heat transfer and pressure drop performance of the water flow boiling in the internally enhanced tube is investigated, and the influence of internal surface pattern on the thermal characteristics is discussed. The relations of the heat transfer coefficient with mass flux, heat flux and vapor quality are analyzed according to the results.

Yang, Cheng-Min↗
DOE OSTI2022

Multi-zone shell and tube heat exchanger

A shell and tube heat exchanger has elongated shell having first and second opposing ends and an open interior. A core divides the open interior of the shell into first and second enclosed portions. The shell has first and second tube fluid openings at opposing ends. End plates divide the first and second enclosed portions into manifold portions and enclosed shell chamber portions. Tubes extend from the end plates, through the enclosed shell chambers to the core. Shell fluid openings are at sides of the elongated shell, a first fluid opening communicating with the first shell chamber, and a second fluid opening communicating with the second shell chamber. The shell has a long axis, and the end plates are angled relative to the long axis. The tubes are polygonal with rounded corners and straight sides. The heat exchanger can be used for both evaporation and condensation processes.

Sabau, Adrian S.↗
DOE OSTI2021

Creating Hydride Rim Structures in Zircaloy 4 Cladding Tubes to Mimic High Burnup

During their long service in commercial light water reactors, zirconium alloy cladding tubes are subject to oxidation and subsequent hydrogen pickup which can degrade the materials mechanical properties [1]. These degradations can lead to premature cladding ruptures during reactor power transients [2] as well as negatively impact the claddings post quench ductility following high temperature steam oxidation in thermal hydraulic transients [3]. Hydrogen has low solid solubility in zirconium and usually precipitates as brittle zirconium hydride platelets in the cladding metal matrix. Due to temperature driven diffusion (Soret effect) and the grain texture of stress relieved zirconium metal tubes, these hydrides precipitate with a circumferential orientation near the outer surface of the cladding tubes forming a hydride rim which can serve as a site for crack initiation during circumferential ‘hoop’ loading of the cladding [4rim formation][5]. In order to better understand the effect of hydride rims on the fracture behavior of stress relieved zirconium alloy cladding tubes a procedure to produce these rim-like structures is being developed at Idaho National Laboratory (INL).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2022

Monocoque shell and tube heat exchanger

A heat exchanger with a monocoque structure transfers heat between a first fluid and a second fluid. The heat exchanger in has a plurality of tubes through which the first fluid may flow in a direction, each of the plurality of tubes has a first mouth end, an N opposing second mouth end and a waist region between the first mouth end and the second mouth end. The heat exchanger also has one or more interconnected fluid channels through which the second fluid may flow, the one or more fluid channels lay generally in a plane, the plurality of tubes and the one or more fluid channels interleave such that heat may be transferred between the plurality of tubes and the one or more fluid channels, and the direction of flow of the first fluid is generally perpendicular to the plane of the one or more fluid channels.

Keolian, Robert M.↗
DOE OSTI2023

EXPERIMENTAL ANALYSIS OF SINGLE EVAPORATION TUBE UTILIZING SINTERED COPPER PARTICLE WICKING STRUCTURES

Wicking structures have been widely used within passive heat transfer devices with high heat fluxes, such as heat pipes, to enhance their thermal performance. While wicking structures promote capillary pumping of the working fluid as well as thin film evaporation, they can result in capillary evaporation and further enhances the evaporation heat transfer. In this study, a 0.5 mm thick layer of 105 microns sintered copper particles was added to the inner wall of a copper tube, aiming to enhance the heat transfer characteristics by taking advantage of capillary evaporation. Acetone was chosen as the working fluid, and the performance of an evaporation tube was tested for power inputs of 10, 30, 50, and 70 W. For each power input, trials were run at inclination angles varying from -90° and 90° to investigate the capillary effects. The temperature measurements showed that the temperature distribution along the evaporation tube is always downward sloping, meaning the temperature at the fluid inlet is larger than the outlet. Interestingly, the surface temperature at some locations is less than the outlet temperature, indicating the effect of capillary evaporation. In addition, a theoretical investigation was performed to investigate the effects of the particle size on the thermal performance of the evaporation tube and found that particle sizes affect capillary evaporation.

