Heat Flow Calorimeter Research Articles

Research of the Thermophysical Properties of CFRP with Different Reinforcements by Methods of a Stationary Heat Flow and Differential Scanning Calorimeter with Temperature Modulation

Research of the Thermophysical Properties of CFRP with Different Reinforcements by Methods of a Stationary Heat Flow and Differential Scanning Calorimeter with Temperature Modulation

Physicochemical fundamentals of processing solutions of thermoplastic poly(ether urethane)s to obtain fibrous-porous polymer composite materials

Objectives. To study the structure and properties of solutions of thermoplastic poly(ether urethane)s (PEUs) to inform their potential use in the production of fibrous-porous polymer composite materials with a given structure and set of performance properties depending on the field of practical application.Methods. The composition of PEUs was studied by attenuated total reflection infrared (ATR-IR) spectroscopy using a program for correcting the spectra on an IR Fourier spectrophotometer, as well by differential scanning calorimetry (DSC) using a heat flow calorimeter. The viscosity of PEU solutions was determined on a rotational viscometer.Results. The chemical composition of PEUs and the nature of the formation of hydrogen bonds were studied. An analysis of the spectra demonstrates the almost complete identity of the PEUs synthesized from the same 4,4'-diphenylmethane diisocyanate. In the studied PEUs of the Vitur and Desmopan® brands, as well as Sanpren, pronounced absorption bands characteristic of urethane groups involved in the formation of hydrogen bonds are visible in the region from 1702 to 1730 cm−1. The temperature transitions and thermal stability of the investigated PEUs were determined by DSC. The influence of the ratio of rigid and flexible blocks, as well as the nature of hydrogen bonds on the melting temperatures of polymers, was shown. Analysis of the DSC curves demonstrated all the studied PEUs to have high melting points ranging from 159 to 215°C. From the studied temperature dependences of the structural viscosity of thermoplastic PEUs solutions, all solutions were established to have a minimum viscosity anomaly; the value of the logarithm of viscosity depends on the chemical composition and structure of the initial PEUs. It is shown that the viscosity anomaly of PEU solutions can be reduced with increasing temperature.Conclusions. A comparison of the chemical composition, structure, thermal and rheological characteristics of thermoplastic PEUs with PEU solutions widely used for the production of fibrous-porous materials and coatings of Sanpren LQ-E-6 and Vitur R 0112 grades demonstrates their practicability as production materials and coatings having a predetermined structure and a set of properties depending on the requirements and operating conditions of finished products.

A microcalorimeter for the determination of combustion heat based on the principle of differential heat flow

A different type of heat-flow calorimeter is developed to measure the energy of combustion. This calorimeter uses differential thermopile as the heat-flow sensor. The calorimeter and oxygen bomb have a special structure to ensure that the heat generated by combustion heat is slowly transferred to the thermopile, and the temperature of the outside interface of the thermopile is constant. The calorific coefficient is determined by chemical calibration, providing for the chemical calibration S=(64.806 ± 0.029) μV mW−1, which means uncertainty is 0.05 % for calibration. The combustion enthalpies of anthracene and naphthalene are measured by using this calorimeter, and the results agree with the literature values or recommended values.

Heat capacity of a MnFe(P,Si,B) compound with first-order magnetic transition

The heat capacity of a MnFe(P,Si,B) giant magnetocaloric material is investigated by several calorimetric techniques and first-principles calculations. Semi-adiabatic relaxation calorimetry, commercial heat flow and home-made Peltier cells Differential Scanning Calorimeters (DSC) are used to record the heat capacity both around the magnetic transition at room temperature and at low temperatures. The ferromagnetic first-order transition is characterized by a sharp and intense latent heat peak corresponding to a transition entropy change of ∼2.23 J mol−1 K−1, while the thermal hysteresis of ∼2 K remains moderate. The analysis of the heat capacity over a broad temperature range provides an estimate of several important parameters, such as the electronic density of states (N(EF) ≈ 7.2 states eV−1f.u.−1) at low temperatures or an estimate of the Debye temperature θD ≈ 455 K. Different methods (non-magnetic reference, Debye function, phonons calculations) were used to model the lattice contribution to the heat capacity. While this study highlights the difficulty to disentangle lattice, electronic and magnetic contributions from a single quantity such as the heat capacity, it reveals that the excess entropy (magnetic contribution plus latent heat) is considerably larger than in the parent Fe2P.

