Tubular Phase Research Articles

The optimum fin length distribution of tabular PCM heat exchanger

AbstractThe study aims to find the optimal fin length distribution for improved heat transfer during melting and solidification in a tubular phase change material (PCM) heat exchanger (HE) designed for heat storage. Three types of horizontal PCM tabular HEs, all with five longitudinal fins, were studied numerically. While maintaining a constant heat‐transfer area, each model depicts a unique fin length distribution design. The first model, which serves as the reference design, has a uniform fin length distribution and each fi\n is 30 mm long. The second model has shorter upper and side fins and longer lower fins. The third model has long lower fins but shorter than that of the second model, with short side fins and no change in upper fin length with reference design. The findings indicate that the second model exhibits the best heat‐transfer performance for the melting process, while the first model is most effective for solidification. Interestingly, the third design emerges as the optimum choice for both melting and solidification processes, where for 1 h of melting operation, results obtained 87%, 92%, and 90% for three models, respectively, from the first uniform model to the third model. While for 2 h of solidification the result obtained 11%, 17%, and 13% liquid fraction for the three models, respectively.

Disorder-driven transition to tubular phase in anisotropic two-dimensional materials

We develop a theory of anomalous elasticity in disordered two-dimensional flexible materials with orthorhombic crystal symmetry. Similar to the clean case, we predict existence of infinitely many flat phases with anisotropic bending rigidity and Young's modulus showing power-law scaling with momentum controlled by a single universal exponent the very same as in the clean isotropic case. With increase of temperature or disorder these flat phases undergo crumpling transition. Remarkably, in contrast to the isotropic materials where crumpling occurs in all spatial directions simultaneously, the anisotropic materials crumple into tubular phase. In distinction to clean case in which crumpling transition happens at unphysically high temperatures, a disorder-induced tubular crumpled phase can exist even at room-temperature conditions. Our results are applied to anisotropic atomic single layers doped by adatoms or disordered by heavy ions bombarding.

The formation mechanism of Al-RE tubular phase in AZ80-Ce magnesium alloy by La doping

In this paper, the effect of La addition on the Al-RE phase in Mg-Al-Zn-Ce magnesium alloy was studied. Melting method was used to prepare AZ80-Ce magnesium alloys with different La content, and the morphological transformation mechanism of Al-RE phase was proposed by XRD, SEM, EPMA, TEM and extraction. The results show that the Al11RE3 phase can be formed by adding RE (Ce/La) into AZ80 magnesium alloy. With the increase of La, the morphology of Al11RE3 phase in the alloy changes from acicular to tubular. La replaces part of Ce in the Al11Ce3 cell and the Al11Ce3 phase is transformed into Al11RE3 phase based on Al11RE3 cell when La is added. In the Al11RE3 phase, the doping of La will cause lattice distortion in the crystal, which increases the surface energy on the growth surface of the Al11RE3 phase and accelerates its growth rate in (001) direction, resulting in the formation of tubular Al11RE3 phase. After forming the tubular structure, the growing process of Al11RE3 phase is divided into three stages owing to different control factors.

Experimental study of a novel strategy to construct the battery thermal management module by using tubular phase change material units

For the thermal management of cylindrical power battery module, the classical cuboid-like phase change material (PCM) module still remains problematic, because the bulky structure remarkably decreases the energy density and secondary heat-dissipation capability of the battery module. Here a novel strategy to construct the PCM module was proposed by substituting the bulky cuboid PCM module with tubular PCM units. Compared to the classical cuboid module, the assembled tubular PCM module confers numerous naturally-formed channels for air flow, an enlarged outer surface area for secondary heat dissipation, and a greatly reduced module weight. As a result, the tubular PCM module demonstrates a superior heat-dissipation performance for cylindrical power batteries. For example, with forced air convection, the temperature and temperature difference can be controlled below 47.2 and 1.0 °C respectively under an extreme working environment, i.e., 10 charge and discharge cycles at a high environment temperature of 40 °C. More importantly, this novel strategy also benefits the flexible assembling and maintenance of the modules, and saves 54% of the PCM amount, thus increasing the energy density of the battery module from 75.5 to 94.4 Wh kg−1.

