Horizontal Temperature Research Articles

Variability of thermohaline regime of see water of the Gulf of Mexico in 2005-2017

The Gulf of Mexico is a large, productive, marine and coastal ecosystem providing the coastal residents and neighbouring regions with goods and services. The Gulf of Mexico's water area plays a significant role in shaping the climate across the coastal zone and the thermal state of the region's water also has a major impact on development of atmospheric processes over the Atlantic and Europe. Long-term climate variability throughout the Gulf of Mexico may affect both the strength of the Gulf Stream and heat transfer patterns within the ocean and the economic activity and environmental stability of the entire Northwest Atlantic Region. This work aims at determining the characteristics of variability of temperature regime and salinity of the Gulf of Mexico over recent decades.
 The study was conducted based on the Gulf of Mexico Regional Climatology (GOM RC) data, version 2, available at the website of the NOAA's National Centers for Environmental Information (NCEI). It analyzes the temperature and salinity values at different depths for the period of 2005-2017. According to the analysis, over 2005-2017 the spatial distribution of the average annual water temperature on the Gulf of Mexico's surface demonstrates its decrease from south to north. Its highest value is observed next to the northwestern coast of Cuba and along the coastal area of the Bay of Campeche, and the lowest temperature is observed at Apalachee Bay located in the northeastern part of the Gulf of Mexico. Though significant horizontal temperature gradients are observed in winter, during the warm period the temperature field is more homogeneous. The minimum average monthly water temperature on the surface is observed in January, the maximum one – in September. The most distinct seasonal changes in temperature are observed in the water of the northern part of the Gulf of Mexico next to the United States' coast. The distribution of average annual salinity of the most of the Gulf of Mexico is homogeneous with the exception of its northern part, especially in the area where the Mississippi River water flows into it, where salinity decreases sharply. Graphs of water temperature and salinity distribution at different depths across different areas of the gulf were constructed in order to determine the water stratification.

Solar energy available and energy generated in photovoltaic systems in different inclinations and orientations of roofs of buildings

This work aimed to determine the solar energy available in different inclinations and orientations of roofs of buildings in the four seasons, using data of Global Solar Irradiation in the horizontal plane, temperatures, and wind speed. The inclined hourly solar irradiation and the energy generated by photovoltaic systems of different capacities installed in Cascavel-PR were simulated, with different orientations and inclinations and types of roofs (ceramic, fiber cement and metal). SWERA (Solar and Wind Energy Resource Assessment) daily global solar irradiation and wind velocity data were used to simulate daily inclined global solar irradiation in PVSyst software. Thus, also with the help of the software, the energy generated by photovoltaic systems of different capacities installed in Cascavel - PR, with different orientations and inclinations of roofs was determined. Consequently, the levels of losses in different seasons of the year were calculated and an analysis of the economic viability of the undertakings was made. Thus, the losses, profits and income of the systems were compared. Solar panels installed in northern oriented ceramic roofs provide better energy production performance throughout the year compared to metallic roofs and fibrocement. However, for the other orientations (South, East and West), the losses for ceramic roofs were twice as high as the metallic and fibrocement roofs in relation to their respective northern orientated slopes. Regarding orientation, roofs oriented to the North receive more Irradiation annually and therefore produce more energy. Then there is East, West and South as the most unfavorable condition.

Comparative study on energy consumption and indoor thermal environment between convective air-conditioning terminals and radiant ceiling terminals

Comparative experimental studies on energy consumption and indoor thermal environment between convective air-conditioning terminals and radiant ceiling terminals, as well as the systematic scientific explanations for their differences, were rarely reported. In this study, comparative experiments have been carried out for convective air-conditioning and radiant ceiling terminals to identify their performance differences in terms of energy consumption and thermal comfort in hot summer and cold winter Zone. The data of energy consumption, indoor air temperature, vertical temperature gradient, and horizontal temperature asymmetry were measured and analyzed. The results show that under the same operative temperature, the radiant ceiling terminal (RC terminal) can save 26.53% and 34.75% of energy consumption compared with the convective air-conditioning terminal (CAC terminal) in the cooling and heating test periods, respectively. Meanwhile, the air temperature of the RC terminal room is 2.4 °C higher than that of the CAC terminal room for cooling season and 2.2 °C lower for heating season. The vertical temperature gradient distribution of the RC terminal room is 0.6–1.5 °C/m, which is only 27.5% of that of the CAC terminal room. Moreover, the horizontal temperature fluctuation of the RC terminal room is only 1/3 of that of the CAC terminal room. Therefore, as for considering energy consumption and indoor thermal comfort level, the RC terminal outperforms than the CAC terminal.

