Melting Temperature Range Research Articles

Analysis of energy requirements versus comfort levels for the integration of phase change materials in buildings

This paper investigates the importance of the design parameters when looking at possible energy savings and comfort enhancement in a building using Phase Change Materials (PCMs). Computer based simulations are performed using a simulation software for modelling a house and its thermal behaviour over a year. It is found that by varying the heating set point and the phase change (melting) temperature range of the PCM, significant changes can be observed. Some poor scenarios show that the integration of PCM can increase both the discomfort (up to 6% more discomfort hours) and the energy requirements (up to 25% more energy needed). On the other hand, appropriate scenarios bring significant energy savings (up to 33% less energy needed) and comfort enhancement (up to 31% less discomfort hours). This highlights the strong need for a clever design when integrating PCM into buildings. The goal is to find a trade-off between energy savings and comfort enhancement. The PCM with a phase change temperature range between 21°C and 26°C shows the best results. The study is based on climate conditions for Auckland City in New Zealand but most of the conclusions drawn can be applied to any climate.

Effects of Sn element on microstructure and properties of Zn–Cu–Bi–Sn high-temperature solder

The microstructures and properties of the Zn–Cu–Bi–Sn (ZCBS) high-temperature solders with various Sn contents were studied using differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results indicate that the increase of Sn content can both decrease the melting temperature and melting range of ZCBS solders and it can also effectively improve the wettability on Cu substrate. The shear strength of solder joints reaches a maximum value with the Sn addition of 5% (mass fraction), which is attributed to the formation of refined β-Sn and primary ɛ-CuZn5 phases in η-Zn matrix. However, when the content of Sn exceeds 5%, the shear strength decreases due to the formation of coarse β-Sn phase, which is net-shaped presented at the grain boundary.

Preparation and properties of gypsum based energy storage materials with capric acid–palmitic acid/expanded perlite composite PCM

Phase change materials (PCMs) have been widely applied to develop building materials with high thermal energy storage capacity. In this study, the capric acid–palmitic acid (CA–PA)/expanded perlite (EP) composite PCM was prepared using vacuum impregnation method and the thermal-regulated gypsum boards were fabricated by adding the prepared composite PCM. Scanning electron microscope images revealed that the CA–PA eutectic mixture was uniformly distributed in pores of EP and the CA–PA/EP composite PCM has a little effect on the interface gypsum crystals growth. Differential scanning calorimeter results showed that the melting temperature range of the composite PCM was 24.1–31°C and the latent heat was 88.39Jg−1. The composite PCM had a good chemical stability by surveying the chemical characterization of the composite PCM. Furthermore, the heat transfer property, thermal conductivity, bending and compressive strength were also tested. The results indicated that the higher the composite PCM volume content, the smaller the thermal conductivity of the gypsum board and the lower the temperature fluctuation in the cubicle system. The bending strength and compressive strength reduced gradually with an increase of the volume fraction of the composite PCM.

Lower purity dimer acid based polyamides used as hot melt adhesives: synthesis and properties

Hot melt polyamides exhibit high adhesive strength. The polyamides synthesized from dimer fatty acids and diamines can present low crystallinity and a broad range of melting temperatures. In this work, polyamides with different compositions of dimer fatty acids, piperazine, ethylenediamine, sebacic acid and stearic acid and different content of secondary diamine (piperazine) and primary diamine (ethylenediamine) were synthesized. Polyamides with higher purity of dimer acids showed greater molecular weight, adhesion performance and a better mechanical resistance evaluated in stress/strain test. Softening point increased with increase in monomers content. By differential scanning calorimetry analysis, it was observed that polyamides with low percentage of monomer content show only one narrow melting peak in 100 °C. The increase in the acids monomer content leads to a larger temperature range of melting peak. The use of dimer fatty acid with a low content of monomers (up to 6%) in the polyamides synthesis promotes the formation of hot melt adhesives with good adhesion performances. The lowest monomer content leads to an increase in molecular weight, viscosity and mechanical properties of polyamide. Increase in the content of primary amines in polyamides increases crystallinity, viscosity and mechanical properties due to the higher number of hydrogen bonds formed by amide groups.