Dynamic performance of a novel air-soil heat exchanger coupling with diversified energy storage components—modelling development, experimental verification, parametrical design and robust operation

A novel vertical air-soil heat exchanger (VASHE) is proposed, coupling with diversified energy storage components, i.e., both annular and tubular phase change material (PCM) components. Compared to traditional air-soil heat exchanger systems, advantages of the new VASHE include the space-saving, higher energy efficiency, centralized discharge of condensate water and smaller fluctuation of outlet air temperature. An enthalpy-based model is developed to characterise the underlying heat transfer mechanism of the sophisticated sensible and latent heat transfer in PCMs. An experimental platform is thereafter constructed for the calibration of the developed enthalpy-based numerical model. Systematic parametrical analysis has been conducted on PCM types, PCM structure and PCM locations. Research results indicated that, the developed enthalpy-based model was accurate to predict the system performance with the maximum relative error at 1.98%. Systematic parametric analysis indicates that, within various PCM types, the RT 20 in the tubular PCM is the most promising with the smallest outlet temperature amplitude. Furthermore, accurate PCM location is an effective solution to the contradiction between daily cooling storage capacity and outlet temperature amplitude. This study demonstrates a novel air-soil heat exchanger with diversified energy storage components, which can provide concrete guidance and pave path for the geothermal energy utilisation.

Enhancing a vertical earth-to-air heat exchanger system using tubular phase change material

Abstract: In this study, a new vertical earth-to-air heat exchanger (VEAHE) system coupled with tubular phase change material (PCM) components was proposed. The proposed system has smaller occupied areas and higher geothermal energy use efficiency than traditional EAHE systems. Moreover, the tubular PCM component enables the system's air temperature at the outlet to be more stable, thereby enhancing the system's thermal performance. In particular, the tubular components' simple geometry, easy fabrication, convenient assembling-disassembling and low-cost facilitate their usage in practical applications. To explore the system's thermal performance, an experimental set-up was established and its numerical model was developed. Then the model was verified through a comparison between the system's simulated and monitored air temperatures at the outlet. The verification produced acceptable results with the maximum absolute relative error of 1.33%. Based on this model, the influences of the tubular PCM component, tube depth, PCM conductivity and container length on the proposed system's thermal performance were investigated. Results indicated that the tubular PCM components can effectively reduce the VEAHE system's air temperature peak and fluctuation at the outlet, and increase its average cooling capacity. For the proposed system, as the tube depths increase from 12 to 24 m, the air temperature peak and fluctuation at the outlet decrease from 25.74 °C and 3.59 °C to 21.01 °C and 0.62 °C, respectively. Different thermal conductivity of PCM has almost same influences on the system's air temperature at the outlet as the container diameter is 50 mm. Such influences, however, become apparent and require to be considered as the container diameter increases to 150 mm. The air temperature fluctuation at the outlet decreases as the container lengths increase, and 12 m can be considered as an appropriate length for the proposed system. Additionally, the system's static payback period was calculated as 18.03 years.

Assessment of Glomerular and Tubular Function in the Evaluation of Diabetic Nephropathy: A Cross-sectional Study.