Convection Modeling of Pure-steam Atmospheres

Abstract Condensable species are crucial to shaping planetary climate. A wide range of planetary climate systems involve understanding nondilute condensable substances and their influence on climate dynamics. There has been progress on large-scale dynamical effects and on 1D convection parameterization, but resolved 3D moist convection remains unexplored in nondilute conditions, though it can have a profound impact on temperature/humidity profiles and cloud structure. In this work, we tackle this problem for pure-steam atmospheres using three-dimensional, high-resolution numerical simulations of convection in postrunaway atmospheres. We show that the atmosphere is composed of two characteristic regions, an upper condensing region dominated by gravity waves and a lower noncondensing region characterized by convective overturning cells. Velocities in the condensing region are much smaller than those in the lower, noncondensing region, and the horizontal temperature variation is small. Condensation in the thermal photosphere is largely driven by radiative cooling and tends to be statistically homogeneous. Some condensation also happens deeper, near the boundary of the condensing region, due to triggering by gravity waves and convective penetrations and exhibits random patchiness. This qualitative structure is insensitive to varying model parameters, but quantitative details may differ. Our results confirm theoretical expectations that atmospheres close to the pure-steam limit do not have organized deep convective plumes in the condensing region. The generalized convective parameterization scheme discussed in Ding & Pierrehumbert is appropriate for handling the basic structure of atmospheres near the pure-steam limit but cannot capture gravity waves and their mixing which appear in 3D convection-resolving models.

Transition phenomena of natural convection of the air in an asymmetrically heated vertical channel with a damper

It was investigated the phenomenon of the air natural convection between vertical parallel plates with a damper installed at the end of the channel under asymmetrical heating conditions. The thermal behavior in the channel analyzed based on the vertically measured wall temperature distributions and bulk temperature distribution and the horizontal profiles of the air temperature measured at four heights. As the operating condition intensified, there was no change in either wall temperature distribution trend whereas the bulk temperature distribution trend changed only near the inlet through a change in the flow regime. This change in the flow regime affected the bulk temperature profile only near the wall. However, the overall temperature distributions and trends of the temperature profiles did not change drastically except near the inlet and they were similar to each other regardless of the operating condition and damper closing angle. On the basis of these results, it was focused on the transition phenomenon of natural convection between vertical parallel plates. It was considered the transition phenomenon from two viewpoints, that is, a change in flow regime and a change in flow pattern. In terms of a change in the flow regime, a distinguishable difference in the overall heat transfer performance was confirmed between laminar and turbulent regimes, but it does not affect the trends of the wall temperature distributions. Regarding the flow pattern change, criteria were suggested for distinguishing flow patterns between the entrance region and fully developed region at the mid-height of the channel according to the vertical temperature distributions and horizontal air temperature profiles. To verify the validity of the proposed concept, we made comparisons with the results of previous research and confirmed that our concept can be well applied.

Behavior of supramolecular cross-links formed by host-guest interactions in hydrogels responding to water contents

