Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “dimensional changes”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 559 records · Page 31
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Correlated k-distribution method for radiative transfer in climate models: Application to effect of cirrus clouds on climate

A radiative transfer method appropriate for use in simple climate models and three dimensional global climate models was developed. It is fully interactive with climate changes, such as in the temperature-pressure profile, cloud distribution, and atmospheric composition, and it is accurate throughout the troposphere and stratosphere. The vertical inhomogeneity of the atmosphere is accounted for by assuming a correlation of gaseous k-distributions of different pressures and temperatures. Line-by-line calculations are made to demonstrate that The method is remarkably accurate. The method is then used in a one-dimensional radiative-convective climate model to study the effect of cirrus clouds on surface temperature. It is shown that an increase in cirrus cloud cover can cause a significant warming of the troposphere and the Earth's surface, by the mechanism of an enhanced green-house effect. The dependence of this phenomenon on cloud optical thickness, altitude, and latitude is investigated.

Lacis, A. A.↗
DOE OSTI2020

Reversible Interlayer Sliding and Conductivity Changes in Adaptive Tetrathiafulvalene-Based Covalent Organic Frameworks

Ordered interlayer stacking is intrinsic in two-dimensional covalent organic frameworks (2D COFs) and has strong implications on COF's optoelectronic properties. Reversible interlayer sliding, corresponding to shearing of 2D layers along their basal plane, is an appealing dynamic control of both structures and properties, yet it remains unexplored in the 2D COF field. In this paper, we demonstrate that the reversible interlayer sliding can be realized in an imine-linked tetrathiafulvalene (TTF)-based COF TTF-DMTA. The solvent treatment induces crystalline phase changes between the proposed staircase-like sql net structure and a slightly slipped eclipsed sql net structure. The solvation-induced crystallinity changes correlate well with reversible spectroscopic and electrical conductivity changes as demonstrated in oriented COF thin films. In contrast, no reversible switching is observed in a related TTF-TA COF, which differs from TTF-DMTA in terms of the absence of methoxy groups on the phenylene linkers. This work represents the first 2D COF example of which eclipsed and staircase-like aggregated states are interchangeably accessed via interlayer sliding, an uncharted structural feature that may enable applications such as chemiresistive sensors.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2016

Mechanotransductive Regulation of Gap-Junction Activity Between MLO-Y4 Osteocyte-Like and MC3T3-E1 Osteoblast-Like Cells in Three-Dimensional Co-Culture.

Cell and animal studies conducted onboard the International Space Station and formerly on Shuttle flights have provided groundbreaking data illuminating the deleterious biological response of bone to mechanical unloading. However the intercellular communicative mechanisms associated with the regulation of bone synthesis and bone resorption cells are still largely unknown. Connexin-43 (CX43), a gap junction protein, is hypothesized to play a significant role in osteoblast and osteocyte signaling. The purpose of this investigation was to evaluate within a novel three-dimensional microenvironment how the osteocyte-osteoblast gap-junction expression changes when cultures are exposed to exaggerated mechanical load. MLO-Y4 osteocyte-like cells were cultured on a 3D-Biotek polystyrene insert and placed in direct contact with an MC3T3-E1 pre-osteoblast co-cultured monolayer and exposed to 48 h of mechanical stimulation (pulsatile fluid flow (PFF) or monolayer cyclic stretch (MCS)) then evaluated for viability, proliferation, metabolism, and CX43 expression. Mono-cultured MLO-Y4 and MC3T3-E1 control experiments were conducted under PFF and MCS stimulation to observe how strain application stimuli (PFF cell membrane shear or MCS cell focal adhesion/attachment loading) initiates different signaling pathways or downstream regulatory controls. TotalLive cell count, viability and metabolic reduction (Trypan Blue, LIVEDead and Alamar Blue analysis respectively) indicate that mechanical activation of MC3T3-E1 cells inhibits proliferation while maintaining an average 1.04E4 reductioncell metabolic rate, *p0.05 n4. MLO-Y4s in monolayer culture increase in number when exposed to MCS loading but the percent of live cells within the population is low (46.3 total count, *p0.05 n4), these results may indicate an apoptotic signaling cascade. PFF stimulation of the three-dimensional co-cultures elicits a universal increase in CX43 in MLO-Y4 and MC3T3-E1 cells, illustrated by immunohistological observation. Increased CX43 expression is also observed with the three-dimensional co-cultures with MC3T3-E1 MCS stimulation but the increased gap-junction protein presence was limited to the osteoblast-osteocyte interface region. Previously reported PCR evaluation of osteogenic markers further corroborate that the co-cultured populations communicative networks play a role in translating mechanical signals to molecular messaging. These findings suggests an osteocyte-osteoblast gap-junction signaling feedback mechanism may regulate mechanotransduction of apoptosis initiation and transcription of cytokine signaling proteins responsible for stem cell niche recruitment much more directly than previously believed.