Examinations of Errors in a D/Pd Gas-loading System when Using a Heat-flow Calorimeter

Measurement of a reaction between deuterium (hydrogen) gas and materials using a calorimeter which is calibrated by nitrogen will show erroneous excess heat power production due to the structure of the reaction chamber and the difference of thermal conductivity of the gases used in the calibration and triggering experiments, which leads to the energy generated in the chamber of the calorimeter has not been totally measured. The error is not obvious at low applied power, and it increases significantly with the increase of applied power. This insidious error is discussed by using a stable heat-flow (Seebeck) calorimeter and procedures to reduce error are put forward. And the authenticity of Rossi’s patent is questioned.

Implications of the Heat Generation of LMR-NCM on the Thermal Behavior of Large-Format Lithium-Ion Batteries

Lithium- and manganese-rich NCM (LMR-NCM) cathode active materials exhibit a pronounced energy inefficiency during charge and discharge that results in a strong heat generation during operation. The implications of such a heat generation are investigated for large-format lithium-ion batteries. Small laboratory cells are generally considered isothermal, but for larger cell formats this heat cannot be neglected. Therefore, the heat generation of LMR-NCM/graphite coin cells and NCA/graphite coin cells as a reference is measured for varying charge/discharge rates in an isothermal heat flow calorimeter and scaled to larger standardized cell formats. With the aid of thermal 3D models, the temperature evolution within these cell formats under different charge/discharge operations and cooling conditions is analyzed. Without an additional heat sink and any active cooling of larger LMR-NCM/graphite cells, discharge C-rates lower than C/2 are advisable to keep the cell temperature below a critical threshold. If the loads are increased, the cooling strategy has to be adapted to the specific cell format, otherwise critical temperatures above 60 °C are easily reached. For the investigated convective surface cooling and base plate cooling scenarios, thick prismatic cell formats with LMR-NCM are generally unfavorable, as the large amount of heat cannot be adequately dissipated.

Study on Calorimetry of Excess Heat in a d/Pd Gas-Loading System

A heat-flow calorimeter was introduced into the D/Pd gas-loading system to confirm the reliability and accuracy of the results obtained by isothermal calorimetry in the previous work. The effects of input power (electrical current) and pressure on excess heat were discussed under different experimental conditions. The results showed that the heat-flow calorimetry had higher accuracy than isothermal calorimetry. Under deuterium pressure of 30 kPa, the excess heat power decreased with the decrease of the input power, and the maximum excess heat power was (6.40 ± 0.19) W with an input power of 380 W. In the experiments of discussing the relationship between pressure and excess heat, the results showed there was a maximum excess power of (10.28 ± 3.40) W when the deuterium pressure was 220 Pa. The excess heat measured in the system was far more than that in chemical reaction. The results of SEM and EDS implied that excess heat came from nuclear transmutation processes.

Эффективная мощность сжатой сварочной дуги с разнополярными импульсами тока

The authors reviewed the research works on the effective power of direct and reverse polarity welding arcs with a non-consumable electrode in argon. The study shows that it is difficult to use the arc effective efficiency for effective power determination. It applies to the constricted arc more than to the free one. Based on data analysis for the effective power of polarities and the effective efficiency of a constricted arc burning toward the cooper heat flow calorimeter, the authors calculated the specific effective power of polarities and arc stresses. The maximum values are 23.2 W/A for the reverse polarity arc; and 14.2 W/A for the direct polarity arc. The study identified that the decrease in the specific effective power of polarities at the current increase within 100–150 A is well described by linear dependencies. With the current increase, there is a linear decrease in the direct polarity arc stress, while the reverse polarity arc stress remains constant. The spread of data for the specific effective power of polarities is about two times less than the spread for effective efficiency. Using a 2D mathematical model of the constricted arc column in a closed area, the authors calculated the power absorbed by plasma-forming argon and nozzle walls. As a result, the authors obtained the dependencies of the power transferred by argon on the nozzle channel length and the arc current. The specific effective power of argon flow for analyzed current densities and argon consumption shows poor dependence on the arc current and is equal to 5.5 W/A approximately. The power contribution of plasma-forming argon to the effective power of the constricted arc increases with the current increase.