Background:Diabetic nephropathy (DN) occurs in 20%–40% of patients with diabetes, and it is characterized by proteinuria and progressive loss of renal functions ultimately leading to end-stage renal disease. Classically, albuminuria is regarded as a consequence of diabetes-induced glomerular damage. It is now being appreciated that the renal tubulointerstitium also plays a role in the development of DN.[1] Urinary cystatin C (UCC) is an emerging marker of DN. It is totally catabolized by proximal tubular cells and is not normally present in the urine. However, in the presence of tubulopathy, it is excreted in urine, and serum levels also are elevated due to lack of catabolism.Materials and Methods:The present study was conducted to evaluate the presence of glomerulopathy and tubulopathy in patients with type 2 diabetes mellitus (T2DM) and to correlate them with established risk factors for nephropathy. We aimed at evaluating the level of UCC as a marker of tubulointerstitial damage in patients with T2DM in relation to the level of albuminuria and other parameters. Seventy-two patients with T2DM (mean age, 47.44 ± 10.40 years) and 45 healthy age- and sex-matched subjects were evaluated for UCC, serum creatinine, and urinary albumin-creatinine ratio (UACR) along with other parameters.Results:Of the 72 patients included in the study, microalbuminuria was found in 26% and macroalbuminuria in 10% of cases. UCC was significantly higher in micro- and macro-albuminuric groups in comparison with normoalbuminuric patients and correlated positively with UACR. Among the 46 patients with normoalbuminuria, 11 had elevated UCC levels indicating early tubular dysfunction.Conclusions:This finding may support the hypothesis of a “tubular phase” of diabetic kidney disease preceding overt DN, and hence, the use of UCC measurement for early evaluation of renal involvement.

Heat transfer and thermal storage performance of an open thermosyphon type thermal storage unit with tubular phase change material canisters

A novel open thermosyphon-type thermal storage unit is presented to improve design and performance of heat pipe type thermal storage unit. In the present study, tubular canisters filled with a solid–liquid phase change material are vertically placed in the middle of the thermal storage unit. The phase change material melts at 100°C. Water is presented as the phase-change heat transfer medium of the thermal storage unit. The tubular canister is wrapped tightly with a layer of stainless steel mesh to increase the surface wettability. The heat transfer mechanism of charging/discharging is similar to that of the thermosyphon. Heat transfer between the heat resource or cold resource and the phase change material in this device occurs in the form of a cyclic phase change of the heat-transfer medium, which occurs on the surface of the copper tubes and has an extremely high heat-transfer coefficient. A series of experiments and theoretical analyses are carried out to investigate the properties of the thermal storage unit, including power distribution, start-up performance, and temperature difference between the phase change material and the surrounding vapor. The results show that the whole system has excellent heat-storage/heat-release performance.

Thermodynamic properties of tubular cobaltite Bi3.7Sr11.4Co8O29−δ

We synthetized a tubular cobaltite Bi3.7Sr11.4Co8O29−δ ceramics and characterized it using X-ray diffraction (XRD) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS). The simultaneous thermal analysis (STA) revealed a very unusual thermal behavior which was eventually ascribed to metastability of tubular phase at lower temperatures. The heat capacity and enthalpy increments were measured by physical property measurement system (PPMS), differential scanning calorimetry (DSC) and drop calorimetry. The oxygen non-stoichiometry was determined using thermogravimetric measurement (TG) and reduction in hydrogen atmosphere. Above room temperature the temperature dependence of the molar heat capacity was derived by simultaneous least squares method from DSC and enthalpy data. The heat capacity was also analyzed in terms of a combined Debye–Einstein model. The molar entropy Smo (298.15)=1349.45Jmol−1K−1 was evaluated from the low temperature heat capacity data.

Monte Carlo studies of a Finsler geometric surface model

This paper presents a new type of surface models constructed on the basis of Finsler geometry. A Finsler metric is defined on the surface by using an underlying vector field, which is an in-plane tilt order. According to the orientation of the vector field, the Finsler length becomes dependent on both position and direction on the surface, and for this reason the parameters such as the surface tension and bending rigidity become anisotropic. To confirm that the model is well-defined, we perform Monte Carlo simulations under several isotropic conditions such as those given by random vector fields. The results are comparable to those of previous simulations of the conventional model. It is also found that a tubular phase appears when the vector field is constant. Moreover, we find that the tilts form the Kosterlitz–Thouless and low temperature configurations, which correspond to two different anisotropic phases such as disk and tubular, in the model in which the tilt variable is assumed to be a dynamical variable. This confirms that the model in this paper may be used as an anisotropic model for membranes.