Reversible or movable cross-links based on host-guest interactions in supramolecular materials create functions such as enhanced mechanical properties and stimulus responsiveness. A supramolecular complex on a polymer side chain achieves the described functions as a reversible cross-link. Generally, 1:1 complex is utilized as a cross-link for the host-guest interaction based-supramolecular materials, but herein, the 1:2 complex between γ-cyclodextrin (γCD) and methyl viologen terminated undecyl acrylate (VC11) was chosen to cross-link three polymeric chains. The obtained supramolecular hydrogels γCD-VC11 (x, y) (x and y represent the mol% of the γCD and VC11 units in feeding, respectively) was prepared by radical copolymerization with acrylamide as a mainchain monomer. Tensile test revealed that toughness (Gf) of γCD-VC11 (x, y) maximized at water content (Wc) ≈ 40 wt.%. The maxima of Gf depended on the amount of γCD and VC11 units. Through dynamic mechanical analysis, Arrhenius style plots between horizontal shift factors and temperature determined activation energies (Ea) of each γCD-VC11 (x, y) and MBAAm (0.5). Ea of MBAAm (0.5) monotonically decreased with the increasing Wc. On the other hand, slope of Ea of γCD-VC11 (x, y) changed at Wc ≈ 40 wt.%. Simultaneously considering results of the tensile tests and DMA, the reversible cross-links formed by γCD and VC11 in γCD-VC11 (x, y) function effectively at appropriate Wc.

Experimental and numerical analysis of air temperature uniformity in occupied zone under stratum ventilation for heating mode

In warm air heating systems, a good indoor air temperature distribution can provide a comfortable indoor environment and reduce energy consumption. Few studies were conducted for the uniformity of air temperature distributions under stratum ventilation (SV) for heating. In this study, the horizontal and vertical air temperature uniformities in an occupied zone were evaluated under SV heating mode. Different indoor thermal environments were created using both experiments and computational fluid dynamics (CFD) simulations. Results showed that the horizontal air temperature uniformity is generally inferior to the vertical direction. Based on the experimental and simulation cases, the maximum horizontal and vertical air temperature gradient is 3.46 °C/m and 2.44 °C/m, respectively. The uniformity of the air temperature distribution can be significantly affected by supply air parameters. The maximum extremum air temperature difference is 6.26 °C at the height of 0.6 m. However, it can be reduced to less than 0.62 °C by varying the supply air velocity, temperature and angle. Appropriate supply air parameters can provide an energy utilization coefficient (EUC) higher than one, showing the potentials of energy saving. A grey relational analysis revealed that the relational degree of the supply air velocity and temperature on the air temperature uniformity is relatively high, followed by the outdoor temperature and then supply vane angle. The results derived from this study can contribute to better understand the characteristics of indoor air temperature distribution under SV heating mode.

Natural double-diffusive convection for the Carreau shear-thinning fluid in a square cavity submitted to horizontal temperature and concentration gradients

• The paper investigated double-diffusive convection of a shear-thinning fluid. • All parameters of the Carreau model influence the convective flows. • When Ra T very high, the Carreau and power-law models give almost the same results. • The results of scale analysis and numerical solution are in good agreement. We study heat and mass transfers by natural convection for shear-thinning non-Newtonian binary fluids confined in a square cavity. Thermal and solutal boundary conditions of the Dirichlet type are applied on the vertical walls of the cavity while the horizontal ones are assumed adiabatic and impermeable. We used the rheological Carreau model, adequate for many non-Newtonian fluids to characterize the shear-thinning behavior. The first part from this study is devoted to the numerical solution of the governing equations, and the effect of the governing parameters, namely, the thermal Rayleigh number Ra T , Prandtl number Pr , Lewis number Le , buoyancy ratio N and the various parameters of Carreau model. Numerical calculations are also carried out by considering the same problem on the basis of the power-law model, and a comparison of the results predicted by the two rheological models is performed. In the second part, a scale analysis is proposed to obtain correlations giving the heat and mass transfers. The results of this approach are validated numerically and a good agreement is found between the two methods.