Reaction Calorimetry for Studying Kinetics in Bulk Phase Polymerization of Propene

AbstractPolypropylene is one of the commercially most important polymers and is produced via coordinative polymerization with supported metal‐organic catalysts in different processes. While kinetic measurements for slurry and gas‐phase polymerization of propene are well‐established, for bulk phase polymerization of propene, often the only kinetic information obtained from an experiment is the yield. In this paper, two calorimetric methods and their application for measurement of kinetics of bulk phase polymerization of propene are discussed. On the one hand a special calibration‐free heat flow calorimeter and on the other hand power compensation calorimetry coupled with a software sensor for online baseline correction.

Thermal kinetics on exothermic reactions of a commercial LiCoO2 18650 lithium-ion battery and its components used in electric vehicles: A review

A review gathering available results on the chemical kinetics in literature for the commercial 18650 lithium-ion batteries containing cathode material of LiCoO2 and related components is summarized and discussed. Most of these kinetic parameters derived from adiabatic and heat-flow calorimeter, some few of them with the fitting of electrochemical-thermal model associated with data of accelerating rate calorimeter. However, due to the complexity of solid-state reaction involving both anode and cathode as well as the difficulty to determine the reaction mechanism function by thermal analysis on the solid electrode, most of the interpretation of calorimetric data set the order to be unity for simplicity. Kinetics-based heat rates under thermal abuses encompass the decomposition of solid electrolyte interface (stage III from 85 to 120 °C), reaction of LixC6 with electrolyte (stage IV from 120 to 170 °C), reaction of LixCoO2 with electrolyte (stage V from 170 to 200 °C), decomposition of LixCoO2 (stage VI > 200 °C), decomposition of solvent (stage VI > 200 °C) induced by internal short, and auto-ignition of solvent (stage VI > 200 °C). To clearly capture the distinctive features of these kinetic behaviors, the standard deviations adopted by the American Society for Testing and Materials E2781 and International Confederation for Thermal Analysis and Calorimetry are applied to enhance the accuracy and precision of the kinetic parameters. A diagram integrating all the Ea and log A values of LiCoO2 battery and its components is depicted, in which a newly phenomenon of compensation effect has been discovered. The linear equation of log A versus Ea tells the truth that some large errors existed in the data acquisition of kinetic parameters. Taking and comparing individually the average kinetic parameters from the decomposition of SEI, reaction of LixC6 with electrolyte, reaction of LixCoO2 with electrolyte to the whole battery, it is noteworthy that the chemical kinetics of the LiCoO2 battery is next door to that of LixCoO2 with electrolyte in n-th order reactions. The autocatalytic model II in Ea versus log A diagram seems to have the biggest deviations. The paradoxical model between the n-th order and autocatalytic type regarding the reaction of LixCoO2 with electrolyte exists and has not been exactly solved. Practically, some unimaginable disagreement among parameters of Ea and logA (sec−1 M1-n) are as yet unsettled, which reveals that the more extensive studies are needed to resolve the existing disputes. For the near future, a breakthrough of exceedingly better technology for acquiring the accurate chemical kinetics of a LiCoO2 battery and its ingredients will be expected earnestly.

A modular 3D printed isothermal heat flow calorimeter for reaction calorimetry in continuous flow

The presented continuous flow calorimeter enables process understanding of novel flow syntheses and the use of highly reactive compounds. Adaptation of the calorimeter is possible via 3D printing and due to its modular and expandable design.

Thermodynamic study of mixtures containing dibromomethane. II: volumes and enthalpies at 298.15 K

Excess molar volumes, VE, of binary mixtures of dibromomethane (DBM) with n-hexane, n-heptane, n-octane, cyclohexane, tetrachloromethane, dipropyl and dibutyl ether, tetrahydrofuran, and 3-pentanone are determined at 298.15 K in the whole composition range by means of a vibrating tube densimeter. For the same DBM mixtures plus with n-pentane and except with dipropyl ether and 3-pentanone, partial molar enthalpies, Hi, and excess molar enthalpies, HE, are obtained through a heat flow calorimeter and a titration method purposely devised. Both excess properties are positive for cyclohexane, tetrachloromethane, and n-alkanes, the latter exhibiting an increase with increasing number of carbon atoms. Dipropyl and dibutyl ether mixtures exhibit negative VE values, while n-hexane, tetrahydrofuran, and 3-pentanone mixtures show an S-shaped VE curve. Negative HEs are observed only for tetrahydrofuran, whereas dibutyl ether exhibits an S-shaped HE curve. HE results are compared with the predictions of the DISQUAC model. The partial molar volumes at infinite dilution, V°, as well as the enthalpies of solvation, ΔsolvH°, of the examined substances in DBM are evaluated and discussed also considering data on other compounds found in the literature. For V° and ΔsolvH°, a group additivity scheme is proposed to enable the estimation of these properties for other molecules and how much structural peculiarities such as chain length, polarity of groups, and cyclic structures influence their values.