Wang, Pengtao↗
DOE OSTI2016

Corrosion test of LWR cladding tubes in high temperature seawater

In the case of cooling system failure in spent fuel pools (SFP) due to station black out and/or loss of coolant accidents, a pool water level must be kept high enough to avoid overheat of spent fuels. Seawater is one of the candidate coolant materials in such emergencies. In the present work, we have studied the corrosion behavior of zirconium alloys in seawater. Tube samples of Zircaloy-2 and -4 claddings were immersed in artificial seawater (3, 10 and 20 wt.%) at high temperature (80 - 85 Celsius degrees). Boric acid was added to the seawater at a corrosion test of Zircaloy-4. Two types of specimens were prepared according to the simulation of circumferential tensile stress. One was a plugged tube specimen, which was pressurized to around fuel rod pressure in a spent fuel pool by argon gas. Another specimen was of C-ring shape, where large circumferential tensile stress was partially induced at the surface. A notch was longitudinally grooved to increase the local tensile stress on some of the C-ring specimens. The specimen surface was observed by a scanning electron microscopy (SEM) after the corrosion test. After the 200 day long corrosion test for the plugged tube specimens without boric acid, Mg(OH){sub 2} deposits were observed on the surface of Zircaloy-2 and -4 specimens whereas Mg(OH){sub 2} was not observed with boric acid because of probably a lower pH. Neither pitting corrosion nor stress corrosion cracking (SCC) was observed on the surface of all plugged tube specimens. Only in the C-ring specimens in 20 wt.% seawater without boric acid and in 3 and 10 wt.% seawater with boric acid, small cracks were observed at the notch. The results of the present work show that Zircaloy-2 and -4 have a high tolerance towards corrosion and SCC in high temperature seawater.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Turbulence Model Study for Pressure and Velocity Distributions for Molten Salts in a Crossflow Tube Bundle

Empirical pressure drop correlations for various compositions of molten salts in crossflow across tube bundles/banks are limited due to the scarcity of experimental data for these fluids. This lack of experimental data presents a limitation when designing heat exchangers for Molten Salt Reactors (MSRs) that utilize cross-flow configurations with turbulent molten salts flowing in the shell side. In an effort to provide a starting point for future design and experimental work, a computational fluid dynamics (CFD) campaign is being conducted to estimate pressure drops over a range of Reynolds numbers, pitch to diameter ratios, and for both staggered and in-line tube banks. In an effort to continue this work, the study of various turbulence models were conducted to determine the applicability for steady RANS simulations. An in-line tube bank with FLiBe (LiF-BeF{sub 2}), a frequently selected molten salt in MSRs, was selected for these simulations. The estimated pressure drops and pressure and velocity distributions for each turbulence model was compared to determine the applicability. The k-ε turbulence model family was found to be the most appropriate model for steady Reynolds averaged Navier Stokes within this type of domain. Difference turbulence models were investigated for simulation of molten salt experiencing crossflow within an in-line tube bundle. The flow was simulated using a steady RANS formulation with different families of turbulence models. The different turbulence models provide a view of this specific flow behavior potential requirements and applicable for steady RANS. Of particular note, the k-ε models were able to converge easily within this domain. The predicted behavior for both models were observed to be mostly similar for both velocity and pressure distributions. Whereas, k-ω SST and SA models did not converge well and had observable differences for the predictions of pressure and velocity distributions. The global behaviors were generally similar, but the variations occurring suggest k-ω SST and SA turbulence models are not useful in the steady RANS formulation of this domain. When comparing to the empirical pressure drop, each turbulence model resulted in overpredictions ranging from 8.7% and 19.75% difference. The standard low-Re k-ε model having the lowest difference is likely the better model for simplified predictions for pressure drops. Further investigations will be conducted to determine the convergence issues for the k-ω SST and SA turbulence models. These might be due to the flow geometry or potentially a revision of the meshing is needed. The flow behavior may not be resolved using these models in a steady formulation due to inherent unsteadiness of the flow. (authors)

42 ENGINEERING↗
DOE OSTI2016

Thermal hydraulic issues of HTGR helical tube once through steam generator: methods and applications - 18478

High Temperature Gas-cooled Reactor (HTGR) usually uses helical tube once through steam generators (OTSG) for steam generation. The most concerned thermal hydraulic issues of HTGR helical tube OTSG are two phase flow instability and temperature non-uniformity. One dimensional transient code and two dimensional code are developed to investigate these two issues. The codes are briefly introduced, then the results are briefly presented and discussed. The main conclusions are that there does not appear two phase instability for all the working conditions for the steam generator of HTR-PM. Tube plugging can introduce temperature non-uniformity in the tube bundle. The temperature non-uniformity can be evened by changing the flow rate distribution through adjusting the throttle orifice at the inlet. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2016

Development and Verification of MATLAB Functions for Pressure Drop Estimation in Crossflow Tube Bundles

The experimental data on drag coefficients in crossflow tube bundles is severely limited. It is largely contained in nomograms for a small range of tube bundle pitch ratios for both in-line and staggered bundles. These monograms and the corresponding correlations/curve fits are not readily accessible. This lack of experimental data presents a limitation when designing crossflow heat exchangers for nuclear reactors. Specifically, Molten Salt Reactors (MSRs) that utilize cross-flow configurations with turbulent molten salts flowing in the shell side are of interest. Current methods of calculating the drag coefficients are outdated and time consuming when conducting design studies (i.e. picking points off a graph). A computer script could easily run the necessary rapid calculations of the pressure drop for a large possible range of Reynolds numbers, pitch ratios and tube bundle configurations. In an effort to facilitate increased access and accuracy to crossflow pressure drop calculations, a set of MATLAB scripts have been created. These are specifically for the pressure drop and drag coefficients for flow over rows of in-line and staggered tube bundles. For verification of the scripts, the nomograms produced by Zukauskas, of which the scripts are built off, served as a comparison to the plot generated by the MATLAB scripts. (authors)