mechanical loading↗
NASA NTRS2016

Mechanotransductive Regulation of Gap-Junction Activity Between MLO-Y4 Osteocyte-Like and MC3T3-E1 Osteoblast-Like Cells in Three-Dimensional Co-Culture

Cell and animal studies conducted onboard the International Space Station and formerly on Shuttle flights have provided groundbreaking data illuminating the deleterious biological response of bone to mechanical unloading. However the intercellular communicative mechanisms associated with the regulation of bone synthesis and bone resorption cells are still largely unknown. Connexin-43 (CX43), a gap junction protein, is hypothesized to play a significant role in osteoblast and osteocyte signaling. The purpose of this investigation was to evaluate within a novel three-dimensional microenvironment how the osteocyte-osteoblast gap-junction expression changes when cultures are exposed to exaggerated mechanical load. MLO-Y4 osteocyte-like cells were cultured on a 3D-Biotek polystyrene insert and placed in direct contact with an MC3T3-E1 pre-osteoblast co-cultured monolayer and exposed to 48 h of mechanical stimulation (pulsatile fluid flow (PFF) or monolayer cyclic stretch (MCS)) then evaluated for viability, proliferation, metabolism, and CX43 expression. Mono-cultured MLO-Y4 and MC3T3-E1 control experiments were conducted under PFF and MCS stimulation to observe how strain application stimuli (PFF cell membrane shear or MCS cell focal adhesionattachment loading) initiates different signaling pathways or downstream regulatory controls. TotalLive cell count, viability and metabolic reduction (Trypan Blue, LIVEDead and Alamar Blue analysis respectively) indicate that mechanical activation of MC3T3-E1 cells inhibits proliferation while maintaining an average 1.04E4 reductioncell metabolic rate, *p0.05 n4. MLO-Y4s in monolayer culture increase in number when exposed to MCS loading but the percent of live cells within the population is low (46.3 total count, *p0.05 n4), these results may indicate an apoptotic signaling cascade. PFF stimulation of the three-dimensional co-cultures elicits a universal increase in CX43 in MLO-Y4 and MC3T3-E1 cells, illustrated by immunohistological observation. Increased CX43 expression is also observed with the three-dimensional co-cultures with MC3T3-E1 MCS stimulation but the increased gap-junction protein presence was limited to the osteoblast-osteocyte interface region. Previously reported PCR evaluation of osteogenic markers further corroborate that the co-cultured populations communicative networks play a role in translating mechanical signals to molecular messaging. These findings suggests an osteocyte-osteoblast gap-junction signaling feedback mechanism may regulate mechanotransduction of apoptosis initiation and transcription of cytokine signaling proteins responsible for stem cell niche recruitment much more directly than previously believed.

Juran, C. M.↗
DOE OSTI2020

Tunable Lattice Reconstruction, Triangular Network of Chiral One-Dimensional States, and Bandwidth of Flat Bands in Magic Angle Twisted Bilayer Graphene

The interplay between interlayer van der Waals interaction and intralayer lattice distortion can lead to structural reconstruction in slightly twisted bilayer graphene (TBG) with the twist angle being smaller than a characteristic angle θ c . Experimentally, the θ c is demonstrated to be very close to the magic angle (θ≈1.08°). Here we address the transition between reconstructed and unreconstructed structures of the TBG across the magic angle by using scanning tunneling microscopy (STM). Our experiment demonstrates that both structures are stable in the TBG around the magic angle. By using a STM tip, we show that the two structures can be changed to each other and a triangular network of chiral one-dimensional states hosted by domain boundaries can be switched on and off. Consequently, the bandwidth of the flat band, which plays a vital role in the emergent strongly correlated states in the magic angle TBG, is tuned. This provides an extra control knob to manipulate the exotic electronic states of the TBG near the magic angle.