Influence of Amount of Calcareous Fly Ash on Heat of Hydration of Portland Cement

For the reason a common strategy to reduce the emitted CO2 the clinker in the cement is oft replace by supplementary cementitious materials, like blast furnace slag or fly ash. Therefore, it is important to investigate the influence of these materials to the hydration in blended cements. This study is dedicated to the contribution of a calcareous fly ash to the hydration of a blended cement. To assess this contribution five calcareous fly ashes were chosen. The hydration of samples of Portland cement and Portland cement with 10% mass of cement (mc), 20% mc and 30% mc of calcareous fly ash was investigated by means of isothermal heat flow calorimetry. Calorimetric investigations were carried out with a TAM Air heat-flow calorimeter. Tests were conducted in 20°C. Water-binder ratio of cement pastes for hydration heat examinations was equal 0, 5. Research had shown that the addition of calcareous fly ash showed a retardation of the hydration reactions and increasing the initial heat period. The induction period of samples of Portland cement with 10%, 20% and 30% mc of calcareous fly ash is retarded compared to the samples of Portland cement. There is no difference in the cumulative heat normalized to the amount of Portland cement with 10% mc of calcareous fly ash compared to the Portland cement after 72 h. When amount of calcareous flay ash increases above 10% mc the cumulative heat is lower.

Monitoring the course of early-age reactions in alkali activated aluminosilicates

In this paper the reaction heat development of alkali activated aluminosilicates is studied by an isothermal heat flow calorimeter. The highest reaction activity is observed during two hours after mixing. The hydration heat power at early time is influenced mainly by the composition of tested mixtures involving ceramic dust as precursor and different amounts of sodium hydroxide and water glass as activators and by temperature.

Determination of thermophysical properties of cyclopentane hydrate using a stirred calorimetric cell

The cyclopentane hydrate, formed by combination of cyclopentane (CP) and water, is frequently used as a model system for clathrate hydrate compounds as it can form at atmospheric pressure and at temperatures below about 280 K. However, due to the immiscibility of CP and water, the dissociation enthalpy is challenging to obtain experimentally because total conversion of water to hydrate is difficult to achieve in quiescent conditions. Only two dissociation enthalpy values are available in literature, and a difference of 25 kJ.mol−1 between them clearly indicates a discrepancy. In this study, a stirring calorimetric cell was used with a Tian-Calvet heat-flow calorimeter, to measure phase change properties. The technical system made it possible to form pure CP-hydrate with complete conversion of water to hydrate. The dissociation temperature and dissociation enthalpy of the CP-hydrate (with max 5 wt% of residual liquid CP) were measured at 280.2 ± 0.5 K and 115,400 ± 7600 J.mol−1 of CP (377 ± 27 J.g−1 of water; 307 ± 21 J.g−1 of hydrate), respectively. This high enthalpy value opens new ways for using CP-hydrates in cold storage and refrigeration applications.

Phase Diagrams of the n-Decane–n-Hexadecane–Cyclododecane, n-Decane–Cyclododecane, and n-Hexadecane–Cyclododecane Systems

The n-decane–n-hexadecane–cyclododecane, n-decane–cyclododecane, and n-hexadecane–cyclododecane systems are studied by means of low-temperature differential thermal analysis using a differential scanning heat flow calorimeter. It is noted that all studied systems belong to the eutectic type. It is concluded that in the n-decane–n-hexadecane–cyclododecane system, the eutectic composition contains 85.0 wt % n-С10Н22, 4.0 wt % n-С16Н34, and 11.0 wt % С12Н24. It has a melting point of −35.0°C.

