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At least 145 records · Page 8

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DOE OSTI2026

Upper ocean mixing, surface heat fluxes, and heat content variability in the upper 150 m during Hurricane Laura (2020)

Observations (from thermistor sensors and a hurricane glider) and model-based temperature were used to answer questions including the following: 1) What physical and environmental conditions explain the rapid intensification of Hurricane Laura? 2) How did the pre-existing warm mixed layer at Stone mooring (StM) influence the degree of cooling in the mixed layer? 3) How did vertical mixing, surface heat fluxes, and advective processes collectively shape the mixed layer heat evolution at StM? Observations measured by thermistor sensors showed that Hurricane Laura induced a cooling of -1.2oC in the mixed layer when Hurricane Laura’s wind speed increased to 47 m/s on 26 August. This contrasts with the -1.04oC mixed layer temperature change estimated from model-based temperature. At StM, the presence of a 31oC warm mixed layer and elevated heat content (60-80kJ/cm2) effectively preconditioned the upper ocean ahead of Hurricane Laura’s passage. After Hurricane Laura passed, turbulent mixing associated with the storm transported the heat anomalies downward into subsurface layers. In addition, this study shows that a surface heat flux of 5.04 kJ/cm2 supported the intensity of Hurricane Laura as it traversed over the StM. Using a mixed layer heat balance model, this study shows that entrainment flux and surface flux mostly contributed to the observed change in the mixed layer temperature.

Tsai, Senam↗

DOE OSTI2023

Heat Transfer of an Integrated Counterflow Ceramic Heat Exchanger

The ceramic-based heat exchanger is one of the leading contenders for high-efficiency concentrating solar power plants using a molten salt heat transfer fluid and a supercritical carbon dioxide Brayton power cycle operating at temperatures above 700 °C due to the excellent resistance of ceramics to corrosion, oxidation, erosion, creep, and fouling. In the present study, the thermal performance of a ceramic silicon carbide prototype heat exchanger, with semi-elliptical heat transfer channels, integrated header channels, and a counterflow configuration fabricated by using binder jetting additive manufacturing, was experimentally investigated. Experimental heat transfer tests of the prototype were conducted at high temperatures and under various test fluid flow rates and inlet temperatures. The experimental heat transfer rates compared favorably with simulation predictions.

Yu, Wenhua (ORCID:0000000219457014)↗

DOE OSTI2024

Novel PCM-based fin and tube heat exchanger system for building heating and cooling applications

In the United States, the building sector accounts for 40% of all energy use, and buildings are responsible for more than two-thirds of electricity consumption. Buildings remain the major driver of energy-related carbon emissions, and such emissions are projected to increase in the years ahead because of urbanization and population growth. To accomplish the low carbon energy goal in the building sector, phase change material (PCM)–based thermal energy storage (TES) is increasingly being adopted because it offers several advantages, such as reducing building peak load and energy consumption, enabling large scale deployment of renewables, and improving grid stability. The integration of TES with thermally anisotropic building envelopes (TABEs) is a promising solution because, TABE can redirect natural thermal energy from a building using hydronic loops to TES, and the stored energy can be used later for heating and cooling applications. In this study, we experimentally investigate the thermal performance of a novel fin-tube heat exchanger TES system designed for potential integration with a TABE. An experimental rig for a 5-gal PCM fin-tube heat exchanger system with water as the heat transfer medium is described which records temperatures at the heated and cooled boundaries of the system. Experimental observations provide insight into the role a TES system can play in offsetting a building’s heating and cooling demand and also offer a means to characterize the performance of PCMs for building applications. The scale and study presented in this work will help in the design of future thermal storage systems optimized for storage capacity while also accounting for overall system costs for building applications.