Rapid fabrication of Cu/40-μm thick full Cu3Sn/Cu joints by applying pulsed high frequency electromagnetic field for high power electronics

With the application of wide bandgap semiconductors for high power electronics, the joints are inevitably faced with a trade-off between withstanding high temperature environments and remaining low bonding temperatures. In this study, a full Cu3Sn intermetallic compounds layer with thickness of 40 μm, which can survive at 679 °C, were obtained between Cu plates using pulsed High Frequency Electromagnetic Field (HFEF) within 10 min at ambient temperature. Output power and frequency of the HFEF was 6 kW and 530 kHz, respectively. In contrast to common Sn-based solder joints, the joints prepared through HFEF consisted predominately of Cu3Sn, because both the horizontal and vertical temperature gradients and the eddy currents within the joints strongly promoted the 3D diffusion of copper atoms. With increasing HFEF exposure time, the Cu3Sn changed from an irregular needle-like to smoothly scalloped or columnar morphology. The HFEF approach enabled Cu3Sn joints to achieve a superior shear strength (>56 MPa) and a greater stand-off height (>30 μm), which are useful to mitigate the coefficient of thermal expansion (CTE) mismatch problems; thereby yielding higher reliability. We envision that these full Cu3Sn joints prove useful in a wide range of applications in high-temperature and high-power electronics.

Natural convection induced by unintended horizontal temperature distribution in a narrow-closed container heated from above

This study aims at expressing the velocity fields of the liquids held in a narrow-closed container heated from above as a function of the dimensions of the container to estimate the diffusion-dominant condition. The motions of tracer particles in liquid salol held in a quasi-two-dimensional glass cell were tracked in cavities of various inner width W through the series of experiments. The mean velocity of the tracer particles, Vmean, decreased almost linearly with the decrease in the values of W. Thermal flow fields were successfully reproduced by the series of numerical simulations. We found that the unintended horizontal temperature difference is realized, which induces the natural convection in the closed narrow cavity heated from above. We derived the correlation between the Reynolds and Grashof numbers, which are described as a function of the mean velocity and the unintended horizontal temperature difference, respectively. The threshold of the convection onset in the present geometry was then proposed.

Inside Katabatic Winds Over the Terra Nova Bay Polynya: 1. Atmospheric Jet and Surface Conditions

AbstractThe atmospheric and surface conditions during a late autumnal strong katabatic wind event were quantified using ship and rawinsonde measurements over the Terra Nova Bay coastal polynya. Wind speeds decreased from 35 to 18 ms−1, while the wind direction decreased 18° over the distance from the Nansen Ice Shelf edge out 99 km eastward toward the Ross Sea. Maximum velocity winds (jet cores) at 173, 238, 179 and 144 m elevation were associated with atmospheric boundary layers capped by temperature inversions with bases at 294, 325, 226 and 196 m elevation. The tops of the inversion layers (near 700 m at all locations) also marked the top of the katabatic wind layer. Boundary layer air temperature and specific humidity increased from −31 to −21°C and 0.1 to 0.6 gkg−1, respectively, in response to the warm polynya surface. The air at 15 ± 8 m elevation was saturated with respect to ice, causing supersaturation and snow growth where the air parcels become cooler in the upper atmospheric boundary layer. The surface was characterized by three zones, a fluid zone (open ocean, frazil, shuga and pancake floes), an accumulation zone (fused, rafted and compressed pancake floes) and a young floe zone (large floes). The surface temperature varied from freezing (−1.7°C) in the fluid zone to near air temperature (−20°C) in the floe zone with the largest horizontal surface temperature gradient occurring in the transition between the fluid zone and the accumulation zone, and at the edges of leads in the floe zone.

Modal and absolute thermal instability in a vertical porous layer

The conduction regime in a vertical porous layer subject to a horizontal temperature gradient is studied. The boundaries are considered as isothermal, with different temperatures, and permeable to the external environment. The linear stability of this basic flow state is analysed by testing the dynamics of the normal modes of perturbation. The numerical solution of the stability eigenvalue problem leads to the determination of the neutral stability condition. Then, the evolution in time of localised wavepacket perturbations is investigated leading to the determination of the threshold to absolute instability.