Effect of basicity and B2O3 on viscosity, melting and crystallization behaviors of low fluorine mold fluxes for casting medium carbon steels

As potential substitutes for fluorides, the influences of basicity and B2O3 content on viscosity, melting and crystallization behaviors of low fluorine mold fluxes for casting medium carbon steels were investigated by using Brookfield viscometer and Single Hot Thermocouple Technique in this study. Results suggested that, the break temperature, crystallization temperature and critical cooling rate of low fluorine mold fluxes were increased with the increase of basicity; while they were decreased with the further addition of B2O3. Meantime, the viscosity and melting temperature range were first attenuated, and then increased greatly with the increase of basicity; however, they would tend to be reduced with the addition of B2O3 content. Also, it was found that the viscosity of mold flux is not only decided by the degree of polymerization of silicate structure, but also greatly affected by its crystallization behavior.

Thermophysical characteristics of Ca1−x Sr x F2 solid-solution Crystals (0 ≤ x ≤ 1)

The thermal conductivity of crystals of a continuous series of isovalent Ca1 − xSrxF2 solid solutions has been experimentally investigated in the temperature ranges of 50–300 K (0 ≤ x ≤ 1) and 54–303 K (x = 0.743). The concentration dependence k(x) of the thermal conductivity has been revealed for Ca1−xSrxF2 crystals. It is shown that k > 3 W/(m K) at 300 K for any x. Being extrapolated to the melting temperature range, the phonon mean free path l(T) in Ca0.257Sr0.743F2 crystal approaches to the unit-cell parameter a.

Atomic force microscopy monitoring of the temperature dependence of the cytochrome BM3 oligomeric state

The change in temperature is one of the factors affecting the activity of enzymes. In this work thermal denaturation and aggregation of cytochrome P450 BM3 were studied by atomic force microscopy. To determine specific temperature transitions the fluorescence analysis was used. In the low melting temperature range, 10-33 degrees C, a decrease in the fluorescence intensity of aromatic residues was observed with an increase in the fluorescence intensity of flavin groups. Protein melting in this range indicated three narrow S-shaped cooperative transitions at temperatures 16, 22 and 29 degrees C. Atomic force microscopy analysis in this temperature range showed that the shape of BM3 molecules remained globular in the form of compact objects (heights h < 7 nm, lateral dimensions d < 50 nm), but protein oligomeric state changed. The first two transitions were accompanied by a decrease in the degree of oligomerization and the third one was accompanied by its increase.

Modeling and simulation of a phase change material system for improving summer comfort in domestic residence

In the current context of thermal improvement in the building sector, research of new solutions to integrate to the retrofitting process is an essential step in the way of saving energy. With the purpose of maintaining or improving the summer comfort after a retrofitting in a residential building, Phase Change Materials (PCM) could be used to bring enough inertia to use the freshness of night for cooling during the warmest hour in the day. Passive solutions of PCM integration have demonstrated their limited benefits. Using PCM in the way proposed in this article goes through the design of a PCM/air system able to store latent heat. This unit is coupled to the ventilation system to ensure that the heat transfers between the ventilated air and the PCM stock are forced convection and then higher than the ones with natural convection. The fusion and solidification temperature for the PCM needs to be carefully chosen to allow the latent heat storage.To analyze the behavior of such a system in a retrofitted house with the climate of 4 different French cities, simulations in different configurations have been carried out. According to these climates, we analyze the necessary conditions for the improvement of efficiency of PCM use. Also, the appropriate PCM melting temperature range is defined with corresponding existing PCM characteristics. After, optimal thickness is obtained considering the diurnal temperature evolutions.The TRNSYS software runs the modeled house, coupled with Matlab for the PCM/air system model. The number of units of such a system can be changed and adapted to the different climates.Results are expressed in terms of percentage of the time when the indoor operative temperature reaches a certain level. Comparisons are made with classical systems without PCM.