1-dimensional systems↗
DOE OSTI2019

Manipulating efficient light emission in two-dimensional perovskite crystals by pressure-induced anisotropic deformation

The hybrid nature and soft lattice of organolead halide perovskites render their structural changes and optical properties susceptible to external driving forces such as temperature and pressure, remarkably different from conventional semiconductors. Here, we investigate the pressure-induced optical response of a typical two-dimensional perovskite crystal, phenylethylamine lead iodide. At a moderate pressure within 3.5 GPa, its photoluminescence red-shifts continuously, exhibiting an ultrabroad energy tunability range up to 320 meV in the visible spectrum, with quantum yield remaining nearly constant. First-principles calculations suggest that an out-of-plane quasi-uniaxial compression occurs under a hydrostatic pressure, while the energy is absorbed by the reversible and elastic tilting of the benzene rings within the long-chain ligands. This anisotropic structural deformation effectively modulates the quantum confinement effect by 250 meV via barrier height lowering. The broad tunability within a relatively low pressure range will expand optoelectronic applications to a new paradigm with pressure as a tuning knob.

36 MATERIALS SCIENCE↗
NASA NTRS1984

An incompressible Navier-Stokes flow solver in three-dimensional curvilinear coordinate systems using primitive variables

An implicit, finite-difference computer code has been developed to solve the incompressible Navier-Stokes equations in a three-dimensional, curvilinear coordinate system. The pressure-field solution is based on the pseudo compressibility approach in which the time derivative pressure term is introduced into the mass conservation equation to form a set of hyperbolic equations. The solution procedure employs an implicit, approximate factorization scheme. The Reynolds stresses, that are uncoupled from the implicit scheme, are lagged by one time-step to facilitate implementing various levels of the turbulence model. Test problems for external and internal flows are computed, and the results are compared with existing experimental data. The application of this technique for general three-dimensional problems is then demonstrated.

Kwak, D.↗
NASA NTRS1988

Anharmonic and screening corrections to the melting of a two-dimensional charged colloidal crystal

The Kosterlitz-Thouless-Halperin-Nelson-Young theory of melting is applied to a two-dimensional charged colloidal crystal. The renormalization of elastic constants due to anharmonic and dislocation pair-screening effects is calculated. For colloidal spheres ('polyballs') suspended in a thin film of water confined between two glass plates whose surfaces are highly charged, as in recent experimental configurations, the corrections to the harmonic results simply require an altered effective polyball charge to reproduce virtually the identical melting curve of the harmonic approximation (which agrees well with experiment). The effect on the melting curve of added salt is also calculated; the corresponding experiments have yet to be performed. For a film between uncharged surfaces the anharmonic correction again softens the lattice significantly. Dislocation pair screening causes an additional but minor reduction of the elastic constants. Neither correction eliminates a nonmelting behavior characteristic of the two-dimensional screened Coulomb system in this configuration.

Chang, Enson↗
NASA NTRS2011

Telescope Spacer Design Investigations

Space-based interferometric gravitational wave observatories will measure changes in the distance between free falling proof masses inside widely separated spacecraft with pm sensitivity. These observatories will use fast telescopes to exchange laser beams. These telescopes are part of the probed optical distances and any length change in the gravitational wave band between secondary and primary can limit the sensitivity of the observatories. Furthermore, the large distance between and space constrains on the spacecraft require to use very fast telescopes with f-numbers approaching unity. These telescopes are very sensitive against any absolute length change which would reduce interferometer visibility and, ultimately, sensitivity. Our group has assembled a Silicon Carbide test structure and investigated its dimensional in the 1 OA-4 to 1 Hz frequency band at different operating temperatures. We also measured the overall length change and started investigating asymmetric length changes during cool down which would lead to misalignments in the telescope.