Tamraparni, Achutha↗

DOE OSTI2021

Verification and Validation Tests of Gamma Library of MC2-3 for Coupled Neutron and Gamma Heating Calculation

For the accurate assessment of the heat generation rate in fast reactors, the gamma library of MC2 -3 and the MC2 -3 + GAMSOR procedure employing the coupled neutron and gamma heating calculation has been thoroughly verified against Monte Carlo results and validated using the ZPPR-15D gamma dose measurement data. NJOY outputs are post-processed in a consistent way with the NJOY procedure to avoid any missing data or double counting of data. Prompt heating for 379 out of 391 isotopes in the gamma library was verified against MCNP6.2 to within 1% relative error in total heating for most isotopes. For both a simple one-dimensional slab problem representing a sodium cooled fast reactor and the Experimental Breeder Reactor II (EBR-II) benchmark problem, the root-mean-square values of assembly power error were less than 0.5% for fuel assemblies, ~1% in blankets and ~1 to ~3% in reflectors compared to MCNP6.2 results. The most plausible cause for the 3% error in a reflector assembly is believed to be the error in the multigroup neutron cross sections for the reflector assembly. For validation, gamma doses measured with thermoluminiscent dosimeters (TLDs) in the ZPPR-15D experiment were calculated using GAMSOR. Due to the uncertainty in the TLD measurement with regards to the energy deposition of photons and neutrons, the validation data leads to a 12.7% uncertainty on the experimental measurement. With this uncertainty bound, the calculated doses all fell within one standard deviation of the measured value. Combined with the accurate calculation of reaction rate distributions and neutron spectrum measurements, these results indicate good agreement for the neutron and gamma heating calculations that were performed.

coupled neutron and gamma heating↗

DOE OSTI2026

Flow dynamics and heat transfer in simplified battery energy storage systems with heated battery modules

Large-scale energy storage systems (ESSs) composed of batteries show promise in addressing current energy challenges, but dissipation of generated heat is important. Here, this paper focuses on buoyant convective flows in simplified ESS battery racks. Natural convection is not generally the primary cooling strategy but can be important in abnormal scenarios where there is module overheat or potentially thermal runaway. We use computational fluid dynamics to investigate the flow dynamics and heat transfer mechanisms in a simplified parameterized rack design. Despite its simplicity, this configuration produces many of the relevant features expected in real ESSs without details of module geometry or hardware, allowing broad conclusions independent of manufacture-specific designs. We start by providing visualizations of the flowfield and measurements of entrainment, heat flux, and pressure. To characterize the dependence on the system parameters, we develop an integral-scale analysis of the average temperature equation to highlight the dominant source terms. We use results from this analysis to derive a steady network model composed of simple algebraic expressions to provide first-order predictions of entrainment through the rack. The network model leads to a linear scaling of the Reynolds number based on convective mass flux with respect to the Grashof number based on the heat source. We deduce empirical relationships that relate the heat exchanged between modules using a surface-averaged Nusselt number as a function of the local Reynolds and Rayleigh numbers. Lastly, we investigate how space between the modules and rack in the spanwise direction creates flow bypass, resulting in different flow pathways.

Battery thermal management↗

DOE OSTI2023

SiC Microchannel Heat Sinks for High Heat Flux Dissipation of 1 kW/cm 2

Thermal management has become a major barrier in the development of high-power micro-devices. Microchannel heat sinks (MCHS) are a promising method to dissipate high heat fluxes from high power density devices. Reducing the thermal resistance will reduce the temperature increase of the electronic device, allowing for higher powers to be achieved while maintaining a safe operating temperature. This paper reports on the use of silicon carbide (Sic) microchannels to dissipate high heat fluxes up to 1 kW/cm 2 over a footprint of 0.25 cm 2 . The use of high aspect ratio and decreased hydraulic diameter channels has allowed for very low thermal resistances to be achieved at higher heat duties compared to previous studies. The experiments performed resulted in heater temperatures of less than 60 °C and thermal resistances as low as 0.024 cm 2 . ° $C$/W between the heater surface and fluid inlet temperature. In conclusion, the demonstrated thermal performance of the SiC MCHS is an encouraging means for dissipating heat from high power density microelectronic devices.