Numerical study of magnetic field effect on natural convection heat and mass transfers in a square enclosure containing non-Newtonian fluid and submitted to horizontal temperature and concentration gradients

Numerical study of magnetic field effect on natural convection heat and mass transfers in a square enclosure containing non-Newtonian fluid and submitted to horizontal temperature and concentration gradients

Improving the thermal structure predictions in the Yellow Sea by conducting targeted observations in the CNOP-identified sensitive areas

Targeted observation is an appealing procedure for improving model predictions. However, studies on oceanic targeted observations have been largely based on modeling efforts, and there is a need for field validating operations. Here, we report the results of a field targeted observation that is designed based on the sensitive areas identified by the Conditional Nonlinear Optimal Perturbation approach to improve the 7th day thermal structure prediction in the Yellow Sea. By introducing the technique of cycle data assimilation and the new concept of time-varying sensitive areas, an observing strategy is designed and validated by a set of Observing System Simulation Experiments. Then, the impact of targeted observations was investigated by a choreographed field campaign in the summer of 2019. The results of the in-field Observing System Experiments show that, compared to conventional local data assimilation, conducting targeted observations in the sensitive areas can yield more benefit at the verification time. Furthermore, dynamic analysis demonstrates that the refinement of vertical thermal structures is mainly caused by the changes in the upstream horizontal temperature advection driven by the Yellow Sea Cold Water Mass circulation. This study highlights the effectiveness of targeted observations on reducing the forecast uncertainty in the ocean.

Thermohaline interleaving induced by horizontal temperature and salinity gradients from above

In this work we show that horizontal gradients of temperature and salinity with compensating effects on density can drive thermohaline intrusion in the fluid layer below. Specifically, different types of double diffusive convection generate differential vertical fluxes from the top boundary, which then sustain horizontal temperature and salinity gradients within the bulk. Interleaving layers develop in the bulk and slope downward towards the cold fresh side, which are of the diffusive type. New layers emerge near the bottom boundary and shift the existing layers upward due to the density difference induced by the divergence of the vertical fluxes through the top surface. Detailed analyses reveal that the present intrusion is consistent with those in the narrow fronts, and both layer thickness and current velocity follow the corresponding scaling laws. Such intrusion process provides an extra path to transfer heat and salinity horizontally towards the cold and fresh side, but transfer the density anomaly towards the warm and salty side. These findings extend the circumstances where thermohaline intrusions may be observed.

ON HEAT SOURCE IN SUBDUCTION ZONE

The subduction of an oceanic plate is studied as the motion of a high-viscosity Newtonian fluid. The subducting plate spreads along the 670-km depth boundary under the influence of oppositely directed horizontal forces. These forces are due to oppositely directed horizontal temperature gradients. We consider the flow structure and heat transfer in the layer that includes both the oceanic lithosphere and the crust and moves underneath a continent. The heat flow is estimated at the contact between the subducting plate and the surrounding mantle in the continental limb of the subduction zone. Our study results show that the crustal layer of the subducting plate can melt and a thermochemical plume can form at the 670-km boundary. Our model of a thermochemical plume in the subduction zone shows the following: (1) formation of a plume conduit in the crustal layer of the subducting plate; (2) formation of a primary magmatic chamber in the area wherein the melting rate equals the rate of subduction; (3) origination of a vertical plume conduit from the primary chamber melting through the continent; (4) plume eruption through the crustal layer to the surface, i.e. formation of a volcano. Our experiments are aimed to model the plume conduit melting in an inclined flat layer above a local heat source. The melt flow structure in the plume conduit is described. Laboratory modeling have revealed that the mechanisms of melt eruption from the plume conduit differ depending on whether a gas cushion is present or absent at the plume roof.

Anisotropy and the Onset of the Thermoconvective Instability in a Vertical Porous Layer

Abstract The thermoconvective instability of the parallel vertical flow in a fluid saturated porous layer bounded by parallel open boundaries is studied. The open boundaries are assumed to be kept at constant uniform pressure while their temperatures are uniform and different, thus forcing a horizontal temperature gradient across the layer. The anisotropic permeability of the porous layer is accounted for by assuming the principal axes to be oriented along the directions perpendicular and parallel to the layer boundaries. A linear stability analysis based on the Fourier normal modes of perturbation is carried out by testing the effect of the inclination of the normal mode wavevector to the vertical. The neutral stability curves and the critical Rayleigh number for the onset of the instability are evaluated by solving numerically the stability eigenvalue problem.

Cyclonic and anticyclonic rotation in a cylinder cooled inhomogeneously on the top.

