Layered Exchangers Research Articles

Comparative analysis of ground thermal conductivity and thermal resistance of borehole heat exchanger in different geological layered sequence

Borehole heat exchanger usually passes through many geological layers of the different thermo-physical properties from one layer to another in practical project of ground-coupled heat pump system. Considering the effect of heterogeneity in geological structures on heat transfer of borehole heat exchanger, it is necessary for in-situ thermal response test analysis to investigate the effect of geological layered sequence on ground thermal conductivity and borehole thermal resistance. Firstly, based on the validated numerical layered borehole heat exchanger model and numerical homogenous borehole heat exchanger model, the simulated distributions of water temperatures in U-pipe and heat flux along the depth in thermal response test are respectively compared and analysed. Then, the effective thermal conductivity and effective borehole thermal resistance estimated by the infinite line source model are respectively obtained based on the simulated thermal response tests carried out in the borehole heat exchanger installed in the six types of geological layered structures. The borehole thermal resistances in the two numerical model were respectively calculated by integrating the local thermal resistance along the depth. Finally, the ground thermal conductivities and borehole thermal resistances are compared in six types of geological layered structures. The results show that the maximum relative error of 7 % between the effective thermal conductivity and the thickness-weighted thermal conductivity in the numerical layered borehole heat exchanger model is located in the sequence of S-L-C due to BOTTOM 60m-thickness clay with lowest thermal conductivity. The relative error between effective borehole thermal resistance and borehole thermal resistance in the numerical layered borehole heat exchanger model are 3.5 %∼7.9 % in the six types of layered geological structures, and the maximum relative error between the two borehole thermal resistances corresponding to the two numerical models is only 1.1 %, which proves that effect of geological layered sequence on the deviation is limited in the two numerical models.

Optimization of double layered horizontal directional drilled ground heat exchangers by water injection into the borehole

Ground Heat Exchangers (GHEs) drilled using Horizontal Directional Drilling (HDD) technology have been proven to be a cost-efficient way of installing ground source heat pump systems (GSHP). They can also be installed in places where conventional horizontal ground heat exchanger (HGHE) would not be possible e.g., due to lack of land.In this research, a double layered horizontal borehole was installed as a GHE in Saga City, Japan. The two holes had a diameter of 114.3 mm and a length of 59 m and 56 m, respectively, while reaching depths of 5 m and 9.5 m. A polyethylene pipe with an outer diameter of 60 mm was inserted as a borehole heat exchanger (BHE). In March 2022, a two days thermal response test (TRT) showed the influence of rainfall on the system. A numerical model developed in FEFLOW based on the GHE dimension and the region's geology was validated using the measured temperatures of the heat medium at the return point and outlet of the GHE during the TRT. The validated model was then used to carry out sensitivity analysis examining different conditions of water injection into the borehole. The result of the sensitivity analysis showed that water injection into the borehole can improve the performance of the system and reduce the temperature change of the heat medium. Varying the injection rate can improve performance to a certain degree and the injection point has a strong influence on the performance. The injection temperature was also found to play a role in the performance, but even high temperatures in the case of heating showed significant improvement. Lastly, the influence of permeability was investigated and showed that impermeable layers are more favorable for injection compared to permeable layers.

Study of thermal-hydraulics of a sinusoidal layered heat exchanger for MSR

Plate-type heat exchangers have been investigated as promising heat exchangers for molten salt reactors. It has been found that the heat transfer coefficient of complex channel geometries such that with S-shaped fins studied as printed circuit heat exchangers (PCHE) is generally very high. However, because there is a risk of blockage in the heat exchanger of the extremely small flow area for a molten salt reactor, a sinusoidal-shaped heat exchanger with a large flow area and a simpler shape has been selected. Thermal-hydraulic analyses of several types of flow channels have been performed using the FLUENT code. The turbulence model and the wall function selected in the present calculation were verified in advance by the experimental data. The calculated results were compared with the experimental results using the zigzag flow channels and experimental correlations. The computation results using FLUENT reproduce the empirical correlations previously obtained with smooth ducts for heat transfer and pressure drop. These comparisons also demonstrate that the turbulence model and the mesh of the computation in this study are appropriate. The proposed heat exchanger with a sinusoidal flow geometry is promising because the heat transfer coefficient is larger than that of the empirical correlation for a smooth duct and is almost the same as that of zigzag geometry. The heat transfer coefficient of the sinusoidal geometry is approximately twice as large as the Dittus and Boelter correlation. The friction factor is far below that of the zigzag geometry. In the case of a heat exchanger of this shape, it has been found from the extrapolation of the results of FLUENT that the number of channels required to remove heat of 175 MW is approximately 6000 sets of hot and cold channels. This result is also supported by a real-scale analysis using the RELAP5-3D code.