42 ENGINEERING↗

DOE OSTI2021

A Comparative Study of Layer Heating and Continuous Heating Methods on Prediction Accuracy of Residual Stresses in Selective Laser Melted Tube Samples

Thermal distortion and residual stresses are two important factors that affect the quality and reliability of steel parts manufactured by laser powder bed fusion (LPBF) processes. A cost-effective model for evaluation of those heat effects is needed to refine the manufacturing process and provides insights into the product design and heat treatment. In this study, the layer heating method and sophisticated track-layer scanning method were applied to simulate the thermo-mechanical response of IN625 tube parts built by LPBF. Based on the similarity of temperature field in each layer deposit, a swept mesh was constructed to perform the thermal analysis for top layer, with the rest of layers referring to the temperature by node number offsetting. A novel explicit finite element analysis code accelerated by graphics processing unit was used for the massive-element numerical analysis. The computational accuracy and efficiency of the layer heating and track-layer scanning methods were compared in detail. It is shown that layer heating method can efficiently capture the pattern of stress distribution with reasonable accuracy in stress magnitude. The grouped track-layer scanning method can predict the residual stress and strain more accurately at a higher cost (5 ~ 10×). The elastic strain distribution was compared with the measurement by X-ray diffraction, confirming the accuracy of residual stress prediction.

36 MATERIALS SCIENCE↗

DOE OSTI2021

Heat and mass transfer during a sudden loss of vacuum in a liquid helium cooled tube - Part III: Heat deposition in He II

A sudden loss of vacuum can be catastrophic for superconducting particle accelerators. In such an event, air leaks into the liquid-helium-cooled accelerator beamline tube and condenses on its inner surface, causing rapid boiling of the helium and dangerous pressure build-up. Understanding the coupled heat and mass transfer processes is important for the design of the beamline cryogenic system. Our past experimental study on nitrogen gas propagating in a copper tube cooled by normal liquid helium (He I) has revealed a nearly exponential slowing down of the gas front. A theoretical model that accounts for the interplay of the gas dynamics and the condensation was developed, which successfully reproduced various key observations. However, since many accelerator beamlines are actually cooled by superfluid helium (He II) in which the heat transfer is via a non-classical thermal counterflow mode, we need to extend our work to the He II cooled tube. This paper reports our systematic measurements using He II and the numerical simulations based on a modified model that accounts for the He II heat-transfer characteristics. By tuning the He II peak heat-flux parameter in our model, we have reproduced the observed gas dynamics in all experimental runs. The fine-tuned model is then utilized to reliably evaluate the heat deposition in He II. Finallly, this work not only advances our understanding of condensing gas dynamics but also has practical implications to the design codes for beamline safety.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

DOE OSTI2021

Iodine capture with mechanically robust heat-treated Ag-Al-Si-O xerogel sorbents

Silver-loaded heat-treated aluminosilicate xerogels (Ag-HTX) were evaluated as sorbents for iodine [I2(g)] capture. The heat treatment step was performed to help increase the mechanical integrity of the gels. The synthesized xerogels were characterized using powder X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Brunauer-Emmett-Teller analysis, gravimetric iodine loading, nanoindentation, and dynamic mechanical analysis. The structural and chemical analyses of Ag-HTX showed uniform distribution of Ag throughout the gel network after Ag-exchange. After I2(g) capture, the AgI crystallites were observed in the sorbent verifying chemisorption as the iodine capture mechanism. Iodine loading of this xerogel was 0.43 g g-1 at 150°C over 1 d and 0.52 g g-1 at 22°C over 33 d. The specific surface area of Ag-HTX was 202 m2 g-1 and decreased to 87 m2 g-1 after iodine loading. The hardness of the heat-treated xerogel was 160 times higher than heat-treated aerogel of the same composition. The heat-treatment process increased the modulus value to 40.77 MPa from 6.99 MPa of as-made xerogel, demonstrating the need for this added step in the synthesis process. These results show that Ag-HTX is a promising sorbent for I2(g) capture with good loading capacity and mechanical stability.

xerogels, aerogels, iodine capture, hardness testi↗

DOE OSTI2023

Role of heating and turbulent heat transfer in HE burning and detonation

Enhanced heat transfer model has been developed due to the turbulence in the cracks and pores in the burning fractured HE. This turbulence then serves in the initialization of the turbulence in the product gas. Enhanced heat transfer is also modeled in the turbulent product gas. Numerical simulations of the onset of HE burning and transition to detonation have been performed with and without the turbulent heat transfer model. Computational results indicate that onset of chemical reactions and transition to detonation is induced by the shockwave formed by the pressure rise caused by the heating. In other words, processes similar to shock-to-detonation transition (SDT) could become the driving mechanism for HE explosion and detonation in the case of heating rather than the temperature alone.