101 異方的に形態変化する脂質分子膜の幾何学的モデル化(OS1-1 オーガナイズドセッション《計算力学と数値シミュレーション》)

Using Monte Carlo simulation technique, we present a numerical result of a geometric surface model for anisotropic membranes. The model is constructed on the basis of Finsler geometric notion. In this model, the bending rigidity and the surface tension become position-dependent and direction-dependent. We see a multitude of anisotropic phases such as a tubular phase, a disk phase and the spherical phase in this model.

Grainy multiverse

I consider a landscape containing three vacua and study the topology of global spacelike slices in eternal inflation. A discrete toy model, which generalizes the well-studied Mandelbrot model, reveals a rich phase structure. Novel phases include monochromatic tubular phases, which contain crossing curves of only one vacuum, and a democratic tubular phase, which contains crossing curves of all three types of vacua. I discuss the generalization to realistic landscapes consisting of many vacua. Generically, the system ends up in a grainy phase, which contains no crossing curves or surfaces and consists of packed regions of different vacua. Other topological phases arise on the scale of several generations of nucleations.

Crumpled-to-Tubule Transition in Anisotropic Polymerized Membranes: Beyond theϵExpansion

Anisotropic D-dimensional polymerized phantom membranes are investigated within a nonperturbative renormalization group framework. One focuses on the transition between a high-temperature, crumpled phase and a low-temperature, tubular phase where the membrane is flat along one direction and crumpled along the other ones. While the upper critical dimension--D(uc)=5/2--is close to D=2, the weak-coupling perturbative approach is qualitatively and quantitatively wrong. We show that our approach is free of the problems encountered within the perturbative framework and provides physically meaningful critical quantities.

Topological phases of eternal inflation

Eternal inflation is a term that describes a number of different phenomena which have been classified by Winitzki. According to Winitzki's classification these phases can be characterized by the topology of the percolating structures in the inflating, "white," region. In this paper we discuss these phases, the transitions between them, and the way they are seen by a "Census Taker"; a hypothetical observer inside the non-inflating, "black," region. We discuss three phases that we call, "black island," "tubular," and "white island." The black island phase is familiar, comprised of rare Coleman De Luccia bubble nucleation events. The Census Taker sees an essentially spherical boundary, described by the conformal field theory of the FRW/CFT correspondence. In the tubular phase the Census Taker sees a complicated infinite genus structure composed of arbitrarily long tubes. The white island phase is even more mysterious from the black side. Surprisingly, when viewed from the non-inflating region this phase resembles a closed, positively curved universe which eventually collapses to a singularity. Nevertheless, pockets of eternal inflation continue forever. In addition there is an "aborted" phase in which no eternal inflation takes place. Rigorous results of Chayes, Chayes, Grannan and Swindle establish the existence of all of these phases, separated by first order transitions, in Mandelbrot percolation, a simple model of eternal inflation.

Shape transformations of a compartmentalized fluid surface

A surface model on compartmentalized spheres is studied by using the Monte Carlo simulation technique with dynamical triangulations. We found that the model exhibits a variety of phases: The spherical phase, the tubular phase, the planar phase, the wormlike planar phase, the wormlike long phase, the wormlike short phase, and the collapsed phase. We also demonstrated that almost all phases are separated from their neighboring phases by first-order transitions. Mechanical strength of the surface is given only by elastic skeletons, which are the compartment boundaries, and therefore vertices diffuse freely inside the compartments. We confirm that the cytoskeletal structure and the lateral diffusion of vertices are origins of such a variety of phases.