Experimental and computational studies of ring-opening polymerization of ethylene brassylate macrolactone and copolymerization with ε-caprolactone and TBD-guanidine organic catalyst

The ring-opening polymerization (ROP) of ethylene brassylate, catalyzed by the cyclic guanidine 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is reported. Several experimental parameters were evaluated for bulk ROP process and polyesters, resulting in molecular weights between 3 and 15 kg mol−1. End-group analysis by 1H nuclear magnetic resonnance (NMR) and matrix assisted laser desorption ionization time of flight computational studies supports the dual behavior of TBD, which can act as both a catalyst and initiator of the polymerization process. Under optimum conditions, semicrystalline poly(ethylene brassylate-co-e-caprolactone) random copolymers were synthesized. Depending on the comonomer content, our results showed a range of melting temperatures between 39 and 69 °C. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 552–561

Interplay between a Strong Memory Effect of Crystallization and Liquid–Liquid Phase Separation in Melts of Broadly Distributed Ethylene–1-Alkene Copolymers

Narrow metallocene-made random ethylene copolymers display a strong memory effect of crystallization above their equilibrium melting point akin to the melt memory effect observed in model ethylene–1-butene copolymers. The onset temperature for self-nucleation or surviving self-seeds displays a bell shape with increasing comonomer content with a maximum at ∼2 mol % branches. Self-seeds do not survive at temperatures above the equilibrium melting point for homopolymers and copolymers either with very low branching or with a branching content >4.5 mol %. The self-seeds are associated with clusters of ethylene sequences that remain in the melt in close proximity and accelerate a subsequent crystallization, as observed by higher crystallization peak temperatures and higher nucleation density. Contrasting this behavior, commercial ethylene–1-alkene copolymers with a broad, bimodal comonomer distribution display an inversion of the crystallization rate in a range of melt temperatures where narrow copolymers show...

Triple‐Shape Effect with Adjustable Switching Temperatures in Crosslinked Poly[ethylene‐co‐(vinyl acetate)

A triple‐shape capability of copolymer networks enabling a variation of the two switching temperatures Tsws by purely physical functionalization is introduced. The polymer networks obtained by covalently crosslinking of poly[ethylene‐co‐(vinyl acetate)] exhibit a broad melting transition. The influence of the two deformation temperatures Tdeforms applied during programming of the triple‐shape effect (TSE) on the two Tsws is explored. Interestingly, it turns out that the deformation geometry plays an important role in the realizability of this concept. Tensile deformations allow adjusting only one Tsw in the lower melting temperature range of 45 to 60 °C, whereas in bending tests, both Tsws can be varied. Finally, two independent TSEs associated to four different Tsws between 45 and 90 °C can be realized in the same specimen. Shape fixity and shape recovery ratios generally exceed 90%, demonstrating an excellent performance of the triple‐shape function. image

A multiscale nonequilibrium model for melting of metal powder bed subjected to constant heat flux

A multiscale numerical model based on nonequilibrium thermal effect for melting of metal powder bed subjected to constant heat flux is developed. The volume shrinkage due to density change is taken into account. The nonequilibrium model is discretized by an implicit finite difference method and solved numerically using an iterative tri-diagonal matrix algorithm. The evolutions of powder bed surface temperature and various interfacial locations as well as the melting temperature range during the melting process are investigated. The results show that liquid region, upper and lower parts of mushy zone are formed on the top of unsintered zone as the melting progresses. The duration of the preheating stage shortens and the melting rate accelerates as the initial porosity or initial temperature increases while particle size has much less effect on the melting process. The parametric study shows the melting temperature range of the powder bed widens with increasing initial porosity, decreasing initial temperature or increasing particle size.

Microstructural Evolution of the Interface Between Pure Titanium and Low Melting Point Zr-Ti-Ni(Cu) Filler Metals

Low melting point Zr-based filler metals with melting point depressants (MPDs) such as Cu and Ni elements are used for titanium brazing. However, the phase transition of the filler metals in the titanium joint needs to be explained, since the main element of Zr in the filler metals differs from that of the parent titanium alloys. In addition, since the MPDs easily form brittle intermetallics, that deteriorate joint properties, the phase evolution they cause needs to be studied. Zr-based filler metals having Cu content from 0 to 12 at. pct and Ni content from 12 to 24 at. pct with a melting temperature range of 1062 K to 1082 K (789 °C to 809 °C) were wetting-tested on a titanium plate to investigate the phase transformation and evolution at the interface between the titanium plate and the filler metals. In the interface, the alloys system with Zr, Zr2Ni, and (Ti,Zr)2Ni phases was easily changed to a Ti-based alloy system with Ti, Ti2Ni, and (Ti,Zr)2Ni phases, by the local melting of parent titanium. The dissolution depths of the parent metal were increased with increasing Ni content in the filler metals because Ni has a faster diffusion rate than Cu. Instead, slow diffusion of Cu into titanium substrate leads to the accumulation of Cu at the molten zone of the interface, which could form undesirable TixCuy intermetallics. This study confirmed that Zr-based filler metals are compatible with the parent titanium metal with the minimum content of MPDs.