In this work, we study the development of vortical structures generated in a rotating cylinder non-homogeneously cooled on the top. In the axisymmetric regime, for moderate vertical temperature differences and any rotation rate, cyclonic and anticyclonic rotations coexist in the flow: a counterclockwise motion at upper levels, giving place to a vertical top-down vortex, and a clockwise rotation at lower levels that generates a spin up motion. For lower rotation rates and high enough vertical temperature differences, only cyclonic top-down vortices survive and get stronger. We perform a force balance analysis to explain the phenomena. In the non-axisymmetric regime, no anticyclonic rotation at the bottom is reported and the cyclonic top-down vortex either disappears or splits up in two top-down vortices, depending on the ambient rotation rate. The intensity of the cooling on the top and how localized this cool region is affect the flow developed. When the horizontal temperature difference on the top is larger than the vertical temperature difference between top and bottom, stable axisymmetric top-down vortices with an inner updraft of warmer air are reported. The more localized the cooling above, the more difficult the development of the inner updraft becomes. Results may contribute to the understanding of the relevance of thermal processes in tornadogenesis.

A novel interconnect design for thermal management of a commercial-scale planar solid oxide fuel cell stack

Solid oxide fuel cell (SOFC) is a promising technology for stable power supply with high efficiency and high quality heat utilization, but it still faces the technical challenge of low long-term durability caused by thermal imbalance of its stack. An effective, novel thermal management method is urgently required for its market deployment. This study proposes a novel interconnect design for effective thermal management and elucidates the influence of its design variables on internal thermal conditions and heat transfer characteristics of a 1-kW planar SOFC stack. Three-dimensional thermo-fluid simulations are performed on the new stack design employing the novel interconnect and the conventional stack design for comparison. The new design is developed for the purpose of uniform in-plane (horizontal) temperature distribution by modifying the displacement of gas manifolds. At the repeating-unit scale, due to the reduced thermal resistance for horizontal heat transfer of the new stack, its in-plane temperature deviation decreases by 35–60 °C. At the stack scale with 30 unit-cells stacked vertically, the average temperature increases by 30 °C, and the vertical temperature difference decreases by 50 °C. Such thermal fields are the combined results of reduced gaseous convection and enhanced vertical solid-phase conduction through each repeating unit. In the new stack, the amount of heat transferred to the gas within each repeating unit is generally decreased, but is recuperated by increasing solid conduction through metallic interconnects. The relatively weakened gaseous heat transfer of the new design provides more thermal load at the lowest unit of the stack than the reference design, which promotes gas pre-heating prior to reaching the unit-cells and hence results in the elevated stack temperature. Such gas pre-heating also reduces the temperature difference in the vertical direction of the new design. The lower temperature differences both in horizontal and vertical directions enable the new stack to reduce its thermal imbalance and potentially to improve long-term durability.

Winter Dynamics in an Epishelf Lake: Quantitative Mixing Estimates and Ice Shelf Basal Channel Considerations

AbstractMilne Ice Shelf is located at the mouth of Milne Fiord (82.6°N, 81.0°W), on Ellesmere Island, Nunavut. This floating ice feature is attached to both sides of the fjord. During the melt season, the ice shelf acts as a floating barrier preventing surface runoff in Milne Fiord from flowing freely to the ocean. This results in a permanent layer of freshwater that floats on top of the seawater of the fjord, commonly known as an epishelf lake. Few studies address the physical characteristics of epishelf lakes. Here, winter data from a mooring installed in Milne Fiord epishelf lake during 2011–2019 is analyzed in the framework of a one‐dimensional model in order to study mixing in the upper water column and infer the characteristics of a basal channel in the ice shelf. The results show that vertical mixing rates are higher in the epishelf lake than in the seawater below. Estimation of the Richardson number using a geostrophic balance approach reveals that enhanced mixing in the epishelf lake is associated with horizontal temperature gradients. In contrast to most studies on basal channels in Greenland and Antarctica, the results presented here show the basal channel of Milne Ice Shelf is apparently not evolving (melting) rapidly.