45 MILITARY TECHNOLOGY, WEAPONRY, AND NATIONAL DEF↗

DOE OSTI2024

Neutronics Analysis of Heating and DPA of the Proton Beam Window and Core Vessel Nozzle Neutronics Heating Analysis for the Second Target Station

This reports details the analysis of the heating rates, dpa values and He production in the Proton Beam Window (PBW) assembly and the Core Vessel (CV) nozzle for the preliminary design for the Second Target Station (STS). This analysis focuses on the heating rates in the cooled beltline component of the CV. Neutronics calculations use a detailed unstructured mesh (UM) converted from a CAD model in SpaceClaim of the PBW and CV design of February 2024. The rest of the geometry is taken from the STS master model in constructive solid geometry (CSG). Heating is evaluated for four beam profiles, which are chosen as the most likely to produce the highest heating in the beltline component. The maximum energy deposition values in the beltline are 0.02-0.08 J/cc/pulse, depending on the beam profile. Detailed point cloud data of the full UM geometry is made available for mechanical analysis. The maximum dpa rate in the beltline steel is approximately 0.02 dpa/year, which corresponds to a lifetime of 3,000 years. These results are in good agreement with previous results for the CV. For the PBW itself, maximal heating, dpa, and He production rates are very similar to the previous analysis.

43 PARTICLE ACCELERATORS↗

DOE OSTI2022

Coupling Chemical Heat Pump with Nuclear Reactor for Temperature Amplification by Delivering Process Heat and Electricity: A Techno-Economic Analysis

The energy economy is continually evolving in response to socio-political factors in the nature of primary energy sources, their conversions to useful forms, such as electricity and heat, and their utilization in different sectors. Nuclear energy has a crucial role to play in the evolution of energy economy due to its clean and non-carbon-emitting characteristics. A techno-economic analysis was undertaken to establish the viability of selling heat along with electricity for an advanced 100 MWth small modular reactor (SMR) and four nuclear hybrid energy system (NHES) configurations featuring the SMR paired with chemical heat pump (ChHP) systems providing a thermal output ranging from 1 to 50 MWth. Net present value, payback period, discounted cash flow rate of return, and levelized cost of energy were evaluated for these systems for different regions of U.S. reflecting a range of electricity and thermal energy costs. The analysis indicated that selling heat to high temperature industrial processes showed profitable outcomes compared to the sale of only electricity. Higher carbon taxes improved the economic parameters of the NHES alternatives significantly. Providing heat to high temperature industries could be very beneficial, helping to cut down the greenhouse gases emission by reducing the fossil fuel consumption.

Gupta, Aman↗

DOE OSTI2021

Heat pipe reactor core and heat exchangers formation and deployment

A heat pipe reactor may include a reactor core and one or more heat exchangers positioned on one or both sides of the reactor core. The heat pipe reactor may also include a plurality of heat pipes extending from the reactor core and out through the one or more heat exchangers. The reactor core may be composed of a plurality of monolithic blocks.

Reid, Robert Stowers↗

DOE OSTI2023

Searching for eco-friendly working fluids for an ejector-driven heat pump for domestic water heating

This study searches for refrigerants with low global warming potential (GWP) and zero ozone depletion potential (ODP) for an ejector heat pump water heater (EHPWH). Several criteria are set, and R1336mzz(Z), R601a, R1233zd(E), R1224yd(Z), R1234ze(Z), and R600a are shortlisted. A theoretical model is built to study the performance of EHPWH and the corresponding ejector design at different operating conditions. For the same ejector design, a refrigerant with a high specific heat ratio produces a high entrainment ratio and heating COP. This is because the expansion wave angle in the ejector is small for refrigerants with a high specific heat ratio, allowing more mass flow rate to be entrained. A higher entrainment ratio does not necessarily correlate to a high COP because the saturation curve of the tested refrigerants is not the same. Results show that the heating COP of R601a is the highest, but it is extremely flammable. R1224yd(Z) and R1234ze(Z) are the most candidates for EHPWH when the trade-off between the COP and safety criteria is considered. The results presented in this work could help building an EHPWH using eco-friendly refrigerants.