Selective Separation/Removal of Cd and Pb Heavy Metal Cations from Solutions Using Layered NH4-SnP Exchanger

Selective Separation/Removal of Cd and Pb Heavy Metal Cations from Solutions Using Layered NH4-SnP Exchanger

Layered hydroxide anion exchanger and their applications related to pesticides: a brief review

Layered double hydroxides and layered hydroxide salts have generated enormous excitement in the inorganic field due to their potential to act as versatile host materials in fabricating novel host–guest layered materials. The ability of the layered hydroxide anion exchanger to be incorporated with a wide range of guest ions enable them to be exploited in various applications related to pesticides. This review sums up the different methods of preparing layered hydroxide anion exchanger, summarises the types of anion intercalated into these layered hydroxide anion exchanger based on their respective systems, and elucidates their potential applications in pesticide-related fields.

Recent Advances in Solid Catalysts Obtained by Metalloporphyrins Immobilization on Layered Anionic Exchangers: A Short Review and Some New Catalytic Results.

Layered materials are a very interesting class of compounds obtained by stacking of two-dimensional layers along the basal axis. A remarkable property of these materials is their capacity to interact with a variety of chemical species, irrespective of their charge (neutral, cationic or anionic). These species can be grafted onto the surface of the layered materials or intercalated between the layers, to expand or contract the interlayer distance. Metalloporphyrins, which are typically soluble oxidation catalysts, are examples of molecules that can interact with layered materials. This work presents a short review of the studies involving metalloporphyrin immobilization on two different anionic exchangers, Layered Double Hydroxides (LDHs) and Layered Hydroxide Salts (LHSs), published over the past year. After immobilization of anionic porphyrins, the resulting solids behave as reusable catalysts for heterogeneous oxidation processes. Although a large number of publications involving metalloporphyrin immobilization on LDHs exist, only a few papers have dealt with LHSs as supports, so metalloporphyrins immobilized on LHSs represent a new and promising research field. This work also describes new results on an anionic manganese porphyrin (MnP) immobilized on Mg/Al-LDH solids with different nominal Mg/Al molar ratios (2:1, 3:1 and 4:1) and intercalated with different anions (CO32− or NO3−). The influence of the support composition on the MnP immobilization rates and the catalytic performance of the resulting solid in cyclooctene oxidation reactions will be reported.

The polyelectrolyte-MoO3 hybrids: Bottom up building of a layered anionic exchanger

One-pot intercalation of poly(diallymethylammonium chloride) (PDDACl) and poly(allylamine hydrochloride) (PAHCl) between the layers of crystalline MoO3 was achieved for the first time using hydrothermal treatment. An experimental study monitoring the time of reaction and temperature of hydrothermal treatment showed that at 96h and 150°C the organic–inorganic [PAHCl]0.18[PAH]0.38MoO3 and [PDDACl]0.26[PDDA]0.24MoO3 hybrid materials were produced. In these conditions the MoO3 host was able to expand its interlayer spacing from 0.64 to ca. 1.1nm upon the intercalation of PDDACl and to approximately 2.2nm with the use of PAHCl. The materials prepared with PAHCl exhibit a larger interlayer space and have a larger amount of intercalated polymer than those with PDDACl because of the PAHCl smaller charge density. The characterization of these hybrid materials using powder XRD, Raman, FTIR, fluorescence and UV–vis DRS spectroscopy, SEM and TG/DTG analysis supported the intercalation of the polymer between MoO3 layers. UV–Vis DRS analysis clearly shows the presence of the mixed-valence Mo5+/Mo6+ couple in the MoO3 framework after the polyelectrolyte intercalation which indicates charge transfer from the polymer to the MoO3 host. FTIR study also revealed short distances structural disorder related to presence of Mo5+ centers after the intercalation. The hybrid materials produced, [PDDACl]0.26[PDDA]0.24MoO3 and [PAHCl]0.18[PAH]0.38MoO3 showed that approximately 53.0% and 32.0% of chloride ions are available for anionic exchange, respectively. These solids were employed as anion exchangers using cyanine dye; the emission band of the dye was monitored after the exchange as an indication of intercalation success. The cyanine dye containing hybrids presented an emission band centered at 602nm even after extensive extraction with methanol.

Layered double hydroxide ion exchangers on superparamagnetic microparticles for recovery of phosphate from waste water

Superparamagnetic microparticles modified with an ion exchange system are reported for the recovery of phosphate from waste water by a magnetic separation technique. Layered double hydroxides (LDH), anionic clays, are precipitated from an aqueous solution and deposited by an ultrasonic treatment on superparamagnetic microparticles consisting of Fe3O4 multicores embedded in a SiO2 matrix. Deposition can be conducted in a batch process as well as in a continuous way, using an ultrasonic flow cell. The obtained composite particles show good magnetic separability and have a specific surface area of around 100 m2 g−1. Zr doped LDH shows improved phosphate adsorption in waste water. After magnetic separation and regeneration, the composite particles are re-used which is demonstrated for four cycles. Phosphate ions are concentrated in the regeneration solution. Simple, low cost, and a fast continuous synthesis of the composite particles paves the way for application beyond lab scale in real waste water treatment plants.