Micro/nano encapsulation of some paraffin eutectic mixtures with poly(methyl methacrylate) shell: Preparation, characterization and latent heat thermal energy storage properties

This work is aimed to prepare, characterize and determine the latent heat thermal energy storage properties of micro/nano encapsulated paraffin eutectic mixtures (PEMs) with polymethylmethacrylate (PMMA) shell. The eutectic combination ratios and optimum melting temperatures of C17C24, C19C18, C19C24 and C20C24 mixtures were find out prior to the encapsulation processes. Four kinds of micro/nano capsules, PMMA/(C17C24), PMMA/(C19C18), PMMA/(C19C24) and PMMA/(C20C24), were synthesized effectively as novel encapsulated phase change materials (PCMs) via emulsion polymerization. The Fourier transform infrared (FTIR) spectroscopy analysis confirmed the polymerization reaction to be occurred around the PEM used as core material. The polarized optical microscopy (POM), scanning electron microscopy (SEM) and particle size distribution (PSD) analysis showed that the fabricated PMMA/PEM micro/nano capsules had spherical shape-appearances with micro/nano sizes. The differential scanning calorimetry (DSC) measurements revealed that the micro/nano capsules containing the highest PEM content had melting temperature range of about 20–36°C and latent heat storage capacities of about 86–169J/g. Thermogravimetry analysis (TGA) results verified that the encapsulated PEMs had good thermal reliability and chemical stability after repeated melting/freezing cycles for 5000 times. Furthermore, the synthesized PMMA/PEM micro/nano capsules had conceivable thermal conductivity values and reversible phase change behaviors.

Determination of the PCM melting temperature range using DSC

The melting temperature range is one of the most important parameters for phase change material (PCM), it affects the PCM application areas and the performance of the system integrated with PCM. The melting temperature range of PCM is usually measured by a differential scanning calorimeter (DSC) with the dynamic measurement method. Unfortunately, the measurement results with this method are dependent of the heating rate. Determination of the melting temperature range of PCM means to find the starting melting temperature at which PCM starts melting and the ending melting temperature at which the melting process is finished. In this paper, a new DSC measurement method, which is the partially-melted DSC measurement method, was proposed to determine the ending melting temperature of PCM. With this method, the actual ending melting temperature of the sample PCM was found out and it was independent of the heating rate. Because there was no clear boundary between the non-melted state and the partially-melted state, the actual starting melting temperature of PCM was not able to be determined accurately.

Conditions of formation of “thick” plastic amorphous Fe-Co microwires in Fe75Si10B15-Co75Si10B15 system

Equilibrium and rapidly quenched Fe-Co-Si-B alloys are studied in Fe75Si10B15-Co75Si10B15 cross section. The polythermal cross section is developed in the range of melting and crystallization temperatures. Amorphous ribbons of alloys are produced by melt spinning, and rapidly quenched microwires in a glass sleeve with diameter of the metal core dcore = 10–100 μm are obtained by the Ulitovskii-Taylor technique. The structure and physical and mechanical properties of the alloys are studied. The concentration range of stability of “thick” amorphous plastic microwires with core diameter dcore ≥ 50 μm is determined using analysis of the phase diagram and content-property diagram. A special two-stage crystallization mechanism responsible for high glass-forming ability of microwires is established.