Mohammed, Ramy H.↗

DOE OSTI2023

Exploration of Heat-Driven Ejector High-Temperature Heat Pumps

Heat-driven ejector heat pumps use a supersonic ejector as a thermo-compressor to replace the mechanical compressor. Supersonic ejectors have many advantages in high-temperature heat pump (HTHP) applications, including high operating temperature tolerance, no need for lubrication, low maintenance, and low cost. The coefficient of performance of ejector HTHPs could be improved by selecting binary fluids with unique thermodynamic properties. Although supersonic ejectors have been widely used in refrigeration systems, their application in spaces and water heating is limited. This study explores the theoretical potential of ejector HTHPs with a sink temperature of 100°C–130°C and a lift temperature of 10°C–30°C. Ejector HTHPs were evaluated with single-fluid ejectors (SFEs) and binary-fluid ejectors (BFEs). A comprehensive, geometry-free theoretical model of BFEs was developed to predict the theoretical maximum entrainment ratios. HFE7500 and R718 (water) were selected as working fluids for SFEs and BFEs. SFEs operating with R718 provided a higher coefficient of performance of ejector HTHPs than SFEs operating with HFE7500 and BFEs. This study preliminarily demonstrates the technical potential of ejector HTHP applications in recovering moderate-temperature heat sources

Wang, Pengtao↗

DOE OSTI2024

Plate heat exchanger for heating or cooling bulk solids

A heat exchanger includes an inlet for receiving bulk solids, a plurality of heat transfer plate assemblies, a plurality of spacers disposed between adjacent heat transfer plate assemblies, and supports for supporting the heat transfer plate assemblies. The heat transfer plate assemblies include a first plate having a first pair of holes extending therethrough, the first plate having channels extending along a surface thereof, for the flow of fluid through the channels, and a second plate bonded to the first plate to enclose the channels, the second plate including a second pair of holes generally aligned with the first pair of holes to form through holes to facilitate flow of the fluid through the through holes and the channels.

Byman, Ashley D.↗

DOE OSTI2024

Economic assessment of a multistage surface-heated vacuum membrane distillation process for the treatment of hypersaline produced water

Here, the treatment and disposal of hypersaline produced water remains a challenge, particularly for oil and gas producers in the Permian basin where production wells generate significant amounts of wastewater, and the traditional method of injecting wastewater into disposal wells is coming under increasing scrutiny. Here we investigate the viability of using solar energy to power a multi-stage, surface heated, vacuum membrane distillation (SHVMD) with energy recovery to treat hypersaline produced wastewater from Midland, Texas. Membrane distillation is a process that can desalinate waters with high total dissolved solids concentration, and when incorporated into a system with surface heating and energy recovery can achieve high water recovery rates. Model results show that a 6-stage SHVMD system with a 54.4 % water recovery rate and a gained output ratio (GOR) of 3.28 has the potential to be economically viable when used to treat hypersaline produced water in the Permian basin. Assuming energy costs of $\$0.03$/kWh thermal and $\$0.12$kWh electric , we estimate a project net present value (NPV) of $\$225,525$ and an internal rate of return (IRR) of 13.5 % when an air cooled condensor is used to cool the distillate and a NPV of $\$570,791$ and IRR of 24.52 % when a liquid coooling source is available.

29 ENERGY PLANNING, POLICY, AND ECONOMY↗

DOE OSTI2022

Numerical Analysis of Liquid Metal MHD Flow and Heat Transfer for Open-Surface Li Divertor in FNSF

Within the ongoing U.S.-based program on the development of liquid metal plasma-facing components, numerical simulations and analyses are performed to address the feasibility of the open-surface Li divertor. In the previous scoping studies (Smolentsev, 2021), heat-removal capabilities of the divertor were assessed using a simplified flow model for a slug-type velocity profile and constant flow thickness. Here, new analyses take into account forces acting on the flowing Li layer. Three reduced-order mathematical models are applied under the conditions of the U.S. Fusion Nuclear Science Facility (FNSF) to access magnetohydrodynamic (MHD) flow development effects, velocity distribution, and surface waves: 1) fully developed MHD flow; 2) quasi-2-D developing MHD flow; and 3) multiphase MHD flow. The obtained results for MHD flows and the surface heat flux computed with the plasma code scrape-off layer plasma simulation for ITER (SOLPS-ITER) are then used as input data to compute the temperature distribution in the divertor by solving the convection–diffusion energy equation.

Smolentsev, Sergey↗