Review of Nuclear Heating Measurement by Calorimetry in France and USA

This paper gives a short review of sensors dedicated to measuring nuclear heating rate inside fission reactors in France and USA and especially inside Material Testing Reactors. These sensors correspond to heat flow calorimeters composed of a single calorimetric cell or of two calorimetric cells at least with a reference cell to obtain a differential calorimeter. The aim of this paper is to present the common running principle of these sensors and their own special characteristics through their design, calibration methods, and in-pile measurement techniques, and to describe multi-sensor probes including calorimeters.

Characterization of Low Level Wastes: a new design for calorimetric measurement

Calorimetry is one of the best solutions to estimate the overall quantity of nuclear material on a wide range of masses, from a few milligrams up to kilograms of radionuclides, by measuring the overall thermal power due to the radioactive decay coming from the waste contained in a metallic drum or a different type of container. It has many advantages as it features a non-destructive method which remains independent of matrix effect or the chemical composition. Until now, calorimetry allows to measure at the lowest 0.5 to 1 mW for samples up to 385 liters. But nowadays, thanks to new technological breakthroughs, KEP-Technologies calorimeters are able to measure as low as 50 μW for 40 liters samples. The μLVC is based on a new design with twin cells, a new temperature regulation loop and a heat-flow measurement system inside a vacuum chamber (Patent deposit P005299 LA/VL). The μLVC is a differential heat-flow calorimeter for precise measurement independent of the residual fluctuations caused by environmental changes. The new calorimeter is an industrial product able to work in environmental conditions with wide temperature variations. The first results have shown a great improvement in the detection of very low thermal effect thanks to the thermal noise reduction. The paper presents the developments in Large Volume Calorimetry as a new tool for quantification of nuclear material to characterize Pu-Am samples, i-graphite, and low tritium samples with high precision and reliability.

Thermal conductivity of aerogel blanket insulation under cryogenic-vacuum conditions in different gas environments

Thermal conductivity of low-density materials in thermal insulation systems varies dramatically with the environment: cold vacuum pressure, residual gas composition, and boundary temperatures. Using a reference material of aerogel composite blanket (reinforcement fibers surrounded by silica aerogel), an experimental basis for the physical heat transmission model of aerogel composites and other low-density, porous materials is suggested. Cryogenic-vacuum testing between the boundary temperatures of 78 K and 293 K is performed using a one meter cylindrical, absolute heat flow calorimeter with an aerogel blanket specimen exposed to different gas environments of nitrogen, helium, argon, or CO2. Cold vacuum pressures include the full range from 1×10-5 torr to 760 torr. The soft vacuum region, from about 0.1 torr to 10 torr, is complex and difficult to model because all modes of heat transfer – solid conduction, radiation, gas conduction, and convection – are significant contributors to the total heat flow. Therefore, the soft vacuum tests are emphasized for both heat transfer analysis and practical thermal data. Results for the aerogel composite blanket are analyzed and compared to data for its component materials. With the new thermal conductivity data, future applications of aerogel-based insulation systems are also surveyed. These include Mars exploration and surface systems in the 5 torr CO2 environment, field joints for vacuum-jacketed cryogenic piping systems, common bulkhead panels for cryogenic tanks on space launch vehicles, and liquid hydrogen cryofuel systems with helium purged conduits or enclosures.

The isobaric heat capacities and thermodynamic properties of ionic liquid 1-ethylpyridinium bis(trifluoromethylsulfonyl)imide

Ionic liquid 1-ethylpyridinium bis(trifluoromethylsulfonyl)imide ([C2py][NTf2]) was synthesized and characterized by 1H NMR spectroscopy, 13C NMR spectroscopy and thermal gravity analysis. The molar heat capacities of [C2py][NTf2] were measured using a heat-flow calorimeter with “3D Calvet” calorimetric sensor from (293 to 312) K. The experiment value of molar heat capacity 502.15 J K−1 mol−1 at 298.15 K was obtained. Moreover, the estimation values of molar heat capacity were calculated by using 4 methods at 298.15 K, and the result showed the Paulechka et al.’s method was more appropriate for predicting the molar heat capacity of IL [C2py][NTf2], and the error was less than 2%. In addition, the freezing point T * was calculated by freezing point depression, which was approximately equal to experimental value 305.08 K. The molar enthalpy of fusion Δf H m = 26.77 kJ mol−1, molar melting entropy Δde S m = 90.60 J mol−1 K−1 and the freezing constant K f were also calculated.