Phase transitions in a fluid surface model with a deficit angle term

Nambu-Goto model is investigated by using the canonical Monte Carlo simulation technique on dynamically triangulated surfaces of spherical topology. We find that the model has four distinct phases; crumpled, branched-polymer, linear, and tubular. The linear phase and the tubular phase appear to be separated by a first-order transition. It is also found that there is no long-range two-dimensional order in the model. In fact, no smooth surface can be seen in the whole region of the curvature modulus α, which is the coefficient of the deficit angle term in the Hamiltonian. The bending energy, which is not included in the Hamiltonian, remains large even at sufficiently large α in the tubular phase. On the other hand, the surface is spontaneously compactified into a one-dimensional smooth curve in the linear phase; one of the two degrees of freedom shrinks, and the other degree of freedom remains along the curve. Moreover, we find that the rotational symmetry of the model is spontaneously broken in the tubular phase just as in the same model on the fixed connectivity surfaces.

Phase structure of a surface model on dynamically triangulated spheres with elastic skeletons

We find three distinct phases; a tubular phase, a planar phase, and the spherical phase, in a triangulated fluid surface model. It is also found that these phases are separated by discontinuous transitions. The fluid surface model is investigated within the framework of the conventional curvature model by using the canonical Monte Carlo simulations with dynamical triangulations. The mechanical strength of the surface is given only by skeletons, and no two-dimensional bending energy is assumed in the Hamiltonian. The skeletons are composed of elastic linear chains and rigid junctions and form a compartmentalized structure on the surface, and for this reason the vertices of triangles can diffuse freely only inside the compartments. As a consequence, an inhomogeneous structure is introduced in the model; the surface strength inside the compartments is different from the surface strength on the compartments. However, the rotational symmetry is not influenced by the elastic skeletons; there is no specific direction on the surface. In addition to the three phases mentioned above, a collapsed phase is expected to exist in the low bending rigidity regime that was not studied here. The inhomogeneous structure and the fluidity of vertices are considered to be the origin of such a variety of phases.

Phase transitions of a tethered surface model with a deficit angle term

The Nambu-Goto model is investigated by using the canonical Monte Carlo simulations on fixed connectivity surfaces of spherical topology. Three distinct phases are found: crumpled, tubular, and smooth. The crumpled and the tubular phases are smoothly connected, and the tubular and the smooth phases are connected by a discontinuous transition. The surface in the tubular phase forms an oblong and one-dimensional object similar to a one-dimensional linear subspace in the Euclidean three-dimensional space R3 . This indicates that the rotational symmetry inherent in the model is spontaneously broken in the tubular phase, and it is restored in the smooth and the crumpled phases.

Lamellar phases confined in quasicylindrical pores: lattice model results.

A two-dimensional (2D) vector lattice model of microemulsions is applied to study the structure of lamellar phases confined in long rectangular pores. One-point distribution functions are calculated within mean field approximation. The effects of pore geometry and surface fields are considered. A 2D analog of an onion phase is favored by a pore with strongly hydrophilic walls. For neutral walls, far from the phase boundaries, the lamellar phase is stable inside the pore. By contrast, close to the lamellar-tubular phase boundary a pore with neutral walls favors a 2D tubular phase. This is the analog of capillary condensation. In all cases the excess pressure is calculated as a function of the pore geometry.

Theory for the bending anisotropy of lipid membranes and tubule formation.

We study the spontaneous symmetry breaking of the bending rigidity of lipid membranes in two principal directions by a Landau mean-field theory. When the temperature is below the tilting temperature (T(c)), the coupling between molecular orientation and membrane local curvature square leads to an increase of the bending rigidity in the tilting direction and therefore a spontaneous symmetry breaking in two principal directions. The asymmetry (Delta) of the bending rigidity undergoes a continuous change upon cooling and grows as T(c)-T for T<T(c). We discuss this anisotropical effect on the tilt structure of the ripple phase P(beta(')) of a nearly flat membrane and the sphere-to-tubule transition in a dilute solution of lipids. The transition between the spherical vesicle phase and the tubular phase is predicted to be first order.