Livas, Jeffrey↗
DOE OSTI2021

Anomalous thermoelectricity at the two-dimensional structural transition of SnSe monolayers

The thermoelectric figure of merit ZT comprises electronic and vibrational contributions that drastically change across phase transitions, and the most common theoretical ab initio approach to thermoelectricity fails to describe the evolution of ZT across finite-temperature structural transitions in its entirety. Furthermore, while the thermoelectric behavior of bulk SnSe has been extensively studied, SnSe monolayers have been experimentally realized only recently, and the existent prediction of thermoelectricity on this two-dimensional material is unreliable because it misses its structural transition altogether. SnSe monolayers (and similar GeS, GeSe, GeTe, SnS, and SnTe monolayers) experience a temperature-induced two-dimensional Pnm2 1 → P4/nmm structural transition precipitated by the softening of vibrational modes, and we describe their thermoelectric properties across the phase transition, using molecular dynamics data to inform both electronic and vibrational coefficients directly and within the same footing. Similar to recent experimental observations pointing to an overestimated ZT past the transition temperature in bulk SnSe, we find a smaller ZT on SnSe monolayers when compared to its value predicted by the standard paradigm, due to the dramatic changes in the electrical conductivity and lattice thermal conductivity as the structural transition ensues. Here, the process described here lends a strong focus to both the vibrational and electronic evolutions throughout the structural transition, and it applies to thermoelectric materials undergoing thermally driven solid-to-solid structural phase transitions in one, two, and three dimensions.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
NASA NTRS1997

Coupling Processes Between Atmospheric Chemistry and Climate

This is the first semi-annual report for NAS5-97039 summarizing work performed for January 1997 through June 1997. Work in this project is related to NAS1-20666, also funded by NASA ACMAP. The work funded in this project also benefits from work at AER associated with the AER three-dimensional isentropic transport model funded by NASA AEAP and the AER two-dimensional climate-chemistry model (co-funded by Department of Energy). The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling tools for this work are the AER two-dimensional chemistry-transport model, the AER two-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry.

Ko, M. K. W.↗
NASA NTRS2005

Actuated Hybrid Mirror Telescope

The figure depicts the planned Actuated Hybrid Mirror Telescope (AHMT), which is intended to demonstrate a new approach to the design and construction of wide-aperture spaceborne telescopes for astronomy and Earth science. This technology is also appropriate for Earth-based telescopes. The new approach can be broadly summarized as using advanced lightweight mirrors that can be manufactured rapidly at relatively low cost. More specifically, it is planned to use precise replicated metallic nanolaminate mirrors to obtain the required high-quality optical finishes. Lightweight, dimensionally stable silicon carbide (SiC) structures will support the nanolaminate mirrors in the required surface figures. To enable diffraction- limited telescope performance, errors in surface figures will be corrected by use of mirror-shape-control actuators that will be energized, as needed, by a wave-front-sensing and control system. The concepts of nanolaminate materials and mirrors made from nanolaminate materials were discussed in several previous NASA Tech Briefs articles. Nanolaminates constitute a relatively new class of materials that can approach theoretical limits of stiffness and strength. Nanolaminate mirrors are synthesized by magnetron sputter deposition of metallic alloys and/or compounds on optically precise master surfaces to obtain optical-quality reflector surfaces backed by thin shell structures. As an integral part of the deposition process, a layer of gold that will constitute the reflective surface layer is deposited first, eliminating the need for a subsequent and separate reflective-coating process. The crystallographic textures of the nanolaminate will be controlled to optimize the performance of the mirror. The entire deposition process for making a nanolaminate mirror takes less than 100 hours, regardless of the mirror diameter. Each nanolaminate mirror will be bonded to its lightweight SiC supporting structure. The lightweight nanolaminate mirrors and SiC supporting structures will be fabricated from reusable master molds. The mirror-shape-control actuators will be low-power, high-capacitance lead magnesium niobate electrostrictive actuators that will be embedded in the SiC structures. The mode of operation of these actuators will be such that once power was applied, they will change in length and once power was removed, they will maintain dimensional stability to nanometer precision. This mode of operation will enable the use of low-power, minimally complex electronic control circuitry. The wave-front-sensing and control system will be designed and built according to a two-stage architecture. The first stage will be implemented by a Shack- Hartmann (SH) sensor subsystem, which will provide a large capture range. The second, higher-performance stage will be implemented by an image-based wave-front-sensing subsystem that will include a phase-retrieval camera (PRC), and will utilize phase retrieval and other techniques to measure wavefront error directly. Phase retrieval is a process in which multiple images of an unresolved object are iterated to estimate the phase of the optical system that acquired the images. The combination of SH and phase-retrieval sensors will afford the virtues of both a dynamic range of 105 and an accuracy of <10 nm.