Neutron and synchrotron probes in the development of Co–Re-based alloys for next generation gas turbines with an emphasis on the influence of boron additives

Nickel-based superalloys are the materials of choice in the hot section of current gas turbines, but they are reaching temperature limits constrained by their melting temperature range. Co–Re alloy development was prompted by a search for new materials for future gas turbines, where the temperature of application will be considerably higher. Addition of the very high melting point refractory metal Re to Co can increase the melting range of Co alloys to much higher temperatures than the commercial Co alloys in use today. The alloy development strategy is first discussed very briefly. In this program, model ternary and quaternary compositions were studied in order to develop a basic understanding of the alloy system.In situneutron and synchrotron measurements (small and wide angle) at high temperatures were extensively used for this purpose and some selected results from thein situmeasurements are presented. In particular, the effect of boron doping in Co–Re–Cr alloys and the stability of the TaC precipitates at high temperatures were investigated. A fine dispersion of TaC precipitates strengthens some Co–Re alloys, and their stability at the application temperature is critical for the long-term creep properties.

A new filler metal with low contents of Cu for high strength aluminum alloy brazed joints

The effect of Cu with low contents of 10, 12, 15wt.% on the microstructure and melting point of Al–Si–Cu–Ni alloy has been investigated. Results showed that low-melting-point properties of Al–Si–Cu–Ni alloys with low contents of Cu were attributed to disappearance of Al–Si binary eutectic reaction and introduction of Al–Si–Cu–Ni quaternary reaction. With raising Cu content from 10 to 15wt.%, the amount of complex eutectic phases formed during low temperature reactions (Al–Cu, Al–Si–Cu and Al–Si–Cu–Ni alloy reactions) increased and the melting temperature of Al–Si–Cu–Ni filler metals declined. Brazing of 6061 aluminum alloy with Al–10Si–15Cu–4Ni (all in wt.%) filler metal of a melting temperature range from 519.3 to 540.2°C has been carried out successfully at 570°C. Sound joints can be obtained with Al–10Si–15Cu–4Ni filler metal when brazed at 570°C for holding time of 60min or more, and achieved high shear strength up to 144.4MPa.

Thermoplastic and solid-like electrolytes with liquid-like ionic conductivity based on poly(ethylene oxide) nanocomposites

Abstract A series of poly(ethylene oxide) (PEO)/lithium trifluoromethanesulfonate (LiTf)/ethylene carbonate (EC)/sepiolite composite electrolytes have been prepared by melt compounding, using neat sepiolite (Sep), sepiolite coated with polyethylene glycol (PEG-Sep) and with d -α-tocopherol polyethylene glycol 1000 succinate (TPGS-Sep) as fillers. The composites (weight ratio EC:PEO ~ 1) present ionic conductivity close to 10− 3 S cm− 1 at 30 °C, i.e. close to liquid electrolytes. Their crystallization and viscoelasticity were investigated evidencing a very complex phase structure and rheological behaviour, both of which dramatically depend on the type of nanofiller introduced in the blend. In the absence of TPGS-Sep as filler, the composites slowly separate into EC-rich and PEO-rich macrophases, what is visually evident in a two month time scale. With TPGS-Sep, the electrolytes are solid-like even at temperatures well above the PEO melting temperature range and do not phase separate in at least two years, constituting a homogeneous and stable blend which keeps its properties for long time periods.

Effect of repeated retrogradation on structural characteristics and in vitro digestibility of waxy potato starch

The effects of repeated retrogradation (RR) treatment on the structural characteristics and in vitro digestibility of waxy potato starch were investigated. The cycling times of RR ranging from 1 to 5 were designated as RR-1, RR-2, RR-3, RR-4, and RR-5, respectively. A maximum SDS content (40.41%) was obtained by RR-2 treatment with the time interval of 48h. RR-2-treated starch product exhibited a narrower melting temperature range, a higher onset temperature and a lower melting enthalpy compared with RR-1 treatment. Compared with native starch, X-ray diffraction patterns of treated starches were altered from B-type to C-type. The variation in relative crystallinity of RR-treated starch products was consistent with that in melting enthalpy. Moreover, compared with RR-1-treated starch, a large number of cavities were observed on the surface of RR-2-treated starch product with a time interval of 48h, whereas more smooth regions were found on the surface of RR-5-treated starch product. This study suggested that structural changes of waxy potato starch treated with different cycling times of RR significantly affected the digestibility.