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2017

Development of Scaling Criteria for Modeling Condensation in Horizontal Tubes Using Reduced Pressure System and Simulant Fluid

Most of the currently operating nuclear power plants (NPPs), generation-II and III, are equipped with active safety systems, which raises concerns regarding those safety systems' operational reliability and the suitability of the accidents prevention measures. Following the severe accidents at nuclear power plants at Three Mile Island, Chernobyl, and recently in Fukushima some advance Pressurized Water Reactors (PWRs) have adopted passively cooled steam generator natural circulation system to remove the decay heat passively through the steam generator (SG). This is done by condensing steam from the steam generator inside a heat exchanger submerged in a tank of water or an air cooled system. The APR+ (Advanced Power Reactor Plus), which is currently being developed in South Korea, has adopted a Passive Auxiliary Feedwater System (PAFS), which removes the decay heat through the steam generator replacing the conventional active auxiliary feedwater system. The main part of the PAFS, in where the steam condenses, is the Passive Condensation Heat Exchanger (PCHX). The steam condenses under high pressure (7.4 MPa, 290 deg. C) in 8.4 m long horizontal tube, with 3 degrees inclination, with inner diameter of 44.8 mm and wall thickness of 3 mm. The PCHX consists of 4 bundles, each bundle has 60 condensation tubes. The performance of the PCHX performance should be evaluated. Condensation has been extensively studied; however, most previous experimental work was directed to low pressure (i.e., near atmospheric pressure) and small condensation tubes. Moreover, studies on the horizontal type heat exchanger are limited, since previous safety systems and experimentation work were directed to the vertical type heat exchangers. Due to the high construction cost of a full size high pressure condensation experiment, a reduced-size reduced-pressure condensation experiment is suggested to evaluate the heat removal performance of a condensation tube of the PAFS heat exchanger. A scaling methodology to be established to design a reduced-size reduced-pressure condensation experiment. This study attempts to develop a scaling criteria for the PAFS condensation system, and to apply it for modeling a high pressure water system by a low pressure Freon system.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
DOE OSTI2012

Microhole Tubing Bending Report

A downhole tubing bending study was made and is reported herein. IT contains a report and 2 excel spreadsheets to calculate tubing bending and to estimate contact points of the tubing to the drilled hole wall (creating a new support point).

15 GEOTHERMAL ENERGY↗
DOE OSTI2022

The annihilation of antiphase boundary tubes and their effect on strengthening in Ni 3 Al

The temperature at which antiphase boundary (APB) tubes anneal out of lightly-strained Ni-rich Ni 3 Al thin foils has been measured via in-situ heating in a transmission electron microscope to be ~530 °C. Given this new information, the wealth of literature on the mechanical properties of Ni 3 Al across the entire temperature regime of the yield stress anomaly, ~25–800 °C, is re-evaluated to consider the impact of APB tubes. Contrary to previous theoretical predications, APB tubes do not appear to affect the strength of Ni 3 Al.

36 MATERIALS SCIENCE↗
DOE OSTI2020

A microchannel shell-and-tube absorber for ammonia-water absorption

A shell-and-tube absorber with microscale geometric features that yields significant volumetric heat duties is investigated. A vertically-oriented baffled shell-and-tube heat exchanger with a tightly packed tube bundle is designed to serve as the absorber for a 10.5 kW nominal cooling capacity absorption chiller. The heat and mass transfer in this absorber is investigated experimentally at operating conditions spanning a wide range of working fluid and coupling fluid flow rates and ambient temperatures. An experimental facility is fabricated to closely simulate the operating conditions in an absorption refrigeration system. Absorption heat duties in the range of 5-15 kW are measured. In addition to operating the absorber in the baseline co-current flow configuration with premixed inlet, fluid ports are provided to enable operation in counter-current flow, where the dilute solution enters from the top and vapor enters from the bottom. The performance of these two flow configurations is compared. A preliminary heat and mass transfer model is developed to quantify the local temperatures, concentrations, and mass flow rates of the solution and vapor streams along the length of the absorber. The model predictions for total heat duty agree with the experimental results within 10% for almost all the data points, with an AAD of ~3.4%. Finally, the results of this study, along with the modeling framework, can guide further development of highly compact and efficient absorbers absorption systems.

42 ENGINEERING↗