Redox sorption of oxygen on a layered cathode-polarized nanocomposite metal-ion exchanger

The redox sorption of molecular oxygen from a flow of deionized water onto a cathode-polarized granular layer of nanocomposite copper-ion exchanger is considered. A mathematical description of it in terms of external diffusion is given. In contrast to better-known approaches, conditions are created that are as close as possible to the limiting diffusion current; this effect can be achieved by dividing the granular layer into shallow layers, each of which is then polarized with a near-limiting current. This allows water to be obtained with a particular value of deoxygenation close to the theoretically calculated value in stationary sorption membrane electrolyzers equipped with a unit containing a nanocomposite copper-ion exchanger. It is established that the lower deoxygenation value relative to the one calculated from the limiting current is associated with the additional reduction of oxygen with copper nanoparticles.

A Simple and Effective Method to Form Metallic Nanoparticles Onto Composites Made Up of Organic Polymers and Layered Inorganic Ion Exchangers as Fillers

A new easy method for the preparation of polymeric nanocomposites supporting metal nanoparticles is presented. The method concerns the use of a layered inorganic ion exchanger converted in the proper metallic form and exfoliated to act as filler of organic polymers with twofold aim of obtaining a composite (or nanocomposite) and to have metal ions that can be suitably reduced with a proper reducing agent to form metal nanoparticles. This strategy has been applied to the system polyvinylidene fluoride (PVDF) filled with layered a-zirconium phosphate in copper form. Several physical techniques (X-ray powder diffraction, atomic force microscopy, high resolution transmission electron microscopy) have been used to characterize the Cu-nanoparticles, whose dimensions range from 5 to 200 nm for those placed inside or on the surface of the polymeric matrix respectively, depending on the dispersion degree of the inorganic filler. The method is simple and can be used for different polymeric matrices and/or metal ions in order to produce metal/polymer systems with promising technological application.

Anion Exchangeable Layered Silicates Modified with Ionic Liquids on the Interlayer Surface

Novel layered materials with two-dimensionally arranged anion exchangeable sites in the interlayer space were prepared by immobilization of imidazolium chloride salts (1-butyl (or 1-octyl)-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium chloride, abbreviated as BimSi(OEt)3Cl or OimSi(OEt)3Cl, respectively) containing terminal triethoxysilyl groups onto layered octosilicate via silylation. More than 80% of SiOH/SiO− groups on the silicate layers were silylated and they are denoted as Bim-Oct and Oim-Oct. The cation exchangeable sites on octosilicate were stoichiometrically converted to anion exchangeable sites. The confronting arrangement of SiOH/SiO− groups on octosilicate is essential for this stoichiometric conversion because the silylation reagents ideally react with the surface SiOH/SiO− groups to form bidentate immobilization on octosilicate. The anion exchangeable capacity of the silylated materials is around 2 mmol g−1. The affinity of these materials for Cl−, Br−, I−, and NO3− is quite different from those of conventional anion exchangeable layered double hydroxides (LDHs). Bim-Oct is stable at pH 1.0, which is in clear contrast to the behavior of LDHs. Bim-Oct exhibits a high capacity for sorption of sulfasalazine, a bulky prodrug. The release behavior of the accommodated sulfasalazine is largely dependent on the pH values of simulated gastric and intestinal fluids, suggesting that these novel layered anion exchangers are potentially applicable to drug delivery systems.

20307 マイクロチャネル積層型熱交換器の伝熱特性とその可能性(OS3 機械工学が支援する微細加工技術(半導体・MEMS・NEMS) 基調講演,オーガナイズドセッション)

20307 マイクロチャネル積層型熱交換器の伝熱特性とその可能性(OS3 機械工学が支援する微細加工技術(半導体・MEMS・NEMS) 基調講演,オーガナイズドセッション)

高耐圧マイクロチャネル積層型熱交換器の伝熱特性(<小特集>究極の除熱性能を目指して)

高耐圧マイクロチャネル積層型熱交換器の伝熱特性(<小特集>究極の除熱性能を目指して)

Determination of 226Ra in aqueous solutions via sorption on thin films and α-spectrometry