Hickey, Gregory↗
DOE OSTI2025

Atomic-scale insights into topotactic transformations in an extra-large-pore zeolite using time-resolved 3D electron diffraction

Understanding the atomic-scale structural dynamics of phase transformations is crucial for developing materials and tailoring their properties. However, many materials are obtained as polycrystalline powders with large unit cells and/or complex structures, making it challenging to investigate detailed structural changes using conventional X-ray diffraction techniques. Here we employ time-resolved three-dimensional electron diffraction to reveal the topotactic reactions and transformations that convert the extra-large-pore silicate zeolite ECNU-45 into ECNU-46. ECNU-45 features three-dimensional interconnecting 24 × 10 × 10-ring channels, while ECNU-46 consists of one-dimensional 24-ring channels connected to 10-ring pockets. ECNU-45 and ECNU-46 are both examples of pure silicate zeolites with pore openings larger than 22-ring. Our findings indicate changes at six distinct tetrahedral silicon sites, involving atom displacement, addition and removal of framework atoms through bond breakage and formation. This work presents the synthesis of zeolites and also provides atomic-level insights into the dynamic processes of topotactic reactions. Our results have implications for advancing materials engineering and understanding complex solid-state reactions at an atomic scale.

Inorganic chemistry↗
DOE OSTI2024

Quantifying the Impacts of Land-Cover Change on the Hydrologic Response to Hurricane Ida in the Lower Mississippi River Basin

Abstract The Lower Mississippi River basin (LMRB) has experienced significant changes in land cover and is one of the most vulnerable regions to hurricanes in the United States. Here, we study the impacts of land-cover change on the hydrologic response to Hurricane Ida in LMRB. By using an integrated surface–subsurface hydrologic model, Energy Exascale Earth System Model (E3SM) Land Model coupled with the three-dimensional ParFlow subsurface flow model (ELM-ParFlow), we simulate the effects of land-cover change on the flood volume and peak timing induced by rainfall from Hurricane Ida. The results show that land-cover changes from 1850 to 2015, which resulted in a smoother surface and less vegetation, exacerbated both flood peak time and volume induced by Hurricane Ida. The effects of land-cover changes can be decomposed into two mechanisms: a smoother surface routes more water faster to a watershed outlet and less vegetation allows more water to contribute to surface runoff. By comparing scenarios in which the two mechanisms were isolated, we found that changes in soil moisture due to vegetation cover change have more dominant effects on floods in the southern part and changes in Manning’s coefficient have the largest effect on floods in the northern part of the LMRB. The study provides important insights into the complex relationship between land-use, land-cover, and hydrologic processes in coastal regions.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1994