An improved spectrometric method to determine the 226Ra activity in aqueous solutions is described. The method involves two stages, a preconcentration stage of 226Ra sorption onto a thin manganese layer and a measurement stage using α-spectrometry. Manganese oxide thin films were prepared and characterized with X-ray diffraction (XRD) and X-ray fluorescence (XRF) analyses. The thin films were found to follow the XRD patterns and chemical formula of the K-birnessite layered exchanger. The preconcentration of radium was studied relative to the initial radium concentration, pH and salt concentrations. The preconcentration kinetics was studied as a function of manganese surface, solution volume and salt concentration. Extensive Monte Carlo calculations were performed to optimise the detection of α-particles. In this way, the thin film preparation procedure as well as the radium sorption and the measurement conditions were optimised and detection limits lower than 0.5 mBq L −1 were obtained for 2 d of procedure completion. The method was validated with IAEA standards and it was applied for the determination of 226Ra in bottled waters and also wastewaters from the major thermoelectric plant in Greece. Moreover, the 226Ra distribution coefficients ( K d) of two differently prepared powder manganese oxides, a crystalline silicotitanate and an aluminium-pillared montmorillonite were determined by γ-spectrometry. 226Ra sorption experiments on silicotitanate thin films were performed and improvements in resolution and reduction of exposure time were observed.

Properties of Layered Inorganic Ion Exchangers with an Intercalated Antifungal Agent

Properties of Layered Inorganic Ion Exchangers with an Intercalated Antifungal Agent

Fractionation of Lithium Isotopes by Intercalation in Layered Inorganic Ion Exchangers

Abstract Layered titanium phosphates and heat-treated tin phosphate showed high separation factors (1.015-1.018) for lithium isotopes; the fractionation properties could be explained by considering two factors: the degree of Li+ dehydration in the solid phase and the affinity of the ion-exchange site toward Li+.

Covalent Bonding of Crown Ethers to γ‐Zirconium Phosphate—New Layered Ion Exchangers Showing Selective Recognition

AbstractThe topotactic exchange reactions of γ‐zirconium phosphate and γ‐zirconium phosphate/methylphosphonate with phosphonic acids derived from azacrown ethers of different sizes was examined. Prior intercalation of hexylamine was necessary in most cases to attain the maximum exchange level predicted by molecular modeling. Materials with imbricated or nonimbricated layers were obtained depending on crown size and exchange level. Exchange of methylphosphonates in γ‐zirconium phosphate/methylphosphonate was only observed when hexylamine had previously been intercalated. The exchange with the bisphosphonic acid derived from 1,10‐diaza[18]‐crown‐6 gave a material with an interlayer distance compatible with pillaring of the γ‐phase. The materials obtained from the exchange reactions of γ‐zirconium phosphate with phosphonic acids derived from [12]crown‐4 and [18]crown‐6 showed thermodynamic selectivities towards Na+ and K+, respectively, that were much higher than those observed for the simple crowns in solution. This observation suggests that the inorganic molecular framework enhances molecular recognition by minimization of solvation effects.

Microwave-hydrothermal processing of layered anion exchangers

We have compared the microwave-hydrothermal (M-H) processing with conventional hydrothermal (C-H) processing in the preparation of two layered anion exchangers, i.e., Mg3Al(OH)8NO3 · nH2O and Ni1-xZn2x(OH)2(CH3COO)2x · nH2O. Both these phases can be crystallized more rapidly (an order of magnitude) under M-H processing compared to C-H processing. The above layered mixed basic salt of Ni and Zn was found to exhibit very high selectivity for PO4= (Kd = 15,000). Its order of selectivity for various anions in the presence of 0.1 N̲ NaC1 (ratio of C1- to anion in question is 100) increases as follows: PO4= ≫ SO4= > NO3-.

Layered basic copper anion exchangers: chemical characterisation and X-ray absorption study

The local structure around copper in Cu2(OH)3OAc·H2O, and in the anhydrous iodide analogue prepared by ion exchange, has been determined by X-ray absorption spectroscopy at 77 K. For both compounds, the copper environment is compatible with a botallackite-type Cu2(OH)3Br arrangement, in which two crystallographically distinct copper atoms lie in 4 + 2 (oxygen + X) and 4 + 1 + 1 (oxygen + oxygen + X) environments (X = exchangeable anion OAc, I, Br etc.). Interatomic distances between copper and the exchangeable anion have been determined to be 2.78 and 3.15 A in Cu2(OH)3OAc·H2O and Cu2(OH)3I, respectively, the latter representing an unusual example of a direct CuII—I bond. At least two Cu—Cu distances could be identified in the radial distribution function: r(CuCu)= 3.16 and 6.32 A, signals from second and more distant neighbours being reinforced by a focussing effect along the linear chain of copper atoms in the layers.

ChemInform Abstract: Synthesis and Characterization of a New Crystalline Tin(IV) Arsenophosphate Ion Exchanger.

AbstractA new tin(IV) based layered ion exchanger consisting of a single crystalline phase containing HPO4 and HAsO4 anions in 1:1 ratio is prepared by precipitation from a solution containing SnCl4, H3PO4, and As2O5 and refluxing of the amorphous precursor after addition of HNO3.