Heating of the nighttime D region by very low frequency transmitters

VLF signals propagating in the Earth-ionosphere waveguide are used to probe the heated nighttime D region over three U.S. Navy very low frequency (VLF,3-30 kHz) transmitters. Ionospheric cooling and heating are observed when a transmitter turns off and on in the course of normal operations. Heating by the 24.0-kHz NAA transmitter in Cutler, Maine, (1000 kW radiated power) was observed by this method in 41 of 52 off/on episodes during December 1992, increasing the amplitude and retarding the phase of the 21.4-kHz NSS probe wave propagating from Annapolis, Maryland, to Gander, Newfoundland, by as much as 0.84 dB and 5.3 deg, respectively. In 6 of these 41 episodes, the amplitude of the 28.5-kHz NAU probe wave propagating from Puerto Rico to Gander was also perturbed by as much as 0.29 dB. The latter observations were unexpected due to the greater than 770 km distance between NAA and the NAU-Gander great circle path. Heating by the NSS (21.4 kHz, 265 kW) and NLK (24.8 kHz, 850 kW) transmitters was observed serendipitously in data from earlier measurements of the amplitudes of VLF signals propagating in the Earth-ionosphere waveguide. A three-dimensional model of wave absorption and electron heating in a magnetized, weakly ionized plasma is used to calculate the extent nad shape of the collision frequency (i.e., electron temperature) enhancement above a VLF transmitter. The enhancements are annular, with a geomagnetic north-south asymmetry and a radius at the outer half-maximum of the collision frequency enhancement of about 150 km. Heating by the NAA transmitter is predicted to increase the nighttime D region electron temperature by as much as a factor of 3. The calculated changes in the D region conductivity are used in a three-dimensional model of propagation in the Earth-ionosphere wavelength to predict the effect of the heated patch on a subionospheric VLF probe wave. The range of predicted scattered field amplitudes is in general consistent with the observed signal perturbations. Discrepanices in the predictions are attributed to lack of knowledge of the D region electron density profile along the probe wave great circle paths.

Rodriguez, Juan V.↗
NASA NTRS1937

Theoretical span loading and moments of tapered wings produced by aileron deflection

The effect of tapered ailerons on linearly tapered wings is theoretically determined. Four different aileron spans are considered for each of three wing aspect ratios and each of four wing taper ratios. The change in lift on one half of the wing, the rolling moment, the additional induced drag, and the yawing moment, due to aileron deflection, are represented by non dimensional coefficients. Similar coefficients are given for the damping and yawing moments, the additional drag, and the change in lift, due to rolling. It was found possible to effect a fairly close agreement between the theoretical and experimental rolling moments by introducing into the theoretical expression for the rolling moment an effective change in angle of attack obtained from an analysis of flap data. The theoretical curves show that the highly tapered wing with long ailerons has a lower ratio of yawing to rolling moment and a lower additional induced drag than wings with less taper.

Pearson, H A↗
DOE OSTI2024

Future of plasma etching for microelectronics: Challenges and opportunities

Plasma etching is an essential semiconductor manufacturing technology required to enable the current microelectronics industry. Along with lithographic patterning, thin-film formation methods, and others, plasma etching has dynamically evolved to meet the exponentially growing demands of the microelectronics industry that enables modern society. At this time, plasma etching faces a period of unprecedented changes owing to numerous factors, including aggressive transition to three-dimensional (3D) device architectures, process precision approaching atomic-scale critical dimensions, introduction of new materials, fundamental silicon device limits, and parallel evolution of post-CMOS approaches. The vast growth of the microelectronics industry has emphasized its role in addressing major societal challenges, including questions on the sustainability of the associated energy use, semiconductor manufacturing related emissions of greenhouse gases, and others. The goal of this article is to help both define the challenges for plasma etching and point out effective plasma etching technology options that may play essential roles in defining microelectronics manufacturing in the future. The challenges are accompanied by significant new opportunities, including integrating experiments with various computational approaches such as machine learning/artificial intelligence and progress in computational approaches, including the realization of digital twins of physical etch chambers through hybrid/coupled models. These prospects can enable innovative solutions to problems that were not available during the past 50 years of plasma etch development in the microelectronics industry. To elaborate on these perspectives, the present article brings together the views of various experts on the different topics that will shape plasma etching for microelectronics manufacturing of the future.

Engineering↗
NASA NTRS1972

Thermal modeling of phase change solidification in thermal control devices including natural convection effects

Natural convection effects in phase change thermal control devices were studied. A mathematical model was developed to evaluate natural convection effects in a phase change test cell undergoing solidification. Although natural convection effects are minimized in flight spacecraft, all phase change devices are ground tested. The mathematical approach to the problem was to first develop a transient two-dimensional conduction heat transfer model for the solidification of a normal paraffin of finite geometry. Next, a transient two-dimensional model was developed for the solidification of the same paraffin by a combined conduction-natural-convection heat transfer model. Throughout the study, n-hexadecane (n-C16H34) was used as the phase-change material in both the theoretical and the experimental work. The models were based on the transient two-dimensional finite difference solutions of the energy, continuity, and momentum equations.

Ukanwa, A. O.↗